TY - JOUR A1 - Ribar, Anita A1 - Huber, Stefan E. A1 - Smialek, Malgorzata A. A1 - Tanzer, Katrin A1 - Neustetter, Michael A1 - Schürmann, Robin A1 - Bald, Ilko A1 - Denifl, Stephan T1 - Hydroperoxyl radical and formic acid formation from common DNA stabilizers upon low energy electron attachment JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - 2-Amino-2-(hydroxymethyl)-1,3-propanediol (TRIS) and ethylenediaminetetraacetic acid ( EDTA) are key components of biological buffers and are frequently used as DNA stabilizers in irradiation studies. Such surface or liquid phase studies are done with the aim to understand the fundamental mechanisms of DNA radiation damage and to improve cancer radiotherapy. When ionizing radiation is used, abundant secondary electrons are formed during the irradiation process, which are able to attach to the molecular compounds present on the surface. In the present study we experimentally investigate low energy electron attachment to TRIS and methyliminodiacetic acid ( MIDA), an analogue of EDTA, supported by quantum chemical calculations. The most prominent dissociation channel for TRIS is through hydroperoxyl radical formation, whereas the dissociation of MIDA results in the formation of formic and acetic acid. These compounds are well-known to cause DNA modifications, like strand breaks. The present results indicate that buffer compounds may not have an exclusive protecting effect on DNA as suggested previously. Y1 - 2018 U6 - https://doi.org/10.1039/c7cp07697e SN - 1463-9076 SN - 1463-9084 VL - 20 IS - 8 SP - 5578 EP - 5585 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schneider, Matthias A1 - Günter, Christina A1 - Taubert, Andreas T1 - Co-deposition of a hydrogel/calcium phosphate hybrid layer on 3D printed poly(lactic acid) scaffolds via dip coating BT - Towards Automated Biomaterials Fabrication JF - Polymers N2 - The article describes the surface modification of 3D printed poly(lactic acid) (PLA) scaffolds with calcium phosphate (CP)/gelatin and CP/chitosan hybrid coating layers. The presence of gelatin or chitosan significantly enhances CP co-deposition and adhesion of the mineral layer on the PLA scaffolds. The hydrogel/CP coating layers are fairly thick and the mineral is a mixture of brushite, octacalcium phosphate, and hydroxyapatite. Mineral formation is uniform throughout the printed architectures and all steps (printing, hydrogel deposition, and mineralization) are in principle amenable to automatization. Overall, the process reported here therefore has a high application potential for the controlled synthesis of biomimetic coatings on polymeric biomaterials. KW - 3D printing KW - dip-coating KW - poly(lactic acid) KW - PLA KW - calcium phosphate KW - gelatin KW - chitosan KW - hydrogel KW - calcium phosphate hybrid material KW - biomaterials Y1 - 2018 U6 - https://doi.org/10.3390/polym10030275 SN - 2073-4360 VL - 10 IS - 3 PB - MDPI CY - Basel ER - TY - JOUR A1 - Farhan, Muhammad A1 - Rudolph, Tobias A1 - Nöchel, Ulrich A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Extractable Free Polymer Chains Enhance Actuation Performance of Crystallizable Poly(epsilon-caprolactone) Networks and Enable Self-Healing JF - Polymers N2 - Crosslinking of thermoplastics is a versatile method to create crystallizable polymer networks, which are of high interest for shape-memory actuators. Here, crosslinked poly(epsilon-caprolactone) thermosets (cPCLs) were prepared from linear starting material, whereby the amount of extractable polymer was varied. Fractions of 5-60 wt % of non-crosslinked polymer chains, which freely interpenetrate the crosslinked network, were achieved leading to differences in the resulting phase of the bulk material. This can be described as "sponge-like" with open or closed compartments depending on the amount of interpenetrating polymer. The crosslinking density and the average network chain length remained in a similar range for all network structures, while the theoretical accessible volume for reptation of the free polymer content is affected. This feature could influence or introduce new functions into the material created by thermomechanical treatment. The effect of interpenetrating PCL in cPCLs on the reversible actuation was analyzed by cyclic, uniaxial tensile tests. Here, high reversible strains of up to Delta epsilon = 24% showed the enhanced actuation performance of networks with a non-crosslinked PCL content of 30 wt % resulting from the crystal formation in the phase of the non-crosslinked PCL and co-crystallization with network structures. Additional functionalities are reprogrammability and self-healing capabilities for networks with high contents of extractable polymer enabling reusability and providing durable actuator materials. KW - shape-memory polymer actuators KW - soft actuators KW - self-healing KW - poly(epsilon-caprolactone) KW - thermoplastics Y1 - 2018 U6 - https://doi.org/10.3390/polym10030255 SN - 2073-4360 VL - 10 IS - 3 PB - MDPI CY - Basel ER - TY - JOUR A1 - Behrendt, Felix Nicolas A1 - Schlaad, Helmut T1 - Entropy-Driven Ring-Opening Disulfide Metathesis Polymerization for the Synthesis of Functional Poly(disulfide)s JF - Macromolecular rapid communications N2 - Metal-free entropy-driven disulfide metathesis polymerization of unsaturated L-cystine based macrocycles produces high-molar-mass heterofunctional poly(disulfide)s, i.e., poly(ester-disulfide-alkene) and poly(amide-disulfide-alkene); M-w(app) = 44-60 kDa, (sic) > 1.7. The polymerization is fast and reaches equilibrium within 1-5 minutes (monomer conversion 70-90%) in polar aprotic solvents such as N,N-dimethylacetamide, dimethylsulfoxide, or y-valerolactone. Thiol-terminated polymers are stable in bulk or when dissolved in weakly polar solvents, but rapidly depolymerize in dilute polar solution. KW - disulfide KW - macrocycles KW - metathesis KW - ring-opening polymerization Y1 - 2018 U6 - https://doi.org/10.1002/marc.201700735 SN - 1022-1336 SN - 1521-3927 VL - 39 IS - 6 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Piluso, Susanna A1 - Vukicevie, Radovan A1 - Nöchel, Ulrich A1 - Braune, Steffen A1 - Lendlein, Andreas A1 - Neffe, Axel T. T1 - Sequential alkyne-azide cycloadditions for functionalized gelatin hydrogel formation JF - European polymer journal N2 - While click chemistry reactions for biopolymer network formation are attractive as the defined reactions may allow good control of the network formation and enable subsequent functionalization, tailoring of gelatin network properties over a wide range of mechanical properties has yet to be shown. Here, it is demonstrated that copper-catalyzed alkyne-azide cycloaddition of alkyne functionalized gelatin with diazides gave hydrogel networks with properties tailorable by the ratio of diazide to gelatin and diazide rigidity. 4,4′-diazido-2,2′-stilbenedisulfonic acid, which has been used as rigid crosslinker, yielded hydrogels with Young’s moduli E of 50–390 kPa and swelling degrees Q of 150–250 vol.%, while the more flexible 1,8-diazidooctane resulted in hydrogels with E = 125–280 kPa and Q = 225–470 vol.%. Storage moduli could be varied by two orders of magnitude (G′ = 100–20,000 Pa). An indirect cytotoxicity test did not show cytotoxic properties. Even when employing 1:1 ratios of alkyne and azide moieties, the hydrogels were shown to contain both, unreacted alkyne groups on the gelatin backbone as well as dangling chains carrying azide groups as shown by reaction with functionalized fluorescein. The free groups, which can be tailored by the employed ratio of the reactants, are accessible for covalent attachment of drugs, as was demonstrated by functionalization with dexamethasone. The sequential network formation and functionalization with click chemistry allows access to multifunctional materials relevant for medical applications. KW - Click chemistry KW - Hydrogel KW - Polymer functionalization KW - Biopolymer KW - Rheology KW - Multifunctionality Y1 - 2018 U6 - https://doi.org/10.1016/j.eurpolymj.2018.01.017 SN - 0014-3057 SN - 1873-1945 VL - 100 SP - 77 EP - 85 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Aravopoulou, Dionysia A1 - Kyriakos, Konstantinos A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Kyritsis, Apostolos T1 - Comparative Investigation of the Thermoresponsive Behavior of Two Diblock Copolymers Comprising PNIPAM and PMDEGA Blocks JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - The thermoresponsive behavior of two diblock copolymers PS-b-PNIPAM and PS-b-PMDEGA, which both comprise a hydrophobic polystyrene (PS) block but different thermoresponsive blocks, also differing in length, poly(N-isopropylacrylamide) (PNIPAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA), respectively, was comparatively investigated in a wide temperature range. Concentrated aqueous solutions containing 25 wt % polymer were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and broadband dielectric spectroscopy (BDS). DSC measurements show that, during the demixing phase transition, the hydration number per oligo(ethylene glycol) side chain in the PS-b-PMDEGA solution decreases rather gradually, even up to 20 °C above the onset of the transition, i.e., the cloud point (CP). In contrast, the PS-b-PNIPAM solution exhibits an abrupt, stepwise dehydration behavior at its CP, indicated by the sharp, narrow endothermic peak. BDS measurements suggest that the organization of the expelled water during the phase transition and the subsequent evolution of the micellar aggregates are different for the two copolymers. In the PS-b-PMDEGA solution, the long-range charge transport process changes significantly at its CP and strong interfacial polarization processes appear, probably due to charge accumulation at the interfaces between the micellar aggregates and the aqueous medium. On the contrary, in the PS-b-PNIPAM solution, the phase transition has only a marginal effect on the long-range conduction process and is accompanied by a reduction in the high-frequency (1 MHz) dielectric permittivity, ε′. The latter effect is attributed to the reduced polarization strength of local chain modes due to an enhancement of intra- and interchain hydrogen bonds (HBs) in the polymer-rich phase during the water detaching process. Surprisingly, our BDS measurements indicate that prior to both the demixing and remixing processes the local chain mobility increases temporally. Our dielectric studies suggest that for PS-b-PNIPAM the water detaching process initiates a few degrees below CP and that the local chain mobility and intra- and/or interchain HBs of the PNIPAM blocks may control its thermoresponsive behavior. Dielectric “jump” experiments show that the kinetics of micellar aggregation in the PS-b-PMDEGA solution is slower than that in the PS-b-PNIPAM solution and is independent of the target temperature within the two-phase region. From the experimental point of view, it is shown that the dielectric susceptibility, especially, the dielectric permittivity, ε′, is a well-suited probe for monitoring both the reversible changes in the molecular dipolar bond polarizability and the long-range interfacial polarization at the phase transition. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcb.7b09647 SN - 1520-6106 VL - 122 IS - 9 SP - 2655 EP - 2668 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schulze-Makuch, Dirk A1 - Wagner, Dirk A1 - Kounaves, Samuel P. A1 - Mangelsdorf, Kai A1 - Devine, Kevin G. A1 - de Vera, Jean-Pierre A1 - Schmitt-Kopplin, Philippe A1 - Grossart, Hans-Peter A1 - Parro, Victor A1 - Kaupenjohann, Martin A1 - Galy, Albert A1 - Schneider, Beate A1 - Airo, Alessandro A1 - Froesler, Jan A1 - Davila, Alfonso F. A1 - Arens, Felix L. A1 - Caceres, Luis A1 - Cornejo, Francisco Solis A1 - Carrizo, Daniel A1 - Dartnell, Lewis A1 - DiRuggiero, Jocelyne A1 - Flury, Markus A1 - Ganzert, Lars A1 - Gessner, Mark O. A1 - Grathwohl, Peter A1 - Guan, Lisa A1 - Heinz, Jacob A1 - Hess, Matthias A1 - Keppler, Frank A1 - Maus, Deborah A1 - McKay, Christopher P. A1 - Meckenstock, Rainer U. A1 - Montgomery, Wren A1 - Oberlin, Elizabeth A. A1 - Probst, Alexander J. A1 - Saenz, Johan S. A1 - Sattler, Tobias A1 - Schirmack, Janosch A1 - Sephton, Mark A. A1 - Schloter, Michael A1 - Uhl, Jenny A1 - Valenzuela, Bernardita A1 - Vestergaard, Gisle A1 - Woermer, Lars A1 - Zamorano, Pedro T1 - Transitory microbial habitat in the hyperarid Atacama Desert JF - Proceedings of the National Academy of Sciences of the United States of America KW - habitat KW - aridity KW - microbial activity KW - biomarker KW - Mars Y1 - 2018 U6 - https://doi.org/10.1073/pnas.1714341115 SN - 0027-8424 VL - 115 IS - 11 SP - 2670 EP - 2675 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Sarem, Melika A1 - Arya, Neha A1 - Heizmann, Miriam A1 - Neffe, Axel T. A1 - Barbero, Andrea A1 - Gebauer, Tim P. A1 - Martin, Ivan A1 - Lendlein, Andreas A1 - Shastri, V. Prasad T1 - Interplay between stiffness and degradation of architectured gelatin hydrogels leads to differential modulation of chondrogenesis in vitro and in vivo JF - Acta biomaterialia N2 - The limited capacity of cartilage to heal large lesions through endogenous mechanisms has led to extensive effort to develop materials to facilitate chondrogenesis. Although physical-chemical properties of biomaterials have been shown to impact in vitro chondrogenesis, whether these findings are translatable in vivo is subject of debate. Herein, architectured 3D hydrogel scaffolds (ArcGel) (produced by crosslinking gelatin with ethyl lysine diisocyanate (LDI)) were used as a model system to investigate the interplay between scaffold mechanical properties and degradation on matrix deposition by human articular chondrocytes (HAC) from healthy donors in vitro and in vivo. Using ArcGel scaffolds of different tensile and shear modulus, and degradation behavior; in this study, we compared the fate of ex vivo engineeredArcGels-chondrocytes constructs, i.e. the traditional tissue engineering approach, with the de novo formation of cartilaginous tissue in HAC laden ArcGels in an ectopic nude mouse model. While the softer and fast degrading ArcGel (LNCO3) was more efficient at promoting chondrogenic differentiation in vitro, upon ectopic implantation, the stiffer and slow degrading ArcGel (LNCO8) was superior in maintaining chondrogenic phenotype in HAC and retention of cartilaginous matrix. Furthermore, surprisingly the de novo formation of cartilage tissue was promoted only in LNCO8. Since HAC cultured for only three days in the LNCO8 environment showed upregulation of hypoxia-associated genes, this suggests a potential role for hypoxia in the observed in vivo outcomes. In summary, this study sheds light on how immediate environment (in vivo versus in vitro) can significantly impact the outcomes of cell-laden biomaterials. Statement of Significance In this study, 3D architectured hydrogels (ArcGels) with different mechanical and biodegradation properties were investigated for their potential to promote formation of cartilaginous matrix by human articular chondrocytes in vitro and in vivo. Two paradigms were explored (i) ex vivo engineering followed by in vivo implantation in ectopic site of nude mice and (ii) short in vitro culture (3 days) followed by implantation to induce de novo cartilage formation. Softer and fast degrading ArcGel were better at promoting chondrogenesis in vitro, while stiffer and slow degrading ArcGel were strikingly superior in both maintaining chondrogenesis in vivo and inducing de novo formation of cartilage. Our findings highlight the importance of the interplay between scaffold mechanics and degradation in chondrogenesis. KW - Cartilage repair KW - Scaffold stiffness KW - Scaffold contraction KW - Scaffold degradation KW - Matrix metalloproteinase KW - Hypoxia Y1 - 2018 U6 - https://doi.org/10.1016/j.actbio.2018.01.025 SN - 1742-7061 SN - 1878-7568 VL - 69 SP - 83 EP - 94 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Rackwitz, Jenny A1 - Bald, Ilko T1 - Low-energy electron-induced strand breaks in telomere-derived DNA sequences BT - influence of DNA sequence and topology JF - Chemistry - a European journal N2 - During cancer radiation therapy high-energy radiation is used to reduce tumour tissue. The irradiation produces a shower of secondary low-energy (<20 eV) electrons, which are able to damage DNA very efficiently by dissociative electron attachment. Recently, it was suggested that low-energy electron-induced DNA strand breaks strongly depend on the specific DNA sequence with a high sensitivity of G-rich sequences. Here, we use DNA origami platforms to expose G-rich telomere sequences to low-energy (8.8 eV) electrons to determine absolute cross sections for strand breakage and to study the influence of sequence modifications and topology of telomeric DNA on the strand breakage. We find that the telomeric DNA 5′-(TTA GGG)2 is more sensitive to low-energy electrons than an intermixed sequence 5′-(TGT GTG A)2 confirming the unique electronic properties resulting from G-stacking. With increasing length of the oligonucleotide (i.e., going from 5′-(GGG ATT)2 to 5′-(GGG ATT)4), both the variety of topology and the electron-induced strand break cross sections increase. Addition of K+ ions decreases the strand break cross section for all sequences that are able to fold G-quadruplexes or G-intermediates, whereas the strand break cross section for the intermixed sequence remains unchanged. These results indicate that telomeric DNA is rather sensitive towards low-energy electron-induced strand breakage suggesting significant telomere shortening that can also occur during cancer radiation therapy. KW - DNA damage KW - DNA strand breaks KW - low-energy electron KW - radiation therapy KW - telomeric DNA Y1 - 2018 U6 - https://doi.org/10.1002/chem.201705889 SN - 0947-6539 SN - 1521-3765 VL - 24 IS - 18 SP - 4680 EP - 4688 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zimmermann, Marc A1 - John, Daniela A1 - Grigoriev, Dmitry A1 - Puretskiy, Nikolay A1 - Böker, Alexander T1 - From 2D to 3D patches on multifunctional particles BT - how microcontact printing creates a new dimension of functionality JF - Soft matter N2 - A straightforward approach for the precise multifunctional surface modification of particles with three-dimensional patches using microcontact printing is presented. By comparison to previous works it was possible to not only control the diameter, but also to finely tune the thickness of the deposited layer, opening up the way for three-dimensional structures and orthogonal multifunctionality. The use of PEI as polymeric ink, PDMS stamps for microcontact printing on silica particles and the influence of different solvents during particle release on the creation of functional particles with three-dimensional patches are described. Finally, by introducing fluorescent properties by incorporation of quantum dots into patches and by particle self-assembly via avidin-biotin coupling, the versatility of this novel modification method is demonstrated. Y1 - 2018 U6 - https://doi.org/10.1039/c8sm00163d SN - 1744-683X SN - 1744-6848 VL - 14 IS - 12 SP - 2301 EP - 2309 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Heiden, Sophia A1 - Yue, Yanhua A1 - Kirsch, Harald A1 - Wirth, Jonas A. A1 - Saalfrank, Peter A1 - Campen, Richard Kramer T1 - Water dissociative adsorption on α-Al2O3(112̅0) is controlled by surface site undercoordination, density, and topology JF - The journal of physical chemistry / publ. weekly by the American Chemical Society : C, Nanomaterials and interfaces N2 - α-Al2O3 surfaces are common in a wide variety of applications and useful models of more complicated, environmentally abundant, alumino-silicate surfaces. While decades of work have clarified that all properties of these surfaces depend sensitively on the crystal face and the presence of even small amounts of water, quantitative insight into this dependence has proven challenging. Overcoming this challenge requires systematic study of the mechanism by which water interacts with various α-Al2O3 surfaces. Such insight is most easily gained for the interaction of small amounts of water with surfaces in ultra high vacuum. In this study, we continue our combined theoretical and experimental approach to this problem, previously applied to water interaction with the α-Al2O3 (0001) and (11̅02) surfaces, now to water interaction with the third most stable surface, that is, the (112̅0). Because we characterize all three surfaces using similar tools, it is straightforward to conclude that the (112̅0) is most reactive with water. The most important factor explaining its increased reactivity is that the high density of undercoordinated surface Al atoms on the (112̅0) surface allows the bidentate adsorption of OH fragments originating from dissociatively adsorbed water, while only monodentate adsorption is possible on the (0001) and (11̅02) surfaces: the reactivity of α-Al2O3 surfaces with water depends strongly, and nonlinearly, on the density of undercoordinated surface Al atoms. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcc.7b10410 SN - 1932-7447 VL - 122 IS - 12 SP - 6573 EP - 6584 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Arias, Hugo R. A1 - Feuerbach, Dominik A1 - Schmidt, Bernd A1 - Heydenreich, Matthias A1 - Paz, Cristian A1 - Ortells, Marcelo O. T1 - Drimane Sesquiterpenoids Noncompetitively Inhibit Human alpha 4 beta 2 Nicotinic Acetylcholine Receptors with Higher Potency Compared to Human alpha 3 beta 4 and alpha 7 Subtypes JF - Journal of natural products N2 - The drimane sesquiterpenoids drimenin, cinnamolide, dendocarbin A, and polygodial were purified from the Canelo tree (Drimys winteri) and chemically characterized by spectroscopic methods. The pharmacological activity of these natural compounds were determined on hα4β2, hα3β4, and hα7 nicotinic acetylcholine receptors (AChRs) by Ca2+ influx measurements. The results established that drimane sesquiterpenoids inhibit AChRs with the following selectivity: hα4β2 > hα3β4 > hα7. In the case of hα4β2 AChRs, the following potency rank order was determined (IC50’s in μM): drimenin (0.97 ± 0.35) > cinnamolide (1.57 ± 0.36) > polygodial (62.5 ± 19.9) ≫ dendocarbin A (no activity). To determine putative structural features underlying the differences in inhibitory potency at hα4β2 AChRs, additional structure–activity relationship and molecular docking experiments were performed. The Ca2+ influx and structural results supported a noncompetitive mechanism of inhibition, where drimenin interacted with luminal and nonluminal (TMD-β2 intrasubunit) sites. The structure–activity relationship results, i.e., the lower the ligand polarity, the higher the inhibitory potency, supported the nonluminal interaction. Ligand binding to both sites might inhibit the hα4β2 AChR by a cooperative mechanism, as shown experimentally (nH > 1). Drimenin could be used as a molecular scaffold for the development of more potent inhibitors with higher selectivity for the hα4β2 AChR. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jnatprod.7b00893 SN - 0163-3864 SN - 1520-6025 VL - 81 IS - 4 SP - 811 EP - 817 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Muzdalo, Anja A1 - Saalfrank, Peter A1 - Vreede, Jocelyne A1 - Santer, Mark T1 - Cis-to-Trans Isomerization of Azobenzene Derivatives Studied with Transition Path Sampling and Quantum Mechanical/Molecular Mechanical Molecular Dynamics JF - Journal of chemical theory and computation N2 - Azobenzene-based molecular photoswitches are becoming increasingly important for the development of photoresponsive, functional soft-matter material systems. Upon illumination with light, fast interconversion between a more stable trans and a metastable cis configuration can be established resulting in pronounced changes in conformation, dipole moment or hydrophobicity. A rational design of functional photosensitive molecules with embedded azo moieties requires a thorough understanding of isomerization mechanisms and rates, especially the thermally activated relaxation. For small azo derivatives considered in the gas phase or simple solvents, Eyring’s classical transition state theory (TST) approach yields useful predictions for trends in activation energies or corresponding half-life times of the cis isomer. However, TST or improved theories cannot easily be applied when the azo moiety is part of a larger molecular complex or embedded into a heterogeneous environment, where a multitude of possible reaction pathways may exist. In these cases, only the sampling of an ensemble of dynamic reactive trajectories (transition path sampling, TPS) with explicit models of the environment may reveal the nature of the processes involved. In the present work we show how a TPS approach can conveniently be implemented for the phenomenon of relaxation–isomerization of azobenzenes starting with the simple examples of pure azobenzene and a push–pull derivative immersed in a polar (DMSO) and apolar (toluene) solvent. The latter are represented explicitly at a molecular mechanical (MM) and the azo moiety at a quantum mechanical (QM) level. We demonstrate for the push–pull azobenzene that path sampling in combination with the chosen QM/MM scheme produces the expected change in isomerization pathway from inversion to rotation in going from a low to a high permittivity (explicit) solvent model. We discuss the potential of the simulation procedure presented for comparative calculation of reaction rates and an improved understanding of activated states. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jctc.7b01120 SN - 1549-9618 SN - 1549-9626 VL - 14 IS - 4 SP - 2042 EP - 2051 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Schmitt, Clemens Nikolaus Zeno A1 - Bargheer, Matias A1 - Koetz, Joachim T1 - Tuned Surface-Enhanced raman scattering performance of undulated Au@Ag triangles JF - ACS applied nano materials N2 - Negatively charged ultraflat gold nanotriangles (AuNTs) stabilized by the anionic surfactant dioctyl sodium sulfosuccinate (AOT) were reloaded with the cationic surfactant benzylhexadecyldimethylammonium chloride (BDAC). Because of the spontaneous formation of a catanionic AOT micelle/BDAC bilayer onto the surface of the reloaded AuNTs, a reduction of Ag+ ions leads to the formation of spherical silver nanoparticles (AgNPs). With increasing concentration of AgNPs on the AuNTs, the localized surface plasmon resonance (LSPR) is shifted stepwise from 1300 to 800 nm. The tunable LSPR enables to shift the extinction maximum to the wavelength of the excitation laser of the Raman microscope at 785 nm. Surface-enhanced Raman scattering (SERS) experiments performed under resonance conditions show an SERS enhancement factor of the analyte molecule rhodamine RG6 of 5.1 X 10(5), which can be related to the silver hot spots at the periphery of the undulated gold nanoplatelets. KW - gold nanotriangles KW - catanionic surfactant bilayer KW - undulated nanoplatelets KW - SERS KW - LSPR Y1 - 2018 U6 - https://doi.org/10.1021/acsanm.8b00570 SN - 2574-0970 VL - 1 IS - 4 SP - 1995 EP - 2003 PB - American Chemical Society CY - Washington 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 - Vishnevetskaya, Natalya S. A1 - Hildebrand, Viet A1 - Dyakonova, Margarita A. A1 - Niebuur, Bart-Jan A1 - Kyriakos, Konstantinos A1 - Raftopoulos, Konstantinos N. A1 - Di, Zhenyu A1 - Müller-Buschbaum, Peter A1 - Laschewsky, Andre A1 - Papadakis, Christine M. T1 - Dual orthogonal switching of the "Schizophrenic" self-assembly of diblock copolymers JF - Macromolecules : a publication of the American Chemical Society N2 - Based on diblock copolymers, a pair of "schizophrenic" micellar systems is designed by combining a nonionic and thermoresponsive block with a zwitterionic block, which is thermoresponsive and salt-sensitive. The nonionic block is poly(N-isopropylacrylamide) (PNIPAM) or poly(N-isopropylmethacrylamide) (PNIPMAM) and exhibits a lower critical solution temperature (LCST) behavior in aqueous solution. The zwitterionic block is a polysulfobetaine, i.e., poly(4((3-methacrylamidopropyl)dimethylammonio)butane-1-sulfonate) (PSBP), and has an upper critical solution temperature (UCST) behavior with the clearing point decreasing with increasing salt concentration. The PSBP-b-PNIPAM and PSBP-b-PNIPMAM diblock copolymers are prepared by successive reversible addition-fragmentation chain transfer (RAFT) polymerizations. The PSBP block is chosen such that the clearing point of the homopolymer is significantly higher in pure water than the cloud point of PNIPAM or PNIPMAM. Using turbidimetry, H-1 NMR, and small-angle neutron scattering, we investigate the overall phase behavior as well as the structure and interaction between the micelles and the intermediate phase, both in salt-free D2O and in 0.004 M NaBr in D2O in a wide temperature range. We find that PSBP-b-PNIPAM at 50 g L-1 in salt-free D2O is turbid in the entire temperature range. It forms spherical micelles below the cloud point of PNIPAM and cylindrical micelles above. Similar behavior is observed for PSBP-b-PNIPMAM at 50 g L-1 in salt-free D2O with a slight and smooth increase of the light transmission below the cloud point of PNIPMAM and an abrupt decrease above. Upon addition of 0.004 M NaBr, the UCST-type cloud point of the PSBP-block is notably decreased, and an intermediate regime is encountered below the cloud point of PNIPMAM, where the light transmission is slightly enhanced. In this regime, the polymer solution exhibits behavior typical for polyelectrolyte solutions. Thus, double thermosensitive and salt-sensitive behavior with "schizophrenic" micelle formation is found, and the width of the intermediate regime, where both blocks are hydrophilic, can be tuned by the addition of electrolyte. Y1 - 2018 U6 - https://doi.org/10.1021/acs.macromol.8b00096 SN - 0024-9297 SN - 1520-5835 VL - 51 IS - 7 SP - 2604 EP - 2614 PB - American Chemical Society CY - Washington 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 - 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 - 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 - 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 - 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 - John, Daniela A1 - Zimmermann, Marc A1 - Böker, Alexander T1 - Generation of 3-dimensional multi-patches on silica particles via printing with wrinkled stamps JF - Soft matter N2 - A simple route towards patchy particles with anisotropic patches with respect to a different functionality and directionality is presented. This method is based on microcontact printing of positively charged polyethylenimine (PEI) on silica particles using wrinkled stamps. Due to the wrinkled surface, the number of patches on the particles as well as the distance between two patches can be controlled. Y1 - 2018 U6 - https://doi.org/10.1039/c8sm00224j SN - 1744-683X SN - 1744-6848 VL - 14 IS - 16 SP - 3057 EP - 3062 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Matic, Aleksandar A1 - Schlaad, Helmut T1 - Thiol-ene photofunctionalization of 1,4-polymyrcene JF - Polymer international N2 - 1,4-Polymyrcene was synthesized by anionic polymerization of -myrcene and was subjected to photochemical functionalization with various thiols (i.e. methyl thioglycolate, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, ethyl 2-mercaptopropionate and 2-methyl-2-propanethiol) using benzophenone/UV light as the radical source. The yield of thiol addition to the trisubstituted double bonds of 1,4-polymyrcene decreased in the order 1 degrees thiol (ca 95%) > 2 degrees thiol (ca 80%) > 3 degrees thiol (<5%), due to the reversibility of the thiol-ene reaction. Remarkably, thiol addition to the side-chain double bonds was 8 - 10 times (1 degrees thiol) or 24 times (2 degrees thiol) faster than to the main-chain double bonds, which can be explained by the different accessibility of the double bonds and steric hindrance. Despite the use of a 10-fold excess of thiol with respect to myrcene units, the thiol-ene addition was accompanied by chain coupling reactions, which in the extreme case of 3 degrees thiol (or in the absence of thiol) resulted in the formation of insoluble crosslinked material. As an example, a methyl-thioglycolate-functionalized 1,4-polymyrcene was saponified/crosslinked to give submicron polyelectrolyte particles in dilute alkaline solution. (c) 2018 Society of Chemical Industry KW - polymyrcene KW - thiol-ene KW - photochemistry KW - regioselectivity Y1 - 2018 U6 - https://doi.org/10.1002/pi.5534 SN - 0959-8103 SN - 1097-0126 VL - 67 IS - 5 SP - 500 EP - 505 PB - Wiley CY - Hoboken 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 - Starke, Ines A1 - Koch, Andreas A1 - Kammer, Stefan A1 - Holdt, Hans-Jürgen A1 - Möller, Heiko Michael T1 - Electrospray mass spectrometry and molecular modeling study of formation and stability of silver complexes with diazaperylene and bisisoquinoline JF - Journal of mass spectrometry N2 - The complex formation of the following diazaperylene ligands (L) 1,12-diazaperylene 1, 1,1-bisisoquinoline 2, 2,11-disubstituted 1,12-diazaperylenes (alkyl=methyl, ethyl, isopropyl, 3, 5, 7), 3,3-disubstituted 1,1-bisisoquinoline (alkyl=methyl, ethyl, isopropyl, 4, 6, 8 and with R=phenyl, 11 and with pyridine 12), and the 5,8-dimethoxy-substituted diazaperylene 9, 6,6-dimethoxy-substituted bisisoquinoline 10 with AgBF4 was investigated. Collision-induced dissociation measurements were used to evaluate the relative stabilities of the ligands themselves and for the [1:1](+) complexes as well as for the homoleptic and heteroleptic silver [1:2](+) complexes in the gas phase. This method is very useful in rapid screening of the stabilities of new complexes in the gas phase. The influence of the spatial arrangement of the ligands and the type of substituents employed for the complexation were examined. The effect of the preorganization of the diazaperylene on the threshold activation voltages and thus of the relative binding energies of the different complexes are discussed. Density functional theory calculations were used to calculate the optimized structures of the silver complexes and compared with the stabilities of the complexes in the gas phase for the first time. KW - electrospray ionization mass spectrometry and modeling KW - silver(1) complexes KW - stability Y1 - 2018 U6 - https://doi.org/10.1002/jms.4071 SN - 1076-5174 SN - 1096-9888 VL - 53 IS - 5 SP - 408 EP - 418 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Bouakline, Foudhil T1 - Unambiguous signature of the berry phase in intense laser dissociation of diatomic molecules JF - The journal of physical chemistry letters N2 - We report strong evidence of Berry phase effects in intense laser dissociation of D-2(+) molecules, manifested as Aharonov-Bohm-like oscillations in the photofragment angular distribution (PAD). Our calculations show that this interference pattern strongly depends on the parity of the diatom initial rotational state, (-1)(j). Indeed, the PAD local maxima (minima) observed in one case (j odd) correspond to local minima (maxima) in the other case (j even). Using simple topological arguments, we clearly show that such interference conversion is a direct signature of the Berry phase. The sole effect of the latter on the rovibrational wave function is a sign change of the relative phase between two interfering components, which wind in opposite senses around a light-induced conical intersection (LICI). Therefore, encirclement of the LICI leads to constructive (j odd) or destructive (j even) self-interference of the initial nuclear wavepacket in the dissociative limit. To corroborate our theoretical findings, we suggest an experiment of strong-field indirect dissociation of D-2(+) molecules, comparing the PAD of the ortho and para molecular species in directions nearly perpendicular to the laser polarization axis. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpclett.8b00607 SN - 1948-7185 VL - 9 IS - 9 SP - 2271 EP - 2277 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Meiling, Till Thomas A1 - Cywinski, Piotr J. A1 - Löhmannsröben, Hans-Gerd T1 - Two-Photon excitation fluorescence spectroscopy of quantum dots BT - photophysical properties and application in bioassays JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - The applications of quantum dots (QDs) in two-photon (2P) excitation applications demand reliable data about their 2P absorption (2PA) cross sections (sigma(2PA)). In the present study, sigma(2PA) values have been determined for a series of commercial colloidal CdSe/ZnS QDs and CdSeTe/ZnS QDs in aqueous media. For the first time for these QDs, the sigma(2PA) values have been determined over a wide spectral range, that is, between 720 and 900 nm, and are compared to the extinction coefficient (epsilon) values obtained under one-photon (1P) excitation. Furthermore, we present a QD in combination with an organic dye in a biotin-streptavidin Forster resonance energy transfer bioassay under 1P and 2P excitation. The results for the bioassay under 2P excitation are compared to those obtained under 1P excitation. The results demonstrate that in the case of the 2P excitation, higher sensitivity can be achieved because of an improved signal-to-noise ratio. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcc.7b12345 SN - 1932-7447 SN - 1932-7455 VL - 122 IS - 17 SP - 9641 EP - 9647 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schultze, Christiane A1 - Schmidt, Bernd T1 - Prenylcoumarins in One or Two Steps by a Microwave-Promoted Tandem Claisen Rearrangement/Wittig Olefination/Cyclization Sequence JF - The journal of organic chemistry N2 - The one-pot synthesis of 8-prenylcoumarins from 1,1-dimethylallylated salicylaldehydes and the stabilized ylide [(ethoxycarbonyl)methylene]triphenylphosphorane under microwave conditions was found to have a limited scope. The sequence suffers from a difficult and sometimes low-yielding synthesis of the precursors and from a competing deprenylation upon microwave irradiation. This side reaction occurs in particular with electron rich arenes with two or more alkoxy groups at adjacent positions, a prominent substitution pattern in naturally occurring 8-prenylcoumarins. Both limitations of this one-step sequence were overcome by a two-step synthesis consisting of a microwave-promoted tandem allyl ether Claisen rearrangement/Wittig olefination and a subsequent olefin cross metathesis with 2-methyl-2-butene. The cross metathesis step proceeds with a high selectivity and yields exclusively the desired prenyl, rather than the alternative crotyl substituent. Several naturally occurring 8-prenylcoumarins that were previously inaccessible have been synthesized in good overall yields along this route. Y1 - 2018 U6 - https://doi.org/10.1021/acs.joc.8b00667 SN - 0022-3263 VL - 83 IS - 9 SP - 5210 EP - 5224 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Lee, Hui-Chun A1 - Hwang, Jongkook A1 - Schilde, Uwe A1 - Antonietti, Markus A1 - Matyjaszewski, Krzysztof A1 - Schmidt, Bernhard V. K. J. T1 - Toward ultimate control of radical polymerization BT - functionalized metal-organic frameworks as a robust environment for Metal-Catalyzed Polymerizations JF - Chemistry of materials : a publication of the American Chemical Society N2 - Herein, an approach via combination of confined porous textures and reversible deactivation radical polymerization techniques is proposed to advance synthetic polymer chemistry, i.e., a connection of metal-organic frameworks (MOFs) and activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Zn-2(benzene-1,4-dicarboxylate)2(1,4-diazabicyclo[2.2.2]-octane) [Zn-2(bdc)(2)(dabco)] is utilized as a reaction environment for polymerization of various methacrylate monomers (methyl, ethyl, benzyl, and isobornyl methacrylate) in a confined nanochannel, resulting in polymers with control over dispersity, end functionalities, and tacticity with respect to distinct molecular size. To refine and reconsolidate the compartmentation effect on polymer regularity, initiator-functionalized Zn MOF was synthesized via cocrystallization with an initiator-functionalized ligand, 2-(2-bromo-2-methylpropanamido)-1,4-benzenedicarboxylate (Brbdc), in different ratios (10%, 20%, and 50%). Through the embedded initiator, surface-initiated ARGET ATRP was directly initiated from the walls of the nanochannels. The obtained polymers had a high molecular weight up to 392 000. Moreover, a significant improvement in end-group functionality and stereocontrol was observed, entailing polymers with obvious increments in isotacticity. The results highlight a combination of MOFs and ATRP that is a promising and universal methodology to prepare various polymers with high molecular weight exhibiting well-defined uniformity in chain length and microstructure as well as the preserved chain-end functionality. Y1 - 2018 U6 - https://doi.org/10.1021/acs.chemmater.8b00546 SN - 0897-4756 SN - 1520-5002 VL - 30 IS - 9 SP - 2983 EP - 2994 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Meiling, Till Thomas A1 - Schürmann, Robin Mathis A1 - Vogel, Stefanie A1 - Ebel, Kenny A1 - Nicolas, Christophe A1 - Milosavljevic, Aleksandar R. A1 - Bald, Ilko T1 - Photophysics and Chemistry of Nitrogen-Doped Carbon Nanodots with High Photoluminescence Quantum Yield JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Fluorescent carbon nanodots (CNDs) are very promising nanomaterials for a broad range of applications because of their high photostability, presumed selective luminescence, and low cost at which they can be produced. In this respect, CNDs are superior to well-established semiconductor quantum dots and organic dyes. However, reported synthesis protocols for CNDs typically lead to low photoluminescence quantum yield (PLQY) and low reproducibility, resulting in a poor understanding of the CND chemistry and photophysics. Here, we report a one-step synthesis of nitrogen-doped carbon nanodots (N-CNDs) from various carboxylic acids, Tris, and ethylenediaminetetraacetic acid resulting in high PLQY of up to 90%. The reaction conditions in terms of starting materials, temperature, and reaction time are carefully optimized and their influence on the photophysical properties is characterized. We find that citric acid-derived N-CNDs can result in a very high PLQY of 90%, but they do not show selective luminescence. By contrast, acetic acid-derived N-CNDs show selective luminescence but a PLQY of 50%. The chemical composition of the surface and core of these two selected N-CND types is characterized among others by high-resolution synchrotron X-ray photoelectron spectroscopy using single isolated N-CND clusters. The results indicate that photoexcitation occurs in the N-CND core, whereas the emission properties are determined by the N-CND surface groups. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcc.8b00748 SN - 1932-7447 VL - 122 IS - 18 SP - 10217 EP - 10230 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Karras, Manfred A1 - Holec, Jan A1 - Bednarova, Lucie A1 - Pohl, Radek A1 - Schmidt, Bernd A1 - Stara, Irena G. A1 - Stary, Ivo T1 - Asymmetric Synthesis of Nonracemic 2-Amino[6]helicenes and Their Self-Assembly into Langmuir Films JF - The journal of organic chemistry N2 - Alternative ways of preparing nonracemic 2-amino[6]helicene derivatives were explored. The enantioselective [2 + 2 + 2] cycloisomerization of a nonchiral triyne under Ni(cod)(2)/(R)-QUINAP catalysis delivered the enantioenriched (+)-(P)-2-aminodibenzo[6]helicene derivative in 67% ee. An ultimate "point-to-helical" chirality transfer was observed in the cyclization of enantiopure triynes mediated by Ni(CO)(2)(PPh3)(2) affording (-)-(M)- or (+)-(P)-7,8-bis(p-tolyl)hexahelicen-2-amine in >99% ee as well as its benzoderivative in >99% ee. The latter mode of stereocontrol was inefficient for a 2-aminobenzo[6]helicene congener with an embedded five-membered ring. The rac-, (-)-(M)-, and (+)-(P)-7,8-bis(p-tolyl)hexahelicen-2-amines formed Langmuir monolayers at the air water interface featuring practically identical surface pressure vs mean molecular area isotherms. The corresponding Langmuir-Blodgett films on quartz or silicon substrates were characterized by UV vis/ECD spectroscopy and AFM microscopy, respectively. Y1 - 2018 U6 - https://doi.org/10.1021/acs.joc.8b00538 SN - 0022-3263 SN - 1520-6904 VL - 83 IS - 10 SP - 5523 EP - 5538 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kim, Yohan A1 - Heyne, Benjamin A1 - Abouserie, Ahed A1 - Pries, Christopher A1 - Ippen, Christian A1 - Günter, Christina A1 - Taubert, Andreas A1 - Wedel, Armin T1 - CuS nanoplates from ionic liquid precursors-Application in organic photovoltaic cells JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Hexagonal p-type semiconductor CuS nanoplates were synthesized via a hot injection method from bis(trimethylsilyl) sulfide and the ionic liquid precursor bis(N-dodecylpyridinium) tetrachloridocuprate( II). The particles have a broad size distribution with diameters between 30 and 680 nm and well-developed crystal habits. The nanoplates were successfully incorporated into organic photovoltaic (OPV) cells as hole conduction materials. The power conversion efficiency of OPV cells fabricated with the nanoplates is 16% higher than that of a control device fabricated without the nanoplates. (C) 2018 Author(s). Y1 - 2018 U6 - https://doi.org/10.1063/1.4991622 SN - 0021-9606 SN - 1089-7690 VL - 148 IS - 19 PB - American Institute of Physics CY - Melville 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 - Ferrer, Beatriz A1 - Peres, Tanara Vieira A1 - dos Santos, Alessandra Antunes A1 - Bornhorst, Julia A1 - Morcillo, Patricia A1 - Goncalves, Cinara Ludvig A1 - Aschner, Michael T1 - Methylmercury affects the expression of hypothalamic neuropeptides that control body weight in C57BL/6J mice JF - Toxicological sciences N2 - Methylmercury (MeHg) is an environmental pollutant that affects primarily the central nervous system (CNS), causing neurological alterations. An early symptom of MeHg poisoning is the loss of body weight and appetite. Moreover, the CNS has an important role in controlling energy homeostasis. It is known that in the hypothalamus nutrient and hormonal signals converge to orchestrate control of body weight and food intake. In this study, we investigated if MeHg is able to induce changes in the expression of key hypothalamic neuropeptides that regulate energy homeostasis. Thus, hypothalamic neuronal mouse cell line GT 1-7 was treated with MeHg at different concentrations (0, 0.5, 1, and 5 mu M). MeHg induced the expression of the anorexigenic neuropeptide pro-omiomelanocortin (Pomc) and the orexigenic peptide Agouti-related peptide (Agrp) in a concentration-dependent manner, suggesting deregulation of mechanisms that control body weight. To confirm these in vitro observations, 8-week-old C57BL/6J mice (males and females) were exposed to MeHg in drinking water, modeling the most prevalent exposure route to this metal. After 30-day exposure, no changes in body weight were detected. However, MeHg treated males showed a significant decrease in fat depots. Moreover, MeHg affected the expression of hypothalamic neuropeptides that control food intake and body weight in a gender-and dose-dependent manner. Thus, MeHg increases Pomc mRNA only in males in a dose-dependent way, and it does not have effects on the expression of Agrp mRNA. The present study shows, for first time, that MeHg is able to induce changes in hypothalamic neuropeptides that regulate energy homeostasis, favoring an anorexigenic/catabolic profile. KW - methylmercury KW - hypothalamus KW - neuropeptides KW - control body weight KW - glucose homeostasis Y1 - 2018 U6 - https://doi.org/10.1093/toxsci/kfy052 SN - 1096-6080 SN - 1096-0929 VL - 163 IS - 2 SP - 557 EP - 568 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Schönemann, Eric A1 - Laschewsky, Andre A1 - Rosenhahn, Axel T1 - Exploring the long-term hydrolytic behavior of zwitterionic polymethacrylates and polymethacrylamides JF - Polymers N2 - The hydrolytic stability of polymers to be used for coatings in aqueous environments, for example, to confer anti-fouling properties, is crucial. However, long-term exposure studies on such polymers are virtually missing. In this context, we synthesized a set of nine polymers that are typically used for low-fouling coatings, comprising the well-established poly(oligoethylene glycol methylether methacrylate), poly(3-(N-2-methacryloylethyl-N,N-dimethyl) ammoniopropanesulfonate) (sulfobetaine methacrylate), and poly(3-(N-3-methacryamidopropyl-N,N-dimethyl)ammoniopropanesulfonate) (sulfobetaine methacrylamide) as well as a series of hitherto rarely studied polysulfabetaines, which had been suggested to be particularly hydrolysis-stable. Hydrolysis resistance upon extended storage in aqueous solution is followed by H-1 NMR at ambient temperature in various pH regimes. Whereas the monomers suffered slow (in PBS) to very fast hydrolysis (in 1 M NaOH), the polymers, including the polymethacrylates, proved to be highly stable. No degradation of the carboxyl ester or amide was observed after one year in PBS, 1 M HCl, or in sodium carbonate buffer of pH 10. This demonstrates their basic suitability for anti-fouling applications. Poly(sulfobetaine methacrylamide) proved even to be stable for one year in 1 M NaOH without any signs of degradation. The stability is ascribed to a steric shielding effect. The hemisulfate group in the polysulfabetaines, however, was found to be partially labile. KW - polyzwitterions KW - stability KW - polymer degradation KW - hydrolysis KW - polysulfobetaine KW - polysulfabetaine KW - anti-fouling materials Y1 - 2018 U6 - https://doi.org/10.3390/polym10060639 SN - 2073-4360 VL - 10 IS - 6 PB - MDPI CY - Basel ER - TY - JOUR A1 - Reeg, Jette A1 - Heine, Simon A1 - Mihan, Christine A1 - Preuss, Thomas G. A1 - McGee, Sean A1 - Jeltsch, Florian T1 - Potential impact of effects on reproductive attributes induced by herbicides on a plant community JF - Environmental Toxicology and Chemistry N2 - Current herbicide risk assessment guidelines for nontarget terrestrial plants require testing effects on young, vulnerable life stages (i.e., seedling emergence [and subsequent growth] and vegetative vigor [growth and dry wt]) but not directly on the reproduction of plants. However, the European Food Safety Authority (EFSA) has proposed that effects on reproduction might be considered when evaluating the potential effects on plants. We adapted the plant community model for grassland (IBC-grass) to give insight into the current debate on the sensitivity of reproductive versus vegetative endpoints in ecological risk assessment. In an extensive sensitivity analysis of this model, we compared plant attributes potentially affected by herbicides and the consequences for long-term plant population dynamics and plant diversity. This evaluation was implemented by reducing reproductive as well as vegetative endpoints by certain percentages (e.g., 10-90%) as a theoretical assumption. Plant mortality and seed sterility (i.e., inability of seeds to germinate) were the most sensitive attributes. Our results indicated that effects on seed production at off-field exposure rates must be very strong to have an impact on the risk assessment. Otherwise, effects on seed production are compensated for by the soil seed bank. The present study highlights the usefulness of community level modeling studies to support regulators in their decisions on the appropriate risk assessment endpoints and provides confidence in their assessments. Environ Toxicol Chem 2018;37:1707-1722. (c) 2018 SETAC KW - Ecological risk assessment KW - Ecotoxicology KW - Herbicide KW - Plant reproduction KW - Plant community model KW - Nontarget terrestrial plants Y1 - 2018 U6 - https://doi.org/10.1002/etc.4122 SN - 0730-7268 SN - 1552-8618 VL - 37 IS - 6 SP - 1707 EP - 1722 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Hartwig, Anne A1 - Hass, Roland T1 - Monitoring lactose crystallization at industrially relevant concentrations by photon density wave spectroscopy JF - Chemical engineering & technology N2 - Lactose is of great industrial importance and its production includes the cooling crystallization from highly concentrated solutions. Monitoring the crystallization process is essential to ensure reproducible product quality. Photon density wave (PDW) spectroscopy enables in-line monitoring of highly concentrated processes in liquid dispersions. It was applied to the determination of the solubility and nucleation points of lactose monohydrate in water, sizing of lactose crystals, and to dissolution as well as crystallization monitoring. Other process analytical technologies (focused-beam reflectance measurement, particle vision and measurement) were used as reference, and the comparison indicates that PDW spectroscopy is very robust against probe fouling and is, thus, a useful tool for monitoring crystallization processes in concentrated suspensions. KW - In-line monitoring KW - Lactose KW - Light scattering KW - Photon density wave spectroscopy KW - Process analytical technology Y1 - 2018 U6 - https://doi.org/10.1002/ceat.201700685 SN - 0930-7516 SN - 1521-4125 VL - 41 IS - 6 SP - 1139 EP - 1146 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Shahinyan, A. A. A1 - Koetz, Joachim T1 - Self-assembled monolayer formation of distorted cylindrical AOT micelles on gold surfaces JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Self-assembling features of sodium dioctyl sulfosuccinate (AOT) molecules and micelle adsorption on gold Au (111) surfaces have been examined using molecular dynamics simulation. We argue that AOT micelles display a strong adsorption on gold surfaces resulting in distorted cylindrical micelles attached to the (111) facets. The well protected Au(111) facets decorated by a dense packed elongated ellipsoidal AOT layer hinder the diffusion of the reactant to the (111) facets and could result in the preferential growth of ultra-thin gold nanoplatelets. KW - Surfactant micelles KW - Adsorption KW - Gold surface KW - Molecular dynamics Y1 - 2018 U6 - https://doi.org/10.1016/j.colsurfa.2018.02.067 SN - 0927-7757 SN - 1873-4359 VL - 546 SP - 20 EP - 27 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pailles, Christine A1 - Sylvestre, Florence A1 - Escobar, Jaime A1 - Tonetto, Alain A1 - Rustig, Sybille A1 - Mazur, Jean-Charles T1 - Cyclotella petenensis and Cyclotella cassandrae, two new fossil diatoms from Pleistocene sediments of Lake Peten-Itza, Guatemala, Central America JF - Phytotaxa : a rapid international journal for accelerating the publication of botanical taxonomy N2 - While analyzing the fossil diatom flora in one of the longest paleolimnological records (core PI-6) from Lake Peten-Itza, lowland Guatemala, we encountered Aulacoseira Thwaites, Cyclotella (Kutzing) and Discostella (Cleve & Grunow) Houk & Klee species appearing successively in the record. Among them, two new species that are assigned to the genus Cyclotella are described herein. Cyclotella petenensis sp. nov. is characterised by a coarse striation marked by a shadow line and a tangentially undulate central area with an arc of central fultoportulae. Cyclotella cassandrae sp. nov. has an elliptically shaped valve, coarse striae and a scattered ring of central fultoportulae in the central area. Classification and differences to similar taxa in the genus Cyclotella are discussed. KW - Diatom KW - Cyclotella KW - Pleistocene KW - Lake Peten-Itza KW - Guatemala Y1 - 2018 U6 - https://doi.org/10.11646/phytotaxa.351.4.1 SN - 1179-3155 SN - 1179-3163 VL - 351 IS - 4 SP - 247 EP - 263 PB - Magnolia Press CY - Auckland ER - TY - JOUR A1 - Hansen, Poul Erik A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Ring current and anisotropy effects on OH chemical shifts in resonance-assisted intramolecular H-bonds JF - Tetrahedron letters N2 - Ring current effects on resonance-assisted and intramolecularly bridged hydrogen bond protons for 10-hydroxybenzo[h]quinoline 1 and a number of related compounds were calculated and the through-space NMR shieldings (TSNMRS) obtained hereby visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. These calculations revealed that this through-space effect is comparably large (up to 2 ppm) dependent on the position of the intramolecularly bridged OH proton, and therefore, contribute considerably to the chemical shift of the latter making it questionable to use delta(OH)/ppm in the estimation of intramolecular hydrogen bond strength without taking this into account. Furthermore, the anisotropy effects of additional groups on the aromatic moiety (e.g. the carbonyl group in salicylaldehyde or in o-hydroxyacetophenone of ca. 0.6 ppm deshielding) should also be considered. These through-space effects need to be taken into account when using OH chemical shifts to estimate hydrogen bond strength. KW - RA-intramolecular hydrogen bond KW - Through-space NMR shieldings (TSNMRS) KW - Iso-chemical-shielding surfaces (ICSS) KW - Ring current effect KW - Anisotropy effect Y1 - 2018 U6 - https://doi.org/10.1016/j.tetlet.2018.05.006 SN - 0040-4039 VL - 59 IS - 23 SP - 2288 EP - 2292 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Ertan, Emelie A1 - Savchenko, Viktoriia A1 - Ignatova, Nina A1 - Vaz da Cruz, Vinicius A1 - Couto, Rafael C. A1 - Eckert, Sebastian A1 - Fondell, Mattis A1 - Dantz, Marcus A1 - Kennedy, Brian A1 - Schmitt, Thorsten A1 - Pietzsch, Annette A1 - Föhlisch, Alexander A1 - Odelius, Michael A1 - Kimberg, Victor T1 - Ultrafast dissociation features in RIXS spectra of the water molecule JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - In this combined theoretical and experimental study we report on an analysis of the resonant inelastic X-ray scattering (RIXS) spectra of gas phase water via the lowest dissociative core-excited state |1s−1O4a11〉. We focus on the spectral feature near the dissociation limit of the electronic ground state. We show that the narrow atomic-like peak consists of the overlapping contribution from the RIXS channels back to the ground state and to the first valence excited state |1b−114a11〉 of the molecule. The spectral feature has signatures of ultrafast dissociation (UFD) in the core-excited state, as we show by means of ab initio calculations and time-dependent nuclear wave packet simulations. We show that the electronically elastic RIXS channel gives substantial contribution to the atomic-like resonance due to the strong bond length dependence of the magnitude and orientation of the transition dipole moment. By studying the RIXS for an excitation energy scan over the core-excited state resonance, we can understand and single out the molecular and atomic-like contributions in the decay to the lowest valence-excited state. Our study is complemented by a theoretical discussion of RIXS in the case of isotopically substituted water (HDO and D2O) where the nuclear dynamics is significantly affected by the heavier fragments' mass. Y1 - 2018 U6 - https://doi.org/10.1039/c8cp01807c SN - 1463-9076 SN - 1463-9084 VL - 20 IS - 21 SP - 14384 EP - 14397 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Öner, Ibrahim Halil A1 - Querebillo, Christine Joy A1 - David, Christin A1 - Gernert, Ulrich A1 - Walter, Carsten A1 - Driess, Matthias A1 - Leimkühler, Silke A1 - Ly, Khoa Hoang A1 - Weidinger, Inez M. T1 - High electromagnetic field enhancement of TiO2 nanotube electrodes JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - We present the fabrication of TiO2 nanotube electrodes with high biocompatibility and extraordinary spectroscopic properties. Intense surface-enhanced resonance Raman signals of the heme unit of the redox enzyme Cytochromeb(5) were observed upon covalent immobilization of the protein matrix on the TiO2 surface, revealing overall preserved structural integrity and redox behavior. The enhancement factor could be rationally controlled by varying the electrode annealing temperature, reaching a record maximum value of over 70 at 475 degrees C. For the first time, such high values are reported for non-directly surface-interacting probes, for which the involvement of charge-transfer processes in signal amplification can be excluded. The origin of the surface enhancement is exclusively attributed to enhanced localized electric fields resulting from the specific optical properties of the nanotubular geometry of the electrode. KW - electromagnetic field enhancement KW - photonic crystals KW - spectro-electrochemistry KW - surface-enhanced Raman spectroscopy KW - TiO2 nanotubes Y1 - 2018 U6 - https://doi.org/10.1002/anie.201802597 SN - 1433-7851 SN - 1521-3773 VL - 57 IS - 24 SP - 7225 EP - 7229 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Heck, Christian A1 - Kanehira, Yuya A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Placement of Single Proteins within the SERS Hot Spots of Self-Assembled Silver Nanolenses JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - This study demonstrates the bottom-up synthesis of silver nanolenses. A robust coating protocol enabled the functionalization of differently sized silver nanoparticles with DNA single strands of orthogonal sequence. Coated particles 10nm, 20nm, and 60nm in diameter were self-assembled by DNA origami scaffolds to form silver nanolenses. Single molecules of the protein streptavidin were selectively placed in the gap of highest electric field enhancement. Streptavidin labelled with alkyne groups served as model analyte in surface-enhanced Raman scattering (SERS) experiments. By correlated Raman mapping and atomic force microscopy, SERS signals of the alkyne labels of a single streptavidin molecule, from a single silver nanolens, were detected. The discrete, self-similar aggregates of solid silver nanoparticles are promising for plasmonic applications. KW - DNA origami KW - protein analysis KW - SERS KW - silver nanoparticles KW - streptavidin Y1 - 2018 U6 - https://doi.org/10.1002/anie.201801748 SN - 1433-7851 SN - 1521-3773 VL - 57 IS - 25 SP - 7444 EP - 7447 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Yan, Wan A1 - Rudolph, Tobias A1 - Nöchel, Ulrich A1 - Gould, Oliver E. C. A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Reversible actuation of thermoplastic multiblock copolymers with overlapping thermal transitions of crystalline and glassy domains JF - Macromolecules : a publication of the American Chemical Society N2 - Polymeric materials possessing specific features like programmability, high deformability, and easy processability are highly desirable for creating modern actuating systems. In this study, thermoplastic shape-memory polymer actuators obtained by combining crystallizable poly(epsilon-caprolactone) (PCL) and poly(3S-isobutylmorpholin-2,5-dione) (PIBMD) segments in multiblock copolymers are described. We designed these materials according to our hypothesis that the confinement of glassy PIBMD domains present at the upper actuation temperature contribute to the stability of the actuator skeleton, especially at large programming strains. The copolymers have a phase-segregated morphology, indicated by the well-separated melting and glass transition temperatures for PIBMD and PCL, but possess a partially overlapping T-m of PCL and T-g of PIBMD in the temperature interval from 40 to 60 degrees C. Crystalline PIBMD hard domains act as strong physical netpoints in the PIBMD-PCL bulk material enabling high deformability (up to 2000%) and good elastic recoverability (up to 80% at 50 degrees C above T-m,T-PCL). In the programmed thermoplastic actuators a high content of crystallizable PCL actuation domains ensures pronounced thermoreversible shape changes upon repetitive cooling and heating. The programmed actuator skeleton, composed of PCL crystals present at the upper actuation temperature T-high and the remaining glassy PIBMD domains, enabled oriented crystallization upon cooling. The actuation performance of PIBMD-PCL could be tailored by balancing the interplay between actuation and skeleton, but also by varying the quantity of crystalline PIBMD hard domains via the copolymer composition, the applied programming strain, and the choice of T-high. The actuator with 17 mol% PIBMD showed the highest reversible elongation of 11.4% when programmed to a strain of 900% at 50 degrees C. It is anticipated that the presented thermoplastic actuator materials can be applied as modern compression textiles. Y1 - 2018 U6 - https://doi.org/10.1021/acs.macromol.8b00322 SN - 0024-9297 SN - 1520-5835 VL - 51 IS - 12 SP - 4624 EP - 4632 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas T1 - Stable Carbenes or Betaines? JF - European journal of organic chemistry N2 - The anisotropy effect in H-1 NMR spectroscopy can be readily employed to indicate the position of carbene/betaine mesomeric equilibria. NR2 substituted carbene/betaines tend to adopt betaine structures, whereas in the absence of NR2 substituents, the betaine structures cannot stabilise the structure through both -donation effects of the NMe2 groups and the electronegativity of the nitrogen atoms, and the corresponding carbene-like structures are preferred. These conclusions are supported by calculated bond orders and (C-13)/ppm values. The spatial magnetic properties of isonitriles and carbon monoxide, which can be counted as stable carbenes or, at least, as carbene-analogues, also exist as stable betaine structures, which is again supported by structural and magnetic properties. KW - Carbenes KW - Betaines KW - Mesomerism KW - Through-space NMR shieldings (TSNMRS) KW - NMR spectroscopy KW - Conformation analysis Y1 - 2018 U6 - https://doi.org/10.1002/ejoc.201800462 SN - 1434-193X SN - 1099-0690 VL - 2018 IS - 24 SP - 3114 EP - 3121 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kasyanenko, Nina A1 - Unksov, Ivan A1 - Bakulev, Vladimir A1 - Santer, Svetlana T1 - DNA interaction with head-to-tail associates of cationic surfactants prevents formation of compact particles JF - Molecules N2 - Cationic azobenzene-containing surfactants are capable of condensing DNA in solution with formation of nanosized particles that can be employed in gene delivery. The ratio of surfactant/DNA concentration and solution ionic strength determines the result of DNA-surfactant interaction: Complexes with a micelle-like surfactant associates on DNA, which induces DNA shrinkage, DNA precipitation or DNA condensation with the emergence of nanosized particles. UV and fluorescence spectroscopy, low gradient viscometry and flow birefringence methods were employed to investigate DNA-surfactant and surfactant-surfactant interaction at different NaCl concentrations, [NaCl]. It was observed that [NaCl] (or the Debye screening radius) determines the surfactant-surfactant interaction in solutions without DNA. Monomers, micelles and non-micellar associates of azobenzene-containing surfactants with head-to-tail orientation of molecules were distinguished due to the features of their absorption spectra. The novel data enabled us to conclude that exactly the type of associates (together with the concentration of components) determines the result of DNA-surfactant interaction. Predomination of head-to-tail associates at 0.01 M < [NaCl] < 0.5 M induces DNA aggregation and in some cases DNA precipitation. High NaCl concentration (higher than 0.8 M) prevents electrostatic attraction of surfactants to DNA phosphates for complex formation. DAPI dye luminescence in solutions with DNA-surfactant complexes shows that surfactant tails overlap the DNA minor groove. The addition of di- and trivalent metal ions before and after the surfactant binding to DNA indicate that the bound surfactant molecules are located on DNA in islets. KW - azobenzene trimethylammonium bromide KW - head-to-tail surfactant associates KW - DNA KW - ionic strength KW - multivalent ions Y1 - 2018 U6 - https://doi.org/10.3390/molecules23071576 SN - 1420-3049 VL - 23 IS - 7 PB - MDPI CY - Basel ER - TY - JOUR A1 - Geroldinger, Gerald A1 - Tonner, Matthias A1 - Fudickar, Werner A1 - De Sarkar, Sritama A1 - Dighal, Aishwarya A1 - Monzote, Lianet A1 - Staniek, Katrin A1 - Linker, Torsten A1 - Chatterjee, Mitali A1 - Gille, Lars T1 - Activation of anthracene endoperoxides in leishmania and impairment of mitochondrial functions JF - Molecules N2 - Leishmaniasis is a vector-borne disease caused by protozoal Leishmania. Because of resistance development against current drugs, new antileishmanial compounds are urgently needed. Endoperoxides (EPs) are successfully used in malaria therapy, and experimental evidence of their potential against leishmaniasis exists. Anthracene endoperoxides (AcEPs) have so far been only technically used and not explored for their leishmanicidal potential. This study verified the in vitro efficiency and mechanism of AcEPs against both Leishmania promastigotes and axenic amastigotes (L. tarentolae and L. donovani) as well as their toxicity in J774 macrophages. Additionally, the kinetics and radical products of AcEPs’ reaction with iron, the formation of radicals by AcEPs in Leishmania, as well as the resulting impairment of parasite mitochondrial functions were studied. Using electron paramagnetic resonance combined with spin trapping, photometry, and fluorescence-based oximetry, AcEPs were demonstrated to (i) show antileishmanial activity in vitro at IC50 values in a low micromolar range, (ii) exhibit host cell toxicity in J774 macrophages, (iii) react rapidly with iron (II) resulting in the formation of oxygen- and carbon-centered radicals, (iv) produce carbon-centered radicals which could secondarily trigger superoxide radical formation in Leishmania, and (v) impair mitochondrial functions in Leishmania during parasite killing. Overall, the data of different AcEPs demonstrate that their structures besides the peroxo bridge strongly influence their activity and mechanism of their antileishmanial action. KW - Leishmania KW - endoperoxides KW - EPR spectroscopy KW - mitochondria KW - radicals Y1 - 2018 U6 - https://doi.org/10.3390/molecules23071680 SN - 1420-3049 VL - 23 IS - 7 PB - MDPI CY - Basel ER - TY - JOUR A1 - Liebig, Ferenc A1 - Moreno, Silvia A1 - Thuenemann, Andreas F. A1 - Temme, Achim A1 - Appelhans, Dietmar A1 - Koetz, Joachim T1 - Toxicological investigations of "naked" and polymer-entrapped AOT-based gold nanotriangles JF - Colloids and surfaces : an international journal devoted to fundamental and applied research on colloid and interfacial phenomena in relation to systems of biological origin ; B, Biointerfaces N2 - Negatively charged ultrathin gold nanotriangles (AuNTs) were synthesized in a vesicular dioctyl sodium sulfosuccinate (AOT)/phospholipid-based template phase. These "naked" AuNTs with localized surface plasmon resonances in the NIR region at about 1300 nm and special photothermal properties are of particular interest for imaging and hyperthermia of cancerous tissues. For these kinds of applications the toxicity and the cellular uptake of the AuNTs is of outstanding importance. Therefore, this study focuses on the toxicity of "naked" AOT-stabilized AuNTs compared to polymer-coated AuNTs. Polymeric coating consisted of non-modified hyperbranched poly(ethyleneimine) (PEI), maltose-modified poly(ethyleneimine) (PEI-Mal) and heparin. The toxicological experiments were carried out with two different cell lines (embryonic kidney carcinoma cell line HEK293T and NK-cell leukemia cell line YTS). This study revealed that the heparin-coating of AuNTs improved biocompatibility by a factor of 50 when compared to naked AuNTs. Of note, the highest nontoxic concentration of the AuNTs coated with PEI and PEI-Mal is drastically decreased. Overall, this is mainly triggered by the different surface charges of polymeric coatings. Therefore, AuNTs coated with heparin were selected to carry out uptake studies. Their promising high biocompatibility and cellular uptake may open future studies in the field of biomedical applications. (C) 2018 Elsevier B.V. All rights reserved. KW - Gold nanotriangles KW - Polymer-coating KW - Toxicity KW - Heparin KW - Cellular uptake Y1 - 2018 U6 - https://doi.org/10.1016/j.colsurfb.2018.04.059 SN - 0927-7765 SN - 1873-4367 VL - 167 SP - 560 EP - 567 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Melani, Giacomo A1 - Nagata, Yuki A1 - Wirth, Jonas A1 - Saalfrank, Peter T1 - Vibrational spectroscopy of hydroxylated alpha-Al2O3(0001) surfaces with and without water BT - an ab initio molecular dynamics study JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Using gradient- and dispersion-corrected density functional theory in connection with ab initio molecular dynamics and efficient, parametrized Velocity-Velocity Autocorrelation Function (VVAF) methodology, we study the vibrational spectra (Vibrational Sum Frequency, VSF, and infrared, IR) of hydroxylated alpha-Al2O3(0001) surfaces with and without additional water. Specifically, by considering a naked hydroxylated surface and the same surface with a particularly stable, "ice-like" hexagonal water later allows us to identify and disentangle main spectroscopic bands of OH bonds, their orientation and dynamics, and the role of water adsorption. In particular, we assign spectroscopic signals around 3700 cm(-1) as being dominated by perpendicularly oriented non-hydrogen bonded aluminol groups, with and without additional water. Furthermore, the thin water layer gives spectroscopic signals which are already comparable to previous theoretical and experimental findings for the solid/(bulk) liquid interface, showing that water molecules closest to the surface play a decisive role in the vibrational response of these systems. From a methodological point of view, the effects of temperature, anharmonicity, hydrogen-bonding, and structural dynamics are taken into account and analyzed, allowing us to compare the calculated IR and VSF spectra with the ones based on normal mode analysis and vibrational density of states. The VVAF approach employed in this work appears to be a computationally accurate yet feasible method to address the vibrational fingerprints and dynamical properties of water/metal oxide interfaces. Published by AIP Publishing. Y1 - 2018 U6 - https://doi.org/10.1063/1.5023347 SN - 0021-9606 SN - 1089-7690 VL - 149 IS - 1 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Saliba, Michael A1 - Correa-Baena, Juan-Pablo A1 - Wolff, Christian Michael A1 - Stolterfoht, Martin A1 - Phung, Thi Thuy Nga A1 - Albrecht, Steve A1 - Neher, Dieter A1 - Abate, Antonio T1 - How to Make over 20% Efficient Perovskite Solar Cells in Regular (n-i-p) and Inverted (p-i-n) Architectures JF - Chemistry of materials : a publication of the American Chemical Society N2 - Perovskite solar cells (PSCs) are currently one of the most promising photovoltaic technologies for highly efficient and cost-effective solar energy production. In only a few years, an unprecedented progression of preparation procedures and material compositions delivered lab-scale devices that have now reached record power conversion efficiencies (PCEs) higher than 20%, competing with most established solar cell materials such as silicon, CIGS, and CdTe. However, despite a large number of researchers currently involved in this topic, only a few groups in the world can reproduce >20% efficiencies on a regular n-i-p architecture. In this work, we present detailed protocols for preparing PSCs in regular (n-i-p) and inverted (p-i-n) architectures with >= 20% PCE. We aim to provide a comprehensive, reproducible description of our device fabrication , protocols. We encourage the practice of reporting detailed and transparent protocols that can be more easily reproduced by other laboratories. A better reporting standard may, in turn, accelerate the development of perovskite solar cells and related research fields. Y1 - 2018 U6 - https://doi.org/10.1021/acs.chemmater.8b00136 SN - 0897-4756 SN - 1520-5002 VL - 30 IS - 13 SP - 4193 EP - 4201 PB - American Chemical Society CY - Washington ER -