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 - 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 - 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 - 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 - 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 -