TY  - JOUR
A1  - Jia, He
A1  - Friebe, Christian
A1  - Schubert, Ulrich S.
A1  - Zhang, Xiaozhe
A1  - Quan, Ting
A1  - Lu, Yan
A1  - Gohy, Jean-Francois
T1  - Core-Shell Nanoparticles with a Redox Polymer Core and a Silica Porous Shell as High-Performance Cathode Material for Lithium-Ion Batteries
JF  - Energy technology : generation, conversion, storage, distribution
N2  - A facile and novel method for the fabrication of core-shell nanoparticles (PTMA@SiO2) based on a poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) core and a porous SiO2 shell is reported. The core-shell nanoparticles are further self-assembled with negatively charged multi-walled carbon nanotubes (MWCNTs), which results in the formation of a free-standing cathode electrode. The porous SiO2 shell not only effectively improves the stability of the linear PTMA redox polymer with low molar mass in organic electrolytes but also leads to the uniform dispersion of PTMA active units in the MWCNTs conductive network. The PTMA@SiO2@MWCNT composite electrode exhibits a specific capacity as high as 73.8 mAh g at 1 C and only 0.11% capacity loss per cycle at a rate of 2 C.
KW  - composite electrodes
KW  - core-shell nanoparticles
KW  - energy storage
KW  - lithium-ion batteries
KW  - redox polymers
Y1  - 2019
U6  - https://doi.org/10.1002/ente.201901040
SN  - 2194-4288
SN  - 2194-4296
VL  - 8
IS  - 3
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Wolff, Christian Michael
A1  - Frischmann, Peter D.
A1  - Schulze, Marcus
A1  - Bohn, Bernhard J.
A1  - Wein, Robin
A1  - Livadas, Panajotis
A1  - Carlson, Michael T.
A1  - Jäckel, Frank
A1  - Feldmann, Jochen
A1  - Würthner, Frank
A1  - Stolarczyk, Jacek K.
T1  - All-in-one visible-light-driven water splitting by combining nanoparticulate and molecular co-catalysts on CdS nanorods
JF  - Nature Energy
N2  - Full water splitting into hydrogen and oxygen on semiconductor nanocrystals is a challenging task; overpotentials must be overcome for both half-reactions and different catalytic sites are needed to facilitate them. Additionally, efficient charge separation and prevention of back reactions are necessary. Here, we report simultaneous H-2 and O-2 evolution by CdS nanorods decorated with nanoparticulate reduction and molecular oxidation co-catalysts. The process proceeds entirely without sacrificial agents and relies on the nanorod morphology of CdS to spatially separate the reduction and oxidation sites. Hydrogen is generated on Pt nanoparticles grown at the nanorod tips, while Ru(tpy)(bpy)Cl-2-based oxidation catalysts are anchored through dithiocarbamate bonds onto the sides of the nanorod. O-2 generation from water was verified by O-18 isotope labelling experiments, and time-resolved spectroscopic results confirmed efficient charge separation and ultrafast electron and hole transfer to the reaction sites. The system demonstrates that combining nanoparticulate and molecular catalysts on anisotropic nanocrystals provides an effective pathway for visible-light-driven photocatalytic water splitting.
Y1  - 2018
U6  - https://doi.org/10.1038/s41560-018-0229-6
SN  - 2058-7546
VL  - 3
IS  - 10
SP  - 862
EP  - 869
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Nagel, Oliver
A1  - Beta, Carsten
A1  - Metzler, Ralf
T1  - Non-Gaussianity, population heterogeneity, and transient superdiffusion in the spreading dynamics of amoeboid cells
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - What is the underlying diffusion process governing the spreading dynamics and search strategies employed by amoeboid cells? Based on the statistical analysis of experimental single-cell tracking data of the two-dimensional motion of the Dictyostelium discoideum amoeboid cells, we quantify their diffusive behaviour based on a number of standard and complementary statistical indicators. We compute the ensemble- and time-averaged mean-squared displacements (MSDs) of the diffusing amoebae cells and observe a pronounced spread of short-time diffusion coefficients and anomalous MSD-scaling exponents for individual cells. The distribution functions of the cell displacements, the long-tailed distribution of instantaneous speeds, and the velocity autocorrelations are also computed. In particular, we observe a systematic superdiffusive short-time behaviour for the ensemble- and time-averaged MSDs of the amoeboid cells. Also, a clear anti-correlation of scaling exponents and generalised diffusivity values for different cells is detected. Most significantly, we demonstrate that the distribution function of the cell displacements has a strongly non-Gaussian shape andusing a rescaled spatio-temporal variablethe cell-displacement data collapse onto a universal master curve. The current analysis of single-cell motions can be implemented for quantifying diffusive behaviours in other living-matter systems, in particular, when effects of active transport, non-Gaussian displacements, and heterogeneity of the population are involved in the dynamics.
Y1  - 2018
U6  - https://doi.org/10.1039/c8cp04254c
SN  - 1463-9076
SN  - 1463-9084
VL  - 20
IS  - 35
SP  - 23034
EP  - 23054
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Release of Singlet Oxygen from Aromatic Endoperoxides by Chemical Triggers
JF  - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition
N2  - The generation of reactive singlet oxygen under mild conditions is of current interest in chemistry, biology, and medicine. We were able to release oxygen from dipyridylanthracene endoperoxides (EPOs) by using a simple chemical trigger at low temperature. Protonation and methylation of such EPOs strongly accelerated these reactions. Furthermore, the methyl pyridinium derivatives are water soluble and therefore serve as oxygen carriers in aqueous media. Methylation of the EPO of the ortho isomer affords the parent form directly without increasing the temperature under very mild conditions. This exceptional behavior is ascribed to the close contact between the nitrogen atom and the peroxo group. Singlet oxygen is released upon this reaction, and can be used to oxygenate an acceptor such as tetramethylethylene in the dark with no heating. Thus, a new chemical source of singlet oxygen has been found, which is triggered by a simple stimulus.
KW  - anthracenes
KW  - donor-acceptor systems
KW  - mild reaction conditions
KW  - selective oxidations
KW  - singlet oxygen
Y1  - 2018
U6  - https://doi.org/10.1002/anie.201806881
SN  - 1433-7851
SN  - 1521-3773
VL  - 57
IS  - 39
SP  - 12971
EP  - 12975
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Koc, Julian
A1  - Simovich, Tomer
A1  - Schönemann, Eric
A1  - Chilkoti, Ashutosh
A1  - Gardner, Harrison
A1  - Swain, Geoffrey W.
A1  - Hunsucker, Kelli
A1  - Laschewsky, André
A1  - Rosenhahn, Axel
T1  - Sediment challenge to promising ultra-low fouling hydrophilic surfaces in the marine environment
JF  - Biofouling : the journal of bioadhesion and biofilm research
N2  - Hydrophilic coatings exhibit ultra-low fouling properties in numerous laboratory experiments. In stark contrast, the antifouling effect of such coatings in vitro failed when performing field tests in the marine environment. The fouling release performance of nonionic and zwitterionic hydrophilic polymers was substantially reduced compared to the controlled laboratory environment. Microscopy and spectroscopy revealed that a large proportion of the accumulated material in field tests contains inorganic compounds and diatomaceous soil. Diatoms adhered to the accumulated material on the coating, but not to the pristine polymer. Simulating field tests in the laboratory using sediment samples collected from the test sites showed that incorporated sand and diatomaceous earth impairs the fouling release characteristics of the coatings. When exposed to marine sediment from multiple locations, particulate matter accumulated on these coatings and served as attachment points for diatom adhesion and enhanced fouling. Future developments of hydrophilic coatings should consider accumulated sediment and its potential impact on the antifouling performance.
KW  - hydrogel
KW  - field test
KW  - fouling release
KW  - marine biofouling
KW  - sediment
Y1  - 2019
U6  - https://doi.org/10.1080/08927014.2019.1611790
SN  - 0892-7014
SN  - 1029-2454
VL  - 35
IS  - 4
SP  - 454
EP  - 462
PB  - Taylor & Francis
CY  - London
ER  - 
TY  - JOUR
A1  - Schuck, Götz
A1  - Lehmann, Frederike
A1  - Ollivier, Jacques
A1  - Mutka, Hannu
A1  - Schorr, Susan
T1  - Influence of chloride substitution on the rotational dynamics of methylammonium in MAPbI(3-x)Cl(x) perovskites
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - Hybrid halide perovskites, MAPbI(3), MAPbI(2.94)Cl(0.0)6, and MAPbCl(3) (MA, methylammonium), were investigated using inelastic and quasielastic neutron scattering (QENS) with the aim of elucidating the impact of chloride substitution on the rotational dynamics of MA. In this context, we discuss the influence of the inelastic neutron scattering caused by low-energy phonons on QENS, resulting from the MA rotational dynamics in MAPbI(3-x)Cl(x). Through a comparative temperature-dependent QENS investigation with different energy resolutions, which allow a wide Fourier time window, we achieved a consistent description of the influence of chlorine substitution in MAPbI(3) on the MA dynamics. Our results showed that chlorine substitution in the low-temperature orthorhombic phase leads to a weakening of the hydrogen bridge bonds, since the characteristic relaxation times of C-3 rotation at 70 K in MAPbCl(3) (135 ps) and MAPbI(2.94)Cl(0.06) (485 ps) are much shorter than that in MAPbI(3) (1635 ps). For the orthorhombic phase, we obtained the activitin energies from the temperature-dependent characteristic relaxation times tau (c3). by Arrhenius fits, indicating lower values of E-a for MAPbCl(3) and MAPbI(2.94)Cl(0.06) compared to that of MAPbI(3). We also performed QENS analyses at 190 K for all three samples. Here, we observed that MAPbCI(3) shows slower MA rotational dynamics than MAPbI(3) in the disordered structure.
Y1  - 2019
U6  - https://doi.org/10.1021/acs.jpcc.9b01238
SN  - 1932-7447
VL  - 123
IS  - 18
SP  - 11436
EP  - 11446
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Yu, Hongtao
A1  - Quan, Ting
A1  - Mei, Shilin
A1  - Kochovski, Zdravko
A1  - Huang, Wei
A1  - Meng, Hong
A1  - Lu, Yan
T1  - Prompt Electrodeposition of Ni Nanodots on Ni Foam to Construct a High-Performance Water-Splitting Electrode
BT  - Efficient, Scalable, and Recyclable
JF  - Nano-Micro Letters
N2  - HighlightsFacile electrodeposition for fabricating active Ni nanodots (NiNDs) on Ni foam (NF) is shown.Binder- and heteroatom-free recyclable NiO/NiNDs@NF electrodes are efficiently made.NiO/NiNDs@NF bifunctional catalytic electrodes are used for water splitting. AbstractIn past decades, Ni-based catalytic materials and electrodes have been intensively explored as low-cost hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts for water splitting. With increasing demands for Ni worldwide, simplifying the fabrication process, increasing Ni recycling, and reducing waste are tangible sustainability goals. Here, binder-free, heteroatom-free, and recyclable Ni-based bifunctional catalytic electrodes were fabricated via a one-step quick electrodeposition method. Typically, active Ni nanodot (NiND) clusters are electrodeposited on Ni foam (NF) in Ni(NO3)(2) acetonitrile solution. After drying in air, NiO/NiND composites are obtained, leading to a binder-free and heteroatom-free NiO/NiNDs@NF catalytic electrode. The electrode shows high efficiency and long-term stability for catalyzing hydrogen and oxygen evolution reactions at low overpotentials ((10)(HER)=119mV and (50)(OER)=360mV) and can promote water catalysis at 1.70V@10mAcm(-2). More importantly, the recovery of raw materials (NF and Ni(NO3)(2)) is quite easy because of the solubility of NiO/NiNDs composites in acid solution for recycling the electrodes. Additionally, a large-sized (S similar to 70cm(2)) NiO/NiNDs@NF catalytic electrode with high durability has also been constructed. This method provides a simple and fast technology to construct high-performance, low-cost, and environmentally friendly Ni-based bifunctional electrocatalytic electrodes for water splitting.
KW  - Electrodeposition
KW  - Ni nanodots
KW  - Bifunctional catalysts
KW  - Water splitting
KW  - Large-size
Y1  - 2019
U6  - https://doi.org/10.1007/s40820-019-0269-x
SN  - 2311-6706
SN  - 2150-5551
VL  - 11
IS  - 41
PB  - Shanghai JIAO TONG univ press
CY  - Shanghai
ER  - 
TY  - JOUR
A1  - Utecht, Manuel Martin
A1  - Gaebel, Tina
A1  - Klamroth, Tillmann
T1  - Desorption induced by low energy charge carriers on Si(111)-7 x 7
BT  - first principles molecular dynamics for benzene derivates
JF  - Journal of computational chemistry : organic, inorganic, physical, biological
N2  - We use clusters for the modeling of local ion resonances caused by low energy charge carriers in STM-induced desorption of benzene derivates from Si(111)-7 x 7. We perform Born-Oppenheimer molecular dynamics for the charged systems assuming vertical transitions to the charged states at zero temperature, to rationalize the low temperature activation energies, which are found in experiment for chlorobenzene. Our calculations suggest very similar low temperature activation energies for toluene and benzene. For the cationic resonance transitions to physisorption are found even at 0 K, while the anion remains chemisorbed during the propagations. Further, we also extend our previous static quantum chemical investigations to toluene and benzene. In addition, an in depth analysis of the ionization potentials and electron affinities, which are used to estimate resonance energies, is given.
KW  - Born-Oppenheimer MD
KW  - STM-induced reactions
KW  - cluster models
KW  - Si(111)-7x7
Y1  - 2018
U6  - https://doi.org/10.1002/jcc.25607
SN  - 0192-8651
SN  - 1096-987X
VL  - 39
IS  - 30
SP  - 2517
EP  - 2525
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Duydu, Yalcin
A1  - Basaran, Nursen
A1  - Aydin, Sevtap
A1  - Ustundag, Aylin
A1  - Yalcin, Can Özgür
A1  - Anlar, Hatice Gul
A1  - Bacanli, Merve
A1  - Aydos, Kaan
A1  - Atabekoglu, Cem Somer
A1  - Golka, Klaus
A1  - Ickstadt, Katja
A1  - Schwerdtle, Tanja
A1  - Werner, Matthias
A1  - Meyer, Sören
A1  - Bolt, Hermann M.
T1  - Evaluation of FSH, LH, testosterone levels and semen parameters in male boron workers under extreme exposure conditions
JF  - Archives of toxicology : official journal of EUROTOX
N2  - Boric acid and sodium borates are currently classified in the EU-CLP regulation as "toxic to reproduction" under "Category 1B", with hazard statement of H360FD. However, so far field studies on male reproduction in China and in Turkey could not confirm such boron-associated toxic effects. As validation by another independent study is still required, the present study has investigated possible boron-associated effects on male reproduction in workers (n = 212) under different boron exposure conditions. The mean daily boron exposure (DBE) and blood boron concentration of workers in the extreme exposure group (n = 98) were 47.17 +/- 17.47 (7.95-106.8) mg B/day and 570.6 +/- 160.1 (402.6-1100) ng B/g blood, respectively. Nevertheless, boron-associated adverse effects on semen parameters, as well as on FSH, LH and total testosterone levels were not seen, even within the extreme exposure group. With this study, a total body of evidence has accumulated that allows to conclude that male reproductive effects are not relevant to humans, under any feasible and realistic conditions of exposure to inorganic boron compounds.
KW  - Boron exposure
KW  - Boric acid
KW  - Reproductive toxicity
KW  - FSH
KW  - LH
KW  - Testosterone
KW  - Semen parameters
Y1  - 2018
U6  - https://doi.org/10.1007/s00204-018-2296-7
SN  - 0340-5761
SN  - 1432-0738
VL  - 92
IS  - 10
SP  - 3051
EP  - 3059
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Yalcinkaya, Hacer
A1  - Bressel, Katharina
A1  - Lindner, Peter
A1  - Gradzielski, Michael
T1  - Controlled formation of vesicles with added styrene and their fixation by polymerization
JF  - Journal of colloid and interface science
N2  - Hypothesis: An effective way for fixating vesicle structures is the insertion of monomers and cross-linking agents into their bilayer, and their subsequent polymerization can lead to the formation of polymeric nanocapsules. Particularly attractive here are vesicle systems that form spontaneously well-defined small vesicles, as obtaining such small nanocapsules with sizes below 100 nm is still challenging. Experiments: A spontaneously forming well-defined vesicle system composed of the surfactants TDMAO (tetradecyldimethylamine oxide), Pluronic L35, and LiPFOS (lithium perfluorooctylsulfonate) mixture was used as template for fixation by polymerization. Therefore, styrene monomer was incorporated into the vesicle bilayer and ultimately these structures were fixated by UV induced radical polymerization. Structural alteration of the vesicles upon loading with monomer and the cross-linker as well as the effect of subsequent polymerization in the membrane were investigated in detail by turbidity measurements, dynamic and static light scattering, (DLS, SLS), and small angle neutron scattering (SANS). Findings: The analysis showed the changes on vesicle structures due to the monomer loading, and that these structures can become permanently fixed by the polymerization process. The potential of this approach to produce well-defined nanocapsules starting from a self-assembled system and following polymerization is critically evaluated. (C) 2018 Elsevier Inc. All rights reserved.
KW  - Template reaction
KW  - Zwitterionic surfactant
KW  - Anionic surfactant
KW  - Styrene
KW  - Vesicle
KW  - Small angle neutron scattering
KW  - Polymerization
Y1  - 2018
U6  - https://doi.org/10.1016/j.jcis.2018.07.097
SN  - 0021-9797
SN  - 1095-7103
VL  - 531
SP  - 672
EP  - 680
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Günther, Erika
A1  - Klauß, André
A1  - Toro-Nahuelpan, Mauricio
A1  - Schüler, Dirk
A1  - Hille, Carsten
A1  - Faivre, Damien
T1  - The in vivo mechanics of the magnetotactic backbone as revealed by correlative FLIM-FRET and STED microscopy
JF  - Scientific reports
N2  - Protein interaction and protein imaging strongly benefit from the advancements in time-resolved and superresolution fluorescence microscopic techniques. However, the techniques were typically applied separately and ex vivo because of technical challenges and the absence of suitable fluorescent protein pairs. Here, we show correlative in vivo fluorescence lifetime imaging microscopy Forster resonance energy transfer (FLIM-FRET) and stimulated emission depletion (STED) microscopy to unravel protein mechanics and structure in living cells. We use magnetotactic bacteria as a model system where two proteins, MamJ and MamK, are used to assemble magnetic particles called magnetosomes. The filament polymerizes out of MamK and the magnetosomes are connected via the linker MamJ. Our system reveals that bacterial filamentous structures are more fragile than the connection of biomineralized particles to this filament. More importantly, we anticipate the technique to find wide applicability for the study and quantification of biological processes in living cells and at high resolution.
Y1  - 2019
U6  - https://doi.org/10.1038/s41598-019-55804-5
SN  - 2045-2322
VL  - 9
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Koetz, Joachim
T1  - The Effect of Surface Modification of Gold Nanotriangles for Surface-Enhanced Raman Scattering Performance
JF  - Nanomaterials
N2  - A surface modification of ultraflat gold nanotriangles (AuNTs) with different shaped nanoparticles is of special relevance for surface-enhanced Raman scattering (SERS) and the photo-catalytic activity of plasmonic substrates. Therefore, different approaches are used to verify the flat platelet morphology of the AuNTs by oriented overgrowth with metal nanoparticles. The most important part for the morphological transformation of the AuNTs is the coating layer, containing surfactants or polymers. By using well established AuNTs stabilized by a dioctyl sodium sulfosuccinate (AOT) bilayer, different strategies of surface modification with noble metal nanoparticles are possible. On the one hand undulated superstructures were synthesized by in situ growth of hemispherical gold nanoparticles in the polyethyleneimine (PEI)-coated AOT bilayer of the AuNTs. On the other hand spiked AuNTs were obtained by a direct reduction of Au³⁺ ions in the AOT double layer in presence of silver ions and ascorbic acid as reducing agent. Additionally, crumble topping of the smooth AuNTs can be realized after an exchange of the AOT bilayer by hyaluronic acid, followed by a silver-ion mediated reduction with ascorbic acid. Furthermore, a decoration with silver nanoparticles after coating the AOT bilayer with the cationic surfactant benzylhexadecyldimethylammonium chloride (BDAC) can be realized. In that case the ultraviolet (UV)-absorption of the undulated Au@Ag nanoplatelets can be tuned depending on the degree of decoration with silver nanoparticles. Comparing the Raman scattering data for the plasmon driven dimerization of 4-nitrothiophenol (4-NTP) to 4,4′-dimercaptoazobenzene (DMAB) one can conclude that the most important effect of surface modification with a 75 times higher enhancement factor in SERS experiments becomes available by decoration with gold spikes.
KW  - undulated
KW  - spiked and crumble gold nanotriangles
KW  - SERS enhancement factor
KW  - dimerization of 4-nitrothiophenol
KW  - AOT bilayer
KW  - PEI coating
Y1  - 2020
U6  - https://doi.org/10.3390/nano10112187
SN  - 2079-4991
VL  - 10
IS  - 11
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Schultze, Christiane
A1  - Schmidt, Bernd
T1  - Functionalized Benzofurans via Microwave-Promoted Tandem Claisen-Rearrangement/5-endo-dig Cyclization
JF  - Journal of heterocyclic chemistry
N2  - Ortho-allyloxy alkinyl benzenes undergo, upon microwave irradiation in dimethylformamide, a tandem sequence of Claisen-rearrangement and 5-endo-dig cyclization to furnish 7-allyl-substituted benzofurans. With terminal alkynes, chroman-4-ones and enaminoketones become the main products. A mechanistic proposal for this observation relies on a reaction of the starting material with the solvent dimethylformamide under the microwave conditions.
Y1  - 2019
U6  - https://doi.org/10.1002/jhet.3671
SN  - 0022-152X
SN  - 1943-5193
VL  - 56
IS  - 9
SP  - 2619
EP  - 2629
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Benzyne - an acetylene- or cumulene-like electronic structure?
JF  - Tetrahedron
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of benzyne 1 and analogues (benzene 2, 1,2,3-cyclohexatriene 3, cyclohexen-3-yne 4, cyclohexen-4-yne 5, cyclohexyne 6) have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values could be employed to compare the diatropic ring current effects of benzene and benzyne, and, when compared with the spatial magnetic properties of the analogues, to answer the question whether the benzyne electronic structure is more acetylene- or cumulene-like, supported by structural data and delta(C-13)/ppm values. (C) 2019 Published by Elsevier Ltd.
KW  - Benzyne-allene or cumulene-like structure
KW  - Trough-space NMR shieldings (TSNMRS)
KW  - NICS
KW  - Iso-chemical shielding surfaces (ICSS)
KW  - Ring current effect
Y1  - 2019
U6  - https://doi.org/10.1016/j.tet.2019.07.011
SN  - 0040-4020
VL  - 75
IS  - 33
SP  - 4663
EP  - 4668
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Note, Carine
A1  - Koetz, Joachim
A1  - Kosmella, Sabine
T1  - Structural changes in poly(ethyleneimine) modified microemulsion
JF  - Journal of colloid and interface science
N2  - The influence of branched poly(ethyleneimine) on the phase behavior of the system sodium dodecylsulfate/toluene-pentanol (1:1)/water has been studied. The isotropic microemulsions still exist when water is replaced with aqueous solutions of PEI (up to 30% in weight), but their stability is significantly influenced. From a polymer concentration of 20 wt%, the polymer enhances the solubilization of water in oil, changes the sign of the spontaneous curvature of the surfactant film, and induces an inversion of the microemulsion type from water-in-oil (L-2) to oil-in-water (L-1), by the formation of a bicontinuous channel. Further investigations show that the addition of polymer in the L-2 phase changes the droplet-droplet interactions as the conductivity drops and the percolation disappears. In the bicontinuous channel, higher viscosities can be detected, as well as a weak percolation followed by a steep increase of the conductivity, which can be related to evident structural changes in the system. DSC measurements allow then to follow the changes of the water properties in the system, from interfacial-water in the L-2 phase to free-water in the sponge-like phase. Finally, all the measurements performed permit to characterize the structural transitions in the system and to understand the role of the added polymer.
KW  - polyelectrolyte
KW  - microemulsion
KW  - bicontinuous phase
Y1  - 2006
U6  - https://doi.org/10.1016/j.jcis.2006.06.071
SN  - 0021-9797
VL  - 302
SP  - 662
EP  - 668
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Wade, Jessica
A1  - Wood, Sebastian
A1  - Collado-Fregoso, Elisa
A1  - Heeney, Martin
A1  - Durrant, James
A1  - Kim, Ji-Seon
T1  - Impact of Fullerene Intercalation on Structural and Thermal Properties of Organic Photovoltaic Blends
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - The performance of organic photovoltaic blend devices is critically dependent on the polymer:fullerene interface. These interfaces are expected to impact the structural and thermal properties of the polymer with regards to the conjugated backbone planarity and transition temperatures during annealing/cooling processes. Here, we report the impact of fullerene intercalation on structural and thermal properties of poly(2,5-bis(3-tetradecylthiophen-2-yOthieno[3,2-b]thiophene (PBTTT), a highly stable material known to exhibit liquid crystalline behavior. We undertake a detailed systematic study of the extent of intercalation in the PBTTT:fullerene blend, considering the use of four different fullerene derivatives and also varying the loading ratios. Resonant Raman spectroscopy allows morphology in situ during controlled heating and cooling. We find that small fullerene molecules readily intercalate into PBTTT crystallites, resulting in a planarization of the polymer backbone, but high fullerene loading ratios or larger fullerenes result in nonintercalated domains. During cooling from melt, nonintercalated blend films are found to return to their original morphology and reproduce all thermal transitions on cooling with minimal hysteresis. Intercalated blend films show significant hysteresis on cooling due to the crystallized fullerene attempting to reintercalate. The strongest hysteresis is for intercalated blend films with excess fullerene loading ratio, which form a distinct nanoribbon morphology and exhibit a reduced geminate recombination rate. These results reveal that careful consideration should be taken during device fabrication, as postdeposition thermal treatments significantly impact the charge generation and recombination dynamics.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.jpcc.7b05893
SN  - 1932-7447
VL  - 121
SP  - 20976
EP  - 20985
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Synthesis of Pyridylanthracenes and Their Reversible Reaction with Singlet Oxygen to Endoperoxides
JF  - The journal of organic chemistry
N2  - The ortho, meta, and para isomers of 9,10-dipyridylanthracene 1 have been synthesized and converted into their endoperoxides 1-O-2 upon oxidation with singlet oxygen. The kinetics of this reaction can be controlled by the substitution pattern and the solvent: in highly polar solvents, the meta isomer is the most reactive, whereas the ortho isomer is oxidized fastest in nonpolar solvents. Heating of the endoperoxides affords the parent anthracenes by release of singlet oxygen.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.joc.7b01765
SN  - 0022-3263
VL  - 82
SP  - 9258
EP  - 9262
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Bauch, Marcel
A1  - Krtitschka, Angela
A1  - Linker, Torsten
T1  - Photooxygenation of oxygen-substituted naphthalenes
JF  - Journal of physical organic chemistry
N2  - The reaction of oxygen-substituted naphthalenes with singlet oxygen (O-1(2)) has been investigated, and labile endoperoxides have been isolated and characterized at -78 degrees C for the first time. Low-temperature kinetics by UV spectroscopy revealed that alkoxy and silyloxy substituents remarkably increase the rate of photooxygenations compared to 1,4-dimethylnaphthalene, whereas acyloxy-substituted acenes are inert towards O-1(2). The reactivities nicely correlate with HOMO energies and free activation energies, which we determined by density functional theory calculations. The lability of the isolated endoperoxides is due to their very fast back reaction to the corresponding naphthalenes even at -20 degrees C under release of O-1(2), making them to superior sources of this reactive species under very mild conditions. Finally, a carbohydrate-substituted naphthalene has been synthesized, which reacts reversibly with O-1(2) and might be applied for enantioselective oxidations in future work.
KW  - kinetics
KW  - labile peroxides
KW  - low-temperature experiments
KW  - naphthalenes
KW  - singlet oxygen
Y1  - 2017
U6  - https://doi.org/10.1002/poc.3734
SN  - 0894-3230
SN  - 1099-1395
VL  - 30
SP  - 6803
EP  - 6813
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - GEN
A1  - Ihmels, Heiko
A1  - Linker, Torsten
A1  - Trofimov, Aleksei
T1  - Editorial
T2  - Journal of physical organic chemistry
Y1  - 2017
U6  - https://doi.org/10.1002/poc.3745
SN  - 0894-3230
SN  - 1099-1395
VL  - 30
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Ryabchun, Alexander
A1  - Sakhno, Oksana
A1  - Stumpe, Joachim
A1  - Bobrovsky, Alexey
T1  - Full-Polymer Cholesteric Composites for Transmission and Reflection Holographic Gratings
JF  - Advanced optical materials
N2  - A new type of self-organized materials based on cholesteric networks filled with photoactive side-chain copolymer is being developed. Supramolecular helical structure of cholesteric polymer network resulting in the selective reflection is used as a photonic scaffold. Photochromic azobenzene-containing nematic copolymer is embedded in cholesteric scaffold and utilized as a photoactive media for optical pattering. 1D and 2D transmission diffraction gratings are successfully recorded in composite films by holographic technique. For the first time the possibility to create selective reflection gratings in cholesteric material mimicking the natural optical properties of cholesteric mesophase is demonstrated. That enables the coexistence of two selective gratings, where one has an intrinsic cholesteric periodic helical structure and the other is a holographic grating generated in photochromic polymer. The full-polymer composites provide high light-induced optical anisotropy due to effective photo-orientation of side-chain fragments of the azobenzene-containing liquid crystalline polymer, and prevent the degradation of the helical superstructure maintaining all optical properties of cholesteric mesophase. The proposed class of optical materials could be easily applied to a broad range of polymeric materials with specific functionality. The versatility of the adjustment and material preprogramming combined with high optical performance makes these materials a highly promising candidate for modern optical and photonic applications.
KW  - azobenzene
KW  - cholesteric scaffolds
KW  - holography
KW  - LC polymer
KW  - polarization diffraction grating
KW  - reflection grating
Y1  - 2017
U6  - https://doi.org/10.1002/adom.201700314
SN  - 2195-1071
VL  - 5
SP  - 376
EP  - 379
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Yang, Guang
A1  - Ding, Hong-ming
A1  - Kochovski, Zdravko
A1  - Hu, Rongting
A1  - Lu, Yan
A1  - Ma, Yu-qiang
A1  - Chen, Guosong
A1  - Jiang, Ming
T1  - Highly Ordered Self-Assembly of Native Proteins into 1D, 2D, and 3D Structures Modulated by the Tether Length of Assembly-Inducing Ligands
JF  - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition
N2  - In nature, proteins self-assemble into various structures with different dimensions. To construct these nanostructures in laboratories, normally proteins with different symmetries are selected. However, most of these approaches are engineering-intensive and highly dependent on the accuracy of the protein design. Herein, we report that a simple native protein LecA assembles into one-dimensional nanoribbons and nanowires, two-dimensional nanosheets, and three-dimensional layered structures controlled mainly by small-molecule assembly-inducing ligands RnG (n = 1, 2, 3, 4, 5) with varying numbers of ethylene oxide repeating units. To understand the formation mechanism of the different morphologies controlled by the small-molecule structure, molecular simulations were performed from microscopic and mesoscopic view, which presented a clear relationship between the molecular structure of the ligands and the assembled patterns. These results introduce an easy strategy to control the assembly structure and dimension, which could shed light on controlled protein assembly.
KW  - carbohydrate-protein interactions
KW  - dual non-covalent interactions
KW  - molecular simulations
KW  - protein self-assembly
Y1  - 2017
U6  - https://doi.org/10.1002/anie.201703052
SN  - 1433-7851
SN  - 1521-3773
VL  - 56
SP  - 10691
EP  - 10695
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Ghaisari, Sara
A1  - Winklhofer, Michael
A1  - Strauch, Peter
A1  - Klumpp, Stefan
A1  - Faivre, Damien
T1  - Magnetosome Organization in Magnetotactic Bacteria Unraveled by Ferromagnetic Resonance Spectroscopy
JF  - Biophysical journal
N2  - Magnetotactic bacteria form assemblies of magnetic nanoparticles called magnetosomes. These magnetosomes are typically arranged in chains, but other forms of assemblies such as clusters can be observed in some species and genetic mutants. As such, the bacteria have developed as a model for the understanding of how organization of particles can influence the magnetic properties. Here, we use ferromagnetic resonance spectroscopy to measure the magnetic anisotropies in different strains of Magnetosprillum gtyphiswaldense MSR-1, a bacterial species that is amendable to genetic mutations. We combine our experimental results with a model describing the spectra. The model includes chain imperfections and misalignments following a Fisher distribution function, in addition to the intrinsic magnetic properties of the magnetosomes. Therefore, by applying the model to analyze the ferromagnetic resonance data, the distribution of orientations in the bulk sample can be retrieved in addition to the average magnetosome arrangement. In this way, we quantitatively characterize the magnetosome arrangement in both wild-type cells and Delta mamJ mutants, which exhibit differing magnetosome organization.
Y1  - 2017
U6  - https://doi.org/10.1016/j.bpj.2017.06.031
SN  - 0006-3495
SN  - 1542-0086
VL  - 113
SP  - 637
EP  - 644
PB  - Cell Press
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Lange, Birger
A1  - Wagner, Jürgen
A1  - Zentel, Rudolf
T1  - Fabrication of robust high-quality ORMOCER (R) inverse opals
JF  - Macromolecular rapid communications
N2  - The nanostructuring of ORMOCER (R) to form inverse opals is described. For this purpose a polymer opal is used as a template and infiltrated with liquid ORMOCER (R). After photopolymerization of the resin the host opal is dissolved in tetrahydrofuran and an ORMOCER (R) inverse opal is obtained. It shows excellent periodicity (by SEM) and optical properties to reveal a high degree of face centered cubic order. This replication process leads to a nanostructured photonic crystal with the outstanding mechanical properties of ORMOCER (R) and high temperature stability up to 350 degrees C.
KW  - colloids
KW  - inverse opals
KW  - ORMOCER (R)
KW  - photonic crystal
KW  - self-assembly
Y1  - 2006
U6  - https://doi.org/10.1002/marc.200600429
SN  - 1022-1336
VL  - 27
SP  - 1746
EP  - 1751
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kapp, A.
A1  - Beissenhirtz, Moritz Karl
A1  - Geyer, F.
A1  - Scheller, F.
A1  - Viezzoli, Maria Silvia
A1  - Lisdat, Fred
T1  - Electrochemical and sensorial behavior of SOD mutants immobilized on gold electrodes in aqueous/organic solvent mixtures
JF  - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis
N2  - A cysteine mutant of a monomeric human Cu, Zn-SOD (Glycine 61, Serine 142) has been immobilized directly on gold electrodes using the thiol groups introduced. The electrochemical behavior of the surface confined protein was studied in mixtures of aqueous buffer and DMSO up to an organic solvent content of 60%. The formal potential was found to be rather independent of the DMSO content. However, half peak width increased and the redoxactive amount clearly decreased with raising DMSO content. In addition, the kinetics of the heterogeneous electron transfer became slower; but still a quasireversible electrochemical conversion of the mutant SOD was feasible. Thus, the electrodes were applied for sensorial superoxide detection. At a potential of +220 mV vs. Ag/AgCl advantage was taken of the partial oxidation reaction of the enzyme. A defined superoxide signal was obtained in solutions up to 40% DMSO. The sensitivity of the mutant electrodes decreased linearly with the organic solvent content in solution but was still higher compared to conventional cyt.c based sensors. At DMSO concentrations higher than 40% no sensor response was detected.
KW  - SOD
KW  - mutants
KW  - gold electrodes
KW  - DMSO
KW  - electrochemistry
Y1  - 2006
U6  - https://doi.org/10.1002/elan.200603620
SN  - 1040-0397
VL  - 18
SP  - 1909
EP  - 1915
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Lai, Feili
A1  - Feng, Jianrui
A1  - Heil, Tobias
A1  - Tian, Zhihong
A1  - Schmidt, Johannes
A1  - Wang, Gui-Chang
A1  - Oschatz, Martin
T1  - Partially delocalized charge in Fe-doped NiCo2S4 nanosheet-mesoporous carbon-composites for high-voltage supercapacitors
JF  - Journal of materials chemistry : A, Materials for energy and sustainability
N2  - Unraveling the effect of transition-metal doping on the energy storage properties of bimetallic sulfides remains a grand challenge. Herein, we construct bimetallic sulfide nanosheets and hence deliberately introduce transition-metal doping domains on their surface. The resulting materials show not only an enhanced density of states near the Fermi level but also partially delocalized charge as shown by density functional theory (DFT) calculations. Fe-doped NiCo2S4 nanosheets wrapped on N,S-doped ordered mesoporous carbon (Fe-NiCo2S4@N,S-CMK-3) are prepared, which show an enhanced specific capacitance of 197.8 F g(-1) in ionic liquid-based supercapacitors at a scan rate of 2 mV s(-1). This is significantly higher as compared to the capacitance of 155.2 and 135.9 F g(-1) of non-iron-doped NiCo2S4@N,S-CMK and Fe-NiCo2S4@CMK-3 electrodes, respectively. This result arises from the enhanced ionic liquid polarization effect and transportation ability from the Fe-NiCo2S4 surface and N,S-CMK-3 structure. Furthermore, the importance of matching multi-dimensional structures and ionic liquid ion sizes in the fabrication of asymmetric supercapacitors (ASCs) is demonstrated. As a result, the ASC device exhibits a high energy density of 107.5 W h kg(-1) at a power density of 100 W kg(-1) in a working-voltage window of 4 V when using Fe-NiCo2S4@N,S-CMK-3 and N,S-CMK-3 as positive and negative electrodes, respectively. This work puts forward a new direction to design supercapacitor composite electrodes for efficient ionic liquid coupling.
Y1  - 2019
U6  - https://doi.org/10.1039/c9ta06250e
SN  - 2050-7488
SN  - 2050-7496
VL  - 7
IS  - 33
SP  - 19342
EP  - 19347
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Shou, Keyun
A1  - Bremer, Anne
A1  - Rindfleisch, Tobias
A1  - Knox-Brown, Patrick
A1  - Hirai, Mitsuhiro
A1  - Rekas, Agata
A1  - Garvey, Christopher J.
A1  - Hincha, Dirk K.
A1  - Stadler, Andreas M.
A1  - Thalhammer, Anja
T1  - Conformational selection of the intrinsically disordered plant stress protein COR15A in response to solution osmolarity - an X-ray and light scattering study
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - The plant stress protein COR15A stabilizes chloroplast membranes during freezing. COR15A is an intrinsically disordered protein (IDP) in aqueous solution, but acquires an alpha-helical structure during dehydration or the increase of solution osmolarity. We have used small- and wide-angle X-ray scattering (SAXS/WAXS) combined with static and dynamic light scattering (SLS/DLS) to investigate the structural and hydrodynamic properties of COR15A in response to increasing solution osmolarity. Coarse-grained ensemble modelling allowed a structure-based interpretation of the SAXS data. Our results demonstrate that COR15A behaves as a biomacromolecule with polymer-like properties which strongly depend on solution osmolarity. Biomacromolecular self-assembly occurring at high solvent osmolarity is initiated by the occurrence of two specific structural subpopulations of the COR15A monomer. The osmolarity dependent structural selection mechanism is an elegant way for conformational regulation and assembly of COR15A. It highlights the importance of the polymer-like properties of IDPs for their associated biological function.
Y1  - 2019
U6  - https://doi.org/10.1039/c9cp01768b
SN  - 1463-9076
SN  - 1463-9084
VL  - 21
IS  - 34
SP  - 18727
EP  - 18740
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Garnier, Sebastien
A1  - Laschewsky, Andre
T1  - Non-ionic amphiphilic block copolymers by RAFT-polymerization and their self-organization
JF  - Colloid and polymer science : official journal of the Kolloid-Gesellschaft
N2  - Water-soluble, amphiphilic diblock copolymers were synthesized by reversible addition fragmentation chain transfer polymerization. They consist of poly(butyl acrylate) as hydrophobic block with a low glass transition temperature and three different nonionic water-soluble blocks, namely, the classical hydrophilic block poly(dimethylacrylamide), the strongly hydrophilic poly(acryloyloxyethyl methylsulfoxide), and the thermally sensitive poly(N-acryloylpyrrolidine). Aqueous micellar solutions of the block copolymers were prepared and characterized by static and dynamic light scattering analysis (DLS and SLS). No critical micelle concentration could be detected. The micellization was thermodynamically favored, although kinetically slow, exhibiting a marked dependence on the preparation conditions. The polymers formed micelles with a hydrodynamic diameter from 20 to 100 nm, which were stable upon dilution. The micellar size was correlated with the composition of the block copolymers and their overall molar mass. The micelles formed with the two most hydrophilic blocks were particularly stable upon temperature cycles, whereas the thermally sensitive poly(N-acryloylpyrrolidine) block showed a temperature-induced precipitation. According to combined SLS and DLS analysis, the micelles exhibited an elongated shape such as rods or worms. It should be noted that the block copolymers with the most hydrophilic poly(sulfoxide) block formed inverse micelles in certain organic solvents.
KW  - macrosurfactants
KW  - block copolymers
KW  - micelles
KW  - inverse micelles
KW  - sulfoxide
Y1  - 2006
U6  - https://doi.org/10.1007/s00396-006-1484-9
SN  - 0303-402X
VL  - 284
SP  - 1243
EP  - 1254
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Nave, Stefan
T1  - Stereoselective syntheses of enantiomerically pure 2,5-disubstituted dihydropyrans based on olefin metathesis
JF  - The journal of organic chemistry
N2  - A short synthesis of 2,5-disubstituted dihydropyrans starting from D-mannitol as a chiral building block is described. Our synthetic approach combines ruthenium-catalyzed ring closing olefin metathesis and palladium-catalyzed nucleophilic substitution.
Y1  - 2006
U6  - https://doi.org/10.1021/jo061190k
SN  - 0022-3263
VL  - 71
IS  - 19
SP  - 7364
EP  - 7369
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - GEN
A1  - Lutz, Jean-Francois
A1  - Kristen, Juliane
A1  - Skrabania, Katja
A1  - Laschewsky, Andre
T1  - POLY 14-Synthetic strategies for preparing multicompartment micelles
T2  - Abstracts of papers / American Chemical Society
N2  - The fabrication of compartmented micellar systems is an exciting new area of research in the field of polymer self-assembly. Multicompartment micelles composed of a water-soluble shell and a segregated hydrophobic core can be obtained via direct aqueous self-assembly of preformed polymeric amphiphiles possessing one hydrophilic segment and two incompatible hydrophobic segments (e.g. hydrocarbon and fluorocarbon blocks). Such macromolecular building-blocks were prepared in the present work principally via reversible addition-fragmentation transfer polymerization (RAFT). Polysoaps or triblock macrosurfactants can be synthesized in high yields by RAFT under relatively straightforward experimental conditions.
Y1  - 2006
SN  - 0-8412-7426-6
SN  - 0065-7727
VL  - 232
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Lendlein, Andreas
A1  - Balk, Maria
A1  - Tarazona, Natalia A.
A1  - Gould, Oliver E. C.
T1  - Bioperspectives for Shape-Memory Polymers as Shape Programmable, Active Materials
JF  - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences
N2  - Within the natural world, organisms use information stored in their material structure to generate a physical response to a wide variety of environmental changes. The ability to program synthetic materials to intrinsically respond to environmental changes in a similar manner has the potential to revolutionize material science. By designing polymeric devices capable of responsively changing shape or behavior based on information encoded into their structure, we can create functional physical behavior, including a shape memory and an actuation capability. Here we highlight the stimuli-responsiveness and shape-changing ability of biological materials and biopolymer-based materials, plus their potential biomedical application, providing a bioperspective on shape-memory materials. We address strategies to incorporate a shape memory (actuation) function in polymeric materials, conceptualized in terms of its relationship with inputs (environmental stimuli) and outputs (shape change). Challenges and opportunities associated with the integration of several functions in a single material body to achieve multifunctionality are discussed. Finally, we describe how elements that sense, convert, and transmit stimuli have been used to create multisensitive materials.
Y1  - 2019
U6  - https://doi.org/10.1021/acs.biomac.9b01074
SN  - 1525-7797
SN  - 1526-4602
VL  - 20
IS  - 10
SP  - 3627
EP  - 3640
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Jia, He
A1  - Quan, Ting
A1  - Liu, Xuelian
A1  - Bai, Lu
A1  - Wang, Jiande
A1  - Boujioui, Fadoi
A1  - Ye, Ran
A1  - Vald, Alexandru
A1  - Lu, Yan
A1  - Gohy, Jean-Francois
T1  - Core-shell nanostructured organic redox polymer cathodes with superior performance
JF  - Nano Energy
N2  - Core-shell nanoparticles stabilized by a cationic surfactant are prepared from the poly(2,2,6,6-tetra-methylpiperidinyloxy-4-yl methacrylate) redox polymer. The nanoparticles are further self-assembled with negatively charged reduced graphene oxide nanosheets and negatively charged mull-walled carbon nanotubes. This results in the formation of a free-standing cathode with a layered nanostructure and a high content of redox polymer that exhibits 100% utilization of the active substance with a measured capacity as high as 105 mAh/g based on the whole weight of the electrode.
KW  - Nanostructured
KW  - Redox polymer
KW  - Organic electrode
KW  - Lithium ion battery
KW  - Energy storage
Y1  - 2019
U6  - https://doi.org/10.1016/j.nanoen.2019.103949
SN  - 2211-2855
SN  - 2211-3282
VL  - 64
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kuroki, Agnes
A1  - Tchoupa, Arnaud Kengmo
A1  - Hartlieb, Matthias
A1  - Peltier, Raoul
A1  - Locock, Katherine E. S.
A1  - Unnikrishnan, Meera
A1  - Perrier, Sebastien
T1  - Targeting intracellular, multi-drug resistant Staphylococcus aureus with guanidinium polymers by elucidating the structure-activity relationship
JF  - Biomaterials : biomaterials reviews online
N2  - Intracellular persistence of bacteria represents a clinical challenge as bacteria can thrive in an environment protected from antibiotics and immune responses. Novel targeting strategies are critical in tackling antibiotic resistant infections. Synthetic antimicrobial peptides (SAMPs) are interesting candidates as they exhibit a very high antimicrobial activity. We first compared the activity of a library of ammonium and guanidinium polymers with different sequences (statistical, tetrablock and diblock) synthesized by RAFT polymerization against methicillin-resistant S. aureus (MRSA) and methicillin-sensitive strains (MSSA). As the guanidinium SAMPs were the most potent, they were used to treat intracellular S. aureus in keratinocytes. The diblock structure was the most active, reducing the amount of intracellular MSSA and MRSA by two-fold. We present here a potential treatment for intracellular, multi-drug resistant bacteria, using a simple and scalable strategy.
KW  - Antimicrobial
KW  - Intracellular bacteria
KW  - Block copolymers
KW  - RAFT polymerization
Y1  - 2019
U6  - https://doi.org/10.1016/j.biomaterials.2019.119249
SN  - 0142-9612
SN  - 1878-5905
VL  - 217
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Trautwein, Matthias
A1  - Fredriksson, Kai
A1  - Möller, Heiko Michael
A1  - Exner, Thomas E.
T1  - Automated assignment of NMR chemical shifts based on a known structure and 4D spectra
JF  - Journal of biomolecular NMR
N2  - Apart from their central role during 3D structure determination of proteins the backbone chemical shift assignment is the basis for a number of applications, like chemical shift perturbation mapping and studies on the dynamics of proteins. This assignment is not a trivial task even if a 3D protein structure is known and needs almost as much effort as the assignment for structure prediction if performed manually. We present here a new algorithm based solely on 4D [H-1, N-15]-HSQC-NOESY-[H-1, N-15]-HSQC spectra which is able to assign a large percentage of chemical shifts (73-82 %) unambiguously, demonstrated with proteins up to a size of 250 residues. For the remaining residues, a small number of possible assignments is filtered out. This is done by comparing distances in the 3D structure to restraints obtained from the peak volumes in the 4D spectrum. Using dead-end elimination, assignments are removed in which at least one of the restraints is violated. Including additional information from chemical shift predictions, a complete unambiguous assignment was obtained for Ubiquitin and 95 % of the residues were correctly assigned in the 251 residue-long N-terminal domain of enzyme I. The program including source code is available at https://github.com/thomasexner/4Dassign.
KW  - Chemical shift assignment
KW  - Protein
KW  - 3D structure
KW  - 4D NOESY
Y1  - 2016
U6  - https://doi.org/10.1007/s10858-016-0050-0
SN  - 0925-2738
SN  - 1573-5001
VL  - 65
SP  - 217
EP  - 236
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Maier, Stefan K.
A1  - Poluektov, Georgiy
A1  - Jester, Stefan-S.
A1  - Möller, Heiko Michael
A1  - Hoeger, Sigurd
T1  - Fast Oxidative Cyclooligomerization towards Low- and High-Symmetry Thiophene Macrocycles
JF  - Chemistry - a European journal
N2  - Macrocycles with quaterthiophene subunits were obtained by cyclooligomerization by direct oxidative coupling of unsubstituted dithiophene moieties. The rings were closed with high selectivity by an α,β′-connection of the thiophenes as proven by NMR spectroscopy. The reaction of the precursor with terthiophene moieties yielded the symmetric α,α′-linked macrocycle in low yield together with various differently connected isomers. Blocking of the β-position of the half-rings yielded selectively the α,α′-linked macrocycle. Selected cyclothiophenes were investigated by scanning tunneling microscopy, which displayed the formation of highly ordered 2D crystalline monolayers.
KW  - cyclooligomers
KW  - scanning tunneling microscopy
KW  - self-assembled monolayers
KW  - shape-persistent macrocycles
KW  - thiophenes
Y1  - 2016
U6  - https://doi.org/10.1002/chem.201503211
SN  - 0947-6539
SN  - 1521-3765
VL  - 22
SP  - 1379
EP  - 1384
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Prestel, Andreas
A1  - Möller, Heiko Michael
T1  - Spatio-temporal control of cellular uptake achieved by photoswitchable cell-penetrating peptides
JF  - Chemical communications
N2  - The selective uptake of compounds into specific cells of interest is a major objective in cell biology and drug delivery. By incorporation of a novel, thermostable azobenzene moiety we generated peptides that can be switched optically between an inactive state and an active, cell-penetrating state with excellent spatio-temporal control.
Y1  - 2016
U6  - https://doi.org/10.1039/c5cc06848g
SN  - 1359-7345
SN  - 1364-548X
VL  - 52
SP  - 701
EP  - 704
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Holert, Johannes
A1  - Yücel, Onur
A1  - Jagmann, Nina
A1  - Prestel, Andreas
A1  - Möller, Heiko Michael
A1  - Philipp, Bodo
T1  - Identification of bypass reactions leading to the formation of one central steroid degradation intermediate in metabolism of different bile salts in Pseudomonas sp strain Chol1
JF  - Environmental microbiology
Y1  - 2016
U6  - https://doi.org/10.1111/1462-2920.13192
SN  - 1462-2912
SN  - 1462-2920
VL  - 18
SP  - 3373
EP  - 3389
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Krüger, Tobias
A1  - Linker, Torsten
T1  - Synthesis of gamma-spirolactams by Birch reduction of arenes
JF  - European journal of organic chemistry
N2  - A convenient method for the synthesis of gamma-spirolactams in only three steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of chloroacetonitrile affords nitriles in moderate to good yields. Suitable precursors are methyl-substituted benzoic acids, naphthoic, and anthroic acid. Subsequent catalytic hydrogenation proceeds smoothly with PtO2 or Raney Ni as catalysts and lactams are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation at different pressures, affording products with 0, 1, or 2 double bonds. Overall, more than 15 new gamma-spirolactams have been synthesized in analytically pure form.
KW  - Arenes
KW  - Birch reduction
KW  - Hydrogenation
KW  - Lactams
KW  - Synthetic methods
Y1  - 2021
U6  - https://doi.org/10.1002/ejoc.202100056
SN  - 1099-0690
VL  - 2021
IS  - 10
SP  - 1585
EP  - 1591
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Metz, Melanie
A1  - Mai-Linde, Yasemin
A1  - Krüger, Tobias
A1  - Kelling, Alexandra
A1  - Sperlich, Eric
A1  - Linker, Torsten
T1  - Influence of functional groups on the ene reaction of singlet oxygen with 1,4-cyclohexadienes
JF  - Photochemistry and photobiology : the official journal of the American Society for Photobiology
N2  - The photooxygenation of 1,4-cyclohexadienes has been studied with a special focus on regio- and stereoselectivities. In all examples, only the methyl-substituted double bond undergoes an ene reaction with singlet oxygen, to afford hydroperoxides in moderate to good yields. We explain the high regioselectivities by a "large-group effect" of the adjacent quaternary stereocenter. Nitriles decrease the reactivity of singlet oxygen, presumably by quenching, but can stabilize proposed per-epoxide intermediates by polar interactions resulting in different stereoselectivities. Spiro lactams and lactones show an interesting effect on regio- and stereoselectivities of the ene reactions. Thus, singlet oxygen attacks the double bond preferentially anti to the carbonyl group, affording only one regioisomeric hydroperoxide. If the reaction occurs from the opposite face, the other regioisomer is exclusively formed by severe electrostatic repulsion in a perepoxide intermediate. We explain this unusual behavior by the fixed geometry of spiro compounds and call it a "spiro effect" in singlet oxygen ene reactions.
Y1  - 2021
U6  - https://doi.org/10.1111/php.13422
SN  - 0031-8655
SN  - 1751-1097
VL  - 97
IS  - 6
SP  - 1289
EP  - 1297
PB  - Wiley
CY  - Malden, Mass.
ER  - 
TY  - JOUR
A1  - Raju, Rajarshi Roy
A1  - Liebig, Ferenc
A1  - Klemke, Bastian
A1  - Koetz, Joachim
T1  - pH-responsive magnetic Pickering Janus emulsions
JF  - Colloid and polymer science : official journal of the Kolloid-Gesellschaft
N2  - We report ultrasonically generated pH-responsive Pickering Janus emulsions of olive oil and silicone oil with controllable droplet size and engulfment. Chitosan was used as a pH-responsive emulsifier. The increase of pH from 2 to 6 leads to a transition from completely engulfed double emulsion droplets to dumbbell-shaped Janus droplets accompanied by a significant decrease of droplet diameter and a more homogeneous size distribution. The results can be elucidated by the conformational change of chitosan from a more extended form at pH 2 to a more flexible form at pH 4-5. Magnetic responsiveness to the emulsion was attributed by dispersing superparamagnetic nanoparticles (Fe3O4 with diameter of 13 +/- 2 nm) in the olive oil phase before preparing the Janus emulsion. Incorporation of magnetic nanoparticles leads to superior emulsion stability, drastically reduced droplet diameters, and opened the way to control movement and orientation of the Janus droplets according to an external magnetic field.
KW  - Janus emulsion
KW  - Chitosan
KW  - pH-responsive
KW  - Magnetic-responsive
KW  - Cryo-SEM
KW  - TEM
Y1  - 2018
U6  - https://doi.org/10.1007/s00396-018-4321-z
SN  - 0303-402X
SN  - 1435-1536
VL  - 296
IS  - 6
SP  - 1039
EP  - 1046
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Krüger, Tobias
A1  - Vorndran, Katja
A1  - Linker, Torsten
T1  - Regioselective arene functionalization : simple substitution of carboxylate by alkyl groups
N2  - Arenes with various alkyl side-chains were synthesized in high yields and excellent regioselectivities. Starting from toluic and naphthoic acids, the carboxylate group was conveniently substituted by alkyl halides by Birch reduction and subsequent decarbonylation. The method is characterized by inexpensive starting materials and reagents, and methylation of arenes was realized. Besides simple alkyl substituents, the scope of arene functionalization was extended by benzyl, fluoro, amino, and ester groups. We were able to control the alkylation of 1-naphthoic acid during Birch reduction by the addition of tert-butanol. This allowed the regioselective synthesis of mono and bis-substituted naphthalenes from the same starting material.
Y1  - 2009
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/26293/
U6  - https://doi.org/10.1002/chem.200901774
SN  - 0947-6539
ER  - 
TY  - JOUR
A1  - Kumke, Michael Uwe
A1  - Eidner, Sascha
A1  - Krüger, Tobias
T1  - Fluorescence quenching and luminescence sensitization in complexes of Tb3+ and Eu3+ with humic substances
N2  - Intrinsic fluorescence quenching of humic substances (HS) and the sensitization of Ln(3+) luminescence (Ln3+ Tb3+, Eu3+) in HS complexes were investigated. Both measurements yielded complementary information on the complexation of metals by HS. Large differences between fulvic acids(FA)and humic acids (HA) were found. From time-resolved luminescence measurements it is concluded that a combination of energy transfer and energy back transfer between HS and Ln(3+) is responsible for the observed luminescence decay characteristics. In the case of Eu3+, an additional participation of charge-transfer states is suggested. A new concept for the evaluation of the sensitized luminescence decays of Ln(3+) was adapted
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Boggio, Jose M. Chavez
A1  - Bodenmueller, D.
A1  - Fremberg, T.
A1  - Haynes, R.
A1  - Roth, Martin M.
A1  - Eisermann, R.
A1  - Lisker, M.
A1  - Zimmermann, L.
A1  - Boehm, Michael
T1  - Dispersion engineered silicon nitride waveguides by geometrical and refractive-index optimization
JF  - Journal of the Optical Society of America : B, Optical physics
N2  - Dispersion engineering in silicon nitride (SiXNY) waveguides is investigated through the optimization of the waveguide transversal dimensions and refractive indices in a multicladding arrangement. Ultraflat dispersion of -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/km between 1670 and 2500 nm is numerically demonstrated. It is shown that typical refractive index fluctuations as well as dimension fluctuations during fabrication of the SiXNY waveguides are a limitation for obtaining ultraflat dispersion profiles. Single- and multicladding waveguides are fabricated and their dispersion profiles measured (over nearly 1000 nm) using a low-coherence frequency domain interferometric technique. By appropriate thickness optimization, the zero-dispersion wavelength is tuned over a large spectral range in single-and multicladding waveguides with small refractive index contrast (3%). A flat dispersion profile with +/- 3.2 ps/nm/km variation over 500 nm is obtained in a multicladding waveguide fabricated with a refractive index contrast of 37%. Finally, we generate a nearly three-octave supercontinuum in this dispersion flattened multicladding SiXNY waveguide. (C) 2014 Optical Society of America
Y1  - 2014
U6  - https://doi.org/10.1364/JOSAB.31.002846
SN  - 0740-3224
SN  - 1520-8540
VL  - 31
IS  - 11
SP  - 2846
EP  - 2857
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Roth, Martin M.
A1  - Löhmannsröben, Hans-Gerd
A1  - Kelz, A.
A1  - Kumke, Michael Uwe
T1  - innoFSPEC : fiber optical spectroscopy and sensing
Y1  - 2008
SN  - 978-0-819-47228-1
ER  - 
TY  - JOUR
A1  - Huwer, Johannes
A1  - Banerji, Amitabh
T1  - Corona sei Dank?!
BT  - Digitalisierung im Chemieunterricht
JF  - Chemie konkret : CHEMKON ; Forum für Unterricht und Didaktik
Y1  - 2020
U6  - https://doi.org/10.1002/ckon.202000037
SN  - 0944-5846
SN  - 1521-3730
VL  - 27
IS  - 3
SP  - 105
EP  - 106
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Hermanns, Jolanda
A1  - Keller, David
T1  - The development, use, and evaluation of digital games and quizzes in an introductory course on organic chemistry for preservice chemistry teachers
JF  - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2  - Due to the COVID pandemic, the introductory course on organic chemistry was developed and conducted as anonline course. To ensure methodical variety in this course,educational games and quizzes have been developed, used, and evaluated. The attendance of the course, and therefore also the use of the quizzes and games, was voluntary. The quizzes'main goalwas to give the students the opportunity to check whether they had memorized the knowledge needed in the course. Another goal was to make transparent which knowledge the students shouldmemorize by rote. The evaluation shows that the students hadnot internalized all knowledge which they should apply in severaltasks on organic chemistry. They answered multiselect questions in general less well than single-select questions. The games shouldcombine fun with learning. The evaluation of the games shows that the students rated them very well. The students used thosegames again for their exam preparation, as the monitoring of accessing the games showed. Students'experiences with usingelectronic devices in general or for quizzes and games have also been evaluated, because their experience could influence thestudents'assessment of the quizzes and games used in our study. However, the students used electronic devices regularly and shouldtherefore be technically competent to use our quizzes and games. The evaluation showed that the use of digital games for learningpurposes is not very common, neither at school nor at university, although the students had worked with such tools before. Thestudents are also very interested in using and developing such digital games not only for their own study, but also for their future work at school
KW  - Organic Chemistry
KW  - Second-Year Undergraduate
KW  - Humor
KW  - Puzzles
KW  - Games;
KW  - Internet
KW  - Web-Based Learning
KW  - Distance Learning
KW  - Self Instruction
Y1  - 2022
U6  - https://doi.org/10.1021/acs.jchemed.2c00058
SN  - 0021-9584
SN  - 1938-1328
VL  - 99
IS  - 4
SP  - 1715
EP  - 1724
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Raju, Rajarshi Roy
A1  - Koetz, Joachim
T1  - Pickering Janus emulsions stabilized with gold nanoparticles
JF  - Langmuir : the ACS journal of surfaces and colloids / American Chemical Society
N2  - We report a modified approach to the batch scale preparation of completely engulfed core-shell emulsions or partially engulfed Janus emulsions with colorful optical properties, containing water, olive oil, and silicone oil. The in situ reduction of gold chloride, forming gold nanoparticles (AuNPs) at the olive oil interface in the absence or presence of chitosan, leads to the formation of compartmentalized olive-silicone oil emulsion droplets in water. In the absence of additional reducing components, time-dependent morphological transformations from partial engulfment to complete engulfment were observed. Similar experiments in the presence of chitosan or presynthesized AuNPs show an opposite time-dependent trend of transformation of core-shell structures into partially engulfed ones. This behavior can be understood by a time-dependent rearrangement of the AuNPs at the interface and changes of the interfacial tension. The Pickering effect of AuNPs at oil-water and oil-oil interfaces brings not only color effects to individual microdroplets, which are of special relevance for the preparation of new optical elements, but also a surprising self-assembly of droplets.
Y1  - 2022
U6  - https://doi.org/10.1021/acs.langmuir.1c02256
SN  - 0743-7463
SN  - 1520-5827
VL  - 38
IS  - 1
SP  - 147
EP  - 155
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
T1  - Determination of Pd2+ by fluorescence enhancement caused by an off-switching of an energy- and an electron transfer
JF  - ChemistrySelect
N2  - In this paper, we introduce a fluorescent dye 1, which is able to detect selectively Pd2+ by a clear fluorescence enhancement (FE) in THF. In the presence of eight Pd2+ equivalents, we observed a fluorescence enhancement factor (FEF) of 28.3. The high Pd2+ induced FEF can be explained by an off switching of multiple quenching processes within 1 by Pd2+. In the free dye 1 a photoinduced electron transfer (PET) and energy transfer (ET) takes place and quenches the anthracenic fluorescence. The coordination of eight Pd2+ units by the alkylthio-substituted porphyrazine receptor suppresses the PET and ET quenching process and the anthracenic fluorescence is switched on.
KW  - Palladium ion
KW  - electron transfer
KW  - energy transfer
KW  - fluorescence
KW  - porphyrazine
Y1  - 2021
U6  - https://doi.org/10.1002/slct.202003975
SN  - 2365-6549
VL  - 6
IS  - 3
SP  - 318
EP  - 322
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Hwang, Jongkook
A1  - Walczak, Ralf
A1  - Oschatz, Martin
A1  - Tarakina, Nadezda
A1  - Schmidt, Bernhard V. K. J.
T1  - Micro-Blooming: Hierarchically Porous Nitrogen-Doped Carbon Flowers Derived from Metal-Organic Mesocrystals
JF  - Small
N2  - Synthesis of 3D flower-like zinc-nitrilotriacetic acid (ZnNTA) mesocrystals and their conformal transformation to hierarchically porous N-doped carbon superstructures is reported. During the solvothermal reaction, 2D nanosheet primary building blocks undergo oriented attachment and mesoscale assembly forming stacked layers. The secondary nucleation and growth preferentially occurs at the edges and defects of the layers, leading to formation of 3D flower-like mesocrystals comprised of interconnected 2D micropetals. By simply varying the pyrolysis temperature (550-1000 degrees C) and the removal method of in the situ-generated Zn species, nonporous parent mesocrystals are transformed to hierarchically porous carbon flowers with controllable surface area (970-1605 m(2) g(-1)), nitrogen content (3.4-14.1 at%), pore volume (0.95-2.19 cm(3) g(-1)), as well as pore diameter and structures. The carbon flowers prepared at 550 degrees C show high CO2/N-2 selectivity due to the high nitrogen content and the large fraction of (ultra)micropores, which can greatly increase the CO2 affinity. The results show that the physicochemical properties of carbons are highly dependent on the thermal transformation and associated pore formation process, rather than directly inherited from parent precursors. The present strategy demonstrates metal-organic mesocrystals as a facile and versatile means toward 3D hierarchical carbon superstructures that are attractive for a number of potential applications.
KW  - 3D flower superstructures
KW  - hierarchically porous carbon
KW  - metal-organic mesocrystals
KW  - thermal transformation mechanism
Y1  - 2019
U6  - https://doi.org/10.1002/smll.201901986
SN  - 1613-6810
SN  - 1613-6829
VL  - 15
IS  - 37
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - GEN
A1  - Prestel, Andreas
A1  - Möller, Heiko Michael
T1  - Spatio-temporal control of cellular uptake achieved by photoswitchable cell-penetrating peptides
N2  - The selective uptake of compounds into specific cells of interest is a major objective in cell biology and drug delivery. By incorporation of a novel, thermostable azobenzene moiety we generated peptides that can be switched optically between an inactive state and an active, cell-penetrating state with excellent spatio-temporal control.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 218 
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89658
SP  - 701
EP  - 704
ER  - 
TY  - JOUR
A1  - Abbas, Ioana M.
A1  - Vranic, Marija
A1  - Hoffmann, Holger
A1  - El-Khatib, Ahmed H.
A1  - Montes-Bayón, María
A1  - Möller, Heiko Michael
A1  - Weller, Michael G.
T1  - Investigations of the Copper Peptide Hepcidin-25 by
LC-MS/MS and NMR⁺
JF  - International Journal of Molecular Sciences
N2  - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.
KW  - hepcidin-25
KW  - copper
KW  - nickel
KW  - copper complex
KW  - ATCUN motif
KW  - metal complex
KW  - MS
KW  - NMR structure
KW  - metal peptide
KW  - metalloprotein
KW  - metallopeptide
KW  - isomerization
KW  - racemization
KW  - purity
KW  - reference material
Y1  - 2018
U6  - https://doi.org/10.3390/ijms19082271
SN  - 1422-0067
SN  - 1661-6596
VL  - 19
IS  - 8
PB  - Molecular Diversity Preservation International
CY  - Basel
ER  - 
TY  - JOUR
A1  - Kastl, Johanna
A1  - Braun, Joachim
A1  - Prestel, Andreas
A1  - Möller, Heiko Michael
A1  - Huhn, Thomas
A1  - Mayer, Thomas U.
T1  - Mad2 Inhibitor-1 (M2I-1): A Small Molecule Protein-Protein Interaction Inhibitor Targeting the Mitotic Spindle Assembly Checkpoint
JF  - ACS chemical biology
N2  - The genetic integrity of each organism depends on the faithful segregation of its genome during mitosis. To meet this challenge, a cellular surveillance mechanism, termed the spindle assembly checkpoint (SAC), evolved that monitors the correct attachment of chromosomes and blocks progression through mitosis if corrections are needed. While the central role of the SAC for genome integrity is well established, its functional dissection has been hampered by the limited availability of appropriate small molecule inhibitors. Using a fluorescence polarization-based screen, we identify Mad2 inhibitor-1 (M2I-1), the first small molecule inhibitor targeting the binding of Mad2 to Cdc20, an essential protein-protein interaction (PPI) within the SAC. Based on computational and biochemical analyses, we propose that M2I-1 disturbs conformational dynamics of Mad2 critical for complex formation with Cdc20. Cellular studies revealed that M2I-1 weakens the SAC response, indicating that the compound might be active in cells. Thus, our study identifies the SAC specific complex formation between Mad2 and Cdc20 as a protein-protein interaction that can be targeted by small molecules.
Y1  - 2015
U6  - https://doi.org/10.1021/acschembio.5b00121
SN  - 1554-8929
SN  - 1554-8937
VL  - 10
IS  - 7
SP  - 1661
EP  - 1666
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Prestel, Andreas
A1  - Möller, Heiko Michael
T1  - Spatio-temporal control of cellular uptake achieved by photoswitchable cell-penetrating peptides
JF  - Chemical communications : ChemComm
N2  - The selective uptake of compounds into specific cells of interest is a major objective in cell biology and drug delivery. By incorporation of a novel, thermostable azobenzene moiety we generated peptides that can be switched optically between an inactive state and an active, cell-penetrating state with excellent spatio-temporal control.
Y1  - 2015
U6  - https://doi.org/10.1039/C5CC06848G
SN  - 1364-548X
IS  - 52
SP  - 701
EP  - 704
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Abbas, Ioana M.
A1  - Vranic, Marija
A1  - Hoffmann, Holger
A1  - El-Khatib, Ahmed H.
A1  - Montes-Bayón, María
A1  - Möller, Heiko Michael
A1  - Weller, Michael G.
T1  - Investigations of the Copper Peptide Hepcidin-25 by
LC-MS/MS and NMR⁺
T2  - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2  - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 701 
KW  - hepcidin-25
KW  - copper
KW  - nickel
KW  - copper complex
KW  - ATCUN motif
KW  - metal complex
KW  - MS
KW  - NMR structure
KW  - metal peptide
KW  - metalloprotein
KW  - metallopeptide
KW  - isomerization
KW  - racemization
KW  - purity
KW  - reference material
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-427926
SN  - 1866-8372
IS  - 701
ER  - 
TY  - JOUR
A1  - Vorburger, Thomas
A1  - Nedielkov, Ruslan
A1  - Brosig, Alexander
A1  - Bok, Eva
A1  - Schunke, Emina
A1  - Steffen, Wojtek
A1  - Mayer, Sonja
A1  - Goetz, Friedrich
A1  - Möller, Heiko Michael
A1  - Steuber, Julia
T1  - Role of the Na+-translocating NADH:quinone oxidoreductase in voltage generation and Na+ extrusion in Vibrio cholerae
JF  - Biochimica et biophysica acta : Bioenergetics
N2  - For Vibrio cholerae, the coordinated import and export of Na+ is crucial for adaptation to habitats with different osmolarities. We investigated the Na+-extruding branch of the sodium cycle in this human pathogen by in vivo Na-23-NMR spectroscopy. The Na+ extrusion activity of cells was monitored after adding glucose which stimulated respiration via the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR). In a V. cholerae deletion mutant devoid of the Na+-NQR encoding genes (nqrA-F), rates of respiratory Na+ extrusion were decreased by a factor of four, but the cytoplasmic Na+ concentration was essentially unchanged. Furthermore, the mutant was impaired in formation of transmembrane voltage (Delta psi, inside negative) and did not grow under hypoosmotic conditions at pH 8.2 or above. This growth defect could be complemented by transformation with the plasmid encoded nqr operon. In an alkaline environment, Na+/H+ antiporters acidify the cytoplasm at the expense of the transmembrane voltage. It is proposed that, at alkaline pH and limiting Na+ concentrations, the Na+-NQR is crucial for generation of a transmembrane voltage to drive the import of H+ by electrogenic Na+/H+ antiporters. Our study provides the basis to understand the role of the Na+-NQR in pathogenicity of V. cholerae and other pathogens relying on this primary Na+ pump for respiration. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Nuclear magnetic resonance (NMR)
KW  - Sodium transport
KW  - Vibrio cholerae
KW  - Respiration
KW  - Na+ homeostasis
KW  - Hypoosmotic stress
Y1  - 2016
U6  - https://doi.org/10.1016/j.bbabio.2015.12.010
SN  - 0005-2728
SN  - 0006-3002
VL  - 1857
SP  - 473
EP  - 482
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Schulze, Sven
A1  - Wehrhold, Michel
A1  - Hille, Carsten
T1  - Femtosecond-Pulsed laser written and etched fiber bragg gratings for fiber-optical biosensing
JF  - Sensors
N2  - We present the development of a label-free, highly sensitive fiber-optical biosensor for online detection and quantification of biomolecules. Here, the advantages of etched fiber Bragg gratings (eFBG) were used, since they induce a narrowband Bragg wavelength peak in the reflection operation mode. The gratings were fabricated point-by-point via a nonlinear absorption process of a highly focused femtosecond-pulsed laser, without the need of prior coating removal or specific fiber doping. The sensitivity of the Bragg wavelength peak to the surrounding refractive index (SRI), as needed for biochemical sensing, was realized by fiber cladding removal using hydrofluoric acid etching. For evaluation of biosensing capabilities, eFBG fibers were biofunctionalized with a single-stranded DNA aptamer specific for binding the C-reactive protein (CRP). Thus, the CRP-sensitive eFBG fiber-optical biosensor showed a very low limit of detection of 0.82 pg/L, with a dynamic range of CRP detection from approximately 0.8 pg/L to 1.2 mu g/L. The biosensor showed a high specificity to CRP even in the presence of interfering substances. These results suggest that the proposed biosensor is capable for quantification of CRP from trace amounts of clinical samples. In addition, the adaption of this eFBG fiber-optical biosensor for detection of other relevant analytes can be easily realized.
KW  - fiber Bragg gratings
KW  - ultra-fast laser inscription
KW  - fiber etching
KW  - nanostructure fabrication
KW  - fiber-optical sensors
KW  - aptamers
KW  - C-reactive protein
KW  - biomarker
Y1  - 2018
U6  - https://doi.org/10.3390/s18092844
SN  - 1424-8220
VL  - 18
IS  - 9
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Paz, Cristian
A1  - Heydenreich, Matthias
A1  - Schmidt, Bernd
A1  - Vadra, Nahir
A1  - Baggio, Ricardo
T1  - Three new dihydro-beta-agarofuran sesquiterpenes from the seeds of Maytenus boaria
JF  - Acta Crystallographica Section C
N2  - As part of a project studying the secondary metabolites extracted from the Chilean flora, we report herein three new beta-agarofuran sesquiterpenes, namely (1S,4S,5S,6R,7R,8R,9R,10S)-6-acetoxy-4,9-dihydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b] oxepine-5,10-diylbis(furan-3-carboxylate), C27H32O11, (II), (1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-9-hydroxy-2,2,5a, 9-tetramethyloctahydro-2H-3,9a-methanobenzo[ b] oxepine-5,10-diyl bis(furan-3-carboxylate), C27H32O10, (III), and (1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-10-(benzoyloxy)-9-hydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]oxepin-5-yl furan-3-carboxylate, C29H34O9, (IV), obtained from the seeds of Maytenus boaria and closely associated with a recently published relative [Paz et al. (2017). Acta Cryst. C73, 451-457]. In the (isomorphic) structures of (II) and (III), the central decalin system is esterified with an acetate group at site 1 and furoate groups at sites 6 and 9, and differ at site 8, with an OH group in (II) and no substituent in (III). This position is also unsubstituted in (IV), with site 6 being occupied by a benzoate group. The chirality of the skeletons is described as 1S, 4S, 5S, 6R, 7R, 8R, 9R, 10S in (II) and 1S, 4S, 5S, 6R, 7R, 9S, 10S in (III) and (IV), matching the chirality suggested by NMR studies. This difference in the chirality sequence among the title structures (in spite of the fact that the three skeletons are absolutely isostructural) is due to the differences in the environment of site 8, i.e. OH in (II) and H in (III) and (IV). This diversity in substitution, in turn, is responsible for the differences in the hydrogen-bonding schemes, which is discussed.
KW  - Celastraceae
KW  - Maytenus boaria
KW  - sesquiterpene
KW  - dihydro-beta-agarofuran
KW  - crystal structure
KW  - NMR
KW  - DSC
Y1  - 2018
U6  - https://doi.org/10.1107/S2053229618005429
SN  - 2053-2296
VL  - 74
SP  - 564
EP  - 570
PB  - International Union of Crystallography
CY  - Chester
ER  - 
TY  - JOUR
A1  - Tian, Guang-Zong
A1  - Hu, Jing
A1  - Zhang, Heng-Xi
A1  - Rademacher, Christoph
A1  - Zou, Xiao-Peng
A1  - Zheng, Hong-Ning
A1  - Xu, Fei
A1  - Wang, Xiao-Li
A1  - Linker, Torsten
A1  - Yin, Jian
T1  - Synthesis and conformational analysis of linear homo- and heterooligomers from novel 2-C-branched sugar amino acids (SAAs)
JF  - Scientific reports
N2  - Sugar amino acids (SAAs), as biologically interesting structures bearing both amino and carboxylic acid functional groups represent an important class of multifunctional building blocks. In this study, we develop an easy access to novel SAAs in only three steps starting from nitro compounds in high yields in analytically pure form, easily available by ceric (IV) mediated radical additions. Such novel SAAs have been applied in the assembly of total nine carbopeptoids with the form of linear homo-and heterooligomers for the structural investigations employing circular dichroism (CD) spectroscopy, which suggest that the carbopeptoids emerge a well-extended, left (or right)-handed conformation similar to polyproline II (PPII) helices. NMR studies also clearly demonstrated the presence of ordered secondary structural elements. 2D-ROESY spectra were acquired to identify i+1NH <-> (C1H)-C-i, (C2H)-C-i correlations which support the conformational analysis of tetramers by CD spectroscopy. These findings provide interesting information of SAAs and their oligomers as potential scaffolds for discovering new drugs and materials.
Y1  - 2018
U6  - https://doi.org/10.1038/s41598-018-24927-6
SN  - 2045-2322
VL  - 8
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - John, Leonard
A1  - Mertens, Monique
T1  - Extending the Class of [1,3]-Dioxolo[4.5-f]benzodioxole (DBD) Fluorescent Dyes
JF  - European journal of organic chemistry
N2  - Synthetic routes to a collection of new fluorescent dyes are described, which are based on the [1,3]-dioxolo[4.5-f]benzodioxole (DBD) core. By introducing different electron withdrawing groups in 4- and 8-position of the DBD moiety the emission wavelength could be adjusted over a large spectral range from blue to orange light.
KW  - Functional organic materials
KW  - Fluorescence
KW  - DBD dyes
KW  - Large Stokes shifts
KW  - Aryllithium compounds
KW  - Heterocycles
Y1  - 2018
U6  - https://doi.org/10.1002/ejoc.201800002
SN  - 1434-193X
SN  - 1099-0690
VL  - 2018
IS  - 14
SP  - 1674
EP  - 1681
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Liebig, Ferenc
A1  - Sarhan, Radwan Mohamed
A1  - Prietzel, Claudia Christina
A1  - Thünemann, Andreas F.
A1  - Bargheer, Matias
A1  - Koetz, Joachim
T1  - Undulated Gold Nanoplatelet Superstructures
BT  - In Situ Growth of Hemispherical Gold Nanoparticles onto the Surface of Gold Nanotriangles
JF  - Langmuir
N2  - Negatively charged flat gold nanotriangles, formed in a vesicular template phase and separated by an AOT-micelle-based depletion flocculation, were reloaded by adding a cationic polyelectrolyte, that is, a hyperbranched polyethylenimine (PEI). Heating the system to 100 degrees C in the presence of a gold chloride solution, the reduction process leads to the formation of gold nanoparticles inside the polymer shell surrounding the nanoplatelets. The gold nanoparticle formation is investigated by UV-vis spectroscopy, small-angle X-ray scattering, and dynamic light scattering measurements in combination with transmission electron microscopy. Spontaneously formed gold clusters in the hyperbranched PEI shell with an absorption maximum at 350 nm grow on the surface of the nanotriangles as hemispherical particles with diameters of similar to 6 nm. High-resolution micrographs show that the hemispherical gold particles are crystallized onto the {111} facets on the bottom and top of the platelet as well as on the edges without a grain boundary. Undulated gold nanoplatelet superstructures with special properties become available, which show a significantly modified performance in SERS-detected photocatalysis regarding both reactivity and enhancement factor.
Y1  - 2018
U6  - https://doi.org/10.1021/acs.langmuir.7b02898
SN  - 0743-7463
VL  - 34
IS  - 15
SP  - 4584
EP  - 4594
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Release of Singlet Oxygen from Organic Peroxides under Mild Conditions
JF  - ChemPhotoChem
N2  - Singlet oxygen can be released in the dark in nearly quantitative yield from endoperoxides of naphthalenes, anthracenes and pyridones as an alternative to its generation by photosensitization. Recently, new donor systems have been designed which operate at very low temperatures but which are prepared from their parent forms at acceptable rates. Enhancement of the reactivity of donors is conveniently achieved by the design of the substitution pattern or through the use of plasmonic heating of nanoparticle-bound donors. The most important aim of these donor molecules is to transfer singlet oxygen in a controlled and directed manner to a target. Low temperatures and the linking between donors and acceptors reduce the random walk of oxygen and may force an attack at the desired position. By using chiral donor systems, new stereocenters might be introduced into prochiral acceptors.
KW  - donor-acceptor systems
KW  - oxygenation
KW  - peroxides
KW  - polycycles
KW  - retro reactions
Y1  - 2018
U6  - https://doi.org/10.1002/cptc.201700235
SN  - 2367-0932
VL  - 2
IS  - 7
SP  - 548
EP  - 558
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Hesse, Julia
A1  - Klier, Dennis Tobias
A1  - Sgarzi, Massimo
A1  - Nsubuga, Anne
A1  - Bauer, Christoph
A1  - Grenzer, Joerg
A1  - Hübner, Rene
A1  - Wislicenus, Marcus
A1  - Joshi, Tanmaya
A1  - Kumke, Michael Uwe
A1  - Stephan, Holger
T1  - Rapid Synthesis of Sub-10nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol((R))66
JF  - ChemistryOpen : including thesis treasury
N2  - We report a simple one-pot method for the rapid preparation of sub-10nm pure hexagonal (-phase) NaYF4-based upconverting nanoparticles (UCNPs). Using Therminol((R))66 as a co-solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase-purity of the as-synthesized core and core-shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X-ray diffraction, and small-angle X-ray scattering studies. In-depth photophysical evaluation of the UCNPs was pursued by using steady-state and time-resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface-related luminescence quenching effects.
KW  - core-shell materials
KW  - lanthanides
KW  - nanostructures
KW  - photoluminescence
KW  - upconversion
Y1  - 2018
U6  - https://doi.org/10.1002/open.201700186
SN  - 2191-1363
VL  - 7
IS  - 2
SP  - 159
EP  - 168
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Yaouba, Souaibou
A1  - Koch, Andreas
A1  - Guantai, Eric M.
A1  - Derese, Solomon
A1  - Irungu, Beatrice
A1  - Heydenreich, Matthias
A1  - Yenesew, Abiy
T1  - Alkenyl cyclohexanone derivatives from Lannea rivae and Lannea schweinfurthii
JF  - Phytochemistry letters / Phytochemical Society of Europe
N2  - Phytochemical investigation of the CH2Cl2/MeOH (1:1) extract of the roots of Lannea rivae (Chiov) Sacleux (Anacardiaceae) led to the isolation of a new alkenyl cyclohexenone derivative: (4R,6S)-4,6-dihydroxy-6-((Z)-nonadec-14′-en-1-yl)cyclohex-2-en-1-one (1), and a new alkenyl cyclohexanol derivative: (2S*,4R*,5S*)-2,4,5-trihydroxy-2-((Z)-nonadec-14′-en-1-yl)cyclohexanone (2) along with four known compounds, namely epicatechin gallate, taraxerol, taraxerone and β-sitosterol; while the stem bark afforded two known compounds, daucosterol and lupeol. Similar investigation of the roots of Lannea schweinfurthii (Engl.) Engl. led to the isolation of four known compounds: 3-((E)-nonadec-16′-enyl)phenol, 1-((E)-heptadec-14′-enyl)cyclohex-4-ene-1,3-diol, catechin, and 1-((E)-pentadec-12′-enyl)cyclohex-4-ene-1,3-diol. The structures of the isolated compounds were determined by NMR spectroscopy and mass spectrometry. The absolute configuration of compound 1 was established by quantum chemical ECD calculations. In an antibacterial activity assay using the microbroth kinetic method, compound 1 showed moderate activity against Escherichia coli while compound 2 exhibited moderate activity against Staphylococcus aureus. Compound 1 also showed moderate activity against E. coli using the disc diffusion method. The roots extract of L. rivae was notably cytotoxic against both the DU-145 prostate cancer cell line and the Vero mammalian cell line (CC50 = 5.24 and 5.20 μg/mL, respectively). Compound 1 was also strongly cytotoxic against the DU-145 cell line (CC50 = 0.55 μg/mL) but showed no observable cytotoxicity (CC50 > 100 μg/mL) against the Vero cell line. The roots extract of L. rivae and L. schweinfurthii, epicatechin gallate as well as compound 1 exhibited inhibition of carageenan-induced inflammation.
KW  - Lannea rivae
KW  - Lannea schweinfurthii
KW  - Alkenyl cyclohexenone
KW  - Alkenyl cyclohexanone
KW  - Anti-inflammatory
KW  - Cytotoxicity
KW  - Antimicrobial
Y1  - 2017
U6  - https://doi.org/10.1016/j.phytol.2017.12.001
SN  - 1874-3900
SN  - 1876-7486
VL  - 23
SP  - 141
EP  - 148
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Sprenger, Heike
A1  - Erban, Alexander
A1  - Seddig, Sylvia
A1  - Rudack, Katharina
A1  - Thalhammer, Anja
A1  - Le, Mai Q.
A1  - Walther, Dirk
A1  - Zuther, Ellen
A1  - Koehl, Karin I.
A1  - Kopka, Joachim
A1  - Hincha, Dirk K.
T1  - Metabolite and transcript markers for the prediction of potato drought tolerance
JF  - Plant Biotechnology Journal
N2  - Potato (Solanum tuberosum L.) is one of the most important food crops worldwide. Current potato varieties are highly susceptible to drought stress. In view of global climate change, selection of cultivars with improved drought tolerance and high yield potential is of paramount importance. Drought tolerance breeding of potato is currently based on direct selection according to yield and phenotypic traits and requires multiple trials under drought conditions. Marker-assisted selection (MAS) is cheaper, faster and reduces classification errors caused by noncontrolled environmental effects. We analysed 31 potato cultivars grown under optimal and reduced water supply in six independent field trials. Drought tolerance was determined as tuber starch yield. Leaf samples from young plants were screened for preselected transcript and nontargeted metabolite abundance using qRT-PCR and GC-MS profiling, respectively. Transcript marker candidates were selected from a published RNA-Seq data set. A Random Forest machine learning approach extracted metabolite and transcript markers for drought tolerance prediction with low error rates of 6% and 9%, respectively. Moreover, by combining transcript and metabolite markers, the prediction error was reduced to 4.3%. Feature selection from Random Forest models allowed model minimization, yielding a minimal combination of only 20 metabolite and transcript markers that were successfully tested for their reproducibility in 16 independent agronomic field trials. We demonstrate that a minimum combination of transcript and metabolite markers sampled at early cultivation stages predicts potato yield stability under drought largely independent of seasonal and regional agronomic conditions.
KW  - drought tolerance
KW  - machine learning
KW  - metabolite markers
KW  - potato (Solanum tuberosum)
KW  - prediction models
KW  - transcript markers
Y1  - 2017
U6  - https://doi.org/10.1111/pbi.12840
SN  - 1467-7644
SN  - 1467-7652
VL  - 16
IS  - 4
SP  - 939
EP  - 950
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Guo, Ranran
A1  - Tian, Ye
A1  - Yang, Yueqi
A1  - Jiang, Qin
A1  - Wang, Yajun
A1  - Yang, Wuli
T1  - A Yolk-Shell nanoplatform for gene-silencing-enhanced photolytic ablation of cancer
JF  - Advanced functional materials
N2  - Noninvasive near-infrared (NIR) light responsive therapy is a promising cancer treatment modality; however, some inherent drawbacks of conventional phototherapy heavily restrict its application in clinic. Rather than producing heat or reactive oxygen species in conventional NIR treatment, here a multifunctional yolk-shell nanoplatform is proposed that is able to generate microbubbles to destruct cancer cells upon NIR laser irradiation. Besides, the therapeutic effect is highly improved through the coalition of small interfering RNA (siRNA), which is codelivered by the nanoplatform. In vitro experiments demonstrate that siRNA significantly inhibits expression of protective proteins and reduces the tolerance of cancer cells to bubble-induced environmental damage. In this way, higher cytotoxicity is achieved by utilizing the yolk-shell nanoparticles than treated with the same nanoparticles missing siRNA under NIR laser irradiation. After surface modification with polyethylene glycol and transferrin, the yolk-shell nanoparticles can target tumors selectively, as demonstrated from the photoacoustic and ultrasonic imaging in vivo. The yolk-shell nanoplatform shows outstanding tumor regression with minimal side effects under NIR laser irradiation. Therefore, the multifunctional nanoparticles that combining bubble-induced mechanical effect with RNA interference are expected to be an effective NIR light responsive oncotherapy.
KW  - cancer
KW  - gene silencing
KW  - near-infrared absorption
KW  - photolytic ablation
KW  - yolk-shell nanoparticles
Y1  - 2018
U6  - https://doi.org/10.1002/adfm.201706398
SN  - 1616-301X
SN  - 1616-3028
VL  - 28
IS  - 14
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Schultze, Christiane
T1  - A one-pot synthesis of pyranocoumarins through microwave-promoted propargyl claisen rearrangement/wittig olefination
JF  - European journal of organic chemistry
N2  - The reaction between propargyl ethers of hydroxybenzaldehydes and the ylide ethyl (triphenylphosphoranylidene)acetate was carried out under microwave irradiation to regioselectively afford angular pyranocoumarins. The chromene and coumarin heterocyclic scaffolds were simultaneously formed in the same synthetic step without changing the reaction conditions. The natural products seselin, braylin, and dipetalolactone were among the products synthesized by this method.
KW  - Domino reactions
KW  - Alkynes
KW  - Arenes
KW  - Oxygen heterocycles
KW  - Microwave chemistry
KW  - Rearrangement
Y1  - 2017
SN  - 1434-193X
SN  - 1099-0690
VL  - 2018
IS  - 2
SP  - 223
EP  - 227
PB  - Wiley-VCH Verl.
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Paramagnetic ring current effects in anti-aromatic structures subject to substitution/annelation quantified by spatial magnetic properties (TSNMRS)
JF  - Tetrahedron
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of the typically anti-aromatic cyclopentadienyl cation, cyclobutadiene, pentalene, s-indacene and of substituted/annelated analogues of the latter structures have been calculated using the CIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values were employed to visualize and quantify the dia(para) magnetic ring current effects in the studied compounds. The interplay of dia(para)magnetic ring current effects due to substitution/annelation caused by heavy exo-cyclic n,pi-electron delocalization can be qualified.
KW  - Aromaticity
KW  - Anti-aromaticity
KW  - Through-space NMR shieldings (TSNMRS)
KW  - GIAO
KW  - NICS
KW  - Annelation effect
Y1  - 2018
U6  - https://doi.org/10.1016/j.tet.2017.12.020
SN  - 0040-4020
VL  - 74
IS  - 7
SP  - 700
EP  - 710
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Petersen, Monib H.
A1  - Braun, Diana
T1  - Bidirectional Synthesis of 6-Acetoxy-5-hexadecanolide, the Mosquito Oviposition Pheromone of Culex quinquefasciatus, from a C-2-Symmetric Building Block Using Olefin Metathesis Reactions
JF  - The journal of organic chemistry
N2  - (5R,6S)-6-Acetoxy-5-hexadecanolide (MOP) is the oviposition pheromone of the mosquito Cx. quinquefasciatus, a vector of pathogens causing a variety of tropical diseases. We describe and evaluate herein three syntheses of MOP starting from mannitol-derived (3R,4R)-hexa-1,5-diene-3,4-diol. This C-2-symmetric building block is elaborated through bidirectional olefin metathesis reactions into 6-epi-MOP, which was converted into MOP via Mitsunobu inversion. The shortest of the three routes makes use of two sequential cross-metathesis reactions and an assisted tandem catalytic olefin reduction, induced by an in situ conversion of a Ru-carbene to a Ru-hydride.
Y1  - 2018
U6  - https://doi.org/10.1021/acs.joc.7b02944
SN  - 0022-3263
VL  - 83
IS  - 3
SP  - 1627
EP  - 1633
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Sun, Fu
A1  - Osenberg, Markus
A1  - Dong, Kang
A1  - Zhou, Dong
A1  - Hilger, Andre
A1  - Jafta, Charl J.
A1  - Risse, Sebastian
A1  - Lu, Yan
A1  - Markoetter, Henning
A1  - Manke, Ingo
T1  - Correlating Morphological Evolution of Li Electrodes with Degrading Electrochemical Performance of Li/LiCoO2 and Li/S Battery Systems
BT  - Investigated by Synchrotron X-ray Phase Contrast Tomography
JF  - ACS energy letters / American Chemical Society
N2  - Efficient Li utilization is generally considered to be a prerequisite for developing next-generation energy storage systems (ESSs). However, uncontrolled growth of Li microstructures (LmSs) during electrochemical cycling has prevented its practical commercialization. Herein, we attempt to understand the correlation of morphological evolution of Li electrodes with degrading electrochemical performances of Li/LiCoO2 and Li/S systems by synchrotron X-ray phase contrast tomography technique. It was found that the continuous transformation of the initial dense Li bulk to a porous lithium interface (PL1) structure intimately correlates with the gradually degrading overall cell performance of these two systems. Additionally, the formation mechanism of the PLI and its correlation with previously reported inwardly growing LmS and the lithium-reacted region have been intensively discussed. The information that we gain herein is complementary to previous investigations and may provide general insights into understanding of degradation mechanisms of Li metal anodes and also provide highly needed guidelines for effective design of reliable next-generation Li metal-based ESSs.
Y1  - 2018
U6  - https://doi.org/10.1021/acsenergylett.7b01254
SN  - 2380-8195
VL  - 3
IS  - 2
SP  - 356
EP  - 365
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Dai, Xiaolin
A1  - Mate, Diana M.
A1  - Glebe, Ulrich
A1  - Garakani, Tayebeh Mirzaei
A1  - Körner, Andrea
A1  - Schwaneberg, Ulrich
A1  - Böker, Alexander
T1  - Sortase-mediated ligation of purely artificial building blocks
JF  - Polymers
N2  - Sortase A (SrtA) from Staphylococcus aureus has been often used for ligating a protein with other natural or synthetic compounds in recent years. Here we show that SrtA-mediated ligation (SML) is universally applicable for the linkage of two purely artificial building blocks. Silica nanoparticles (NPs), poly(ethylene glycol) and poly(N-isopropyl acrylamide) are chosen as synthetic building blocks. As a proof of concept, NP-polymer, NP-NP, and polymer-polymer structures are formed by SrtA catalysis. Therefore, the building blocks are equipped with the recognition sequence needed for SrtA reaction-the conserved peptide LPETG-and a pentaglycine motif. The successful formation of the reaction products is shown by means of transmission electron microscopy (TEM), matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-ToF MS), and dynamic light scattering (DLS). The sortase catalyzed linkage of artificial building blocks sets the stage for the development of a new approach to link synthetic structures in cases where their synthesis by established chemical methods is complicated.
KW  - sortase-mediated ligation
KW  - enzymes
KW  - block copolymers
KW  - nanoparticles
Y1  - 2018
U6  - https://doi.org/10.3390/polym10020151
SN  - 2073-4360
VL  - 10
IS  - 2
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Roder, Phillip
A1  - Hille, Carsten
T1  - Local tissue manipulation via a force- and pressure-controlled AFM micropipette for analysis of cellular processes
JF  - Scientific reports
N2  - Local manipulation of complex tissues at the single-cell level is challenging and requires excellent sealing between the specimen and the micromanipulation device. Here, biological applications for a recently developed loading technique for a force-and pressure-controlled fluidic force microscope micropipette are described. This technique allows for the exact positioning and precise spatiotemporal control of liquid delivery. The feasibility of a local loading technique for tissue applications was investigated using two fluorescent dyes, with which local loading behaviour could be optically visualised. Thus, homogeneous intracellular distribution of CellTracker Red and accumulation of SYTO 9 Green within nuclei was realised in single cells of a tissue preparation. Subsequently, physiological micromanipulation experiments were performed. Salivary gland tissue was pre-incubated with the Ca2+-sensitive dye OGB-1. An intracellular Ca2+ rise was then initiated at the single-cell level by applying dopamine via micropipette. When pre-incubating tissue with the nitric oxide (NO)-sensitive dye DAF-FM, NO release and intercellular NO diffusion was observed after local application of the NO donor SNP. Finally, local micromanipulation of a well-defined area along irregularly shaped cell surfaces of complex biosystems was shown for the first time for the fluidic force microscope micropipette. Thus, this technique is a promising tool for the investigation of the spatiotemporal effects of locally applied substances in complex tissues.
Y1  - 2018
U6  - https://doi.org/10.1038/s41598-018-24255-9
SN  - 2045-2322
VL  - 8
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Kirpichenko, Svetlana
A1  - Shainyan, Bagrat A.
A1  - Kleinpeter, Erich
A1  - Shlykov, Sergey A.
A1  - Tran Dinh Phien, 
A1  - Albanov, Alexander
T1  - Synthesis of 3-fluoro-3-methyl-3-silatetrahydropyran and its conformational preferences in gas and solution by GED, NMR and theoretical calculations
JF  - Tetrahedron
N2  - The 3,3-disubstitued 3-silaheterocyclohexane with an electronegative substituent at silicon, 3-fluoro-3-methyl-3-silatetrahydropyran 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED) and low temperature C-13 and F-19 NMR spectroscopy. Quantum-chemical calculations were carried out both for the isolated species and Hcomplexes in gas and in polar medium. The predominance of the 1-FeqMeax conformer (1-F-eq:1-F-ax ratio of 65:35, Delta G degrees = 0.37 kcal/mol) determined from GED is close to the theoretically estimated conformational equilibrium, especially at the DFT level. In solution, low temperature NMR spectroscopy showed no decoalescence of the signals in C-13 (down to 95 K) and F-19 NMR spectra (down to 123 K). However, the calculated F-19 chemical shift of -173.6 ppm for the 1-FeqMeax conformer practically coincides with the experimentally observed value (-173 to -175 ppm) as distinct from that for the 1-FaxMeeq conformer (-188.8 ppm), suggesting compound 1 to be anancomeric in solution, in compliance with its theoretical and experimental preference in the gas phase.
KW  - 3-Fluoro-3-methyl-3-silatetrahydropyran
KW  - Conformational analysis
KW  - Gas phase electron diffraction
KW  - Low-temperature NMR
KW  - DFT
KW  - MP2 and CCSD(T) calculations
Y1  - 2018
U6  - https://doi.org/10.1016/j.tet.2018.02.055
SN  - 0040-4020
VL  - 74
IS  - 15
SP  - 1859
EP  - 1867
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - THES
A1  - Hermanns, Jolanda
T1  - Development, use and evaluation of concepts and materials for teaching organic chemistry at university
Y1  - 2021
ER  - 
TY  - JOUR
A1  - Sand, Patrick
A1  - Schmidt, Bernd
T1  - Pd-catalyzed oxidative sulfoalkenylation of acetanilides and traceless removal of the catalyst directing group
JF  - ChemistrySelect
N2  - The palladium-catalyzed oxidative Heck-reaction, also referred to as Fujiwara-Moritani-reaction, has been investigated for the synthesis of styrenylsulfonyl compounds. Acetanilides and vinylsulfonyl compounds undergo dehydrogenative coupling reactions in moderate to quantitative yields, using benzoquinone as the oxidant of choice. Potassium peroxodisulfate, which had previously been identified as a superior oxidant for the coupling with acrylates, did not provide any coupling products with these olefins. Traceless removal of the catalyst directing group through a deacetylation-diazotation-coupling (DDC) sequence was demonstrated for 2-arylethene sulfones.
KW  - arenes
KW  - C− H activation
KW  - Heck reactions
KW  - Palladium
KW  - sulfones
Y1  - 2021
U6  - https://doi.org/10.1002/slct.202101009
SN  - 2365-6549
VL  - 6
IS  - 14
SP  - 3563
EP  - 3567
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Schmidt, Marco F.
A1  - Korb, Oliver
A1  - Abell, Chris
T1  - Antagonists of the miRNA-Argonaute 2 Protein Complex
BT  - Anti-miR-AGOs
JF  - Drug Target miRNA: Methods and Protocols
N2  - microRNAs (miRNAs) have been identified as high-value drug targets. A widely applied strategy in miRNA inhibition is the use of antisense agents. However, it has been shown that oligonucleotides are poorly cell permeable because of their complex chemical structure and due to their negatively charged backbone. Consequently, the general application of oligonucleotides in therapy is limited. Since miRNAs’ functions are executed exclusively by the Argonaute 2 protein, we therefore describe a protocol for the design of a novel miRNA inhibitor class: antagonists of the miRNA-Argonaute 2 protein complex, so-called anti-miR-AGOs, that not only block the crucial binding site of the target miRNA but also bind to the protein’s active site. Due to their lower molecular weight and, thus, more drug-like chemical structure, the novel inhibitor class may show better pharmacokinetic properties than reported oligonucleotide inhibitors, enabling them for potential therapeutic use.
KW  - Drug design
KW  - microRNA
KW  - miRNA-Argonaute 2 protein complex
KW  - miRNA inhibitors
KW  - miRNA seed region
Y1  - 2016
SN  - 978-1-4939-6563-2
SN  - 978-1-4939-6561-8
SN  - 978-1-4939-8236-3
U6  - https://doi.org/10.1007/978-1-4939-6563-2_17
SN  - 1064-3745
SN  - 1940-6029
VL  - 1517
SP  - 239
EP  - 249
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Haubitz, Toni
A1  - Fudickar, Werner
A1  - Linker, Torsten
A1  - Kumke, Michael Uwe
T1  - pH-sensitive fluorescence switching of pyridylanthracenes
BT  - the effect of the isomeric pattern
JF  - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - 9,10-substituted anthracenes are known for their useful optical properties like fluorescence, which makes them frequently used probes in sensing applications. In this article, we investigate the fundamental photophysical properties of three pyridyl-substituted variants. The nitrogen atoms in the pyridinium six-membered rings are located in the ortho-, meta-, and para-positions in relation to the anthracene core. Absorption, fluorescence, and transient absorption measurements were carried out and were complemented by theoretical calculations. We monitored the photophysics of the anthracene derivatives in chloroform and water investigating the protonated as well as their nonprotonated forms. We found that the optical properties of the nonprotonated forms are strongly determined by the anthracene chromophore, with only small differences to other 9,10-substituted anthracenes, for example diphenyl anthracene. In contrast, protonation leads to a strong decrease in fluorescence intensity and lifetime. Transient absorption measurements and theoretical calculations revealed the formation of a charge-transfer state in the protonated chromophores, where electron density is shifted from the anthracene moiety toward the protonated pyridyl substituents. While the para- and ortho-derivatives' charge transfer is still moderately fluorescent, the meta-derivative is affected much stronger and shows nearly no fluorescence. This nitrogen-atom-position-dependent sensitivity to hydronium activity makes a combination of these fluorophores very attractive for pH-sensing applications covering a broadened pH range.
KW  - Absorption
KW  - Aromatic compounds
KW  - Fluorescence
KW  - Hydrocarbons
KW  - Reaction mechanisms
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jpca.0c09911
SN  - 1089-5639
SN  - 1520-5215
VL  - 124
IS  - 52
SP  - 11017
EP  - 11024
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Wessig, Pablo
A1  - Freyse, Daniel
A1  - Schuster, David
A1  - Kelling, Alexandra
T1  - Fluorescent dyes with large stokes shifts based on Benzo[1,2-d:4,5-d']bis([1,3]dithiole) (“S4-DBD Dyes”)
JF  - Europan journal of organic chemistry
N2  - We report on a further development of [1,3]-dioxolo[4.5-f]benzodioxole (DBD) fluorescent dyes by replacement of the four oxygen atoms of the heterocyclic core by sulfur atoms. This variation causes striking changes of the photophysical properties. Whereas absorption and emission significantly shifted to longer wavelength, the fluorescence lifetimes and quantum yields are diminished compared to DBD dyes. The latter effect is presumably caused by an enhanced intersystem crossing to the triplet state due to the sulfur atoms. The very large Stokes shifts of the S-4-DBD dyes ranging from 3000 cm(-1) to 7400 cm(-1) (67 nm to 191 nm) should be especially emphasized. By analogy with DBD dyes a broad variation of absorption and emission wavelength is possible by introducing different electron withdrawing substituents. Moreover, some derivatives for coupling with biomolecules were developed.
KW  - fluorescent dyes
KW  - sulfur
KW  - heterocycles
KW  - stokes shift
KW  - photophysics
Y1  - 2020
U6  - https://doi.org/10.1002/ejoc.202000093
SN  - 1434-193X
SN  - 1099-0690
VL  - 2020
IS  - 11
SP  - 1732
EP  - 1744
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Lood, Kajsa
A1  - Schmidt, Bernd
T1  - Stereoselective synthesis of conjugated polyenes based on tethered olefin metathesis and carbonyl olefination
BT  - application to the total synthesis of (+)-bretonin B
JF  - The journal of organic chemistry
N2  - The combination of a highly stereoselective tethered olefin metathesis reaction and a Julia-Kocienski olefination is presented as a strategy for the synthesis of conjugated polyenes with at least one Z-configured C=C bond. The strategy is exemplified by the synthesis of the marine natural product (+)-bretonin B.
KW  - absolute-configuration
KW  - natural-products
KW  - formal synthesis
KW  - oxidation
KW  - derivatives
KW  - aldehydes
KW  - catalysts
KW  - alcohols
KW  - sponge
KW  - ethers
Y1  - 2020
U6  - https://doi.org/10.1021/acs.joc.0c00446
SN  - 0022-3263
SN  - 1520-6904
VL  - 85
IS  - 7
SP  - 5122
EP  - 5130
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - GEN
A1  - Krueger, Tobias
A1  - Kelling, Alexandra
A1  - Linker, Torsten
A1  - Schilde, Uwe
T1  - Crystal structures of three cyclohexane‑based γ‑spirolactams
BT  - determination of configurations and conformations
T2  - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2  - The title compounds, 2-azaspiro[4.5]deca-1-one, C₉H₁₅NO, (1a), cis-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1b), and trans-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1c), were synthesized from benzoic acids 2 in only 3 steps in high yields. Crystallization from n-hexane afforded single crystals, suitable for X-ray diffraction. Thus, the configurations, conformations, and interesting crystal packing effects have been determined unequivocally. The bicyclic skeleton consists of a lactam ring, attached by a spiro junction to a cyclohexane ring. The lactam ring adopts an envelope conformation and the cyclohexane ring has a chair conformation. The main difference between compound 1b and compound 1c is the position of the carbonyl group on the 2-pyrrolidine ring with respect to the methyl group on the 8-position of the cyclohexane ring, which is cis (1b) or trans (1c). A remarkable feature of all three compounds is the existence of a mirror plane within the molecule. Given that all compounds crystallize in centrosymmetric space groups, the packing always contains interesting enantiomer-like pairs. Finally, the structures are stabilized by intermolecular N–H···O hydrogen bonds.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 738 
KW  - 2-Azaspiro[4.5]deca-1-ones
KW  - Cis- and trans-form
KW  - Configuration
KW  - Conformation
KW  - Lactams
Y1  - 1019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-434911
IS  - 738
ER  - 
TY  - JOUR
A1  - Mai-Linde, Yasemin
A1  - Linker, Torsten
T1  - Radical clock probes to determine carbohydrate radical stabilities
JF  - Organic letters
N2  - Carbohydrate radical stabilities in the 1- and 2-position have been determined by a radical clock approach, starting from cyclopropanated sugars with xanthates as precursors. Various hexoses and pentoses afforded 1-deoxy sugars as main products, indicating that anomeric radicals are more stable than radicals in the 2-position. An additional influence of the configurations on radical stabilities has been observed. Our results should be interesting for the understanding of 1,2-radical rearrangements in carbohydrate chemistry and offer an easy access to deoxy-vinyl sugars.
KW  - stereoselective-synthesis
KW  - convenient synthesis
KW  - chemistry
KW  - cyclopropanation
KW  - mechanism
KW  - glycals
KW  - beta-(acyloxy)alkylrear
KW  - rangement
KW  - sugars
Y1  - 2020
U6  - https://doi.org/10.1021/acs.orglett.0c00111
SN  - 1523-7060
SN  - 1523-7052
VL  - 22
IS  - 4
SP  - 1525
EP  - 1529
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schultze, Christiane
A1  - Foß, Stefan
A1  - Schmidt, Bernd
T1  - 8-Prenylflavanones through microwave promoted tandem claisen rearrangement/6-endo-trig cyclization and cross metathesis
JF  - European journal of organic chemistry
N2  - Prenylated flavanones were obtained from ortho-allyloxy chalcones through a one-pot sequence of Claisen rearrangement and 6-endo-trig cyclization, followed by olefin cross metathesis of the intermediate allyl flavanones with 2-methyl-2-butene. The synthetic utility of this route is illustrated for the synthesis of several naturally occurring prenyl flavanones.
KW  - tandem reactions
KW  - arenes
KW  - oxygen heterocycles
KW  - microwave chemistry
KW  - rearrangement
Y1  - 2020
U6  - https://doi.org/10.1002/ejoc.202001378
SN  - 1434-193X
SN  - 1099-0690
VL  - 2020
IS  - 47
SP  - 7373
EP  - 7384
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - THES
A1  - Gabriel, Christina
T1  - Entwicklung neuer Stärkederivate für die Anwendung als wasserbasierte Filmbildner in Farben und Lacken
T1  - Development of new starch derivatives for application as water-based film formers in paints and varnishes
N2  - In den letzten Jahrzehnten fand auch in der Beschichtungsindustrie ein Umdenken hin zu umweltfreundlicheren Farben und Lacken statt. Allerdings basieren auch neue Lösungen meist nicht auf Biopolymeren und in einem noch geringeren Anteil auf wasserbasierten Beschichtungssystemen aus nachwachsenden Rohstoffen. Dies stellt den Anknüpfungspunkt dieser Arbeit dar, in der untersucht wurde, ob das Biopolymer Stärke das Potenzial zum wasserbasierten Filmbildner für Farben und Lacke besitzt. Dabei müssen angelehnt an etablierte synthetische Marktprodukte die folgenden Kriterien erfüllt werden: Die wässrige Dispersion muss mindestens einen 30%igen Feststoffgehalt haben, bei Raumtemperatur verarbeitet werden können und Viskositäten zwischen 10^2-10^3 mPa·s aufweisen. Die finale Beschichtung muss einen geschlossenen Film bilden und sehr gute Haftfestigkeiten zu einer spezifischen Oberfläche, in dieser Arbeit Glas, besitzen. Als Grundlage für die Modifizierung der Stärke wurde eine Kombination von molekularem Abbau und chemischer Funktionalisierung ausgewählt. Da nicht bekannt war, welchen Einfluss die Stärkeart, die gewählte Abbaureaktion als auch verschiedene Substituenten auf die Dispersionsherstellung und deren Eigenschaften sowie die Beschichtungseigenschaften ausüben könnten, wurden die strukturellen Parameter getrennt voneinander untersucht.
Das erste Themengebiet beinhaltete den oxidativen Abbau von Kartoffel- und Palerbsenstärke mittels des Hypochlorit-Abbaus (OCl-) und des ManOx-Abbaus (H2O2, KMnO4). Mit beiden Abbaureaktionen konnten vergleichbare gewichtsmittlere Molmassen (Mw) von 2·10^5-10^6 g/mol (GPC-MALS) hergestellt werden. Allerdings führten die gewählten Reaktionsbedingungen beim ManOx-Abbau zur Bildung von Gelpartikeln. Diese lagen im µm-Bereich (DLS und Kryo-REM-Messungen) und hatten zur Folge, dass die ManOx-Proben deutlich erhöhte Viskositäten (c: 7,5 %; 9-260 mPa·s) im Vergleich zu den OCl--Proben (4-10 mPa·s) bei scherverdünnendem Verhalten besaßen und die Eigenschaften von viskoelastischen Gelen (G‘ > G‘‘) zeigten. Des Weiteren wiesen sie reduzierte Heißwasserlöslichkeiten (95 °C, vorrangig: 70-99 %) auf. Der OCl--Abbau führte zu hydrophileren (Carboxylgruppengehalt bis zu 6,1 %; ManOx: bis zu 3,1 %), nach 95 °C-Behandlung vollständig wasserlöslichen abgebauten Stärken, die ein Newtonsches Fließverhalten mit Eigenschaften einer viskoelastischen Flüssigkeit (G‘‘ > G‘) hatten. Die OCl--Proben konnten im Vergleich zu den ManOx-Produkten (10-20 %) zu konzentrierteren Dispersionen (20-40 %) verarbeitet werden, die gleichzeitig die Einschränkung von anwendungsrelevanten Mw auf < 7·10^5 g/mol zuließen (Konzentration sollte > 30 % sein). Außerdem führten nur die OCl--Proben der Kartoffelstärke zu transparenten (alle anderen waren opak) geschlossenen Beschichtungsfilmen. Somit hebt sich die Kombination von OCl--Abbau und Kartoffelstärke mit Hinblick auf die Endanwendung ab.
Das zweite Themengebiet umfasste Untersuchungen zum Einfluss von Ester- und Hydroxyalkylether-Substituenten auf Basis einer industriell abgebauten Kartoffelstärke (Mw: 1,2·10^5 g/mol) vor allem auf die Dispersionsherstellung, die rheologischen Eigenschaften der Dispersionen und die Beschichtungseigenschaften in Kombination mit Glassubstraten. Dazu wurden Ester und Ether mit DS/MS-Werten von 0,07-0,91 synthetisiert. Die Derivate konnten zu wasserbasierten Dispersionen mit Konzentrationen von 30-45 % verarbeitet werden, wobei bei hydrophoberen Modifikaten ein Co-Lösemittel, Diethylenglycolmonobutylether (DEGBE), eingesetzt werden musste. Die Feststoffgehalte sanken dabei für beide Derivatklassen vor allem mit zunehmender Alkylkettenlänge. Die anwendungsrelevanten Viskositäten (323-1240 mPa·s) stiegen auf Grund von Wechselwirkungen tendenziell mit DS/MS und Alkylkettenlänge an. Hinsichtlich der Beschichtungseigenschaften erwiesen sich die Ester vergleichend zu den Ethern als die bevorzugte Substituentenklasse, da nur die Ester geschlossene, defektfreie und mehrheitlich transparente Beschichtungsfilme bildeten, die exzellente bis sehr gute Haftfestigkeiten (ISO Klasse: 0 und 1) auf Glas besaßen. Die Ether bildeten mehrheitlich brüchige Filme. Basierend auf der Kombination der Ergebnisse aus Lösemittelaustausch, den rheologischen Untersuchungen und zusätzlichen Oberflächenspannungsmessungen (30-61 mN/m) konnte geschlossen werden, dass wahrscheinlich fehlende oder schlechte Haftfestigkeiten vorrangig akkumuliertem Wasser in den Beschichtungsfilmen (visuell: trüb oder weiß) geschuldet sind, während die Brüchigkeit vermutlich auf Wechselwirkungen (H-Brücken Wechselwirkungen, hydrophobe Wechselwirkungen) zwischen den Polymeren zurückgeführt werden kann. 
Insgesamt scheint die Kombination aus Kartoffelstärke basierend auf dem OCl--Abbau mit Mw < 7·10^5 g/mol und einem Estersubstituenten eine gute Wahl für wasserbasierte Dispersionen mit hohen Feststoffkonzentrationen (> 30 %), guter Filmbildung und exzellenten Haftungen auf Glas zu sein.
N2  - In the last few decades, the coating industry, like many other industries, has changed its thinking towards more environmentally friendly paints and varnishes. However, even new solutions are usually not based on biopolymers and, to an even lesser extent, on water-based coating systems made from renewable raw materials. This is the starting point of this work, which aimed to investigate whether the biopolymer starch has the potential to be a water-based film former for paints and varnishes. Based on established synthetic market products, the following criteria must be fulfilled: The aqueous dispersion must have a solid content of at least 30%, be processable at room temperature and have viscosities of 10^2-10^3 mPa·s. The final coating must form a continuous film and have very good adhesion to a specific substrate, in this thesis glass. A combination of molecular degradation and chemical functionalisation was selected as the basis for the modification of the starch. Since it was not known what influence the type of starch, the chosen degradation reaction as well as different substituents could have on the dispersion production and its properties as well as on the coating properties, the structural parameters were investigated separately.
The first part dealt with the oxidative degradation of potato and smooth pea starch by hypochlorite degradation (OCl-) and ManOx degradation (H2O2, KMnO4). With both degradation reactions comparable weight average molar masses (Mw) of 2·10^5-10^6 g/mol (SEC-MALS) could be synthesized. However, the selected reaction conditions led to the formation of gel particles during ManOx degradation. These were in the µm-range (DLS and cryo-REM measurements) and resulted in ManOx samples having significantly higher viscosities (c: 7.5%; 9-260 mPa·s) compared to OCl- samples (4-10 mPa·s) with shear-thinning behaviour and showing the properties of viscoelastic gels (G' > G''). Furthermore, they exhibited reduced hot water solubilities (95 °C, primarily: 70-99%). OCl- degradation led to more hydrophilic (carboxyl group content up to 6.1%; ManOx: up to 3.1%), after 95 °C treatment completely water-soluble degraded starches, which had Newtonian flow behaviour with properties of a viscoelastic liquid (G'' > G'). Compared to the ManOx products (10-20%), the OCl- samples could be processed to more concentrated dispersions (20-40%), which at the same time allowed the restriction of application-relevant Mw to < 7·10^5 g/mol (concentration should be > 30%). In addition, only the OCl- samples of the potato starch led to transparent (all others were opaque) continuous coating films. Thus, the combination of OCl- degradation and potato starch stands out with regard to the final application.
The second part included investigations on the influence of ester and hydroxyalkyl ether substituents on the basis of an industrially degraded potato starch (Mw: 1.2·10^5 g/mol), particularly on dispersion preparation, rheological properties of the dispersions and the coating properties in combination with glass substrates. For this purpose, esters and ethers with DS/MS values of 0.07-0.91 were synthesized. The derivatives could be prepared to water-based dispersions with concentrations of 30-45%, whereby a co-solvent, diethylene glycol monobutyl ether (DEGBE), had to be used for more hydrophobic derivatives. The solid content of both derivative classes decreased most of all with increasing alkyl chain length. The application-relevant viscosities (323-1240 mPa·s) tended to increase due to interactions with DS/MS and alkyl chain length. With regard to the coating properties, esters proved to be the preferred substituent class compared to ethers, since only the esters formed continuous, defect free and mostly transparent coating films which had excellent to very good adhesion (ISO class: 0 and 1) on glass. The majority of ethers formed brittle films. Based on the combination of the results from solvent exchange, rheological investigations and additional surface tension measurements (30-61 mN/m), it could be concluded that probably missing or poor adhesion was primarily due to accumulated water in the coating films (visually: turbid or white), while the brittleness can probably be attributed to interactions (H-bridge interactions, hydrophobic interactions) between the polymers. 
Overall, the combination of potato starch based on OCl- degradation with Mw < 7·10^5 g/mol and an ester substituent seems to be a good choice for water-based dispersions with high solid concentrations (> 30%), good film formation and excellent adhesion to glass.
KW  - Stärke
KW  - starch
KW  - Filmbildner
KW  - film former
KW  - Beschichtung
KW  - coating
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-432942
ER  - 
TY  - JOUR
A1  - Raju, Rajarshi Roy
A1  - Koetz, Joachim
T1  - Inner rotation of Pickering Janus emulsions
JF  - Nanomaterials : open access journal
N2  - Janus droplets were prepared by vortex mixing of three non-mixable liquids, i.e., olive oil, silicone oil and water, in the presence of gold nanoparticles (AuNPs) in the aqueous phase and magnetite nanoparticles (MNPs) in the olive oil. The resulting Pickering emulsions were stabilized by a red-colored AuNP layer at the olive oil/water interface and MNPs at the oil/oil interface. The core–shell droplets can be stimulated by an external magnetic field. Surprisingly, an inner rotation of the silicon droplet is observed when MNPs are fixed at the inner silicon droplet interface. This is the first example of a controlled movement of the inner parts of complex double emulsions by magnetic manipulation via interfacially confined magnetic nanoparticles.
KW  - Janus droplets
KW  - Pickering emulsions
KW  - magnetic manipulation
KW  - gold nanoparticles
KW  - magnetite nanoparticles
Y1  - 2021
U6  - https://doi.org/10.3390/nano11123312
SN  - 2079-4991
VL  - 11
IS  - 12
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Hermanns, Jolanda
A1  - Keller, David
T1  - School-related content knowledge in organic chemistry
BT  - How does the Bachelor and Master studies?
JF  - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2  - In this paper the development, use, and evaluation of tasks based on the construct of school-related content knowledge are described. The tasks were used in seminars on organic chemistry for bachelor and master preservice chemistry teachers at a German university. For the evaluation a questionnaire with open and closed items was used. The tasks were rated by the preservice chemistry teachers as relevant for their future profession as a chemistry teacher if the content of the tasks is part of the school curriculum. If the content does not belong to the school curriculum, they rated the nature of the tasks still as relevant; they seem to recognize the importance of conceptual knowledge for their future profession. However, the master's preservice teachers argued with this conceptual knowledge more often than the bachelor's preservice teachers. Although the study is cross-sectional, a certain shift from the focus on the content to conceptual knowledge from bachelor's to master's preservice teachers can be observed.
KW  - Organic Chemistry
KW  - Second-Year Undergraduate
KW  - Analogies/Transfer
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jchemed.0c01415
SN  - 0021-9584
SN  - 1938-1328
VL  - 98
IS  - 3
SP  - 763
EP  - 773
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schwarze, Thomas
A1  - Riemer, Janine
T1  - Highly K+ selective probes with fluorescence emission wavelengths higher than 500 nm in water
JF  - ChemistrySelect
N2  - Herein, we report on the synthesis of highly K+/Na+ selective fluorescent probes in a feasible number of synthetic steps. These K+ selective fluorescent probes, so called fluoroionophores, 1 and 2 consists of different highly K+/Na+ selective building blocks the alkoxy-substituted N-phenylaza-18-crown-6 lariat ethers (ionophores) and "green" (cf. coumarin unit in 1) or "red" (cf. nile red unit in 2) fluorescent moieties (fluorophores). The fluorescent probes 1 and 2 show K+ induced fluorescence enhancement factors of 4.1 for 1 and 1.9 for 2 and dissociation constants for the corresponding K+ complexes of 43 mM (1+K+) and 18 mM (2+K+) in buffered aqueous solution. The fluorescence signal of 1 and 2 is changed by less than 5 % by pH values in the range of 6.8 to 8.8. Thus, 1 and 2 are capable fluorescent tools to determine extracellular K+ levels by fluorescence enhancements at wavelengths higher than 500 nm.
KW  - potassium
KW  - sodium
KW  - fluorescence
KW  - selectivity
KW  - probes
Y1  - 2020
U6  - https://doi.org/10.1002/slct.202003785
SN  - 2365-6549
VL  - 5
IS  - 42
SP  - 13174
EP  - 13178
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Intramolecular carbene stabilization via 3c,2e bonding on basis of the magnetic criterion
JF  - Tetrahedron : the international journal for the rapid publication of full original research papers and critical reviews in organic chemistry
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRS), of bent cyclobutylcarbene 8, 1,2-diboretane-3-ylidene 9, and some carbene analogues of boron 14-18 as most intriguing examples of carbenes, which can be stabilized as homoaromatic systems with 3c,2e bonding, have been calculated using the GIAO perturbation method employing the nucleus independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. The TSNMRS values (actually, ring current effect/anisotropy effects as measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the degree of present 3c,2e-homoaromaticity. Results are confirmed by geometry (bond angles and bond lengths) and spectroscopic data, the delta(B-11)/ppm data and the C-13 chemical shifts of the carbene electron-deficient centre.
KW  - Cyclobutylcarbene
KW  - 1,2-diboretane-3-ylidene
KW  - 3c,2e-bonding
KW  - Through-space NMR shieldings (TSNMRS)
KW  - NICS
Y1  - 2021
U6  - https://doi.org/10.1016/j.tet.2021.132357
SN  - 0040-4020
SN  - 1464-5416
VL  - 95
PB  - Elsevier Science
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Picconi, David
T1  - Nonadiabatic quantum dynamics of the coherent excited state intramolecular proton transfer of 10-hydroxybenzo[h]quinoline
JF  - Photochemical & photobiological sciences
N2  - The photoinduced nonadiabatic dynamics of the enol-keto isomerization of 10-hydroxybenzo[h]quinoline (HBQ) are studied computationally using high-dimensional quantum dynamics. The simulations are based on a diabatic vibronic coupling Hamiltonian, which includes the two lowest pi pi* excited states and a n pi* state, which has high energy in the Franck-Condon zone, but significantly stabilizes upon excited state intramolecular proton transfer. A procedure, applicable to large classes of excited state proton transfer reactions, is presented to parametrize this model using potential energies, forces and force constants, which, in this case, are obtained by time-dependent density functional theory. The wave packet calculations predict a time scale of 10-15 fs for the photoreaction, and reproduce the time constants and the coherent oscillations observed in time- resolved spectroscopic studies performed on HBQ. In contrast to the interpretation given to the most recent experiments, it is found that the reaction initiated by 1 pi pi* <- S-0 photoexcitation proceeds essentially on a single potential energy surface, and the observed coherences bear signatures of Duschinsky mode-mixing along the reaction path. The dynamics after the 2 pi pi* <- S-0 excitation are instead nonadiabatic, and the n pi* state plays a major role in the relaxation process. The simulations suggest a mainly active role of the proton in the isomerization, rather than a passive migration assisted by the vibrations of the benzoquinoline backbone. <br /> [GRAPHICS] <br /> .
KW  - Excited state proton transfer
KW  - Quantum dynamics
KW  - Nonadiabatic effects
KW  - Spectroscopy
KW  - Coherences
Y1  - 2021
U6  - https://doi.org/10.1007/s43630-021-00112-z
SN  - 1474-905X
SN  - 1474-9092
VL  - 20
IS  - 11
SP  - 1455
EP  - 1473
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Koch, Andreas
T1  - Quantification of sigma-acceptor and pi-donor stabilization in O, S and Hal analogues of N-heterocyclic carbenes (NHCs) on the magnetic criterion
JF  - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory
N2  - The spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of stable O, S and Hal analogues of N-heterocyclic carbenes (NHCs) have been calculated using the GIAO perturbation method employing the nucleus-independent chemical shift (NICS) concept and the results visualized as iso-chemical-shielding surfaces (ICSSs) of various sizes and directions. The TSNMRS values (actually the anisotropy effects measurable in H-1 NMR spectroscopy) are employed to qualify and quantify the position of the present mesomeric equilibria (carbenes <-> ylides). The results are confirmed by geometry (bond angles and bond lengths), IR spectra, UV spectra, and C-13 chemical shifts of the electron-deficient carbon centers.
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jpca.1c05257
SN  - 1089-5639
SN  - 1520-5215
VL  - 125
IS  - 33
SP  - 7235
EP  - 7245
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Hermanns, Jolanda
A1  - Keller, David
T1  - How do preservice chemistry teachers rate tasks following the construct of school-related content knowledge in a concept-orientated course on organic chemistry?
JF  - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2  - In this paper, we describe a study on tasks following the construct of school-related content knowledge. We know from previous studies that such tasks were rated by the preservice chemistry teachers as important for their future profession. Those studies were conducted in a traditional course on organic chemistry which was organized around chemical families. Therefore, we used and evaluated the tasks again in a new course on organic chemistry which is organized around basic concepts in organic chemistry. The results of this evaluation show that the students rate the tasks equally well but use other arguments for their rating. They do not focus only on the content of the tasks and whether this content belongs to the school curriculum or not. The students of the conceptual course rated the content more often (95%) as important for their future profession compared with the students in the traditional course (57%). Both groups of students rated the importance of the nature of the task the same way.
KW  - Organic chemistry
KW  - Second-Year undergraduate
KW  - Alcohols
KW  - Curriculum
KW  - Molecular structure
KW  - Organic structure
KW  - Students
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jchemed.1c00593
SN  - 0021-9584
SN  - 1938-1328
VL  - 98
IS  - 11
SP  - 3442
EP  - 3449
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Lood, Kajsa
A1  - Tikk, Triin
A1  - Krüger, Mandy
A1  - Schmidt, Bernd
T1  - Methylene capping facilitates cross-metathesis reactions of enals
BT  - a short synthesis of 7-methoxywutaifuranal from the xylochemical isoeugenol
JF  - The journal of organic chemistry
N2  - Four combinations of type-I olefins isoeugenol and 4-hydroxy-3-methoxystyrene with type-II olefins acrolein and crotonaldehyde were investigated in cross-metathesis (CM) reactions. While both type-I olefins are suitable CM partners for this transformation, we observed synthetically useful conversions only with type-II olefin crotonaldehyde. For economic reasons, isoeugenol, a cheap xylochemical available from renewable lignocellulose or from clove oil, is the preferred type-I CM partner. Nearly quantitative conversions to coniferyl aldehyde by the CM reaction of isoeugenol and crotonaldehyde can be obtained at ambient temperature without a solvent or at high substrate concentrations of 2 mol.L-1 with the second-generation Hoveyda-Grubbs catalyst. Under these conditions, the ratio of reactants can be reduced to 1:1.5 and catalyst loadings as low as 0.25 mol % are possible. The high reactivity of the isoeugenol/crotonaldehyde combination in olefin metathesis reactions was demonstrated by a short synthesis of the natural product 7-methoxywutaifuranal, which was obtained from isoeugenol in a 44% yield over five steps. We suggest that the superior performance of crotonaldehyde in the CM reactions investigated can be rationalized by "methylene capping", i.e., the steric stabilization of the propagating Ru-alkylidene species.
KW  - Aldehydes
KW  - Catalysts
KW  - Hydrocarbons
KW  - Metathesis
KW  - Mixtures
Y1  - 2022
U6  - https://doi.org/10.1021/acs.joc.1c02851
SN  - 0022-3263
SN  - 1520-6904
VL  - 87
IS  - 5
SP  - 3079
EP  - 3088
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Hermanns, Jolanda
A1  - Schmidt, Bernd
A1  - Glowinski, Ingrid
A1  - Keller, David
T1  - Online teaching in the course "organic chemistry" for nonmajor chemistry students
BT  - from necessity to opportunity
JF  - Journal of chemical education
N2  - In this communication the development of an online course on the topic organic chemistry for nonmajor chemistry students is described and discussed. For this online course, the existing classroom course was further developed. New elements such as podcasts, task navigators, and a forum for discussing the solving of tasks or problems with the content were added. This new online course was evaluated. Therefore, a questionnaire was developed. This consists of questions with regard to the longtime learning behavior of the students and to the online learning. The results of this evaluation show that a preference for online learning and a preference for classroom teaching can be measured separately in two scales. Students values on the scale representing a preference for online learning correlate positively and significantly with confidence in the choice of the study subject, enthusiasm about the subject, and the ability to organize their learning, learning environment, and time management. They correlate also with the satisfaction concerning the materials provided. Students values for one of those teaching methods also correlate with their rating with regard to their exam preparation. Values representing a preference for online teaching correlate positively with students better feeling of exam preparation. Values representing a preference for classroom teaching show negative correlations with the values representing students similar or even better preparation for the exams as a result of online teaching. It is therefore not surprising that the ratings for the two scales correlate with the wish for a combination of online teaching and classroom teaching in the future. As a solution, a new course concept for the time after the corona virus crisis that suits all students is outlined in the outlook.
KW  - first-year undergraduate/general
KW  - organic chenlistry
KW  - computer-based
KW  - learning
KW  - distance learning/self instruction
Y1  - 2020
U6  - https://doi.org/10.1021/acs.jchemed.0c00658
SN  - 0021-9584
SN  - 1938-1328
VL  - 97
IS  - 9
SP  - 3140
EP  - 3146
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Structural motives controlling the binding affinity of 9,10-bis(methylpyridinium)anthracenes towards DNA
JF  - Bioorganic & medicinal chemistry : a Tetrahedron publication for the rapid dissemination of full original research papers and critical reviews on biomolecular chemistry, medicinal chemistry and related disciplines
N2  - In the search of new DNA groove binding agents a series of substituted 9,10-methylpyridiniumanthracenes have been synthesized and their interactions with DNA have been studied by UV/vis absorption, CD and fluorescence spectroscopy. A minor groove binding mode is confirmed by DNA melting studies, strong CD effects, the dependence of the binding affinity on ionic strength, and the differentiation between AT and GC base pairs. No binding occurs to GC sequences. Binding constants to calf thymus DNA (ct-DNA) and poly(dA:dT) in the range between 1 x 10(4) and 3 x 10(5) M-1 have been determined. The binding strength decreases with the size of substituents attached at the anthracene site. Variation of the substitution pattern of the charged groups shows that methyl groups in meta position cause slightly stronger binding than methyl groups in para position. In contrast, with these groups in ortho position, no binding interaction has been observed. The strongest binding is achieved with an expansion of the peripheral heterocycle from pyridine to quinoline. Molecular modeling reveals the pivotal role of the substitution pattern: Anthracenes with para and meta pyridines align along the minor grooves. On the other hand, the ortho derivative adopts no groove-alignment.
KW  - groove binding
KW  - anthracenes
KW  - ct-DNA
KW  - fluorescence enhancement
KW  - docking
Y1  - 2020
U6  - https://doi.org/10.1016/j.bmc.2020.115432
SN  - 0968-0896
SN  - 1464-3391
VL  - 28
IS  - 8
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Hermanns, Jolanda
T1  - The task navigator following the STRAKNAP concept
BT  - Development, application, and evaluation of a new scaffold to support nonmajor chemistry students while solving tasks in organic chemistry
JF  - Journal of chemical education / Division of Chemical Education, Inc., American Chemical Society
N2  - Educational Scaffolding was first mentioned in 1976 by Wood et al. Several examples for scaffolding in chemistry are also known from the literature. As written scaffolds, stepped supporting tools to support students while solving problems in organic chemistry were developed, applied, and evaluated. Although the students rated the tool as very helpful, a think-aloud study showed that the support given by this scaffold was not sufficient. As a further development of stepped supporting tools, task navigators were therefore developed, applied, and evaluated. This new scaffold gives tips on strategy, knowledge, and application of knowledge after the STRAKNAP concept. The evaluation of this tool shows that the students rated the tool as being very helpful. A think-aloud study showed that the scaffold supports the students while they solve a problem. Because of the stepwise construction of the task navigators and the providing of the knowledge needed for the application, the students can solve parts of the task successfully even if they do not solve all parts correctly; the students can always start from scratch. When students use the tool regularly, their knowledge of organic chemistry increases compared to students who did not use the tool at all. The task navigator is not only a scaffold for the content of the task but also for the development of methodological competences on the field of strategies and applying knowledge.
KW  - First-Year Undergraduate/General
KW  - Organic Chemistry
KW  - Distance
KW  - Learning/Chemistry Education Research
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jchemed.0c01162
SN  - 0021-9584
SN  - 1938-1328
VL  - 98
IS  - 4
SP  - 1077
EP  - 1087
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Krtitschka, Angela
A1  - Krüger, Tobias
A1  - Linker, Torsten
T1  - NMR spectroscopic conformational analysis of 4-methylene-cyclohexyl pivalateThe effect of sp(2) hybridization
JF  - Magnetic resonance in chemistry
N2  - The conformational equilibrium of the axial/equatorial conformers of 4-methylene-cyclohexyl pivalate is studied by dynamic NMR spectroscopy in a methylene chloride/freon mixture. At 153K, the ring interconversion gets slow on the nuclear magnetic resonance timescale, the conformational equilibrium (-G degrees) can be examined, and the barrier to ring interconversion (G(#)) can be determined. The structural influence of sp(2) hybridization on both G degrees and G(#) of the cyclohexyl moiety can be quantified.
KW  - 4-methylene-cyclohexyl pivalate
KW  - conformational analysis
KW  - dynamic NMR spectroscopy
KW  - exo-methylene conformational effect at cyclohexane
KW  - quantum chemical calculations
Y1  - 2017
U6  - https://doi.org/10.1002/mrc.4630
SN  - 0749-1581
SN  - 1097-458X
VL  - 55
SP  - 1073
EP  - 1078
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Krüger, Tobias
A1  - Bramborg, Andrea
A1  - Kelling, Alexandra
A1  - Sperlich, Eric
A1  - Linker, Torsten
T1  - Birch Reduction of Arenes as an Easy Entry to γ-Spirolactones
JF  - European journal of organic chemistry
N2  - A convenient method for the synthesis of γ-spirolactones in only 2–3 steps is described. Birch reduction of inexpensive and commercially available aromatic carboxylic acids in the presence of ethylene oxide affords hydroxy acids, which undergo direct lactonization during work-up. Suitable precursors are methyl-substituted benzoic acids, naphthoic, and dicarboxylic acids. Subsequent hydrogenation proceeds smoothly with Pd/C as catalyst and saturated γ-spirolactones are isolated in excellent yields and stereoselectivities. Thus, up to 3 new stereogenic centers can be constructed as sole diastereomers from achiral benzoic acids. Furthermore, it is possible to control the degree of saturation with Raney nickel or Wilkinson's catalyst to obtain products with 1 double bond. Overall, more than 30 new γ-spirolactones have been synthesized in analytically pure form.
KW  - Arenes
KW  - Birch reduction
KW  - Hydrogenation
KW  - Lactones
KW  - Synthetic methods
Y1  - 2021
U6  - https://doi.org/10.1002/ejoc.202101018
SN  - 1434-193X
SN  - 1099-0690
VL  - 2021
IS  - 46
SP  - 6383
EP  - 6391
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Krüger, Tobias
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Linker, Torsten
T1  - Simple Synthesis of gamma-Spirolactams by Birch Reduction of Benzoic Acids
JF  - European journal of organic chemistry
N2  - A convenient synthesis of gamma-spirolactams in only two steps was developed. Birch reduction of benzoic acids and immediate alkylation with chloroacetonitrile afforded cyclohexadienes in high yields. The products could be isolated by crystallization on a large scale in analytically pure form. Subsequent hydrogenation with platinum(IV) oxide as the catalyst reduced the nitrile functionality and the double bonds in the same step with excellent stereoselectivity. The relative configurations were determined unequivocally by X-ray analyses. Direct cyclization of the intermediary formed amino acids afforded the desired gamma-spirolactams in excellent overall yields. The procedure is characterized by few steps, cheap reagents, and can be performed on a large scale, interesting for industrial processes.
KW  - Diastereoselectivity
KW  - Hydrogenation
KW  - Lactams
KW  - Reduction
KW  - Synthetic methods
Y1  - 2016
U6  - https://doi.org/10.1002/ejoc.201601650
SN  - 1434-193X
SN  - 1099-0690
IS  - 6
SP  - 1074
EP  - 1077
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - THES
A1  - Kuhrts, Lucas
T1  - The effect of Polycations on the Formation of Magnetite Nanoparticles
N2  - Nanoparticles of magnetite (Fe3O4) are envisioned to find used in diverse applications, ranging from magnetic data storage, inks, ferrofluids as well as in magnetic resonance imaging, drug delivery, and hyperthermia cancer treatment. Their magnetic properties strongly depend on their size and morphology, two properties that can be synthetically controlled. Achieving appropriate control under soft chemical conditions has so far remained a challenging endeavor. One proven way of exerting this desired control has been using a biomimetic approach that emulates the proteome of magnetotactic bacteria by adding poly-L-arginine in the co- precipitation of ferrous and ferric chloride. The objective of the work presented here is to understand the impact of this polycation on the formation mechanism of magnetite and, through rational design, to enhance the control we can exert on magnetite nanoparticle size and morphology. We developed a SAXS setup to temporally and structurally resolve the formation of magnetite in the presence of poly-L-arginine in situ. Using analytical scattering models, we were able to separate the scattering contribution of a low-density 5 nm iron structure from the contribution of the growing nanoparticles. We identified that the low-density iron structure is a metastable precursor to the magnetite particles and that it is electrostatically stabilized by poly-L-arginine. In a process analogous to biomineralization, the presence of the charged macromolecule thus shifts the reaction mechanism from a thermodynamically controlled one to a kinetically controlled one. We identify this shift in reactions mechanism as the cornerstone of the proposed mechanism and as the crucial step in the paradigm of this extraordinary nanoparticle morphology and size control. Based on SAXS data, theoretical considerations suggest that an observed morphological transition between spherical, solid, and sub-structured mesocrystalline magnetite nanoparticles is induced through a pH-driven change in the wettability of the nanoparticle surface. With these results, we further demonstrate that SAXS can be an invaluable tool for investigating nanoparticle formation. We were able to change particle morphology from spherically solid particles to sub-structured mesocrystals merely by changing the precipitation pH. Improving the synthesis sustainability by substituting poly-L-arginine with renewable, polysaccharide-based polycations produced at the metric ton scale, we demonstrated that the ability to alter the reaction mechanism of magnetite can be generically attributed to the presence of polycations. Through meticulous analysis and the understanding of the formation mechanism, we were able to exert precise control over particle size and morphology, by adapting crucial synthesis parameters. We were thus able to grow mesocrystals up to 200 nm and solid nanocrystals of 100 nm by adding virtually any strong polycation. We further found a way to produce stable single domain magnetite at only slightly increased alkalinity, as magnetotactic bacteria do it. Thus through the understanding of the biological system, the consecutive biomimetic synthesis of magnetite and the following understanding of the mechanism involved in the in vitro synthesis, we managed to improve the synthetic control over the co-precipitation of magnetite, coming close biomineralization of magnetite in magnetotactic bacteria. Polyanions, in both natural as well as in synthetic systems, have been in the spotlight of recent research, yet our work shows the pivotal influence polycations have on the nucleation of magnetite. This work will contribute significantly to our ability to tailor magnetite nanoparticle size and morphology; in addition, we presume it will provide us with a model system for studying biomineralization of magnetite in vitro, putting the spotlight on the important influence of polycations, which have not had the scientific attention they deserve.
T2  - Der Effekt von Polykationen auf die Bildung von Magnetitnanopartikeln
KW  - Mechanism
KW  - Nanoparticle
KW  - SAXS
KW  - Biomimetic
KW  - Magnetite
Y1  - 
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Polley, Nabarun
A1  - Werner, Peter
A1  - Balderas-Valadez, Ruth Fabiola
A1  - Pacholski, Claudia
T1  - Bottom, top, or in between
BT  - combining plasmonic nanohole arrays and hydrogel microgels for optical fiber snsor applications
JF  - Advanced materials interfaces
N2  - Attractive label-free plasmonic optical fiber sensors can be developed by cleverly choosing the arrangement of plasmonic nanostructures and other building blocks. Here, the final response depends very much on the alignment and position (stacking) of the individual elements. In this work, three different types of fiber optic sensing geometries fabricated by simple layer-by-layer stacking are presented, consisting of stimulus-sensitive poly-N-isopropylacrylamide (polyNIPAM) microgel arrays and plasmonic nanohole arrays (NHAs), namely NHA/polyNIPAM, polyNIPAM/NHA, polyNIPAM/NHA/polyNIPAM. Their optical response to a representative stimulus, namely temperature, is investigated. NHA/polyNIPAM monitors the volume phase transition of polyNIPAM microgels through changes in the spectral position and the amplitude of the reflection minimum of plasmonic NHA. In contrast, polyNIPAM/NHA shows a more complex response to the swelling and collapse of polyNIPAM microgels in their reflectance spectra. The most pronounced changes in optical response are observed by monitoring the amplitude of the reflectance minimum of this sensor during heating/cooling cycles. Finally, the triple stack of polyNIPAM/NHA/polyNIPAM at the end of a optical fiber tip combines the advantages of the NHA/polyNIPAM, polyNIPAM/NHA double stacks for optical sensing. The unique layer-by-layer stacking of microgel and nanostructure is customizable and can be easily adopted for other applications.
KW  - bottom-up fabrication
KW  - layer-by-layer stacking
KW  - microgel arrays
KW  - optical
KW  - fiber sensors
KW  - plasmonic nanohole arrays
Y1  - 2022
U6  - https://doi.org/10.1002/admi.202102312
SN  - 2196-7350
VL  - 9
IS  - 15
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - GEN
A1  - Pacholski, Claudia
A1  - Agarwal, Vivechana
A1  - Balderas-Valadez, Ruth Fabiola
T1  - Fabrication of porous silicon-based optical sensors using metal-assisted chemical etching
N2  - Optical biosensors based on porous silicon were fabricated by metal assisted chemical etching. Thereby double layered porous silicon structures were obtained consisting of porous pillars with large pores on top of a porous silicon layer with smaller pores. These structures showed a similar sensing performance in comparison to electrochemically produced porous silicon interferometric sensors.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 316 
KW  - fourier-transform spectroscopy
KW  - nanostructures
KW  - nanowires
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394426
SP  - 21430
EP  - 21434
ER  - 
TY  - JOUR
A1  - Balderas-Valadez, Ruth Fabiola
A1  - Antunez, E. E.
A1  - Olive-Mendez, Sion Federico
A1  - Pacholski, Claudia
A1  - Campos-Alvarez, Jose
A1  - Bokhimi, Xim
A1  - Agarwal, V.
T1  - Porous silicon pillar and bilayer structure as a nucleation center for the formation of aligned vanadium pentoxide nanorods
JF  - Ceramics International
N2  - Porous silicon single layer (PSM), bilayer (PSB) and pillar (PSP) structures have been evaluated as nucleation centers for vanadium pentoxide (V2O5) crystals. Deposition of vanadium precursor over different substrates (drop casting technique), followed by annealing treatment under Ar-H-2 (5% H-2) atmosphere, induced crystallization of vanadium oxide. With respect to c-Si/SiO2 substrate, V2O5 nanorods with relatively large aspect ratio were formed over and within PSP structures. On the other hand, pores in PSM and PSB were found to be filled with relatively smaller crystals. Additionally, PSB provided a nucleation substrate capable to align the nanocrystals in a preferential orientation, while V2O5 crystals grown on PSP were found to be randomly aligned around the nanoporous pillar microstructure. Nanorods and nanocrystals were identified as V2O5 by temperature-controlled XRD measurements and evidence of their crystalline nature was observed via transmission electron microscopy. A careful analysis of electronic microscopy images allows the identification of the facets composing the ends of the crystals and its corresponding surface free energy has been evaluated employing the Wulff theorem. Such high surface area composite structures have potential applications as cathode material in Lithium-ion batteries.
KW  - Porous silicon
KW  - Vanadium pentoxide
KW  - Nanorods
KW  - Crystallization
KW  - Nanostructures
Y1  - 2017
U6  - https://doi.org/10.1016/j.ceramint.2017.03.114
SN  - 0272-8842
SN  - 1873-3956
VL  - 43
SP  - 8023
EP  - 8030
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Balderas-Valadez, Ruth Fabiola
A1  - Schürmann, Robin Mathis
A1  - Pacholski, Claudia
T1  - One Spot-Two Sensors: Porous Silicon Interferometers in Combination With Gold Nanostructures Showing Localized Surface Plasmon Resonance
JF  - Frontiers in chemistry
N2  - Sensors composed of a porous silicon monolayer covered with a film of nanostructured gold layer, which provide two optical signal transduction methods, are fabricated and thoroughly characterized concerning their sensing performance. For this purpose, silicon substrates were electrochemically etched in order to obtain porous silicon monolayers, which were subsequently immersed in gold salt solution facilitating the formation of a porous gold nanoparticle layer on top of the porous silicon. The deposition process was monitored by reflectance spectroscopy, and the appearance of a dip in the interference pattern of the porous silicon layer was observed. This dip can be assigned to the absorption of light by the deposited gold nanostructures leading to localized surface plasmon resonance. The bulk sensitivity of these sensors was determined by recording reflectance spectra in media having different refractive indices and compared to sensors exclusively based on porous silicon or gold nanostructures. A thorough analysis of resulting shifts of the different optical signals in the reflectance spectra on the wavelength scale indicated that the optical response of the porous silicon sensor is not influenced by the presence of a gold nanostructure on top. Moreover, the adsorption of thiol-terminated polystyrene to the sensor surface was solely detected by changes in the position of the dip in the reflectance spectrum, which is assigned to localized surface plasmon resonance in the gold nanostructures. The interference pattern resulting from the porous silicon layer is not shifted to longer wavelengths by the adsorption indicating the independence of the optical response of the two nanostructures, namely porous silicon and nanostructured gold layer, to refractive index changes and pointing to the successful realization of two sensors in one spot.
KW  - porous silicon
KW  - interferometry
KW  - gold nanostructures
KW  - surface plasmon resonance
KW  - optical sensor
Y1  - 2019
U6  - https://doi.org/10.3389/fchem.2019.00593
SN  - 2296-2646
VL  - 7
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  -