TY - JOUR A1 - Zühlke, Martin A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Andreotti, Sandro A1 - Reinert, Knut A1 - Zenichowski, Karl A1 - Diener, Marc T1 - High-performance liquid chromatography with electrospray ionization ion mobility spectrometry: Characterization, data management, and applications JF - Journal of separation science N2 - The combination of high-performance liquid chromatography and electrospray ionization ion mobility spectrometry facilitates the two-dimensional separation of complex mixtures in the retention and drift time plane. The ion mobility spectrometer presented here was optimized for flow rates customarily used in high-performance liquid chromatography between 100 and 1500 mu L/min. The characterization of the system with respect to such parameters as the peak capacity of each time dimension and of the 2D spectrum was carried out based on a separation of a pesticide mixture containing 24 substances. While the total ion current chromatogram is coarsely resolved, exhibiting coelutions for a number of compounds, all substances can be separately detected in the 2D plane due to the orthogonality of the separations in retention and drift dimensions. Another major advantage of the ion mobility detector is the identification of substances based on their characteristic mobilities. Electrospray ionization allows the detection of substances lacking a chromophore. As an example, the separation of a mixture of 18 amino acids is presented. A software built upon the free mass spectrometry package OpenMS was developed for processing the extensive 2D data. The different processing steps are implemented as separate modules which can be arranged in a graphic workflow facilitating automated processing of data. KW - Amino acids KW - Electrospray ionization KW - Ion mobility spectrometry KW - Pesticides KW - Two-dimensional separations Y1 - 2016 U6 - https://doi.org/10.1002/jssc.201600749 SN - 1615-9306 SN - 1615-9314 VL - 39 SP - 4756 EP - 4764 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zhou, Qihui A1 - Wuennemann, Patrick A1 - Kuhn, Philipp Till A1 - de Vries, Joop A1 - Helmin, Marta A1 - Böker, Alexander A1 - van Kooten, Theo G. A1 - van Rijn, Patrick T1 - Mechanical Properties of Aligned Nanotopologies for Directing Cellular Behavior JF - Advanced materials interfaces N2 - Tailoring cell–surface interactions is important for the of design medical implants as well as regenerative medicine and tissue engineering materials. Here the single parameter system is transcended via translating hard nanotopology into soft polymeric hydrogel structures via hydrogel imprinting lithography. The response of these cells to the nanotopology of the same dimensions but with different mechanical properties displays unexpected behavior between “hard” tissue cells and “soft” tissue cells. Y1 - 2016 U6 - https://doi.org/10.1002/admi.201600275 SN - 2196-7350 VL - 3 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Zhong, Qi A1 - Metwalli, Ezzeldin A1 - Rawolle, Monika A1 - Kaune, Gunar A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Wang, Jiping A1 - Müller-Buschbaum, Peter T1 - Influence of Hydrophobic Polystyrene Blocks on the Rehydration of Polystyrene-block-poly(methoxy diethylene glycol acrylate)-block-polystyrene Films Investigated by in Situ Neutron Reflectivity JF - Macromolecules : a publication of the American Chemical Society N2 - The rehydration of thermoresponsive polystyrene-block-poly(methoxy diethylene glycol acrylate)-block-polystyrene (PS-b-PMDEGA-b-PS) films forming a lamellar microphase-separated structure is investigated by in situ neutron reflectivity in a D2O vapor atmosphere. The rehydration of collapsed PS-b-PMDEGA-b-PS films is realized by a temperature change from 45 to 23 degrees C and comprises (1) condensation and absorption of D2O, (2) evaporation of D2O, and (3) reswelling of the film due to internal rearrangement. The hydrophobic PS layers hinder the absorption of condensed D2O, and a redistribution of embedded D2O between the hydrophobic PS layers and the hydrophilic PMDEGA layers is observed. In contrast, the rehydration of semiswollen PS-b-PMDEGA-b-PS films (temperature change from 35 to 23 degrees C) shows two prominent differences: A thicker D2O layer condenses on the surface, causing a more enhanced evaporation of D2O. The rehydrated films differ in film thickness and volume fraction of D2O, which is due to the different thermal protocols, although the final temperature is identical. Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.5b02279 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 317 EP - 326 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zhang, Pengfei A1 - Behl, Marc A1 - Peng, Xingzhou A1 - Razzaq, Muhammad Yasar A1 - Lendlein, Andreas T1 - Ultrasonic Cavitation Induced Shape-Memory Effect in Porous Polymer Networks JF - Macromolecular rapid communications N2 - Inspired by the application of ultrasonic cavitation based mechanical force (CMF) to open small channels in natural soft materials (skin or tissue), it is explored whether an artificial polymer network can be created, in which shape-changes can be induced by CMF. This concept comprises an interconnected macroporous rhodium-phosphine (Rh-P) coordination polymer network, in which a CMF can reversibly dissociate the Rh-P microphases. In this way, the ligand exchange of Rh-P coordination bonds in the polymer network is accelerated, resulting in a topological rearrangement of molecular switches. This rearrangement of molecular switches enables the polymer network to release internal tension under ultrasound exposure, resulting in a CMF-induced shape-memory capability. The interconnected macroporous structure with thin pore walls is essential for allowing the CMF to effectively permeate throughout the polymer network. Potential applications of this CMF-induced shape-memory polymer can be mechanosensors or ultrasound controlled switches. Y1 - 2016 U6 - https://doi.org/10.1002/marc.201600439 SN - 1022-1336 SN - 1521-3927 VL - 37 SP - 1897 EP - 1903 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zeng, Ting A1 - Frasca, Stefano A1 - Rumschöttel, Jens A1 - Koetz, Joachim A1 - Leimkühler, Silke A1 - Wollenberger, Ursula T1 - Role of Conductive Nanoparticles in the Direct Unmediated Bioelectrocatalysis of Immobilized Sulfite Oxidase JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis KW - Direct electron transfer KW - Protein voltammetry KW - Human sulfite oxidase KW - Bioelectrocatalysis KW - Nanoparticles Y1 - 2016 U6 - https://doi.org/10.1002/elan.201600246 SN - 1040-0397 SN - 1521-4109 VL - 28 SP - 2303 EP - 2310 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zehbe, Rolf A1 - Zehbe, Kerstin T1 - Strontium doped poly-epsilon-caprolactone composite scaffolds made by reactive foaming JF - The European journal of the history of economic thought N2 - In the reconstruction and regeneration of bone tissue, a primary goal is to initiate bone growth and to stabilize the surrounding bone. In this regard, a potentially useful component in biomaterials for bone tissue engineering is strontium, which acts as cationic active agent, triggering certain intracellular pathways and acting as so called dual action bone agent which inhibits bone resorption while stimulating bone regeneration. In this study we established a novel processing for the foaming of a polymer (poly-epsilon-caprolactone) and simultaneous chemical reaction of a mixture of calcium and strontium hydroxides to the respective carbonates using supercritical carbon dioxide. The resultant porous composite scaffold was optimized in composition and strontium content and was characterized via different spectroscopic (infrared and Raman spectroscopy, energy dispersive X-ray spectroscopy), imaging (SEM, mu CT), mechanical testing and in vitro methods (fluorescence vital staining, MTT-assay). As a result, the composite scaffold showed good in vitro biocompatibility with partly open pore structure and the expected chemistry. First mechanical testing results indicate sufficient mechanical stability to support future in vivo applications. (C) 2016 Elsevier B.V. All rights reserved. KW - Strontium KW - Poly-epsilon-caprolactone KW - Porous scaffold KW - CAL-72 osteoblasts KW - L-929 fibroblasts KW - Reactive foaming KW - mu CT imaging KW - Spectroscopy Y1 - 2016 U6 - https://doi.org/10.1016/j.msec.2016.05.045 SN - 0928-4931 SN - 1873-0191 VL - 67 SP - 259 EP - 266 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Zabel, André A1 - Winter, Alette A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Strauch, Peter T1 - Tetrabromidocuprates(II)-Synthesis, Structure and EPR JF - International journal of molecular sciences N2 - Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several “onium” cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g|| and gK) of the tensors could be determined and information on the structural changes in the [CuBr4]2- anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids. KW - tetrabromidocuprate(II) KW - X-ray structure KW - electron paramagnetic resonance KW - copper(II) Y1 - 2016 U6 - https://doi.org/10.3390/ijms17040596 VL - 17 IS - 4 PB - MDPI CY - Basel ER - TY - JOUR A1 - Zabel, Andre A1 - Winter, Alette A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Strauch, Peter T1 - Tetrabromidocuprates(II)-Synthesis, Structure and EPR JF - International journal of molecular sciences N2 - Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several "onium" cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g|| and g(perpendicular to)) of the tensors could be determined and information on the structural changes in the [CuBr4](2-) anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids. KW - tetrabromidocuprate(II) KW - X-ray structure KW - electron paramagnetic resonance KW - copper(II) Y1 - 2016 U6 - https://doi.org/10.3390/ijms17040596 SN - 1422-0067 VL - 17 PB - MDPI CY - Basel ER - TY - JOUR A1 - Yan, Wan A1 - Fang, Liang A1 - Nöchel, Ulrich A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Influence of programming strain rates on the shape-memory performance of semicrystalline multiblock copolymers JF - Journal of polymer science : B, Polymer physics N2 - Multiblock copolymers named PCL-PIBMD consisting of crystallizable poly(epsilon-caprolactone) segments and crystallizable poly[oligo(3S-iso-butylmorpholine-2,5-dione)] segments coupled by trimethyl hexamethylene diisocyanate provide a versatile molecular architecture for achieving shape-memory effects (SMEs) in polymers. The mechanical properties as well as the SME performance of PCL-PIBMD can be tailored by the variation of physical parameters during programming such as deformation strain or applied temperature protocols. In this study, we explored the influence of applying different strain rates during programming on the resulting nanostructure of PCL-PIBMD. Programming was conducted at 50 degrees C by elongation to epsilon(m)=50% with strain rates of 1 or 10 or 50 mmmin(-1). The nanostructural changes were visualized by atomic force microscopy (AFM) measurements and investigated by in situ wide and small angle X-ray scattering experiments. With increasing the strain rate, a higher degree of orientation was observed in the amorphous domains. Simultaneously the strain-induced formation of new PIBMD crystals as well as the fragmentation of existing large PIBMD crystals occurred. The observed differences in shape fixity ratio and recovery stress of samples deformed with various strain rates can be attributed to their different nanostructures. The achieved findings can be relevant parameters for programming the shape-memory polymers with designed recovery forces. (c) 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1935-1943 KW - atomic force microscopy (AFM) KW - crystal structures KW - crystallization KW - multiblock copolymer KW - stimuli-sensitive polymers KW - SAXS KW - shape-memory effect KW - WAXS KW - X-ray scattering Y1 - 2016 U6 - https://doi.org/10.1002/polb.24097 SN - 0887-6266 SN - 1099-0488 VL - 54 SP - 1935 EP - 1943 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Wuennemann, Patrick A1 - Noyong, Michael A1 - Kreuels, Klaus A1 - Bruex, Roland A1 - Gordiichuk, Pavlo A1 - van Rijn, Patrick A1 - Plamper, Felix A. A1 - Simon, Ulrich A1 - Böker, Alexander T1 - Microstructured Hydrogel Templates for the Formation of Conductive Gold Nanowire Arrays JF - Macromolecular rapid communications N2 - Microstructured hydrogel allows for a new template-guided method to obtain conductive nanowire arrays on a large scale. To generate the template, an imprinting process is used in order to synthesize the hydrogel directly into the grooves of wrinkled polydimethylsiloxane (PDMS). The resulting poly(N-vinylimidazole)-based hydrogel is defined by the PDMS stamp in pattern and size. Subsequently, tetrachloroaurate(III) ions from aqueous solution are coordinated within the humps of the N-vinylimidazole-containing polymer template and reduced by air plasma. After reduction and development of the gold, to achieve conductive wires, the extension perpendicular to the long axis (width) of the gold strings is considerably reduced compared to the dimension of the parental hydrogel wrinkles (from approximate to 1 mu m down to 200-300 nm). At the same time, the wire-to-wire distance and the overall length of the wires is preserved. The PDMS templates and hydrogel structures are analyzed with scanning force microscopy (SFM) and the gold structures via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. The conductivity measurements of the gold nanowires are performed in situ in the SEM, showing highly conductive gold leads. Hence, this method can be regarded as a facile nonlithographic top-down approach from micrometer-sized structures to nanometer-sized features. KW - 1D structures KW - Au nanoarrays KW - microgel KW - nanoimprint KW - lithography KW - thin films Y1 - 2016 U6 - https://doi.org/10.1002/marc.201600287 SN - 1022-1336 SN - 1521-3927 VL - 37 SP - 1446 EP - 1452 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wu, Lei A1 - Glebe, Ulrich A1 - Böker, Alexander T1 - Synthesis of Hybrid Silica Nanoparticles Densely Grafted with Thermo and pH Dual-Responsive Brushes via Surface-Initiated ATRP JF - Macromolecules : a publication of the American Chemical Society Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.6b01792 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 9586 EP - 9596 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wong, Joseph K. -H. A1 - Ast, Sandra A1 - Yu, Mingfeng A1 - Flehr, Roman A1 - Counsell, Andrew J. A1 - Turner, Peter A1 - Crisologo, Patrick A1 - Todd, Matthew H. A1 - Rutledge, Peter J. T1 - Synthesis and Evaluation of 1,8-Disubstituted-Cyclam/Naphthalimide Conjugates as Probes for Metal Ions JF - ChemistryOpen : including thesis treasury N2 - Fluorescent molecular probes for metal ions have a raft of potential applications in chemistry and biomedicine. We report the synthesis and photophysical characterisation of 1,8-disubstituted-cyclam/naphthalimide conjugates and their zinc complexes. An efficient synthesis of 1,8-bis-(2-azidoethyl)cyclam has been developed and used to prepare 1,8-disubstituted triazolyl-cyclam systems, in which the pendant group is connected to triazole C4. UV/Vis and fluorescence emission spectra, zinc binding experiments, fluorescence quantum yield and lifetime measurements and pH titrations of the resultant bis-naphthalimide ligand elucidate a complex pattern of photophysical behaviour. Important differences arise from the inclusion of two fluorophores in the one probe and from the variation of triazole substitution pattern (dye at C4 vs. N1). Introducing a second fluorophore greatly extends fluorescence lifetimes, whereas the altered substitution pattern at the cyclam amines exerts a major influence on fluorescence output and metal binding. Crystal structures of two key zinc complexes evidence variations in triazole coordination that mirror the solution-phase behaviour of these systems. KW - chromophores KW - click triazoles KW - fluorescent probes KW - macrocyclic compounds KW - photophysics Y1 - 2016 U6 - https://doi.org/10.1002/open.201600010 SN - 2191-1363 VL - 5 SP - 375 EP - 385 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Wischke, Christian A1 - Lendlein, Andreas T1 - Functional nanocarriers by miniaturization of polymeric materials T2 - Nanomedicine KW - function KW - microscale KW - morphology KW - nanoscale KW - polymer Y1 - 2016 U6 - https://doi.org/10.2217/nnm.16.45 SN - 1743-5889 SN - 1748-6963 VL - 11 SP - 1507 EP - 1509 PB - Future Medicine CY - London ER - TY - JOUR A1 - Wirth, Jonas A1 - Schacht, Julia A1 - Saalfrank, Peter A1 - Paulus, Beate T1 - Fluorination of the Hydroxylated alpha-Al2O3 (0001) and Its Implications for Water Adsorption: A Theoretical Study JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Fluorination of the hydroxylated alpha-Al2O3 (0001) surface is studied using periodic density functional theory calculations. On the basis of a hypothetical reaction substituting surface hydroxyl groups with fluorine atoms, we find surface fluorination to be strongly exergonic but kinetically hindered. Fluorinated surface areas turn out to be rather hydrophobic as compared to hydroxylated areas, suggesting fluorination as a potential route for tuning oxide surface properties such as hydrophilicity. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpcc.5b10975 SN - 1932-7447 VL - 120 SP - 9713 EP - 9718 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wirth, Jonas A1 - Kirsch, Harald A1 - Wlosczyk, Sebastian A1 - Tong, Yujin A1 - Saalfrank, Peter A1 - Campen, Richard Kramer T1 - Characterization of water dissociation on alpha-Al2O3(1(1)over-bar02): theory and experiment JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - The interaction of water with a-alumina (i.e. alpha-Al2O3) surfaces is important in a variety of applications and a useful model for the interaction of water with environmentally abundant aluminosilicate phases. Despite its significance, studies of water interaction with alpha-Al2O3 surfaces other than the (0001) are extremely limited. Here we characterize the interaction of water (D2O) with a well defined alpha-Al2O3(1 (1) over bar 02) surface in UHV both experimentally, using temperature programmed desorption and surface-specific vibrational spectroscopy, and theoretically, using periodic-slab density functional theory calculations. This combined approach makes it possible to demonstrate that water adsorption occurs only at a single well defined surface site (the so-called 1-4 configuration) and that at this site the barrier between the molecularly and dissociatively adsorbed forms is very low: 0.06 eV. A subset of OD stretch vibrations are parallel to this dissociation coordinate, and thus would be expected to be shifted to low frequencies relative to an uncoupled harmonic oscillator. To quantify this effect we solve the vibrational Schrodinger equation along the dissociation coordinate and find fundamental frequencies red-shifted by more than 1500 cm(-1). Within the context of this model, at moderate temperatures, we further find that some fraction of surface deuterons are likely delocalized: dissociatively and molecularly absorbed states are no longer distinguishable. Y1 - 2016 U6 - https://doi.org/10.1039/c6cp01397j SN - 1463-9076 SN - 1463-9084 VL - 18 SP - 14822 EP - 14832 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - White, Alec F. A1 - Heide, Chiara Josephine A1 - Saalfrank, Peter A1 - Head-Gordon, Martin A1 - Luppi, Eleonora T1 - Computation of high-harmonic generation spectra of the hydrogen molecule using time-dependent configuration-interaction JF - Molecular physics N2 - Here we apply and expand the knowledge developed in the case of the H atom to describe high-harmonic generation (HHG) for the H-2 molecule by using time-dependent configuration interaction with single excitations. The implications of using a finite atomic orbital basis set and the impact of a heuristic lifetime model which addresses ionisation losses are discussed. We also examine the influence of the angular momentum of the basis on the computed HHG spectra. Moreover, we discuss the impact of adding diffuse functions and ghost atoms in different geometrical configurations around the molecule. The effects of these additional centres on the HHG spectra are correlated with the physical interpretation of this nonlinear optical phenomenon as given by the three-step model, relating the maximal radial extent of the electron as predicted by the model to the radial extent of the Gaussian basis sets. [GRAPHICS] . KW - High-harmonic generation KW - strong field KW - time-dependent configuration interaction Y1 - 2016 U6 - https://doi.org/10.1080/00268976.2015.1119900 SN - 0026-8976 SN - 1362-3028 VL - 114 SP - 947 EP - 956 PB - Springer CY - Abingdon ER - TY - JOUR A1 - Wessig, Pablo A1 - Gerngross, Maik A1 - Freyse, Daniel A1 - Bruhn, P. A1 - Przezdziak, Marc A1 - Schilde, Uwe A1 - Kelling, Alexandra T1 - Molecular Rods Based on Oligo-spiro-thioketals JF - The journal of organic chemistry N2 - We report on an extension of the previously established concept of oligospiroketal (OSK) rods by replacing a part or all ketal moieties by thioketals leading to oligospirothioketal (OSTK) rods. In this way, some crucial problems arising from the reversible formation of ketals are circumvented. Furthermore, the stability of the rods toward hydrolysis is considerably improved. To successfully implement this concept, we first developed a number of new oligothiol building blocks and improved the synthetic accessibility of known oligothiols, respectively. Another advantage of thioacetals is that terephthalaldehyde (TAA) sleeves, which are too flexible in the case of acetals can be used in OSTK rods. The viability of the OSTK approach was demonstrated by the successful preparation of some OSTK rods with a length of some nanometers. Y1 - 2016 U6 - https://doi.org/10.1021/acs.joc.5b02670 SN - 0022-3263 VL - 81 SP - 1125 EP - 1136 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wessig, Pablo A1 - Behrends, Nicole A1 - Kumke, Michael Uwe A1 - Eisold, Ursula A1 - Meiling, Til A1 - Hille, Carsten T1 - Two-photon FRET pairs based on coumarin and DBD dyes JF - RSC Advances N2 - The synthesis and photophysical properties of two new FRET pairs based on coumarin as a donor and DBD dye as an acceptor are described. The introduction of a bromo atom dramatically increases the two-photon excitation (2PE) cross section providing a 2PE-FRET system, which is also suitable for 2PE-FLIM. Y1 - 2016 U6 - https://doi.org/10.1039/c6ra03983a SN - 2046-2069 VL - 6 SP - 33510 EP - 33513 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Wessig, Pablo A1 - Behrends, Nicole A1 - Kumke, Michael Uwe A1 - Eisold, Ursula T1 - FRET Pairs with Fixed Relative Orientation of Chromophores JF - European journal of organic chemistry N2 - Synthetic routes to different oligospirothioketal (OSTK) Forster resonance energy transfer (FRET) constructs are described and the photophysics of these constructs were explored in different solvents. The FRET efficiencies were determined from the experimental data and compared with theoretical values. The influence of the outstanding rigidity of the novel OSTK compounds on the FRET is discussed. KW - Fluorescence KW - Energy transfer KW - FRET KW - Chromophores KW - Spiro compounds Y1 - 2016 U6 - https://doi.org/10.1002/ejoc.201600489 SN - 1434-193X SN - 1099-0690 VL - 145 SP - 4476 EP - 4486 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wentrup, Curt A1 - Koch, Rainer A1 - Kleinpeter, Erich T1 - Twisted C=C Double Bonds with Very Low Rotational Barriers in Dioxanediones and Isoxazolones Determined by Low-Temperature Dynamic NMR Spectroscopy and Computational Chemistry JF - European journal of organic chemistry KW - NMR spectroscopy KW - Twisted double bonds KW - Push-pull effect KW - Density functional calculations Y1 - 2016 U6 - https://doi.org/10.1002/ejoc.201600931 SN - 1434-193X SN - 1099-0690 SP - 4985 EP - 4990 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Weiler, Markus A1 - Menzel, Christoph A1 - Pertsch, Thomas A1 - Alaee, Rasoul A1 - Rockstuhl, Carsten A1 - Pacholski, Claudia T1 - Bottom-Up Fabrication of Hybrid Plasmonic Sensors: Gold-Capped Hydrogel Microspheres Embedded in Periodic Metal Hole Arrays JF - Polymer : the international journal for the science and technology of polymers N2 - The high potential of bottom-up fabrication strategies for realizing sophisticated optical sensors combining the high sensitivity of a surface plasmon resonance with the exceptional properties of stimuli-responsive hydrogel is demonstrated. The sensor is composed of a periodic hole array in a gold film whose holes are filled with gold-capped poly(N-isoproyl-acrylamide) (polyNIPAM) microspheres. The production of this sensor relies on a pure chemical approach enabling simple, time-efficient, and cost-efficient preparation of sensor platforms covering areas of cm(2). The transmission spectrum of this plasmonic sensor shows a strong interaction between propagating surface plasmon polaritons at the metal film surface and localized surface plasmon resonance of the gold cap on top of the polyNIPAM microspheres. Computer simulations support this experimental observation. These interactions lead to distinct changes in the transmission spectrum, which allow for the simultaneous, sensitive optical detection of refractive index changes in the surrounding medium and the swelling state of the embedded polyNIPAM microsphere under the gold cap. The volume of the polyNIPAM microsphere located underneath the gold cap can be changed by certain stimuli such as temperature, pH, ionic strength, and distinct molecules bound to the hydrogel matrix facilitating the detection of analytes which do not change the refractive index of the surrounding medium significantly. KW - bottom-up KW - hydrogel KW - hole array KW - sensor KW - surface plasmon resonance Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b08636 SN - 1944-8244 VL - 8 SP - 26392 EP - 26399 PB - American Chemical Society CY - Washington ER - TY - THES A1 - Wei, Chunxiang T1 - On the role of monomer drops and swelling in aqueous heterophase polymerization Y1 - 2016 ER - TY - JOUR A1 - Wagner, Tom A1 - Lazar, Jaroslav A1 - Schnakenberg, Uwe A1 - Böker, Alexander T1 - In situ Electrothemical Impedance Spectroscopy of Electrostatically Driven Selective Gold Nanoparticle Adsorption on Block Copolymer Lamellae JF - Trials N2 - Electrostatic attraction between charged nano particles and oppositely charged nanopatterned polymeric films enables tailored structuring of functional nanoscopic surfaces. The bottom-up fabrication of organic/inorganic composites for example bears promising potential toward cheap fabrication of catalysts, optical sensors, and the manufacture of miniaturized electric circuitry. However, only little is known about the time-dependent adsorption behavior and the electronic or ionic charge transfer in the film bulk and at interfaces during nanoparticle assembly via electrostatic interactions. In situ electrochemical impedance spectroscopy (EIS) in combination with a microfluidic system for fast and reproducible liquid delivery was thus applied to monitor the selective deposition of negatively charged gold nanoparticles on top of positively charged poly(2-vinylpyridinium) (qP2VP) domains of phase separated lamellar poly(styrene)-block-poly(2-vinylpyridinium) (PS-b-qP2VP) diblock copolymer thin films. The acquired impedance data delivered information with respect to interfacial charge alteration, ionic diffusion, and the charge dependent nanoparticle adsorption kinetics, considering this yet unexplored system. We demonstrate that the selective adsorption of negatively charged gold nanoparticles (AuNPs) on positively charged qP2VP domains of lamellar PS-b-qP2VP thin films can indeed be tracked by EIS. Moreover, we show that the nanoparticle adsorption kinetics and the nanoparticle packing density are functions of the charge density in the qP2VP domains. KW - impedance spectroscopy KW - block copolymers KW - nanoparticles KW - electrostatics KW - adsorption kinetics Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b07708 SN - 1944-8244 VL - 8 SP - 27282 EP - 27290 PB - American Chemical Society CY - Washington 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 - von Reppert, Alexander A1 - Sarhan, Radwan Mohamed A1 - Stete, Felix A1 - Pudell, Jan-Etienne A1 - Del Fatti, N. A1 - Crut, A. A1 - Koetz, Joachim A1 - Liebig, Ferenc A1 - Prietzel, Claudia Christina A1 - Bargheer, Matias T1 - Watching the Vibration and Cooling of Ultrathin Gold Nanotriangles by Ultrafast X-ray Diffraction JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - We study the vibrations of ultrathin gold nanotriangles upon optical excitation of the electron gas by ultrafast X-ray diffraction. We quantitatively measure the strain evolution in these highly asymmetric nano-objects, providing a direct estimation of the amplitude and phase of the excited vibrational motion. The maximal strain value is well reproduced by calculations addressing pump absorption by the nanotriangles and their resulting thermal expansion. The amplitude and phase of the out-of-plane vibration mode with 3.6 ps period dominating the observed oscillations are related to two distinct excitation mechanisms. Electronic and phonon pressures impose stresses with different time dependences. The nanosecond relaxation of the expansion yields a direct temperature sensing of the nano-object. The presence of a thin organic molecular layer at the nanotriangle/substrate interfaces drastically reduces the thermal conductance to the substrate. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpcc.6b11651 SN - 1932-7447 VL - 120 SP - 28894 EP - 28899 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Vishnevetskaya, Natalya S. A1 - Hildebrand, Viet A1 - Niebuur, Bart-Jan A1 - Grillo, Isabelle A1 - Filippov, Sergey K. A1 - Laschewsky, Andre A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Aggregation Behavior of Doubly Thermoresponsive Polysulfobetaine-b-poly(N-isopropylacrylamide) Diblock Copolymers JF - Macromolecules : a publication of the American Chemical Society N2 - A 2-fold thermoresponsive diblock copolymer PSPP430-b-PNIPAM(200) consisting of a zwitterionic polysulfobetaine (PSPP) block and a nonionic poly(N-isopropylacrylamide) (PNIPAM) block is prepared by successive RAFT polymerizations. In aqueous solution, the corresponding homopolymers PSPP and PNIPAM feature both upper and lower critical solution temperature (UCST and LCST) behavior, respectively. The diblock copolymer exhibits thermally induced "schizophrenic" aggregation behavior in aqueous solutions. Moreover, the ion sensitivity of the, cloud point of the zwitterionic PSPP block to both the ionic strength and the nature of the salt offers the possibility to create switchable systems which respond sensitively to changes of the temperature and of the electrolyte type and concentration. The diblock copolymer solutions in D2O are investigated by means of turbidimetry and small-angle neutron scattering (SANS) with respect to the phase behavior and the self-assembled structures in dependence on temperature and electrolyte content. Marked, differences of the aggregation below the UCST-type and above the LCST-type transition are observed. The addition of a small amount of NaBr (0.004 M) does not affect the overall behavior, and only the UCST-type transition and aggregate structures are slightly altered, reflecting the well-known ion sensitivity of the zwitterionic PSPP block. Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.6b01186 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 6655 EP - 6668 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Villatoro, José Andrés A1 - Zühlke, Martin A1 - Riebe, Daniel A1 - Riedel, Jens A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd T1 - IR-MALDI ion mobility spectrometry JF - Analytical and bioanalytical chemistry : a merger of Fresenius' journal of analytical chemistry and Analusis N2 - The novel combination of infrared matrix-assisted laser dispersion and ionization (IR-MALDI) with ion mobility (IM) spectrometry makes it possible to investigate biomolecules in their natural environment, liquid water. As an alternative to an ESI source, the IR-MALDI source was implemented in an in-house-developed ion mobility (IM) spectrometer. The release of ions directly from an aqueous solution is based on a phase explosion, induced by the absorption of an IR laser pulse (lambda = 2.94 mu m, 6 ns pulse width), which disperses the liquid as nano- and micro-droplets. The prerequisites for the application of IR-MALDI-IM spectrometry as an analytical method are narrow analyte ion signal peaks for a high spectrometer resolution. This can only be achieved by improving the desolvation of ions. One way to full desolvation is to give the cluster ions sufficient time to desolvate. Two methods for achieving this are studied: the implementation of an additional drift tube, as in ESI-IM-spectrometry, and the delayed extraction of the ions. As a result of this optimization procedure, limits of detection between 5 nM and 2.5 mu M as well as linear dynamic ranges of 2-3 orders of magnitude were obtained for a number of substances. The ability of this method to analyze simple mixtures is illustrated by the separation of two different surfactant mixtures. KW - Ion mobility spectrometry KW - IR-MALDI KW - Laser Y1 - 2016 U6 - https://doi.org/10.1007/s00216-016-9739-x SN - 1618-2642 SN - 1618-2650 VL - 408 SP - 6259 EP - 6268 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Villatoro, José Andrés A1 - Zühlke, Martin A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Weber, Marcus A1 - Riedel, Jens A1 - Löhmannsröben, Hans-Gerd T1 - IR-MALDI ion mobility spectrometry: physical source characterization and application as HPLC detector JF - International journal for ion mobility spectrometry : official publication of the International Society for Ion Mobility Spectrometry N2 - Infrared matrix-assisted laser dispersion and ionization (IR-MALDI) in combination with ion mobility (IM) spectrometry enables the direct analysis of biomolecules in aqueous solution. The release of ions directly from an aqueous solution is based on a phase explosion, induced by the absorption of an IR laser pulse, which disperses the liquid as vapor, nano-and micro-droplets. The ionization process is characterized initially by a broad spatial distribution of the ions, which is a result of complex fluid dynamics and desolvation kinetics. These processes have a profound effect on the shape and width of the peaks in the IM spectra. In this work, the transport of ions by the phase explosion-induced shockwave could be studied independently from the transport by the electric field. The shockwave-induced mean velocities of the ions at different time scales were determined through IM spectrometry and shadowgraphy. The results show a deceleration of the ions from 118 m.s(-1) at a distance of 400 mu m from the liquid surface to 7.1 m.s(-1) at a distance of 10 mm, which is caused by a pile-up effect. Furthermore, the desolvation kinetics were investigated and a first-order desolvation constant of 325 +/- 50 s(-1) was obtained. In the second part, the IR-MALDI-IM spectrometer is used as an HPLC detector for the two-dimensional separation of a pesticide mixture. KW - Ion mobility spectrometry KW - IR-MALDI KW - Shadowgraphy KW - Laser KW - Imaging KW - HPLC Y1 - 2016 U6 - https://doi.org/10.1007/s12127-016-0208-1 SN - 1435-6163 SN - 1865-4584 VL - 19 SP - 197 EP - 207 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Vargas-Ruiz, Salome A1 - Schulreich, Christoph A1 - Kostevic, Angelika A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Kakorin, Sergej A1 - von Klitzing, Regine A1 - Jung, Martin A1 - Hellweg, Thomas A1 - Wellert, Stefan T1 - Extraction of model contaminants from solid surfaces by environmentally compatible microemulsions JF - Journal of colloid and interface science N2 - In the present contribution, we evaluate the efficiency of eco-friendly microemulsions to decontaminate solid surfaces by monitoring the extraction of non-toxic simulants of sulfur mustard out of model surfaces. The extraction process of the non-toxic simulants has been monitored by means of spectroscopic and chromatographic techniques. The kinetics of the removal process was analyzed by different empirical models. Based on the analysis of the kinetics, we can assess the influence of the amounts of oil and water and the microemulsion structure on the extraction process. (C) 2016 Elsevier Inc. All rights reserved. KW - Microemulsions KW - Decontamination KW - Surface removal KW - Kinetic analysis KW - Extraction Y1 - 2016 U6 - https://doi.org/10.1016/j.jcis.2016.03.006 SN - 0021-9797 SN - 1095-7103 VL - 471 SP - 118 EP - 126 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Vacogne, Charlotte D. A1 - Schopferer, Michael A1 - Schlaad, Helmut T1 - Physical Gelation of alpha-Helical Copolypeptides JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences N2 - Owing to its rod-like alpha-helical secondary structure, the synthetic polypeptide poly(gamma-benzyl-L-glutamate) (PBLG) can form physical and thermoreversible gels in helicogenic solvents such as toluene. The versatility of PBLG can be increased by introducing functionalizable comonomers, such as allylglycine (AG). In this work we examined the secondary structure of PBLG and a series of statistical poly(gamma-benzyl-L-glutamate-co-allylglycine) copolypeptides, varying in composition and chain length, by circular dichroism (CD), Fourier-transform infrared (FTIR) and Raman spectroscopy, and wide-angle X-ray scattering (WAXS). The secondary structure of PBLG and the copolypeptides presented dissimilarities that increased with increasing AG molar fraction, especially when racemic AG units were incorporated. The physical gelation behavior of these copolypeptides was analyzed by temperature-sweep H-1 NMR and rheological measurements. The study revealed that both copolypeptide composition and chain length affected secondary structure, gelation temperature, and gel stiffness. Y1 - 2016 U6 - https://doi.org/10.1021/acs.biomac.6b00427 SN - 1525-7797 SN - 1526-4602 VL - 17 SP - 2384 EP - 2391 PB - American Chemical Society CY - Washington ER - TY - THES A1 - Täuber, Karoline T1 - Porous Membranes from Imidazolium- and Pyridinium-based Poly(ionic liquid)s with Targeted Properties Y1 - 2016 ER - TY - JOUR A1 - Tritschler, Ulrich A1 - Zlotnikov, Igor A1 - Fratzl, Peter A1 - Schlaad, Helmut A1 - Gruener, Simon A1 - Coelfen, Helmut T1 - Gas barrier properties of bio-inspired Laponite-LC polymer hybrid films JF - PLoS one N2 - Bio-inspired Laponite (clay)-liquid crystal (LC) polymer composite materials with high clay fractions (>80%) and a high level of orientation of the clay platelets, i.e. with structural features similar to the ones found in natural nacre, have been shown to exhibit a promising behavior in the context of reduced oxygen transmission. Key characteristics of these bio-inspired composite materials are their high inorganic content, high level of exfoliation and orientation of the clay platelets, and the use of a LC polymer forming the organic matrix in between the Laponite particles. Each single feature may be beneficial to increase the materials gas barrier property rendering this composite a promising system with advantageous barrier capacities. In this detailed study, Laponite/LC polymer composite coatings with different clay loadings were investigated regarding their oxygen transmission rate. The obtained gas barrier performance was linked to the quality, respective Laponite content and the underlying composite micro-and nanostructure of the coatings. Most efficient oxygen barrier properties were observed for composite coatings with 83% Laponite loading that exhibit a structure similar to sheet-like nacre. Further on, advantageous mechanical properties of these Laponite/LC polymer composites reported previously give rise to a multifunctional composite system. KW - gas permeation KW - liquid crystal KW - Laponite KW - liquid crystal polymer KW - bio-inspired KW - organic-inorganic composite material KW - self-organization Y1 - 2016 U6 - https://doi.org/10.1088/1748-3190/11/3/035005 SN - 1748-3182 SN - 1748-3190 VL - 11 PB - IOP Publ. Ltd. CY - Bristol 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 - Titov, Evgenii A1 - Saalfrank, Peter T1 - Exciton Splitting of Adsorbed and Free 4-Nitroazobenzene Dimers: A Quantum Chemical Study JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - Molecular photoswitches such as azobenzenes, which undergo photochemical trans <-> cis isomerizations, are often mounted for possible applications on a surface and/or surrounded by other switches, for example, in self-assembled monolayers. This may suppress the isomerization cross section due to possible steric reasons, or, as recently speculated, by exciton coupling to. neighboring switches, leading to ultrafast electronic quenching (Gahl et al., J. Am. Chem. Soc. 2010, 132, 1831). The presence of exciton coupling has been anticipated from a blue shift of the optical absorption band, compared to molecules in solution. From the theory side the need arises to properly analyze and quantify the change of absorption spectra of interacting and adsorbed switches. In particular, suitable methods should be identified, and effects of intermolecule and molecule surface interactions on spectra should be disentangled. In this paper by means of time-dependent Hartree-Fock. (TD-HF), various flavors of time-dependent density functional theory (TD-DFT), and the correlated wave function based, coupled cluster (CC2) method we investigated the 4-nitroazobenzene molecule as an:example: The low-lying singlet excited states in the isolated trans monomer and dieter as well as their composites with a silicon pentamantane nanocluster, which serves also as a crude model for a silicon surface, were determined. As most important results we found that (i) HF, CC2, range-separated density functionals, or global hybrids with large amount of exact exchange are able to describe exciton (Davydov) splitting properly, while hybrids with small amount of exact exchange fail producing spurious charge transfer. (ii) The exciton splitting in a free dimer would lead to a blue shift of the absorption signal; however, this effect is almost nullified or even overcompensated by the shift arising from van der Waals interactions between the two molecules. (iii) Adsorption on the Si "surface" leads to a further, strong red shift for the present system. (iv) At a next-nearest neighbor distance (of similar to 3.6 angstrom), the exciton splitting is similar to 0.3 eV, with or without "surface", suggesting a rapid quenching of the molecular pi ->pi* excitation. At larger distances, exciton splitting decreases rapidly. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpca.5b10376 SN - 1089-5639 VL - 120 SP - 3055 EP - 3070 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Titov, Evgenii A1 - Granucci, Giovanni A1 - Goetze, Jan Philipp A1 - Persico, Maurizio A1 - Saalfrank, Peter T1 - Dynamics of Azobenzene Dimer Photoisomerization: Electronic and Steric Effects JF - The journal of physical chemistry letters N2 - While azobenzenes readily photoswitch in solution, their photoisomerization in densely packed self-assembled monolayers (SAMs) can be suppressed. Reasons for this can be steric hindrance and/or electronic quenching, e.g., by exciton coupling. We address these possibilities by means of nonadiabatic molecular dynamics with trajectory surface hopping calculations, investigating the trans -> cis isomerization of azobenzene after excitation into the pi pi* absorption band. We consider a free monomer, an isolated dimer and a dimer embedded in a SAM-like environment of additional azobenzene molecules, imitating in this way the gradual transition from an unconstrained over an electronically coupled to an electronically coupled and sterically hindered, molecular switch. Our simulations reveal that in comparison to the single molecule the quantum yield of the trans -> cis photoisomerization is similar for the isolated dimer, but greatly reduced in the sterically constrained situation. Other implications of dimerization and steric constraints are also discussed. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpciett.6b01401 SN - 1948-7185 VL - 7 SP - 3591 EP - 3596 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Thielke, Michael W. A1 - Secker, Christian A1 - Schlaad, Helmut A1 - Theato, Patrick T1 - Electrospinning of Crystallizable Polypeptoid Fibers JF - Macromolecular rapid communications N2 - A unique fabrication process of low molar mass, crystalline polypeptoid fibers is described. Thermoresponsive fiber mats are prepared by electrospinning a homogeneous blend of semicrystalline poly(N-(n-propyl) glycine) (PPGly; 4.1 kDa) with high molar mass poly(ethylene oxide) (PEO). Annealing of these fibers at approximate to 100 degrees C selectively removes the PEO and produces stable crystalline fiber mats of pure PPGly, which are insoluble in aqueous solution but can be redissolved in methanol or ethanol. The formation of water-stable polypeptoid fiber mats is an important step toward their utilization in biomedical applications such as tissue engineering or wound dressing. KW - biomaterials KW - crystallization KW - electrospinning KW - polypeptoids KW - thermoresponsive Y1 - 2016 U6 - https://doi.org/10.1002/marc.201500502 SN - 1022-1336 SN - 1521-3927 VL - 37 SP - 100 EP - 104 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Tetali, Sarada D. A1 - Jankowski, Vera A1 - Luetzow, Karola A1 - Kratz, Karl A1 - Lendlein, Andreas A1 - Jankowski, Joachim T1 - Adsorption capacity of poly(ether imide) microparticles to uremic toxins JF - Clinical hemorheology and microcirculation : blood flow and vessels N2 - Uremia is a phenomenon caused by retention of uremic toxins in the plasma due to functional impairment of kidneys in the elimination of urinary waste products. Uremia is presently treated by dialysis techniques like hemofiltration, dialysis or hemodiafiltration. However, these techniques in use are more favorable towards removing hydrophilic than hydrophobic uremic toxins. Hydrophobic uremic toxins, such as hydroxy hipuric acid (OH-HPA), phenylacetic acid (PAA), indoxyl sulfate (IDS) and p-cresylsulfate (pCRS), contribute substantially to the progression of chronic kidney disease (CKD) and cardiovascular disease. Therefore, objective of the present study is to test adsorption capacity of highly porous microparticles prepared from poly(ether imide) (PEI) as an alternative technique for the removal of uremic toxins. Two types of nanoporous, spherically shaped microparticles were prepared from PEI by a spraying/coagulation process. PEI particles were packed into a preparative HPLC column to which a mixture of the four types of uremic toxins was injected and eluted with ethanol. Eluted toxins were quantified by analytical HPLC. PEI particles were able to adsorb all four toxins, with the highest affinity for PAA and pCR. IDS and OH-HPA showed a partially non-reversible binding. In summary, PEI particles are interesting candidates to be explored for future application in CKD. KW - Adsorption of uremic toxins KW - chronic kidney disease (CKD) KW - hydrophobic uremic toxins KW - poly(ether imide) KW - microparticles KW - uremia Y1 - 2016 U6 - https://doi.org/10.3233/CH-152026 SN - 1386-0291 SN - 1875-8622 VL - 61 SP - 657 EP - 665 PB - IOS Press CY - Amsterdam ER - TY - JOUR A1 - Sun, Jing A1 - Cernoch, Peter A1 - Völkel, Antje A1 - Wei, Yuhan A1 - Ruokolainen, Janne A1 - Schlaad, Helmut T1 - Aqueous Self-Assembly of a Protein-Mimetic Ampholytic Block Copolypeptide JF - Macromolecules : a publication of the American Chemical Society N2 - This report describes the aggregation behavior of an ABC-type ampholytic block copolypeptide, poly(ethylene oxide)-block-poly(L-lysine)-block-poly(L-glutamate), in aqueous media in dependence of pH. Polypeptide secondary structures and self-assemblies are investigated by circular dichroism (CD), Fourier transform infrared (FT-IR) and NMR spectroscopy, zeta potential measurements, analytical ultracentrifugation (AUC), dynamic/static light scattering (DLS/SLS), and cryogenic transmission electron microscopy (cryoTEM). The polymer chains tend to form vesicles when the hydrophobic polypeptide helix is located at the chain end (acidic pH) and are existing as single chains when it is located in the center and flanked by the two hydrophilic segments (basic pH). Precipitation occurs in the intermediate pH range due to polyion complexation of the charged polypeptide segments. Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.6b00817 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 5494 EP - 5501 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Sun, Haitao A1 - Ryno, Sean A1 - Zhong, Cheng A1 - Ravva, Mahesh Kumar A1 - Sun, Zhenrong A1 - Körzdörfer, Thomas A1 - Bredas, Jean-Luc T1 - Ionization Energies, Electron Affinities, and Polarization Energies of Organic Molecular Crystals: Quantitative Estimations from a Polarizable Continuum Model (PCM)-Tuned Range-Separated Density Functional Approach JF - Journal of chemical theory and computation N2 - We propose a new methodology for the first principles description of the electronic properties relevant for charge transport in organic molecular crystals. This methodology, which is based on the combination of a nonempirical, optimally tuned range separated hybrid functional with the polarizable continuum model, is applied to a series of eight representative molecular semiconductor crystals. We show that it provides ionization energies, electron affinities, and transport gaps in very good agreement with experimental values, as well as with the results of many-body perturbation theory-within the GW approximation at a fraction of the computational cost. Hence, this approach represents an easily applicable and computationally efficient tool to estimate the gas-to crystal phase shifts of the frontier-orbital quasiparticle energies in organic electronic materials. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jctc.6b00225 SN - 1549-9618 SN - 1549-9626 VL - 12 SP - 2906 EP - 2916 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Strauch, Peter A1 - Kossmann, Alexander A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - EPR on bis(1,2-dithiosquarato)cuprate(II) in the bis(1,2-dithiosquarato)nickelate(II) host lattice - structure and spectroscopy JF - Chemical papers N2 - EPR spectroscopy is a well suited analytical tool to monitor the electronic situation around paramagnetic metal centres as copper(II) and therefore the structural influences on the paramagnetic ion. 1,2-Dithiosquaratometalates are available by direct synthesis from metal salts with dipotassium-1,2-dithiosquarate and the appropriate counter cations. Synthesis and characterisation of bis(benzyltributylammonium)1,2-dithiosquaratonickelate(II), (BzlBu(3)N)(2)[Ni(dtsq)(2)], and bis(benzyltributylammonium)1,2-dithiosquaratocuprate(II), (BzlBu(3)N)(2)[Cu(dtsq)(2)], with benzyltributylammonium as the counter ion is reported and the X-ray structures of two complexes, (BzlBu(3)N)(2)[Ni(dtsq)(2)] and (BzlBu(3)N)(2)[Cu(dtsq)(2)], are presented. Both complexes, crystallising in the monoclinic space group P2(1)/c, are isostructural with only small differences in the coordination sphere due to the different metal ions. The diamagnetic nickel complex is therefore well suited as a host lattice for the paramagnetic Cu(II) complex to measure EPR for additional structural information. (c) 2015 Institute of Chemistry, Slovak Academy of Sciences KW - 1,2-dithiosquarate KW - 1,2-dithiosquaratometalate KW - X-ray structure KW - EPR spectroscopy Y1 - 2016 U6 - https://doi.org/10.1515/chempap-2015-0154 SN - 0366-6352 SN - 1336-9075 VL - 70 SP - 61 EP - 68 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Storch, Golo A1 - Maier, Frank A1 - Wessig, Pablo A1 - Trapp, Oliver T1 - Rotational Barriers of Substituted BIPHEP Ligands: A Comparative Experimental and Theoretical Study JF - European journal of organic chemistry N2 - The interconversion barriers of 14 different 3,3- and 5,5-disubstituted tropos BIPHEP [2,2-bis(diphenylphosphino)-1,1-biphenyl] and BIPHEP(O) [2,2-bis(diphenylphosphoryl)-1,1-biphenyl] ligands were investigated by enantioselective dynamic high performance liquid chromatography (DHPLC) and DFT calculations using the B3LYP/6-31G* and M06-2X/6-31G* levels of theory. The experimentally determined enantiomerization barriers varied from 86.8 to 101.4 kJmol(-1) and were found to be in excellent agreement with the calculated data. The root-mean-square deviations are 7.3 kJmol(-1) for the B3LYP functional and 11.3 kJmol(-1) for the M06-2X method. KW - Rotational barriers KW - Density functional calculations KW - Enantioselectivity KW - P ligands KW - Biaryls KW - Liquid chromatography Y1 - 2016 U6 - https://doi.org/10.1002/ejoc.201600836 SN - 1434-193X SN - 1099-0690 VL - 22 SP - 5123 EP - 5126 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Steeples, Elliot A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Esposito, Davide T1 - Amino acid-derived N-heterocyclic carbene palladium complexes for aqueous phase Suzuki-Miyaura couplings JF - New journal of chemistry N2 - In this work, three ligands produced from amino acids were synthesized and used to produce five bis- and PEPPSI-type palladium-NHC complexes using a novel synthesis route from sustainable starting materials. Three of these complexes were used as precatalysts in the aqueous-phase Suzuki-Miyaura coupling of various substrates displaying high activity. TEM and mercury poisoning experiments provide evidence for Pd-nanoparticle formation stabilized in water. Y1 - 2016 U6 - https://doi.org/10.1039/c5nj03337c SN - 1144-0546 SN - 1369-9261 VL - 40 SP - 4922 EP - 4930 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Soliveres, Santiago A1 - Manning, Peter A1 - Prati, Daniel A1 - Gossner, Martin M. A1 - Alt, Fabian A1 - Arndt, Hartmut A1 - Baumgartner, Vanessa A1 - Binkenstein, Julia A1 - Birkhofer, Klaus A1 - Blaser, Stefan A1 - Bluethgen, Nico A1 - Boch, Steffen A1 - Boehm, Stefan A1 - Boerschig, Carmen A1 - Buscot, Francois A1 - Diekoetter, Tim A1 - Heinze, Johannes A1 - Hoelzel, Norbert A1 - Jung, Kirsten A1 - Klaus, Valentin H. A1 - Klein, Alexandra-Maria A1 - Kleinebecker, Till A1 - Klemmer, Sandra A1 - Krauss, Jochen A1 - Lange, Markus A1 - Morris, E. Kathryn A1 - Mueller, Joerg A1 - Oelmann, Yvonne A1 - Overmann, Jörg A1 - Pasalic, Esther A1 - Renner, Swen C. A1 - Rillig, Matthias C. A1 - Schaefer, H. Martin A1 - Schloter, Michael A1 - Schmitt, Barbara A1 - Schoening, Ingo A1 - Schrumpf, Marion A1 - Sikorski, Johannes A1 - Socher, Stephanie A. A1 - Solly, Emily F. A1 - Sonnemann, Ilja A1 - Sorkau, Elisabeth A1 - Steckel, Juliane A1 - Steffan-Dewenter, Ingolf A1 - Stempfhuber, Barbara A1 - Tschapka, Marco A1 - Tuerke, Manfred A1 - Venter, Paul A1 - Weiner, Christiane N. A1 - Weisser, Wolfgang W. A1 - Werner, Michael A1 - Westphal, Catrin A1 - Wilcke, Wolfgang A1 - Wolters, Volkmar A1 - Wubet, Tesfaye A1 - Wurst, Susanne A1 - Fischer, Markus A1 - Allan, Eric T1 - Locally rare species influence grassland ecosystem multifunctionality JF - Philosophical transactions of the Royal Society of London : B, Biological sciences N2 - Species diversity promotes the delivery of multiple ecosystem functions (multifunctionality). However, the relative functional importance of rare and common species in driving the biodiversity multifunctionality relationship remains unknown. We studied the relationship between the diversity of rare and common species (according to their local abundances and across nine different trophic groups), and multifunctionality indices derived from 14 ecosystem functions on 150 grasslands across a land use intensity (LUI) gradient. The diversity of above- and below-ground rare species had opposite effects, with rare above-ground species being associated with high levels of multifunctionality, probably because their effects on different functions did not trade off against each other. Conversely, common species were only related to average, not high, levels of multifunctionality, and their functional effects declined with LUI. Apart from the community level effects of diversity, we found significant positive associations between the abundance of individual species and multifunctionality in 6% of the species tested. Species specific functional effects were best predicted by their response to LUI: species that declined in abundance with land use intensification were those associated with higher levels of multifunctionality. Our results highlight the importance of rare species for ecosystem multifunctionality and help guiding future conservation priorities. KW - biodiversity KW - common species KW - ecosystem function KW - identity hypothesis KW - land use KW - multitrophic Y1 - 2016 U6 - https://doi.org/10.1098/rstb.2015.0269 SN - 0962-8436 SN - 1471-2970 VL - 371 SP - 3175 EP - 3185 PB - Royal Society CY - London ER - TY - JOUR A1 - Senge, Mathias O. A1 - Flanagan, Keith J. A1 - Ryan, Aoife A. A1 - Ryppa, Claudia A1 - Donath, Mandy A1 - Twamley, Brendan T1 - Conformational and structural studies of meso monosubstituted metalloporphyrins-Edge-on molecular interactions of porphyrins in crystals JF - Tetrahedron N2 - A series of meso monosubstituted metalloporphyrins were synthesized to assess the structural chemistry of porphyrins with only one substituent. The structures of four nickel(II) and zinc(II) complexes with either alkyl or aryl residues indicate primarily planar macrocycles. This gives rise to a different type of pi-interactions in the crystal and the formation of dimeric, trimeric or tetrameric porphyrin units that function as building blocks for the overall crystal structure. Notably, some structures exhibit a unique edge-on packing of porphyrins, while the molecules of (5-n-butylporphyrinato)nickel(II) forms an unusual bilayer type structure where rows of two porphyrin macrocycles are separated by the alkyl residues arranged in a head-to-head fashion. This adds to the canon of intermolecular porphyrin packing arrangements and is of relevance for the preparation of ordered nanoscopic porphyrin devices. (C) 2015 Elsevier Ltd. All rights reserved. KW - Porphyrins KW - Conformational analysis KW - Tetrapyrroles KW - Crystal structure KW - Crystal packing Y1 - 2016 U6 - https://doi.org/10.1016/j.tet.2015.11.008 SN - 0040-4020 VL - 72 SP - 105 EP - 115 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Secker, Christian A1 - Voelkel, Antje A1 - Tiersch, Brigitte A1 - Koetz, Joachim A1 - Schlaad, Helmut T1 - Thermo-Induced Aggregation and Crystallization of Block Copolypeptoids in Water JF - Macromolecules : a publication of the American Chemical Society N2 - Block copolypeptoids comprising a thermosensitive, crystallizable poly(N-(n-propyl)glycine) block and a watersoluble poly(N-methylglycine) block, P70My (y = 23, 42, 76, 153, and 290), were synthesized bY ring-opening polymerization of the corresponding N-alkylglycine N-carboxyanhydrides (NCAs) and examined according to their thermo-induced aggregation and crystallization in water by turbidimetty, micro-differential scanning calorimetry (micro-DSC); cryogenic scanning electron microscopy (cryo-SEM), analytical ultracentrifugation (AUC), and static light scattering (SLS). At a temperature above the cloud point temperature, the initially formed micellar aggregates started to crystallize and grow into larger complex assemblies of about 100-500 nm, exhibiting flower-like (P70M23), ellipsoidal (P70M42 and P70M72) or irregular shapes (P70M153 and.P70M290). Y1 - 2016 U6 - https://doi.org/10.1021/acs.macromol.5b02481 SN - 0024-9297 SN - 1520-5835 VL - 49 SP - 979 EP - 985 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Sechi, Antonio A1 - Freitas, Joana M. G. A1 - Wünnemann, Patrick A1 - Töpel, Alexander A1 - Paschoalin, Rafaella Takehara A1 - Ullmann, Sabrina A1 - Schröder, Ricarda A1 - Aydin, Gülcan A1 - Rütten, Stephan A1 - Böker, Alexander A1 - Zenke, Martin A1 - Pich, Andrij T1 - Surface-Grafted Nanogel Arrays Direct Cell Adhesion and Motility JF - Advanced materials interfaces N2 - It has long been appreciated that material chemistry and topology profoundly affect cell adhesion and migration. Here, aqueous poly(N- isopropyl acrylamide) nanogels are designed, synthesized and printed in form of colloidal arrays on glass substrates using wrinkled polydimethylsiloxane templates. Using low-temperature plasma treatment, nanogels are chemically grafted onto glass supports thus leading to highly stable nanogel layers in cell culture media. Liquid cell atomic force microscopy investigations show that surface-grafted nanogels retain their swelling behavior in aqueous media and that extracellular matrix protein coating do not alter their stability and topography. It is demonstrated that surface-grafted nanogels could serve as novel substrates for the analysis of cell adhesion and migration. Nanogels influence size, speed, and dynamics of focal adhesions and cell motility forcing cells to move along highly directional trajectories. Moreover, modulation of nanogel state or spacing serves as an effective tool for regulation of cell motility. It is suggested that nanogel arrays deposited on solid surfaces could be used to provide a precise and tunable system to understand and control cell migration. Additionally, such nanogel arrays will contribute to the development of implantable systems aimed at supporting and enhancing cell migration during, for instance, wound healing and tissue regeneration. Y1 - 2016 U6 - https://doi.org/10.1002/admi.201600455 SN - 2196-7350 VL - 3 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Schürmann, Robin Mathis A1 - Bald, Ilko T1 - Decomposition of DNA Nucleobases by Laser Irradiation of Gold Nanoparticles Monitored by Surface-Enhanced Raman Scattering JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Different approaches have been proposed to treat cancer cells using gold nanoparticles (AuNPs) in combination with radiation ranging from infrared lasers to high-energy ion beams. Here we study the decomposition of the DNA/RNA nucleobases thymine (T) and uracil (U) and the well-known radiosensitizer 5-bromouracil (BrU) in close vicinity to AuNPs, which are irradiated with a nanosecond pulsed laser (532 nm) matching the surface plasmon resonance of the AuNPs. The induced damage of nucleobases is analyzed by UV-vis absorption spectroscopy and surface-enhanced Raman scattering (SERS). A clear DNA damage is observed upon laser irradiation. SERS spectra indicate the fragmentation of the aromatic ring system of T and U as the dominant form of damage, whereas with BrU mainly the cleavage of the Br-C bond and formation of Br- ions is observed. This is accompanied by a partial transformation of BrU into U. The observed damage is at least partly ascribed to the intermediate formation of low energy electrons from the laser-excited AuNPs and subsequent dissociative electron attachment to T, U, and BrU. These reactions represent basic DNA damage pathways occurring on the one hand in plasmon-assisted cancer therapy and on the other hand in conventional cancer radiation therapy using AuNPs as sensitizing agents. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpcc.5b10564 SN - 1932-7447 VL - 120 SP - 3001 EP - 3009 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schürings, Marco-Philipp A1 - Nevskyi, Oleksii A1 - Eliasch, Kamill A1 - Michel, Ann-Katrin A1 - Liu, Bing A1 - Pich, Andrij A1 - Böker, Alexander A1 - von Plessen, Gero A1 - Wöll, Dominik T1 - Diffusive Motion of Linear Microgel Assemblies in Solution JF - Polymers N2 - Due to the ability of microgels to rapidly contract and expand in response to external stimuli, assemblies of interconnected microgels are promising for actuation applications, e.g., as contracting fibers for artificial muscles. Among the properties determining the suitability of microgel assemblies for actuation are mechanical parameters such as bending stiffness and mobility. Here, we study the properties of linear, one-dimensional chains of poly(N-vinylcaprolactam) microgels dispersed in water. They were fabricated by utilizing wrinkled surfaces as templates and UV-cross-linking the microgels. We image the shapes of the chains on surfaces and in solution using atomic force microscopy (AFM) and fluorescence microscopy, respectively. In solution, the chains are observed to execute translational and rotational diffusive motions. Evaluation of the motions yields translational and rotational diffusion coefficients and, from the translational diffusion coefficient, the chain mobility. The microgel chains show no perceptible bending, which yields a lower limit on their bending stiffness. KW - microgels KW - linear assemblies KW - in situ fluorescence microscopy KW - shape analysis KW - rotational diffusion KW - translational diffusion KW - bending stiffness KW - actuation Y1 - 2016 U6 - https://doi.org/10.3390/polym8120413 SN - 2073-4360 VL - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Schöne, Anne-Christin A1 - Schulz, Burkhard A1 - Lendlein, Andreas T1 - Stimuli Responsive and Multifunctional Polymers: Progress in Materials and Applications JF - Macromolecular rapid communications Y1 - 2016 U6 - https://doi.org/10.1002/marc.201600650 SN - 1022-1336 SN - 1521-3927 VL - 37 SP - 1856 EP - 1859 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schöne, Anne-Christin A1 - Kratz, Karl A1 - Schulz, Burkhard A1 - Lendlein, Andreas T1 - The relevance of hydrophobic segments in multiblock copolyesterurethanes for their enzymatic degradation at the air-water interface JF - Polymer : the international journal for the science and technology of polymers N2 - The interplay of an enzyme with a multiblock copolymer PDLCL containing two segments of different hydrophilicity and degradability is explored in thin films at the air-water interface. The enzymatic degradation was studied in homogenous Langmuir monolayers, which are formed when containing more than 40 wt% oligo(epsilon-caprolactone) (OCL). Enzymatic degradation rates were significantly reduced with increasing content of hydrophobic oligo(omega-pentadecalactone) (OPDL). The apparent deceleration of the enzymatic process is caused by smaller portion of water-soluble degradation fragments formed from degradable OCL fragments. Beside the film degradation, a second competing process occurs after adding lipase from Pseudomonas cepacia into the subphase, namely the enrichment of the lipase molecules in the polymeric monolayer. The incorporation of the lipase into the Langmuir film is experimentally revealed by concurrent surface area enlargement and by Brewster angle microscopy (BAM). Aside from the ability to provide information about the degradation behavior of polymers, the Langmuir monolayer degradation (LMD) approach enables to investigate polymer-enzyme interactions for non-degradable polymers. (C) 2016 Elsevier Ltd. All rights reserved. KW - Multiblock copolymer KW - Enzymatic polymer degradation KW - Oligo(omega-pentadecalactone) KW - Oligo(epsilon-caprolactone) KW - Langmuir monolayer degradation technique Y1 - 2016 U6 - https://doi.org/10.1016/j.polymer.2016.09.001 SN - 0032-3861 SN - 1873-2291 VL - 102 SP - 92 EP - 98 PB - Elsevier CY - Oxford ER -