TY - JOUR A1 - Madaan, Nitesh A1 - Romriell, Naomi A1 - Tuscano, Joshua A1 - Schlaad, Helmut A1 - Linford, Matthew R. T1 - Introduction of thiol moieties, including their thiol-ene reactions and air oxidation, onto polyelectrolyte multilayer substrates JF - Journal of colloid and interface science KW - Thiol-ene KW - Layer-by-layer KW - XPS KW - ToF-SIMS KW - Hydrophobic KW - AFM KW - Ellipsometry Y1 - 2015 U6 - https://doi.org/10.1016/j.jcis.2015.08.017 SN - 0021-9797 SN - 1095-7103 VL - 459 SP - 199 EP - 205 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Mai, Tobias A1 - Boye, Susanne A1 - Yuan, Jiayin A1 - Voelkel, Antje A1 - Graewert, Marlies A1 - Günter, Christina A1 - Lederer, Albena A1 - Taubert, Andreas T1 - Poly(ethylene oxide)-based block copolymers with very high molecular weights for biomimetic calcium phosphate mineralization JF - RSC Advances N2 - The present article is among the first reports on the effects of poly(ampholyte)s and poly(betaine) s on the biomimetic formation of calcium phosphate. We have synthesized a series of di- and triblock copolymers based on a non-ionic poly(ethylene oxide) block and several charged methacrylate monomers, 2-(trimethylammonium) ethyl methacrylate chloride, 2-((3-cyanopropyl)-dimethylammonium)ethyl methacrylate chloride, 3-sulfopropyl methacrylate potassium salt, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide. The resulting copolymers are either positively charged, ampholytic, or betaine block copolymers. All the polymers have very high molecular weights of over 10(6) g mol(-1). All polymers are water-soluble and show a strong effect on the precipitation and dissolution of calcium phosphate. The strongest effects are observed with triblock copolymers based on a large poly(ethylene oxide) middle block (nominal M-n = 100 000 g mol(-1)). Surprisingly, the data show that there is a need for positive charges in the polymers to exert tight control over mineralization and dissolution, but that the exact position of the charge in the polymer is of minor importance for both calcium phosphate precipitation and dissolution. Y1 - 2015 U6 - https://doi.org/10.1039/c5ra20035k SN - 2046-2069 VL - 5 IS - 125 SP - 103494 EP - 103505 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Mai, Tobias A1 - Boye, Susanne A1 - Yuan, Jiayin A1 - Völkel, Antje A1 - Gräwert, Marlies A1 - Günter, Christina A1 - Lederer, Albena A1 - Taubert, Andreas T1 - Poly(ethylene oxide)-based block copolymers with very high molecular weights for biomimetic calcium phosphate mineralization N2 - The present article is among the first reports on the effects of poly(ampholyte)s and poly(betaine)s on the biomimetic formation of calcium phosphate. We have synthesized a series of di- and triblock copolymers based on a non-ionic poly(ethylene oxide) block and several charged methacrylate monomers, 2-(trimethylammonium)ethyl methacrylate chloride, 2-((3-cyanopropyl)-dimethylammonium)ethyl methacrylate chloride, 3-sulfopropyl methacrylate potassium salt, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide. The resulting copolymers are either positively charged, ampholytic, or betaine block copolymers. All the polymers have very high molecular weights of over 106 g mol−1. All polymers are water-soluble and show a strong effect on the precipitation and dissolution of calcium phosphate. The strongest effects are observed with triblock copolymers based on a large poly(ethylene oxide) middle block (nominal Mn = 100 000 g mol−1). Surprisingly, the data show that there is a need for positive charges in the polymers to exert tight control over mineralization and dissolution, but that the exact position of the charge in the polymer is of minor importance for both calcium phosphate precipitation and dissolution. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 208 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-85299 ER - TY - JOUR A1 - Mai, Tobias A1 - Boye, Susanne A1 - Yuan, Jiayin A1 - Völkel, Antje A1 - Gräwert, Marlies A1 - Günter, Christina A1 - Lederer, Albena A1 - Taubert, Andreas T1 - Poly(ethylene oxide)-based block copolymers with very high molecular weights for biomimetic calcium phosphate mineralization JF - RSC Advances : an international journal to further the chemical sciences N2 - The present article is among the first reports on the effects of poly(ampholyte)s and poly(betaine)s on the biomimetic formation of calcium phosphate. We have synthesized a series of di- and triblock copolymers based on a non-ionic poly(ethylene oxide) block and several charged methacrylate monomers, 2-(trimethylammonium)ethyl methacrylate chloride, 2-((3-cyanopropyl)-dimethylammonium)ethyl methacrylate chloride, 3-sulfopropyl methacrylate potassium salt, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide. The resulting copolymers are either positively charged, ampholytic, or betaine block copolymers. All the polymers have very high molecular weights of over 106 g mol−1. All polymers are water-soluble and show a strong effect on the precipitation and dissolution of calcium phosphate. The strongest effects are observed with triblock copolymers based on a large poly(ethylene oxide) middle block (nominal Mn = 100 000 g mol−1). Surprisingly, the data show that there is a need for positive charges in the polymers to exert tight control over mineralization and dissolution, but that the exact position of the charge in the polymer is of minor importance for both calcium phosphate precipitation and dissolution. Y1 - 2015 U6 - https://doi.org/10.1039/c5ra20035k SN - 2046-2069 IS - 5 SP - 103494 EP - 103505 PB - RSC Publishing CY - London ER - TY - JOUR A1 - Mardoukhi, Yousof A1 - Jeon, Jae-Hyung A1 - Metzler, Ralf T1 - Geometry controlled anomalous diffusion in random fractal geometries BT - looking beyond the infinite cluster JF - Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies N2 - We investigate the ergodic properties of a random walker performing (anomalous) diffusion on a random fractal geometry. Extensive Monte Carlo simulations of the motion of tracer particles on an ensemble of realisations of percolation clusters are performed for a wide range of percolation densities. Single trajectories of the tracer motion are analysed to quantify the time averaged mean squared displacement (MSD) and to compare this with the ensemble averaged MSD of the particle motion. Other complementary physical observables associated with ergodicity are studied, as well. It turns out that the time averaged MSD of individual realisations exhibits non-vanishing fluctuations even in the limit of very long observation times as the percolation density approaches the critical value. This apparent non-ergodic behaviour concurs with the ergodic behaviour on the ensemble averaged level. We demonstrate how the non-vanishing fluctuations in single particle trajectories are analytically expressed in terms of the fractal dimension and the cluster size distribution of the random geometry, thus being of purely geometrical origin. Moreover, we reveal that the convergence scaling law to ergodicity, which is known to be inversely proportional to the observation time T for ergodic diffusion processes, follows a power-law BT� h with h o 1 due to the fractal structure of the accessible space. These results provide useful measures for differentiating the subdiffusion on random fractals from an otherwise closely related process, namely, fractional Brownian motion. Implications of our results on the analysis of single particle tracking experiments are provided. Y1 - 2015 U6 - https://doi.org/10.1039/c5cp03548a SN - 1439-7641 IS - 17 SP - 30134 EP - 30147 PB - Wiley-VCH Verl. CY - Weinheim ER - TY - GEN A1 - Mardoukhi, Yousof A1 - Jeon, Jae-Hyung A1 - Metzler, Ralf T1 - Geometry controlled anomalous diffusion in random fractal geometries BT - looking beyond the infinite cluster N2 - We investigate the ergodic properties of a random walker performing (anomalous) diffusion on a random fractal geometry. Extensive Monte Carlo simulations of the motion of tracer particles on an ensemble of realisations of percolation clusters are performed for a wide range of percolation densities. Single trajectories of the tracer motion are analysed to quantify the time averaged mean squared displacement (MSD) and to compare this with the ensemble averaged MSD of the particle motion. Other complementary physical observables associated with ergodicity are studied, as well. It turns out that the time averaged MSD of individual realisations exhibits non-vanishing fluctuations even in the limit of very long observation times as the percolation density approaches the critical value. This apparent non-ergodic behaviour concurs with the ergodic behaviour on the ensemble averaged level. We demonstrate how the non-vanishing fluctuations in single particle trajectories are analytically expressed in terms of the fractal dimension and the cluster size distribution of the random geometry, thus being of purely geometrical origin. Moreover, we reveal that the convergence scaling law to ergodicity, which is known to be inversely proportional to the observation time T for ergodic diffusion processes, follows a power-law BT� h with h o 1 due to the fractal structure of the accessible space. These results provide useful measures for differentiating the subdiffusion on random fractals from an otherwise closely related process, namely, fractional Brownian motion. Implications of our results on the analysis of single particle tracking experiments are provided. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 207 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-85247 ER - TY - JOUR A1 - Martinez-Mesa, Aliezer A1 - Saalfrank, Peter T1 - Semiclassical modelling of finite-pulse effects on non-adiabatic photodynamics via initial condition filtering: The predissociation of NaI as a test case JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Femtosecond-laser pulse driven non-adiabatic spectroscopy and dynamics in molecular and condensed phase systems continue to be a challenge for theoretical modelling. One of the main obstacles is the "curse of dimensionality" encountered in non-adiabatic, exact wavepacket propagation. A possible route towards treating complex molecular systems is via semiclassical surface-hopping schemes, in particular if they account not only for non-adiabatic post-excitation dynamics but also for the initial optical excitation. One such approach, based on initial condition filtering, will be put forward in what follows. As a simple test case which can be compared with exact wavepacket dynamics, we investigate the influence of the different parameters determining the shape of a laser pulse (e.g., its finite width and a possible chirp) on the predissociation dynamics of a NaI molecule, upon photoexcitation of the A(0(+)) state. The finite-pulse effects are mapped into the initial conditions for semiclassical surface-hopping simulations. The simulated surface-hopping diabatic populations are in qualitative agreement with the quantum mechanical results, especially concerning the subpicosend photoinduced dynamics, the main deviations being the relative delay of the non-adiabatic transitions in the semiclassical picture. Likewise, these differences in the time-dependent electronic populations calculated via the semiclassical and the quantum methods are found to have a mild influence on the overall probability density distribution. As a result, the branching ratios between the bound and the dissociative reaction channels and the time-evolution of the molecular wavepacket predicted by the semiclassical method agree with those computed using quantum wavepacket propagation. Implications for more challenging molecular systems are given. (C) 2015 AIP Publishing LLC. Y1 - 2015 U6 - https://doi.org/10.1063/1.4919780 SN - 0021-9606 SN - 1089-7690 VL - 142 IS - 19 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Matis, Jochen Rene A1 - Schoenborn, Jan Boyke A1 - Saalfrank, Peter T1 - A multi-reference study of the byproduct formation for a ring-closed dithienylethene photoswitch JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Photodriven molecular switches are sometimes hindered in their performance by forming byproducts which act as dead ends in sequences of switching cycles, leading to rapid fatigue effects. Understanding the reaction pathways to unwanted byproducts is a prerequisite for preventing them. This article presents a study of the photochemical reaction pathways for byproduct formation in the photochromic switch 1,2-bis-(3-thienyl)-ethene. Specifically, using single-and multi-reference methods the post-deexcitation reaction towards the byproduct in the electronic ground state S-0 when starting from the S-1-S-0 conical intersection (CoIn), is considered in detail. We find an unusual low-energy pathway, which offers the possibility for the formation of a dyotropic byproduct. Several high-energy pathways can be excluded with high probability. Y1 - 2015 U6 - https://doi.org/10.1039/c5cp00987a SN - 1463-9076 SN - 1463-9084 VL - 17 IS - 21 SP - 14088 EP - 14095 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Matis, Jochen René A1 - Schönborn, Jan Boyke A1 - Saalfrank, Peter T1 - A multi-reference study of the byproduct formation for a ring-closed dithienylethene photoswitch N2 - Photodriven molecular switches are sometimes hindered in their performance by forming byproducts which act as dead ends in sequences of switching cycles, leading to rapid fatigue effects. Understanding the reaction pathways to unwanted byproducts is a prerequisite for preventing them. This article presents a study of the photochemical reaction pathways for byproduct formation in the photochromic switch 1,2-bis-(3-thienyl)-ethene. Specifically, using single- and multi-reference methods the post-deexcitation reaction towards the byproduct in the electronic ground state S0 when starting from the S1–S0 conical intersection (CoIn), is considered in detail. We find an unusual low-energy pathway, which offers the possibility for the formation of a dyotropic byproduct. Several high-energy pathways can be excluded with high probability. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 215 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89594 SP - 14088 EP - 14095 ER - TY - JOUR A1 - Matis, Jochen René A1 - Schönborn, Jan Boyke A1 - Saalfrank, Peter T1 - A multi-reference study of the byproduct formation for a ring-closed dithienylethene photoswitch JF - Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies N2 - Photodriven molecular switches are sometimes hindered in their performance by forming byproducts which act as dead ends in sequences of switching cycles, leading to rapid fatigue effects. Understanding the reaction pathways to unwanted byproducts is a prerequisite for preventing them. This article presents a study of the photochemical reaction pathways for byproduct formation in the photochromic switch 1,2-bis-(3-thienyl)-ethene. Specifically, using single- and multi-reference methods the post-deexcitation reaction towards the byproduct in the electronic ground state S0 when starting from the S1–S0 conical intersection (CoIn), is considered in detail. We find an unusual low-energy pathway, which offers the possibility for the formation of a dyotropic byproduct. Several high-energy pathways can be excluded with high probability. Y1 - 2015 U6 - https://doi.org/10.1039/C5CP00987A SN - 1463-9076 SN - 1463-9084 IS - 17 SP - 14088 EP - 14095 PB - The Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Megow, Jörg T1 - How Van der Waals Interactions Influence the Absorption Spectra of Pheophorbide a Complexes: A Mixed Quantum-Classical Study JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - The computation of dispersive site energy shifts due to van der Waals interaction (London dispersion forces) was combined with mixed quantum-classical methodology to calculate the linear optical absorption spectra of large pheophorbide a (Pheo) dendrimers. The computed spectra agreed very well with the measurements considering three characteristic optical features occurring with increasing aggregate size: a strong line broadening, a redshift, and a low-energy shoulder. The improved mixed quantum-classical methodology is considered a powerful tool in investigating molecular aggregates. KW - dispersion KW - electrostatic interactions KW - mixed quantum-classical methodology KW - optical spectra KW - supramolecular chemistry Y1 - 2015 U6 - https://doi.org/10.1002/cphc.201500326 SN - 1439-4235 SN - 1439-7641 VL - 16 IS - 14 SP - 3101 EP - 3107 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Megow, Jörg A1 - Körzdörfer, Thomas A1 - Renger, Thomas A1 - Sparenberg, Mino A1 - Blumstengel, Sylke A1 - Henneberger, Fritz A1 - May, Volkhard T1 - Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift Delta epsilon(m) is mainly caused by dispersion effects and depends sensitively on the molecules specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide Delta epsilon(m)= -QW(m) in two factors, where Q depends only on the molecular species and accounts for all nonresonant electronic transitions contributing to the dispersion while W-m is a geometry factor expressing the site dependence of the shift in a given molecular structure. The ability of our approach to predict absorption spectra is demonstrated using the example of polycrystalline films of 3,4,9,10-perylenetetracarboxylic diimide (PTCDI). Y1 - 2015 U6 - https://doi.org/10.1021/acs.jpcc.5b01587 SN - 1932-7447 VL - 119 IS - 10 SP - 5747 EP - 5751 PB - American Chemical Society CY - Washington ER - TY - INPR A1 - Megow, Jörg A1 - Körzdörfer, Thomas A1 - Renger, Thomas A1 - Sparenberg, Mino A1 - Blumstengel, Sylke A1 - May, Volkhard T1 - Reply to "Comment on 'Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction" T2 - The journal of physical chemistry : C, Nanomaterials and interfaces Y1 - 2015 U6 - https://doi.org/10.1021/acs.jpcc.5b05536 SN - 1932-7447 VL - 119 IS - 32 SP - 18818 EP - 18820 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Megow, Jörg A1 - Röhr, Merle I. S. A1 - Busch, Marcel A1 - Renger, Thomas A1 - Mitric, Roland A1 - Kirstein, Stefan A1 - Rabe, Jürgen P. A1 - May, Volkhard T1 - Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - The simulation of the optical properties of supramolecular aggregates requires the development of methods, which are able to treat a large number of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chemistry, the Frenkel exciton model is a valuable alternative. In this work we show how the Frenkel exciton model can be extended in order to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding molecules. The experimentally observed splitting is well explained by the site-dependent energy shift of molecules placed at the inner or outer side of the double-walled tube, respectively. Therefore we can conclude that inclusion of the site-dependent dispersive effect in the theoretical description of optical properties of nanoscaled dye aggregates is mandatory. Y1 - 2015 U6 - https://doi.org/10.1039/c4cp05945j SN - 1463-9076 SN - 1463-9084 VL - 17 IS - 10 SP - 6741 EP - 6747 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Megow, Jörg A1 - Röhr, Merle I. S. A1 - Schmidt am Busch, Marcel A1 - Renger, Thomas A1 - Mitrić, Roland A1 - Kirstein, Stefan A1 - Rabe, Jürgen P. A1 - May, Volkhard T1 - Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates N2 - The simulation of the optical properties of supramolecular aggregates requires the development of methods, which are able to treat a large number of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chemistry, the Frenkel exciton model is a valuable alternative. In this work we show how the Frenkel exciton model can be extended in order to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding molecules. The experimentally observed splitting is well explained by the site-dependent energy shift of molecules placed at the inner or outer side of the double-walled tube, respectively. Therefore we can conclude that inclusion of the site-dependent dispersive effect in the theoretical description of optical properties of nanoscaled dye aggregates is mandatory. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 191 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-79978 SP - 6741 EP - 6747 ER - TY - JOUR A1 - Megow, Jörg A1 - Röhr, Merle I. S. A1 - Schmidt am Busch, Marcel A1 - Renger, Thomas A1 - Mitrić, Roland A1 - Kirstein, Stefan A1 - Rabe, Jürgen P. A1 - May, Volkhard T1 - Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies N2 - The simulation of the optical properties of supramolecular aggregates requires the development of methods, which are able to treat a large number of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chemistry, the Frenkel exciton model is a valuable alternative. In this work we show how the Frenkel exciton model can be extended in order to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding molecules. The experimentally observed splitting is well explained by the site-dependent energy shift of molecules placed at the inner or outer side of the double-walled tube, respectively. Therefore we can conclude that inclusion of the site-dependent dispersive effect in the theoretical description of optical properties of nanoscaled dye aggregates is mandatory. Y1 - 2015 U6 - https://doi.org/10.1039/c4cp05945j SN - 1463-9084 SN - 1463-9076 VL - 17 IS - 10 SP - 6741 EP - 6747 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Mergel, Olga A1 - Wuennemann, Patrick A1 - Simon, Ulrich A1 - Böker, Alexander A1 - Plamper, Felix A. T1 - Microgel Size Modulation by Electrochemical Switching JF - Chemistry of materials : a publication of the American Chemical Society N2 - In this work we present the first e-microgel, whose size can be adjusted by application of an electrochemical potential, as seen by dynamic light scattering (3D-DLS in dependence of equilibrium potential) and scanning force microscopy (SFM). Hereby, polyelectrolyte microgels with attracted electroactive counterions provide an effective platform for the manipulation of the microgel size by electrochemical means. The reversible switching of guest molecules, namely, hexacyanoferrates, between oxidized ferricyanide [Fe(CN)(6)](3-) and reduced ferrocyanide [Fe(CN)(6)](4-), influences the cationic host microgel, poly(N-isopropylacrylamide-co-methacrylamidopropyltrimethylammonium chloride) P(NIPAM-co-MAPTAC), and hence the swelling properties of the microgel. The combination of thermo- and redox-responsiveness in one particle leads to a novel type of multistimuli responsive material. In addition, the use of hydrodynamic voltammetry detects directly the preferred uptake of ferricyanide and enables the determination of the nominal charge ratio (ncr) between microgel and entrapped counterions at different states of switching. Further, electrochemical impedance spectroscopy allows a more detailed mechanistic insight into the microgel modulation. Y1 - 2015 U6 - https://doi.org/10.1021/acs.chemmater.5b02740 SN - 0897-4756 SN - 1520-5002 VL - 27 IS - 21 SP - 7306 EP - 7312 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Meyer, S. A1 - Raber, G. A1 - Ebert, Franziska A1 - Leffers, L. A1 - Müller, Sandra Marie A1 - Taleshi, M. S. A1 - Francesconi, Kevin A. A1 - Schwerdtle, Tanja T1 - In vitro toxicological characterisation of arsenic-containing fatty acids and three of their metabolites JF - Toxicology research N2 - Arsenic-containing fatty acids are a group of fat-soluble arsenic species (arsenolipids) which are present in marine fish and other seafood. Recently, it has been shown that arsenic-containing hydrocarbons, another group of arsenolipids, exert toxicity in similar concentrations comparable to arsenite although the toxic modes of action differ. Hence, a risk assessment of arsenolipids is urgently needed. In this study the cellular toxicity of a saturated (AsFA 362) and an unsaturated (AsFA 388) arsenic-containing fatty acid and three of their proposed metabolites (DMAV, DMAPr and thio-DMAPr) were investigated in human liver cells (HepG2). Even though both arsenic-containing fatty acids were less toxic as compared to arsenic-containing hydrocarbons and arsenite, significant effects were observable at μM concentrations. DMAV causes effects in a similar concentration range and it could be seen that it is metabolised to its highly toxic thio analogue thio-DMAV in HepG2 cells. Nevertheless, DMAPr and thio-DMAPr did not exert any cytotoxicity. In summary, our data indicate that risks to human health related to the presence of arsenic-containing fatty acids in marine food cannot be excluded. This stresses the need for a full in vitro and in vivo toxicological characterisation of these arsenolipids. Y1 - 2015 U6 - https://doi.org/10.1039/c5tx00122f SN - 2045-4538 VL - 5 IS - 4 SP - 1289 EP - 1296 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Meyer, S. A1 - Raber, G. A1 - Ebert, Franziska A1 - Leffers, L. A1 - Müller, Sandra Marie A1 - Taleshi, M. S. A1 - Francesconi, Kevin A. A1 - Schwerdtle, Tanja T1 - In vitro toxicological characterisation of arsenic-containing fatty acids and three of their metabolites N2 - Arsenic-containing fatty acids are a group of fat-soluble arsenic species (arsenolipids) which are present in marine fish and other seafood. Recently, it has been shown that arsenic-containing hydrocarbons, another group of arsenolipids, exert toxicity in similar concentrations comparable to arsenite although the toxic modes of action differ. Hence, a risk assessment of arsenolipids is urgently needed. In this study the cellular toxicity of a saturated (AsFA 362) and an unsaturated (AsFA 388) arsenic-containing fatty acid and three of their proposed metabolites (DMAV, DMAPr and thio-DMAPr) were investigated in human liver cells (HepG2). Even though both arsenic-containing fatty acids were less toxic as compared to arsenic-containing hydrocarbons and arsenite, significant effects were observable at μM concentrations. DMAV causes effects in a similar concentration range and it could be seen that it is metabolised to its highly toxic thio analogue thio-DMAV in HepG2 cells. Nevertheless, DMAPr and thio-DMAPr did not exert any cytotoxicity. In summary, our data indicate that risks to human health related to the presence of arsenic-containing fatty acids in marine food cannot be excluded. This stresses the need for a full in vitro and in vivo toxicological characterisation of these arsenolipids. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 199 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-82008 ER - TY - JOUR A1 - Mirskova, Anna N. A1 - Adamovich, Sergey N. A1 - Mirskov, Rudolf G. A1 - Kolesnikova, Olga P. A1 - Schilde, Uwe T1 - Immunoactive ionic liquids based on 2-hydroxyethylamines and 1-R-indol-3-ylsulfanylacetic acids. Crystal and molecular structure of immunodepressant tris-(2-hydroxyethyl)ammonium indol-3-ylsulfanylacetate JF - Open chemistry : formerly Central European journal of chemistry N2 - Immunoactive ionic liquids (2-hydroxyethyl) ammonium 1-R-indol-3-ylsulfanyl-acetates HN+R1R2(CH2CH2OH)center dot O-(O)CCH2S-Ind-R-3-1(1-5), were synthesized by the reaction of (2-hydroxyethyl)amines with indol-3-ylsulfanylacetic- or 1-benzylindol-3-ylsulfanylacetic acid. 1: R-1 = R-2 = CH2CH2OH, R-3 = H; 2: R-1 =CH3, R-2=CH2CH2OH, R3 = H; 3: R-1 = R-2 = CH3, R-3 = H; 4: R-1 = R-2 = CH2CH2OH, R-3 = CH2C6H5; 5: R-1 = CH3; R-2 = CH2CH2OH; R-3 = CH2C6H5. The structure of each compound was elucidated by IR, NMR H-1, C-13, and N-15 techniques and their composition was confirmed by elemental analysis. The crystal structure of tris-(2-hydroxyethyl) ammonium indol-3-ylsulfanylacetate was investigated by X-ray diffraction analysis. Immunoactive properties of the title compounds were screened. KW - Protic 2-hydroxyethylammonium ionic liquids KW - 2-Hydroxyethylammonium 1-R-indol-3-ylsulfanylacetates KW - Crystal and molecular structure KW - Immunoactive properties Y1 - 2015 U6 - https://doi.org/10.1515/chem-2015-0018 SN - 2391-5420 VL - 13 IS - 1 SP - 149 EP - 155 PB - De Gruyter Open CY - Warsaw ER - TY - THES A1 - Molinari, Valerio T1 - Ni-based materials for the catalytic conversion of lignocellulosic biomass into valuable products Y1 - 2015 ER - TY - JOUR A1 - Mondal, Suvendu Sekhar A1 - Behrens, Karsten A1 - Kelling, Alexandra A1 - Nabein, Hans-Peter A1 - Schilde, Uwe A1 - Holdt, Hans-Jürgen T1 - Two Cd-II/Co-II-Imidazolate Coordination Polymers: Syntheses, Crystal Structures, Stabilities, and Luminescent/Magnetic Properties JF - Zeitschrift für anorganische und allgemeine Chemie N2 - Cadmium(II) based 2D coordination polymer [Cd(L1)(2)(DMF)(2)] (1) (L1 = 4,5-dicyano-2-methylimidazolate, DMF = N,N'-dimethylformamide) and 2D cobalt(II)-imidazolate framework [Co(L3)(4)] (2) (L3 = 4,5-diamide-2-ethoxyimidazolate) were synthesized under solvothermal reaction conditions. The materials were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction measurement (PXRD) and single-crystal X-ray diffraction. Compound 1 has hexacoordinate Cd-II ions and forms a zigzag chain-like coordination polymer structure, whereas compound 2 exhibits a 2D square grid type structure. The thermal stability analysis reveals that 2 showed an exceptional thermal stability up to 360 degrees C. Also, 2 maintained its fully crystalline integrity in boiling water as confirmed by PXRD. The solid state luminescent property of 1 was not observed at room temperature. Compound 2 showed an independent high spin central Co-II atom. KW - Cobalt KW - Cadmium KW - Coordination polymers KW - Crystal structures KW - Imidazole Y1 - 2015 U6 - https://doi.org/10.1002/zaac.201500526 SN - 0044-2313 SN - 1521-3749 VL - 641 IS - 11 SP - 1991 EP - 1997 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Mondal, Suvendu Sekhar A1 - Behrens, Karsten A1 - Matthes, Philipp R. A1 - Schönfeld, Fabian A1 - Nitsch, Jörn A1 - Steffen, Andreas A1 - Primus, Philipp-Alexander A1 - Kumke, Michael Uwe A1 - Müller-Buschbaum, Klaus A1 - Holdt, Hans-Jürgen T1 - White light emission of IFP-1 by in situ co-doping of the MOF pore system with Eu3+ and Tb3+ JF - Journal of materials chemistry : C, Materials for optical and electronic devices N2 - Co-doping of the MOF 3∞[Zn(2-methylimidazolate-4-amide-5-imidate)] (IFP-1 = Imidazolate Framework Potsdam-1) with luminescent Eu3+ and Tb3+ ions presents an approach to utilize the porosity of the MOF for the intercalation of luminescence centers and for tuning of the chromaticity to the emission of white light of the quality of a three color emitter. Organic based fluorescence processes of the MOF backbone as well as metal based luminescence of the dopants are combined to one homogenous single source emitter while retaining the MOF's porosity. The lanthanide ions Eu3+ and Tb3+ were doped in situ into IFP-1 upon formation of the MOF by intercalation into the micropores of the growing framework without a structure directing effect. Furthermore, the color point is temperature sensitive, so that a cold white light with a higher blue content is observed at 77 K and a warmer white light at room temperature (RT) due to the reduction of the organic emission at higher temperatures. The study further illustrates the dependence of the amount of luminescent ions on porosity and sorption properties of the MOF and proves the intercalation of luminescence centers into the pore system by low-temperature site selective photoluminescence spectroscopy, SEM and EDX. It also covers an investigation of the border of homogenous uptake within the MOF pores and the formation of secondary phases of lanthanide formates on the surface of the MOF. Crossing the border from a homogenous co-doping to a two-phase composite system can be beneficially used to adjust the character and warmth of the white light. This study also describes two-color emitters of the formula Ln@IFP-1a–d (Ln: Eu, Tb) by doping with just one lanthanide Eu3+ or Tb3+. Y1 - 2015 U6 - https://doi.org/10.1039/C4TC02919D SN - 2050-7534 SN - 2050-7526 VL - 18 IS - 3 SP - 4623 EP - 4631 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Mondal, Suvendu Sekhar A1 - Behrens, Karsten A1 - Matthes, Philipp R. A1 - Schönfeld, Fabian A1 - Nitsch, Jörn A1 - Steffen, Andreas A1 - Primus, Philipp-Alexander A1 - Kumke, Michael Uwe A1 - Müller-Buschbaum, Klaus A1 - Holdt, Hans-Jürgen T1 - White light emission of IFP-1 by in situ co-doping of the MOF pore system with Eu3+ and Tb3+ JF - Journal of materials chemistry : C, Materials for optical and electronic devices Y1 - 2015 U6 - https://doi.org/10.1039/c4tc02919d SN - 2050-7526 SN - 2050-7534 VL - 3 IS - 18 SP - 4623 EP - 4631 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Mondal, Suvendu Sekhar A1 - Marquardt, Dorothea A1 - Janiak, Christoph A1 - Holdt, Hans-Jürgen T1 - Use of a 4,5-dicyanoimidazolate anion based ionic liquid for the synthesis of iron and silver nanoparticles N2 - Sixteen new ionic liquids (ILs) with tetraethylammonium, 1-butyl-3-methylimidazolium, 3-methyl-1-octylimidazolium and tetrabutylphosphonium cations paired with 2-substituted 4,5-dicyanoimidazolate anions (substituent at C2 = methyl, trifluoromethyl, pentafluoroethyl, N,N′-dimethyl amino and nitro) have been synthesized and characterized by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA). The effects of cation and anion type and structure of the resulting ILs, including several room temperature ionic liquids (RTILs), are reflected in the crystallization, melting points and thermal decomposition of the ILs. ILs exhibited large liquid and crystallization ranges and formed glasses on cooling with glass transition temperatures in the range of −22 to −71 °C. We selected one of the newly designed ILs due to its bigger size, compared to the common conventional IL anion and high electron-withdrawing nitrile group leads to an overall stabilization anion that may stabilize the metal nanoparticles. Stable and better separated iron and silver nanoparticles are obtained by the decomposition of corresponding Fe2(CO)9 and AgPF6, respectively, under N2-atmosphere in newly designed nitrile functionalized 4,5-dicyanoimidazolate anion based IL. Very small and uniform size for Fe-nanoparticles of about 1.8 ± 0.6 nm were achieved without any additional stabilizers or capping molecules. Comparatively bigger size of Ag-nanoparticles was obtained through the reduction of AgPF6 by hydrogen gas. Additionally, the AgPF6 precursor was decomposed under microwave irradiation (MWI), fabricating nut-in-shell-like, that is, core-separated-from-shell Ag-nano-structures. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 220 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89696 SP - 5476 EP - 5483 ER - TY - JOUR A1 - Mondal, Suvendu Sekhar A1 - Thomas, Arne A1 - Holdt, Hans-Jürgen T1 - In situ synthesis of amide-imidate-imidazolate ligand and formation of metal-organic frameworks: Application for gas storage JF - Microporous and mesoporous materials : zeolites, clays, carbons and related materials N2 - In this review article, we highlight the synthesis, structures and gas-sorption properties of a series of nine isostructural IFPs (IFP = Imidazolate Framework Potsdam) and two H-bonded networks. IFPs were synthesized by in situ partial hydrolysis of a 4,5-dicyanoimidazole under solvothermal conditions and hence an imidazolate-4-amide-5-imidate linker (C5H3N4O2) was generated, forming the metal -amide-imidate-imidazolateframeworks [M(C5H3N4O2)-R]. Varying R in the 2-substitued linker (R = Me, Cl, Br, Et, OMe and OEt) and metal centre (M2+ = zinc and cobalt) allowed the variation in channel diameter (4.2-03 angstrom) and a fine-tuning of the polarity and functionality of the channel walls of IFPs. Furthermore, we show that using ethyl or alkoxy substituted IFPs the flexible groups act as molecular gates for guest molecules. This allows highly selective CO2 sorption over Ny and CH4 gases. Moreover, during the synthesis of methoxy substituted IFPs (IFP-7 and -8), an imidazolate-4,5-diamide-2-olate linker (C5H4N4O3) formed in situ leads to the formation of a molecular building block (MBB) with a M-6 octahedron inscribed in a M-8 cube (M Zn2+ and Co2+). The MBBs connect by amide amide hydrogen bonds to a 3D robust supramolecular networks [Zn-14(C5H4N4O3)(12)(O) (OH)(2) (DMF)(4) denoted as 1 and 2, respectively, DMF = N,N'-dimethylformamide], which can be activated for N-2, CO2, CH4, and H-2 gas-sorption. (C) 2015 Elsevier Inc. All rights reserved. KW - Flexible linker KW - Gas sorption KW - Gate-effects KW - Hydrogen-bonding KW - Solvothermal synthesis Y1 - 2015 U6 - https://doi.org/10.1016/j.micromeso.2015.01.049 SN - 1387-1811 SN - 1873-3093 VL - 216 SP - 2 EP - 12 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Morgner, Frank A1 - Lecointre, Alexandre A1 - Charbonniere, Loic J. A1 - Löhmannsröben, Hans-Gerd T1 - Detecting free hemoglobin in blood plasma and serum with luminescent terbium complexes JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Hemolysis, the rupturing of red blood cells, can result from numerous medical conditions (in vivo) or occur after collecting blood specimen or extracting plasma and serum out of whole blood (in vitro). In clinical laboratory practice, hemolysis can be a serious problem due to its potential to bias detection of various analytes or biomarkers. Here we present the first "mix-and-measure' method to assess the degree of hemolysis in biosamples using luminescence spectroscopy. Luminescent terbium complexes (LTC) were studied in the presence of free hemoglobin (Hb) as indicators for hemolysis in TRIS-buffer, and in fresh human plasma with absorption, excitation and emission measurements. Our findings indicate dynamic as well as resonance energy transfer (FRET) between the LTC and the porphyrin ligand of hemoglobin. This transfer leads to a decrease in luminescence intensity and decay time even at nanomolar hemoglobin concentrations either in buffer or plasma. Luminescent terbium complexes are very sensitive to free hemoglobin in buffer and blood plasma. Due to the instant change in luminescence properties of the LTC in presence of Hb it is possible to access the concentration of hemoglobin via spectroscopic methods without incubation time or further treatment of the sample thus enabling a rapid and sensitive detection of hemolysis in clinical diagnostics. Y1 - 2015 U6 - https://doi.org/10.1039/c4cp04206a SN - 1463-9076 SN - 1463-9084 VL - 17 IS - 3 SP - 1740 EP - 1745 PB - Royal Society of Chemistry CY - Cambridge ER - TY - THES A1 - Munzke, Dorit T1 - Faseroptische Spektroskopie mit hochfrequent modulierten Diodenlasern zur Analyse kleinster Volumina Y1 - 2015 ER - TY - JOUR A1 - Munzke, Dorit A1 - Böhm, Michael A1 - Reich, Oliver T1 - Gaseous Oxygen Detection Using Hollow-Core Fiber-Based Linear Cavity Ring-Down Spectroscopy JF - Journal of lightwave technology N2 - We demonstrate a method for the calibration-free and quantitative analysis of small volumes of gaseous samples. A 10 m hollow-core photonic bandgap fiber is used as the sample cell (volume = 0.44 mu L) and is placed inside a linear resonator setup. The application of cavity ring-down spectroscopy and in consideration of rather small coupling losses, this leads to an increased effective optical path length of up to 70 m. This implies a volume per optical interaction path length of 6.3 nL.m(-1). We used tunable diode laser spectroscopy at 760 nm and scanned the absorption for oxygen sensing. The optical loss due to sample absorption is obtained by measuring the ring-down time of light propagating inside the cavity. The resultant absorption coefficient shows a discrepancy of only 5.1% comparing to the HITRAN database. This approach is applicable for sensitive measurements if only submicroliter sample volumes are available. KW - Cavity ring-down spectroscopy KW - gas sensing KW - hollow-core photonic bandgap fiber KW - oxygen Y1 - 2015 U6 - https://doi.org/10.1109/JLT.2015.2397177 SN - 0733-8724 SN - 1558-2213 VL - 33 IS - 12 SP - 2524 EP - 2529 PB - Inst. of Electr. and Electronics Engineers CY - Piscataway ER - TY - JOUR A1 - Nazir, Rashid A1 - Meiling, Till Thomas A1 - Cywinski, Piotr J. A1 - Gryko, Daniel T. T1 - Synthesis and Optical Properties of alpha,beta-Unsaturated Ketones Bearing a Benzofuran Moiety JF - Asian journal of organic chemistry : an ACES journal N2 - Five pi-expanded alpha,beta-unsaturated ketones have been prepared from a strongly electron-rich benzofuran derivative via Knoevenagel reaction and aldol condensation. The incorporation of two 6-didodecylaminobenzofuran-2-yl groups at the periphery of D-pi-A and D-pi-A-pi-D molecules resulted in dyes with excellent solubility in the majority of organic solvents. In contrast to the majority of alpha,beta-unsaturated ketones, these dyes emit relatively strongly in the red region with a fluorescence quantum yield up to 40%. They also display strong solvatofluorochromism with emission shifting from 570 nm in toluene to 670 nm in CHCl3. Depending on the chemical structure, they two-photon cross-sections (sigma(2)) are up to 1700 GM (1 GM=10(50) cm(4)s photon(-1)). KW - aldol reaction KW - benzofurans KW - fluorescence KW - ketones KW - two-photon absorption Y1 - 2015 U6 - https://doi.org/10.1002/ajoc.201500242 SN - 2193-5807 SN - 2193-5815 VL - 4 IS - 9 SP - 929 EP - 935 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Neffe, Axel T. A1 - Lendlein, Andreas T1 - Going Beyond Compromises in Multifunctionality of Biomaterials JF - Advanced healthcare materials Y1 - 2015 U6 - https://doi.org/10.1002/adhm.201400724 SN - 2192-2640 SN - 2192-2659 VL - 4 IS - 5 SP - 642 EP - 645 PB - Wiley-Blackwell CY - Hoboken ER - TY - GEN A1 - Niedl, Robert Raimund A1 - Beta, Carsten T1 - Hydrogel-driven paper-based microfluidics N2 - Paper-based microfluidics provide an inexpensive, easy to use technology for point-of-care diagnostics in developing countries. Here, we combine paper-based microfluidic devices with responsive hydrogels to add an entire new class of functions to these versatile low-cost fluidic systems. The hydrogels serve as fluid reservoirs. In response to an external stimulus, e.g. an increase in temperature, the hydrogels collapse and release fluid into the structured paper substrate. In this way, chemicals that are either stored on the paper substrate or inside the hydrogel pads can be dissolved, premixed, and brought to reaction to fulfill specific analytic tasks. We demonstrate that multi-step sequences of chemical reactions can be implemented in a paper-based system and operated without the need for external precision pumps. We exemplify this technology by integrating an antibody-based E. coli test on a small and easy to use paper device. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 193 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-81083 SP - 2452 EP - 2459 ER - TY - JOUR A1 - Niedl, Robert Raimund A1 - Beta, Carsten T1 - Hydrogel-driven paper-based microfluidics JF - LAB on a chip : miniaturisation for chemistry and biology N2 - Paper-based microfluidics provide an inexpensive, easy to use technology for point-of-care diagnostics in developing countries. Here, we combine paper-based microfluidic devices with responsive hydrogels to add an entire new class of functions to these versatile low-cost fluidic systems. The hydrogels serve as fluid reservoirs. In response to an external stimulus, e.g. an increase in temperature, the hydrogels collapse and release fluid into the structured paper substrate. In this way, chemicals that are either stored on the paper substrate or inside the hydrogel pads can be dissolved, premixed, and brought to reaction to fulfill specific analytic tasks. We demonstrate that multi-step sequences of chemical reactions can be implemented in a paper-based system and operated without the need for external precision pumps. We exemplify this technology by integrating an antibody-based E. coli test on a small and easy to use paper device. Y1 - 2015 U6 - https://doi.org/10.1039/c5lc00276a SN - 1473-0197 SN - 1473-0189 VL - 11 IS - 15 SP - 2452 EP - 2459 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Nöchel, Ulrich A1 - Reddy, Chaganti Srinivasa A1 - Wang, Ke A1 - Cui, Jing A1 - Zizak, Ivo A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Nanostructural changes in crystallizable controlling units determine the temperature-memory of polymers N2 - Temperature-memory polymers remember the temperature, where they were deformed recently, enabled by broad thermal transitions. In this study, we explored a series of crosslinked poly[ethylene-co-(vinyl acetate)] networks (cPEVAs) comprising crystallizable polyethylene (PE) controlling units exhibiting a pronounced temperature-memory effect (TME) between 16 and 99 °C related to a broad melting transition (∼100 °C). The nanostructural changes in such cPEVAs during programming and activation of the TME were analyzed via in situ X-ray scattering and specific annealing experiments. Different contributions to the mechanism of memorizing high or low deformation temperatures (Tdeform) were observed in cPEVA, which can be associated to the average PE crystal sizes. At high deformation temperatures (>50 °C), newly formed PE crystals, which are established during cooling when fixing the temporary shape, dominated the TME mechanism. In contrast, at low Tdeform (<50 °C), corresponding to a cold drawing scenario, the deformation led preferably to a disruption of existing large crystals into smaller ones, which then fix the temporary shape upon cooling. The observed mechanism of memorizing a deformation temperature might enable the prediction of the TME behavior and the knowledge based design of other TMPs with crystallizable controlling units. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 194 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-81124 SP - 8284 EP - 8293 ER - TY - JOUR A1 - Nöchel, Ulrich A1 - Reddy, Chaganti Srinivasa A1 - Wang, Ke A1 - Cui, Jing A1 - Zizak, Ivo A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Nanostructural changes in crystallizable controlling units determine the temperature-memory of polymers JF - Journal of Materials Chemistry A, Materials for energy and sustainability N2 - Temperature-memory polymers remember the temperature, where they were deformed recently, enabled by broad thermal transitions. In this study, we explored a series of crosslinked poly[ethylene-co-(vinyl acetate)] networks (cPEVAs) comprising crystallizable polyethylene (PE) controlling units exhibiting a pronounced temperature-memory effect (TME) between 16 and 99 °C related to a broad melting transition (∼100 °C). The nanostructural changes in such cPEVAs during programming and activation of the TME were analyzed via in situ X-ray scattering and specific annealing experiments. Different contributions to the mechanism of memorizing high or low deformation temperatures (Tdeform) were observed in cPEVA, which can be associated to the average PE crystal sizes. At high deformation temperatures (>50 °C), newly formed PE crystals, which are established during cooling when fixing the temporary shape, dominated the TME mechanism. In contrast, at low Tdeform (<50 °C), corresponding to a cold drawing scenario, the deformation led preferably to a disruption of existing large crystals into smaller ones, which then fix the temporary shape upon cooling. The observed mechanism of memorizing a deformation temperature might enable the prediction of the TME behavior and the knowledge based design of other TMPs with crystallizable controlling units. Y1 - 2015 U6 - https://doi.org/10.1039/c4ta06586g SN - 2050-7488 SN - 2050-7496 VL - 16 IS - 3 SP - 8284 EP - 8293 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Nöchel, Ulrich A1 - Reddy, Chaganti Srinivasa A1 - Wang, Ke A1 - Cui, Jing A1 - Zizak, Ivo A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Nanostructural changes in crystallizable controlling units determine the temperature-memory of polymers JF - Journal of materials chemistry : A, Materials for energy and sustainability N2 - Temperature-memory polymers remember the temperature, where they were deformed recently, enabled by broad thermal transitions. In this study, we explored a series of crosslinked poly[ethylene-co-(vinyl acetate)] networks (cPEVAs) comprising crystallizable polyethylene (PE) controlling units exhibiting a pronounced temperature-memory effect (TME) between 16 and 99 degrees C related to a broad melting transition (similar to 100 degrees C). The nanostructural changes in such cPEVAs during programming and activation of the TME were analyzed via in situ X-ray scattering and specific annealing experiments. Different contributions to the mechanism of memorizing high or low deformation temperatures (T-deform) were observed in cPEVA, which can be associated to the average PE crystal sizes. At high deformation temperatures (>50 degrees C), newly formed PE crystals, which are established during cooling when fixing the temporary shape, dominated the TME mechanism. In contrast, at low T-deform (<50 degrees C), corresponding to a cold drawing scenario, the deformation led preferably to a disruption of existing large crystals into smaller ones, which then fix the temporary shape upon cooling. The observed mechanism of memorizing a deformation temperature might enable the prediction of the TME behavior and the knowledge based design of other TMPs with crystallizable controlling units. Y1 - 2015 U6 - https://doi.org/10.1039/c4ta06586g SN - 2050-7488 SN - 2050-7496 VL - 3 IS - 16 SP - 8284 EP - 8293 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Olejko, Lydia A1 - Cywinski, Piotr J. A1 - Bald, Ilko T1 - Ion-Selective formation of a guanine quadruplex on DNA origami structures JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - DNA origami nanostructures are a versatile tool that can be used to arrange functionalities with high local control to study molecular processes at a single-molecule level. Here, we demonstrate that DNA origami substrates can be used to suppress the formation of specific guanine (G) quadruplex structures from telomeric DNA. The folding of telomeres into G-quadruplex structures in the presence of monovalent cations (e.g. Na+ and K+) is currently used for the detection of K+ ions, however, with insufficient selectivity towards Na+. By means of FRET between two suitable dyes attached to the 3- and 5-ends of telomeric DNA we demonstrate that the formation of G-quadruplexes on DNA origami templates in the presence of sodium ions is suppressed due to steric hindrance. Hence, telomeric DNA attached to DNA origami structures represents a highly sensitive and selective detection tool for potassium ions even in the presence of high concentrations of sodium ions. KW - DNA nanotechnology KW - FRET KW - G-quadruplexes KW - nanostructures KW - self-assembly Y1 - 2015 U6 - https://doi.org/10.1002/anie.201409278 SN - 1433-7851 SN - 1521-3773 VL - 54 IS - 2 SP - 673 EP - 677 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Pape, Simon A1 - Wessig, Pablo A1 - Brunner, Heiko T1 - A new and environmentally benign synthesis of aroylguanidines using iron trichloride N2 - A new synthetic approach for the guanylation of aroylthioureas using iron trichloride is presented. Our synthetic method distinguishes itself by benign reaction conditions, low costs and a broad product spectrum. The scope of the reaction and calorimetric studies are described. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 308 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102720 SP - 101408 EP - 101411 ER - TY - JOUR A1 - Pape, Simon A1 - Wessig, Pablo A1 - Brunner, Heiko T1 - A new and environmentally benign synthesis of aroylguanidines using iron trichloride JF - RSC Advances N2 - A new synthetic approach for the guanylation of aroylthioureas using iron trichloride is presented. Our synthetic method distinguishes itself by benign reaction conditions, low costs and a broad product spectrum. The scope of the reaction and calorimetric studies are described. Y1 - 2015 U6 - https://doi.org/10.1039/c5ra20869f SN - 2046-2069 VL - 5 IS - 123 SP - 101408 EP - 101411 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Paz, Cristian A1 - Becerra, Jose A1 - Silva, Mario A1 - Burgos, Viviana A1 - Heydenreich, Matthias A1 - Schmidt, Bernd A1 - Thu Tran, A1 - Vetter, Irina T1 - (-)-Pentylsedinine, a New Alkaloid from the Leaves of Lobelia tupa with Agonist Activity at Nicotinic Acetylcholine Receptor JF - Natural product communications : an international journal for communications and reviews N2 - Lobelia tupa, also called devil's tobacco, is a native plant from the center-south of Chile which has been used by the native people of Chile as a hallucinogenic and anesthetic plant. A new piperidine alkaloid, called pentylsedinine, which comprises five carbons in the side chain, was isolated from the aerial part of L. tupa, along with lobeline and lobelanidine. The structure was established on the basis of 1D and 2D NMR spectroscopy. While lobeline is a neutral antagonist at alpha 3 beta 2/alpha 3 beta 4 nAChR and alpha 7 nAChR, both lobelanidine and pentylsedinine act as partial agonists at nAChR KW - Lobelia tupa KW - Piperidine alkaloid KW - nAChR KW - Pentylsedinine Y1 - 2015 SN - 1934-578X SN - 1555-9475 VL - 10 IS - 8 SP - 1355 EP - 1357 PB - NPC CY - Westerville ER - TY - JOUR A1 - Perez-Anes, Alexandra A1 - Rodrigues, Fernanda A1 - Caminade, Anne-Marie A1 - Stefaniu, Cristina A1 - Tiersch, Brigitte A1 - Turrin, Cedric-Olivier A1 - Blanzat, Muriel T1 - Influence of structural parameters on the self-association properties of anti-HIV catanionic dendrimers JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - The self-association properties of anti-HIV catanionic dendrimers as multivalent galactosylceramide (GalCer)-derived inhibitors are presented. The study was designed to elucidate the origin of the relatively high cytotoxicity values of these antiHIV catanionic dendrimers, which have previously been found to exhibit in vitro anti-HIV activity in the submicromolar range. The physicochemical properties of these catanionic dendrimers were studied to tentatively correlate the structural parameters with self-association and biological properties. We can conclude from this study that the absence of correlation between the hydrophobicity and the cytotoxicity of the catanionic systems could be explained by the partial segregation of the different partners of the catanionic entities. KW - anti-HIV KW - catanionic surfactants KW - dendrimers KW - galactosylceramide KW - glycolipids Y1 - 2015 U6 - https://doi.org/10.1002/cphc.201500484 SN - 1439-4235 SN - 1439-7641 VL - 16 IS - 16 SP - 3433 EP - 3437 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Pester, Christian W. A1 - Schmidt, Kristin A1 - Ruppel, Markus A1 - Schoberth, Heiko G. A1 - Böker, Alexander T1 - Electric-Field-Induced Order-Order Transition from Hexagonally Perforated Lamellae to Lamellae JF - Macromolecules : a publication of the American Chemical Society N2 - Block copolymers form a variety of microphase morphologies due to their ability to phase separate. The hexagonally perforated lamellar (HPL) morphology represents an unusually long-lived, nonequilibrium transient structure between lamellar and cylindrical phases. We present a detailed study of a concentrated, HPL-forming poly(styrene-b-isoprene) diblock copolymer solution in toluene in the presence of an electric field. We will show that this phase is readily aligned by a moderate electric field and provide experimental evidence for an electric-field-induced order order transition toward the lamellar phase under sufficiently strong fields. This process is shown to be fully reversible as lamellar perforations reconnect immediately upon secession of the external stimulus, recovering highly aligned perforated lamellae. Y1 - 2015 U6 - https://doi.org/10.1021/acs.macromol.5b01336 SN - 0024-9297 SN - 1520-5835 VL - 48 IS - 17 SP - 6206 EP - 6213 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Plehn, Thomas A1 - Ziemann, Dirk A1 - Megow, Jörg A1 - May, Volkhard T1 - Frenkel to Wannier-Mott Exciton Transition: Calculation of FRET Rates for a Tubular Dye Aggregate Coupled to a CdSe Nanocrystal JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - The coupling is investigated of Frenkel-like exciton states formed in a tubular dye aggregate (TDA) to Wannier-Mott-like excitations of a semiconductor nanocrystal (NC). A double well TDA of the cyanine dye C8S3 with a length of 63.4 nm and a diameter of 14.7 nm is considered. The TDA interacts with a spherical Cd819Te630 NC of 4.5 nm diameter. Electronic excitations of the latter are described in a tight-binding model of the electrons and holes combined with a configuration interaction scheme to consider their mutual Coulomb coupling. To achieve a proper description of TDA excitons, a recently determined structure has been used, the energy transfer coupling has been defined as a screened interaction of atomic centered transition charges, and the site energies of the dye molecules have been the subject of a polarization correction. Even if both nanoparticles are in direct contact, the energy transfer coupling between the exciton levels of the TDA and of the NC stays below 1 meV. It results in FRET-type energy transfer with rates somewhat larger than 10(9)/s. They coincide rather well with recent preliminary experiments. Y1 - 2015 U6 - https://doi.org/10.1021/jp5111696 SN - 1520-6106 VL - 119 IS - 24 SP - 7467 EP - 7472 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Poghosyan, Armen H. A1 - Arsenyan, Levon H. A1 - Antonyan, Lilit A. A1 - Shahinyan, Aram A. A1 - Koetz, Joachim T1 - Molecular dynamics simulations of branched polyethyleneimine in water-in-heptanol micelles stabilized by zwitterionic surfactants JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - We have performed a 50 ns molecular dynamics simulation of a hyperbranched polymer, i.e. polyethyleneimine (PEI), inside inverse micelles formed with zwitterionic surfactants 3-(N, N-dimethyldodecylammoniio)-propansulfonate (SB) in heptanol. The runs were performed using the GROMACS simulation package. During simulation time the PEI molecule undergoes a conformational deformation and compaction. The radius of gyration of the PEI molecule finally located in the center of the water droplet is decreased from 3 nm to 1.7 nm. The unusual shrinking of the PEI molecule inside the micelle explains the extraordinary template effect of these microemulsions by making cadmium sulfide or gold clusters. (C) 2015 Elsevier B.V. All rights reserved. KW - Surfactant micelles KW - Molecular dynamics simulations KW - Polyethyleneimine Y1 - 2015 U6 - https://doi.org/10.1016/j.colsurfa.2015.03.053 SN - 0927-7757 SN - 1873-4359 VL - 479 SP - 18 EP - 24 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Prestel, Andreas A1 - Möller, Heiko Michael T1 - Spatio-temporal control of cellular uptake achieved by photoswitchable cell-penetrating peptides N2 - The selective uptake of compounds into specific cells of interest is a major objective in cell biology and drug delivery. By incorporation of a novel, thermostable azobenzene moiety we generated peptides that can be switched optically between an inactive state and an active, cell-penetrating state with excellent spatio-temporal control. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 218 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89658 SP - 701 EP - 704 ER - TY - JOUR A1 - Prestel, Andreas A1 - Möller, Heiko Michael T1 - Spatio-temporal control of cellular uptake achieved by photoswitchable cell-penetrating peptides JF - Chemical communications : ChemComm N2 - The selective uptake of compounds into specific cells of interest is a major objective in cell biology and drug delivery. By incorporation of a novel, thermostable azobenzene moiety we generated peptides that can be switched optically between an inactive state and an active, cell-penetrating state with excellent spatio-temporal control. Y1 - 2015 U6 - https://doi.org/10.1039/C5CC06848G SN - 1364-548X IS - 52 SP - 701 EP - 704 PB - Royal Society of Chemistry CY - Cambridge ER - TY - THES A1 - Primus, Philipp-Alexander T1 - High resolution spectroscopy as a tool to unravel structure-reactivity relationships in Eu3+ doped ceria/ceria-zirconia based catalyst nanomaterials Y1 - 2015 ER - TY - JOUR A1 - Primus, Philipp-Alexander A1 - Menski, Antonia A1 - Yeste, Maria Pilar A1 - Cauqui, Miguel Angel A1 - Kumke, Michael Uwe T1 - Fluorescence Line-Narrowing Spectroscopy as a Tool to Monitor Phase Transitions and Phase Separation in Efficient Nanocrystalline CexZr1-xO2:Eu3+ Catalyst Materials JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Despite the wide range of industrial applications for ceria-zirconia mixed oxides (CexZr1-xO2), the complex correlation between their atomic structure and catalytic performance is still under debate. Catalytically interesting CexZr1-xO2 nanomaterials can form homogeneous solid solutions and, depending on the composition, show phase separation under the formation of small domains. The characterization of homogeneity and atomic structure of these materials remains a major challenge. High-resolution emission spectroscopy recorded under cryogenic conditions using Eu3+ as a structural probe in doped CeZrO2 nanoparticles offers an effective way to identify the different atomic environments of the Eu3+ dopants and, subsequently, to monitor structural parameters of the ceria-zirconia mixed oxides. It is found that, in stoichiometric CeZrO2:Eu3+, phase separation occurs at elevated temperatures beginning with the gradual formation of (pseudo)cubic crystallites in the amorphous materials at 500 degrees C and a sudden phase separation into tetragonal, zirconia-rich and cubic, ceria-rich domains over 900 degrees C. The presented technique allows us to easily monitor subtle changes even in amorphous, high surface area samples, yielding structural information not accessible by conventional techniques such as X-ray diffraction (XRD) and Raman. Moreover, in reference experiments investigating the reducibility of largely unordered Ce0.2Zr0.8O2:Eu3+, the main reduction peak in temperature-programmed reduction measurements appeared at exceptionally low temperatures below 200 degrees C, thus suggesting the outstanding potential of this oxide to activate catalytic oxidation reactions. This effect was found to be dependent on the amount of Eu3+ dopant introduced into the CeZrO2 matrix as well as to be connected to the atomic structure of the catalyst material. Y1 - 2015 U6 - https://doi.org/10.1021/acs.jpcc.5b01271 SN - 1932-7447 VL - 119 IS - 19 SP - 10682 EP - 10692 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Rading, M. Michael A1 - Sandmann, Michael A1 - Steup, Martin A1 - Chiarugi, Davide A1 - Valleriani, Angelo T1 - Weak correlation of starch and volume in synchronized photosynthetic cells JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - In cultures of unicellular algae, features of single cells, such as cellular volume and starch content, are thought to be the result of carefully balanced growth and division processes. Single-cell analyses of synchronized photoautotrophic cultures of the unicellular alga Chlamydomonas reinhardtii reveal, however, that the cellular volume and starch content are only weakly correlated. Likewise, other cell parameters, e.g., the chlorophyll content per cell, are only weakly correlated with cell size. We derive the cell size distributions at the beginning of each synchronization cycle considering growth, timing of cell division and daughter cell release, and the uneven division of cell volume. Furthermore, we investigate the link between cell volume growth and starch accumulation. This work presents evidence that, under the experimental conditions of light-dark synchronized cultures, the weak correlation between both cell features is a result of a cumulative process rather than due to asymmetric partition of biomolecules during cell division. This cumulative process necessarily limits cellular similarities within a synchronized cell population. Y1 - 2015 U6 - https://doi.org/10.1103/PhysRevE.91.012711 SN - 1539-3755 SN - 1550-2376 VL - 91 IS - 1 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Roch, Toralf A1 - Kratz, Karl A1 - Ma, Nan A1 - Lendlein, Andreas T1 - Polymeric inserts differing in their chemical composition as substrates for dendritic cell cultivation JF - Clinical hemorheology and microcirculation : blood flow and vessels N2 - Dendritic cells (DC) contribute to immunity by presenting antigens to T cells and shape the immune response by the secretion of cytokines. Due to their immune stimulatory potential DC-based therapies are promising approaches to overcome tolerance e.g. against tumors. In order to enforce the immunogenicity of DCs, they have to be matured and activated in vitro, which requires an appropriate cell culture substrate, supporting their survival expansion and activation. Since most cell culture devices are not optimized for DC growth, it is hypothesized that polymers with certain physicochemical properties can positively influence the DC cultures. With the aim to evaluate the effects that polymers with different chemical compositions have on the survival, the activation status, and the cytokine/chemokine secretion profile of DC, their interaction with polystyrene (PS), polycarbonate (PC), poly(ether imide) (PEI), and poly(styrene-co-acrylonitrile) (PSAN)-based cell culture inserts was investigated. By using this insert system, which fits exactly into 24 well cell culture plates, effects induced from the culture dish material can be excluded. The viability of untreated DC after incubation with the different inserts was not influenced by the different inserts, whereas LPS-activatedDCshowed an increased survival after cultivation on PC, PS, and PSAN compared to tissue culture polystyrene (TCP). The activation status of DC estimated by the expression of CD40, CD80, CD83, CD86 and HLA-DR expression was not altered by the different inserts in untreated DC but slightly reduced when LPS-activated DC were cultivated on PC, PS, PSAN, and PEI compared to TCP. For each polymeric cell culture insert a distinct cytokine profile could be observed. Since inserts with different chemical compositions of the inserts did not substantially alter the behavior of DC all insert systems could be considered as alternative substrate. The observed increased survival on some polymers, which showed in contrast to TCP a hydrophobic surface, could be beneficial for certain applications such as T cell expansion and activation. KW - Biomaterials KW - dendritic cells KW - cell culture device KW - amorphous polymers Y1 - 2015 U6 - https://doi.org/10.3233/CH-152004 SN - 1386-0291 SN - 1875-8622 VL - 61 IS - 2 SP - 347 EP - 357 PB - IOS Press CY - Amsterdam ER - TY - JOUR A1 - Roder, Phillip A1 - Hille, Carsten T1 - A Multifunctional Frontloading Approach for Repeated Recycling of a Pressure-Controlled AFM Micropipette JF - PLoS ONE N2 - Fluid force microscopy combines the positional accuracy and force sensitivity of an atomic force microscope (AFM) with nanofluidics via a microchanneled cantilever. However, adequate loading and cleaning procedures for such AFM micropipettes are required for various application situations. Here, a new frontloading procedure is described for an AFM micropipette functioning as a force- and pressure-controlled microscale liquid dispenser. This frontloading procedure seems especially attractive when using target substances featuring high costs or low available amounts. Here, the AFM micropipette could be filled from the tip side with liquid from a previously applied droplet with a volume of only a few μL using a short low-pressure pulse. The liquid-loaded AFM micropipettes could be then applied for experiments in air or liquid environments. AFM micropipette frontloading was evaluated with the well-known organic fluorescent dye rhodamine 6G and the AlexaFluor647-labeled antibody goat anti-rat IgG as an example of a larger biological compound. After micropipette usage, specific cleaning procedures were tested. Furthermore, a storage method is described, at which the AFM micropipettes could be stored for a few hours up to several days without drying out or clogging of the microchannel. In summary, the rapid, versatile and cost-efficient frontloading and cleaning procedure for the repeated usage of a single AFM micropipette is beneficial for various application situations from specific surface modifications through to local manipulation of living cells, and provides a simplified and faster handling for already known experiments with fluid force microscopy. Y1 - 2015 U6 - https://doi.org/10.1371/journal.pone.0144157 SN - 1932-6203 VL - 10 IS - 12 PB - Public Library of Science CY - Lawrence, Kan. ER - TY - GEN A1 - Roder, Phillip A1 - Hille, Carsten T1 - A Multifunctional Frontloading Approach for Repeated Recycling of a Pressure-Controlled AFM Micropipette N2 - Fluid force microscopy combines the positional accuracy and force sensitivity of an atomic force microscope (AFM) with nanofluidics via a microchanneled cantilever. However, adequate loading and cleaning procedures for such AFM micropipettes are required for various application situations. Here, a new frontloading procedure is described for an AFM micropipette functioning as a force- and pressure-controlled microscale liquid dispenser. This frontloading procedure seems especially attractive when using target substances featuring high costs or low available amounts. Here, the AFM micropipette could be filled from the tip side with liquid from a previously applied droplet with a volume of only a few μL using a short low-pressure pulse. The liquid-loaded AFM micropipettes could be then applied for experiments in air or liquid environments. AFM micropipette frontloading was evaluated with the well-known organic fluorescent dye rhodamine 6G and the AlexaFluor647-labeled antibody goat anti-rat IgG as an example of a larger biological compound. After micropipette usage, specific cleaning procedures were tested. Furthermore, a storage method is described, at which the AFM micropipettes could be stored for a few hours up to several days without drying out or clogging of the microchannel. In summary, the rapid, versatile and cost-efficient frontloading and cleaning procedure for the repeated usage of a single AFM micropipette is beneficial for various application situations from specific surface modifications through to local manipulation of living cells, and provides a simplified and faster handling for already known experiments with fluid force microscopy. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 209 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-86592 ER - TY - JOUR A1 - Roder, Phillip A1 - Hille, Carsten T1 - A Multifunctional Frontloading Approach for Repeated Recycling of a Pressure-Controlled AFM Micropipette JF - PLoS one N2 - Fluid force microscopy combines the positional accuracy and force sensitivity of an atomic force microscope (AFM) with nanofluidics via a microchanneled cantilever. However, adequate loading and cleaning procedures for such AFM micropipettes are required for various application situations. Here, a new frontloading procedure is described for an AFM micropipette functioning as a force-and pressure-controlled microscale liquid dispenser. This frontloading procedure seems especially attractive when using target substances featuring high costs or low available amounts. Here, the AFM micropipette could be filled from the tip side with liquid from a previously applied droplet with a volume of only a few mu L using a short low-pressure pulse. The liquid-loaded AFM micropipettes could be then applied for experiments in air or liquid environments. AFM micropipette frontloading was evaluated with the well-known organic fluorescent dye rhodamine 6G and the AlexaFluor647-labeled antibody goat anti-rat IgG as an example of a larger biological compound. After micropipette usage, specific cleaning procedures were tested. Furthermore, a storage method is described, at which the AFM micropipettes could be stored for a few hours up to several days without drying out or clogging of the microchannel. In summary, the rapid, versatile and cost-efficient frontloading and cleaning procedure for the repeated usage of a single AFM micropipette is beneficial for various application situations from specific surface modifications through to local manipulation of living cells, and provides a simplified and faster handling for already known experiments with fluid force microscopy. Y1 - 2015 U6 - https://doi.org/10.1371/journal.pone.0144157 SN - 1932-6203 VL - 10 IS - 12 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Ryabchun, Alexander A1 - Bobrovsky, Alexey A1 - Stumpe, Joachim A1 - Shibaev, Valery T1 - Electroinduced Diffraction Gratings in Cholesteric Polymer with Phototunable Helix Pitch JF - Advanced optical materials N2 - For the first time the cholesteric mixture containing nematic polymer with small amount of chiral-photochromic dopant is used for electroinduced diffraction gratings production. The gratings are obtained by applying electric field to the planar-aligned cholesteric polymer layer causing its periodical distortion. Material developed permits manipulating supramolecular helical structure by means of UV exposure resulting in helix untwisting. Photo-controlling of helix pitch brings to change parameters of the electroinduced gratings. Due to macromolecular "nature" of the material one can easily stabilize electroinduced gratings by fast sample cooling. All-known cholesteric grating types are realized in the studied polymer material. It is observed that the grating vector can be oriented along or perpendicular to the rubbing direction of the cell. It is shown that the diffraction efficiency is dictated by grating type and the amplitude of the applied electric field and can achieve about 80%. Moreover, the period of gratings can be tuned upon UV light illumination. The possibility of 2D gratings creation is also demonstrated. The described material and approach gives an opportunity to easily fabricate a variety of diffraction gratings with flexibly controllable parameters. Such gratings can be potentially applied in optics, optoelectronics, and photonics as intelligent diffraction elements. Y1 - 2015 U6 - https://doi.org/10.1002/adom.201500293 SN - 2195-1071 VL - 3 IS - 10 SP - 1462 EP - 1469 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Saatchi, Mersa A1 - Behl, Marc A1 - Nöchel, Ulrich A1 - Lendlein, Andreas T1 - Copolymer Networks From Oligo(epsilon-caprolactone) and n-Butyl Acrylate Enable a Reversible Bidirectional Shape-Memory Effect at Human Body Temperature JF - Macromolecular rapid communications N2 - Exploiting the tremendous potential of the recently discovered reversible bidirectional shape-memory effect (rbSME) for biomedical applications requires switching temperatures in the physiological range. The recent strategy is based on the reduction of the melting temperature range (T-m) of the actuating oligo(epsilon-caprolactone) (OCL) domains in copolymer networks from OCL and n-butyl acrylate (BA), where the reversible effect can be adjusted to the human body temperature. In addition, it is investigated whether an rbSME in the temperature range close or even above T-m,T-offset (end of the melting transition) can be obtained. Two series of networks having mixtures of OCLs reveal broad T(m)s from 2 degrees C to 50 degrees C and from -10 degrees C to 37 degrees C, respectively. In cyclic, thermomechanical experiments the rbSME can be tailored to display pronounced actuation in a temperature interval between 20 degrees C and 37 degrees C. In this way, the application spectrum of the rbSME can be extended to biomedical applications. KW - body temperature KW - broad melting temperature range KW - orientational memory KW - reversible bidirectional shape-memory polymer KW - copolymer networks Y1 - 2015 U6 - https://doi.org/10.1002/marc.201400729 SN - 1022-1336 SN - 1521-3927 VL - 36 IS - 10 SP - 880 EP - 884 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Sachse, Dirk A1 - Dawson, Todd E. A1 - Kahmen, Ansgar T1 - Seasonal variation of leaf wax n-alkane production and delta H-2 values from the evergreen oak tree, Quercus agrifolia JF - Isotopes in environmental and health studies N2 - In order to understand the timing of leaf wax synthesis in higher plants, we analysed the variability in leaf wax n-alkane concentration, composition (expressed as average chain length (ACL)), and delta H-2(wax) values as well as plant source water delta H-2 values (xylem and leaf water) in the evergreen tree Quercus agrifolia over a period of 9 months, beginning with leaf flush. We identified three distinct periods of leaf development with the first month following leaf flush being characterized by de novo synthesis and possibly removal of n-alkanes. During the following 3 months, n-alkane concentrations increased sevenfold and delta H-2(wax) and ACL values increased, suggesting this period was the major leaf wax n-alkane formation period. During the remaining 4 months of the experiment, stable values suggest cessation of leaf wax n-alkane formation. We find that n-alkane synthesis in Q. agrifolia takes place over 4 months, substantially longer than that observed for deciduous trees. KW - leaf wax KW - oak tree KW - hydrogen-2 KW - isotope ecology KW - n-alkanes Y1 - 2015 U6 - https://doi.org/10.1080/10256016.2015.1011636 SN - 1025-6016 SN - 1477-2639 VL - 51 IS - 1 SP - 124 EP - 142 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Schab-Balcerzak, Ewa A1 - Flakus, Henryk A1 - Jarczyk-Jedryka, Anna A1 - Konieczkowska, Jolanta A1 - Siwy, Mariola A1 - Bijak, Katarzyna A1 - Sobolewska, Anna A1 - Stumpe, Joachim T1 - Photochromic supramolecular azopolyimides based on hydrogen bonds JF - Optical materials : an international journal on the physics and chemistry of optical materials and their applications, including devices N2 - The approach of deriving new photoresponsive active supramolecular azopolymers based on the hydrogen bonds is described. Polymers with imide rings, i.e., poly(esterimide)s and poly(etherimide)s, with phenolic hydroxyl or carboxylic groups were applied as matrixes for the polymer dye supramolecular systems. Supramolecular films were built on the basis of the hydrogen bonds between the functional groups of the polymers and various azochromophores, that is, 4-phenylazophenol, 4-[4-(6-hydroxyhexy loxy)phenylazo]benzene, 4[4-(6-hexadecaneoxy)phenylazo]pyridine and 4-(4-hydroxyphenylazo)-pyridine. The hydrogen bonding interaction in azo-systems were studied by Fourier transform infrared spectroscopy and for selected assembles by H-1 NMR technique. The obtained polyimide azo-assembles were characterized by X-ray diffraction and DSC measurements. H-bonds allow attaching a chromophore to each repeating unit of the polymer, thereby suppressing the macroscopic phase separation except for the systems based on 4-[4-(6-hydroxyhexyloxy)phenylazo]benzene. H-bonds systems were amorphous and revealed glass transition temperatures lower than for the polyimide matrixes (170-260 degrees C). The photoresponsive behavior of the azo-assemblies was tasted in holographic recording experiment. (C) 2015 Elsevier B.V. All rights reserved. KW - Azobenzene KW - Polyimides KW - Photoinduced optical anisotropy KW - Surface relief grating Y1 - 2015 U6 - https://doi.org/10.1016/j.optmat.2015.06.029 SN - 0925-3467 SN - 1873-1252 VL - 47 SP - 501 EP - 511 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schildknecht, Stefan A1 - Pape, Regina A1 - Meiser, Johannes A1 - Karreman, Christiaan A1 - Strittmatter, Tobias A1 - Odermatt, Meike A1 - Cirri, Erica A1 - Friemel, Anke A1 - Ringwald, Markus A1 - Pasquarelli, Noemi A1 - Ferger, Boris A1 - Brunner, Thomas A1 - Marx, Andreas A1 - Moeller, Heiko M. A1 - Hiller, Karsten A1 - Leist, Marcel T1 - Preferential Extracellular Generation of the Active Parkinsonian Toxin MPP+ by Transporter-Independent Export of the Intermediate MPDP+ JF - Antioxidants & redox signaling N2 - Aims: 1-Methyl-4-phenyl-tetrahydropyridine (MPTP) is among the most widely used neurotoxins for inducing experimental parkinsonism. MPTP causes parkinsonian symptoms in mice, primates, and humans by killing a subpopulation of dopaminergic neurons. Extrapolations of data obtained using MPTP-based parkinsonism models to human disease are common; however, the precise mechanism by which MPTP is converted into its active neurotoxic metabolite, 1-methyl-4-phenyl-pyridinium (MPP+), has not been fully elucidated. In this study, we aimed to address two unanswered questions related to MPTP toxicology: (1) Why are MPTP-converting astrocytes largely spared from toxicity? (2) How does MPP+ reach the extracellular space? Results: In MPTP-treated astrocytes, we discovered that the membrane-impermeable MPP+, which is generally assumed to be formed inside astrocytes, is almost exclusively detected outside of these cells. Instead of a transporter-mediated export, we found that the intermediate, 1-methyl-4-phenyl-2,3-dihydropyridinium (MPDP+), and/or its uncharged conjugate base passively diffused across cell membranes and that MPP+ was formed predominately by the extracellular oxidation of MPDP+ into MPP+. This nonenzymatic extracellular conversion of MPDP+ was promoted by O-2, a more alkaline pH, and dopamine autoxidation products. Innovation and Conclusion: Our data indicate that MPTP metabolism is compartmentalized between intracellular and extracellular environments, explain the absence of toxicity in MPTP-converting astrocytes, and provide a rationale for the preferential formation of MPP+ in the extracellular space. The mechanism of transporter-independent extracellular MPP+ formation described here indicates that extracellular genesis of MPP+ from MPDP is a necessary prerequisite for the selective uptake of this toxin by catecholaminergic neurons. Y1 - 2015 U6 - https://doi.org/10.1089/ars.2015.6297 SN - 1523-0864 SN - 1557-7716 VL - 23 IS - 13 SP - 1001 EP - 1016 PB - Liebert CY - New Rochelle ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli A1 - Riemer, Nastja A1 - Hölter, Frank T1 - Acetamidoarenediazonium Salts: Opportunities for Multiple Arene Functionalization JF - European journal of organic chemistry N2 - Unlike their ortho counterparts, meta- and para-acetamidoanilines can be converted into the corresponding acetamidoarenediazonium salts. These offer various opportunities for multiple Pd-catalyzed arene functionalization reactions, such as Matsuda-Heck-, Suzuki-Miyaura- or Fujiwara-Moritani couplings. KW - Arenes KW - Amides KW - C-C coupling KW - Cross-coupling KW - Palladium Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201500795 SN - 1434-193X SN - 1099-0690 IS - 26 SP - 5826 EP - 5841 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Elizarov, Nelli A1 - Schilde, Uwe A1 - Kelling, Alexandra T1 - Dual Role of Acetanilides: Traceless Removal of a Directing Group through Deacetylation/Diazotation and Palladium-Catalyzed C-C-Coupling Reactions JF - The journal of organic chemistry N2 - The acetamide group enables regioselective oxidative ortho-C-H activation reactions, such as Pd-catalyzed acylation. The synthetic utility of these transformations can be significantly enhanced by using the acetamide as a quasi-leaving group in a subsequent conventional Pd-catalyzed coupling or cross-coupling reaction. The concept is illustrated herein for the synthesis of o-alkenyl- and o-arylphenones, which have potential for the synthesis of arylated aromatic heterocycles. Y1 - 2015 U6 - https://doi.org/10.1021/acs.joc.5b00272 SN - 0022-3263 VL - 80 IS - 9 SP - 4223 EP - 4234 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin T1 - Synthesis of Magnaldehydes B and E and Dictyobiphenyl B by Microwave-Promoted Cross-Coupling of Boronophenols JF - European journal of organic chemistry N2 - Magnaldehydes B and E along with their 4'-methylated derivatives are naturally occurring 2,4'-biphenols that have been isolated from the Magnoliaceae. Herein, these natural products have been synthesized from a common intermediate, which was obtained by a microwave-promoted, hetero-geneously catalyzed, and protecting-group-free Suzuki-Miyaura coupling reaction in an aqueous medium. These reaction conditions were also successfully applied to a one-step synthesis of the slime mold metabolite dictyobiphenyl B. KW - Total synthesis KW - Natural products KW - Cross-coupling KW - Palladium KW - Biaryls KW - Phenols Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201500350 SN - 1434-193X SN - 1099-0690 IS - 17 SP - 3760 EP - 3766 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Riemer, Martin A1 - Schilde, Uwe T1 - Tandem Claisen Rearrangement/6-endo Cyclization Approach to Allylated and Prenylated Chromones JF - European journal of organic chemistry N2 - Allyl, dimethylallyl and prenyl ethers derived from o-acyl-phenols reacted upon microwave irradiation to form C-allylated or -prenylated chromone derivatives, depending on the substitution pattern of the arene and the allyl substituent. The reaction proceeds through a tandem Claisen rearrangement and 6-endo-trig or 6-endo-dig cyclization sequence. For prenyl ethers, the tandem sequence can be extended by a Cope rearrangement to furnish 6-prenylchromones. The method is potentially useful for the synthesis of natural products and drugs. KW - Allylic compounds KW - Arenes KW - Oxygen heterocycles KW - Microwave chemistry KW - Rearrangement KW - Michael addition Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201501151 SN - 1434-193X SN - 1099-0690 IS - 34 SP - 7602 EP - 7611 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Joachim T1 - Die Arbeit bei irreversibler Druck-Volumen-Änderung BT - Varianten der Berechnung N2 - For the calculation of the work in an irreversible pressure-volume change, we propose approxima-tions, which in contrast to the usual representation in the literature reflect the work performed during expansion and compression symmetrically. The calculations are based on the Reversible-Share-Theorem: Is used the force to overcome for calculating the work, so it captures only the configurational reversible work share. KW - physics KW - physical chemistry KW - thermodynamics KW - irreversible volume-change KW - reversible-share-theorem KW - total work KW - reversible work share KW - irreversible work share Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74931 ER - TY - JOUR A1 - Schmitt, Clemens Nikolaus Zeno A1 - Winter, Alette A1 - Bertinetti, Luca A1 - Masic, Admir A1 - Strauch, Peter A1 - Harrington, Matthew J. T1 - Mechanical homeostasis of a DOPA-enriched biological coating from mussels in response to metal variation JF - Interface : journal of the Royal Society N2 - Protein metal coordination interactions were recently found to function as crucial mechanical cross-links in certain biological materials. Mussels, for example, use Fe ions from the local environment coordinated to DOPA-rich proteins to stiffen the protective cuticle of their anchoring byssal attachment threads. Bioavailability of metal ions in ocean habitats varies significantly owing to natural and anthropogenic inputs on both short and geological spatio-temporal scales leading to large variations in byssal thread metal composition; however, it is not clear how or if this affects thread performance. Here, we demonstrate that in natural environments mussels can opportunistically replace Fe ions in the DOPA coordination complex with V and Al. In vitro removal of the native DOPA metal complexes with ethylenediaminetetraacetic acid and replacement with either Fe or V does not lead to statistically significant changes in cuticle performance, indicating that each metal ion is equally sufficient as a DOPA cross-linking agent, able to account for nearly 85% of the stiffness and hardness of the material. Notably, replacement with Al ions also leads to full recovery of stiffness, but only 82% recovery of hardness. These findings have important implications for the adaptability of this biological material in a dynamically changing and unpredictable habitat. KW - mussel byssus KW - DOPA KW - metal coordination KW - coating Y1 - 2015 U6 - https://doi.org/10.1098/rsif.2015.0466 SN - 1742-5689 SN - 1742-5662 VL - 12 IS - 110 PB - Royal Society CY - London ER - TY - JOUR A1 - Schulze, Michael A1 - Utecht, Manuel Martin A1 - Hebert, Andreas A1 - Rück-Braun, Karola A1 - Saalfrank, Peter A1 - Tegeder, Petra T1 - Reversible Photoswitching of the Interfacial Nonlinear Optical Response JF - The journal of physical chemistry letters N2 - Incorporating photochromic molecules into organic/inorganic hybrid materials may lead to photoresponsive systems. In such systems, the second-order nonlinear properties can be controlled via external stimulation with light at an appropriate wavelength. By creating photochromic molecular switches containing self-assembled monolayers on Si(111), we can demonstrate efficient reversible switching, which is accompanied by a pronounced modulation of the nonlinear optical (NLO) response of the system. The concept of utilizing functionalized photoswitchable Si surfaces could be a way for the generation of two-dimensional NLO switching materials, which are promising for applications in photonic and optoelectronic devices. Y1 - 2015 U6 - https://doi.org/10.1021/jz502477m SN - 1948-7185 VL - 6 IS - 3 SP - 505 EP - 509 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Schulze, Michael A1 - Utecht, Manuel Martin A1 - Moldt, Thomas A1 - Przyrembel, Daniel A1 - Gahl, Cornelius A1 - Weinelt, Martin A1 - Saalfrank, Peter A1 - Tegeder, Petra T1 - Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers N2 - The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10−18 cm2 for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 196 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-81198 ER - TY - JOUR A1 - Schulze, Michael A1 - Utecht, Manuel Martin A1 - Moldt, Thomas A1 - Przyrembel, Daniel A1 - Gahl, Cornelius A1 - Weinelt, Martin A1 - Saalfrank, Peter A1 - Tegeder, Petra T1 - Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10(-18) cm(2) for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions. Y1 - 2015 U6 - https://doi.org/10.1039/c5cp03093e SN - 1463-9076 SN - 1463-9084 VL - 17 IS - 27 SP - 18079 EP - 18086 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Schulze, Michael A1 - Utecht, Manuel Martin A1 - Moldt, Thomas A1 - Przyrembel, Daniel A1 - Gahl, Cornelius A1 - Weinelt, Martin A1 - Saalfrank, Peter A1 - Tegeder, Petra T1 - Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers JF - Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies N2 - The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10−18 cm2 for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions. Y1 - 2015 U6 - https://doi.org/10.1039/c5cp03093e SN - 1463-9076 SN - 1463-9084 VL - 27 IS - 17 SP - 18079 EP - 18086 PB - Royal Society of Chemistry CY - Cambridge ER - TY - THES A1 - Schwarz, Dana T1 - Nanoporous melamine resin materials BT - synthetic strategies, shape control and adsorption proberties Y1 - 2015 ER - TY - JOUR A1 - Schwarze, Thomas A1 - Riemer, Janine A1 - Eidner, Sascha A1 - Holdt, Hans-Jürgen T1 - A Highly K+-Selective Two-Photon Fluorescent Probe JF - Chemistry - a European journal N2 - A highly K+-selective two-photon fluorescent probe for the in vitro monitoring of physiological K+ levels in the range of 1-100 mM is reported. The two-photon excited fluorescence (TPEF) probe shows a fluorescence enhancement (FE) by a factor of about three in the presence of 160 mM K+, independently of one-photon (OP, 430 nm) or two-photon (TP, 860 nm) excitation and comparable K+-induced FEs in the presence of competitive Na+ ions. The estimated dissociation constant (K-d) values in Na+-free solutions (K-d(OP)=(28 +/- 5) mM and K-d(TP)=(36 +/- 6) mM) and in combined K+/Na+ solutions (K-d(OP)=(38 +/- 8) mM and K-d(TP)=(46 +/- 25) mM) reflecting the high K+/Na+ selectivity of the fluorescent probe. The TP absorption cross-section (sigma(2PA)) of the TPEF probe+160 mMK(+) is 26 GM at 860 nm. Therefore, the TPEF probe is a suitable tool for the in vitro determination of K+. KW - click chemistry KW - fluorescence KW - fluorescent probes KW - potassium KW - two-photon Y1 - 2015 U6 - https://doi.org/10.1002/chem.201501473 SN - 0947-6539 SN - 1521-3765 VL - 21 IS - 32 SP - 11306 EP - 11310 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schöne, Anne-Christin A1 - Richau, Klaus A1 - Kratz, Karl A1 - Schulz, Burkhard A1 - Lendlein, Andreas T1 - Influence of Diurethane Linkers on the Langmuir Layer Behavior of Oligo[(rac-lactide)-co-glycolide]-based Polyesterurethanes JF - Macromolecular rapid communications N2 - Three oligo[(rac-lactide)-co-glycolide] based polyesterurethanes (OLGA-PUs) containing different diurethane linkers are investigated by the Langmuir monolayer technique and compared to poly[(rac-lactide)-co-glycolide] (PLGA) to elucidate the influence of the diurethane junction units on hydrophilicity and packing motifs of these polymers at the air-water interface. The presence of diurethane linkers does not manifest itself in the Langmuir layer behavior both in compression and expansion experiments when monomolecular films of OLGA-PUs are spread on the water surface. However, the linker retard the evolution of morphological structures at intermediate compression level under isobaric conditions (with a surface pressure greater than 11 mN m(-1)) compared to the PLGA, independent on the chemical structure of the diurethane moiety. The layer thicknesses of both OLGA-PU and PLGA films decrease in the high compression state with decreasing surface pressure, as deduced from ellipsometric data. All films must be described with the effective medium approximation as water swollen layers. KW - Brewster angle microscopy KW - Langmuir monolayer KW - poly[(rac-lactide)-co-glycolide] KW - polyesterurethanes KW - spectroscopic ellipsometry Y1 - 2015 U6 - https://doi.org/10.1002/marc.201500316 SN - 1022-1336 SN - 1521-3927 VL - 36 IS - 21 SP - 1910 EP - 1915 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Secker, Christian A1 - Brosnan, Sarah M. A1 - Limberg, Felix Rolf Paul A1 - Braun, Ulrike A1 - Trunk, Matthias A1 - Strauch, Peter A1 - Schlaad, Helmut T1 - Thermally Induced Crosslinking of Poly(N-Propargyl Glycine) JF - Macromolecular chemistry and physics N2 - As polypeptoids become increasingly popular, they present a more soluble and processable alternative to natural and synthetic polypeptides; the breadth of their potential functionality slowly comes into focus. This report analyzes the ability of an alkyne-functionalized polypeptoid, poly(N-propargyl glycine), to crosslink upon heating. The crosslinking process is analyzed by thermal analysis (differential scanning calorimetry and thermogravimetric analysis), Fourier-transform infrared, electron paramagnetic resonance, and solid-state NMR spectroscopy. While a precise mechanism cannot be confidently assigned, it is clear that the reaction proceeds by a radical mechanism that exclusively involves the alkyne functionality, which, upon crosslinking, yields alkene and aromatic products. KW - Fourier-transform infrared KW - metal-free crosslinking KW - polypeptoid KW - propargyl KW - solid-state NMR Y1 - 2015 U6 - https://doi.org/10.1002/macp.201500223 SN - 1022-1352 SN - 1521-3935 VL - 216 IS - 21 SP - 2080 EP - 2085 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Secker, Christian A1 - Brosnan, Sarah M. A1 - Luxenhofer, Robert A1 - Schlaad, Helmut T1 - Poly(alpha-Peptoid)s Revisited: Synthesis, Properties, and Use as Biomaterial JF - Macromolecular bioscience N2 - Polypeptoids have been of great interest in the polymer science community since the early half of the last century; however, they had been basically forgotten materials until the last decades in which they have enjoyed an exciting revival. In this mini-review, we focus on the recent developments in polypeptoid chemistry, with particular focus on polymers synthesized by the ring-opening polymerization (ROP) of amino acid N-carboxyanhydrides (NCAs). Specifically, we will review traditional monomer synthesis (such as Leuchs, Katchalski, and Kricheldorf) and recent advances in polymerization methods to yield both linear, cyclic, and functional polymers, solution and bulk thermal properties, and preliminary results on the use of polypeptoids as biomaterials (i.e immunogenicity, biodistribution, degradability, and drug delivery). KW - amino acid N-carboxyanhydride (NCA) KW - biomaterials KW - peptides KW - properties KW - ring-opening polymerization Y1 - 2015 U6 - https://doi.org/10.1002/mabi.201500023 SN - 1616-5187 SN - 1616-5195 VL - 15 IS - 7 SP - 881 EP - 891 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Secker, Christian A1 - Robinson, Joshua W. A1 - Schlaad, Helmut T1 - Alkyne-X modification of polypeptoids JF - European polymer journal N2 - Poly(N-propargyl glycine) (PNPG) can be readily prepared by ring-opening polymerization of N-propargyl glycine N-carboxyanhydride (NCA) and modified using various addition reactions such as copper catalyzed [3+2] cycloaddition of azide, radical (photo-)addition of thiol, nucleophilic addition of ethylene oxide, and thermal induced cross-linking. It is demonstrated that PNPG can serve as a modular platform to produce a bibliography of novel functional polypeptoid or pseudopeptide materials, including polypeptoid ionic liquids and graft copolymers. KW - Polypeptoid KW - NCA KW - Post-polymerization modification KW - Click chemistry Y1 - 2015 U6 - https://doi.org/10.1016/j.eurpolymj.2014.08.028 SN - 0014-3057 SN - 1873-1945 VL - 62 SP - 394 EP - 399 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Senge, Mathias O. A1 - Dahms, Katja A1 - Holdt, Hans-Jürgen A1 - Kelling, Alexandra T1 - Porphyrin substituent regiochemistry, conformation and packing - the case of 5,10-diphenylporphyrin JF - Zeitschrift für Naturforschung : B, Chemical sciences N2 - 5,10-Disubstituted porphyrins are more recent additions to the family of meso-substituted porphyrins. A crystallographic comparison of 5,10-diphenylporphyrin with the regioisomeric 5,15-disubstituted system reveals striking differences in their conformation. In the free base porphyrins the former uses mainly out-of-plane distortion to alleviate steric strain while in-plane core elongation predominates in the latter. In contrast, the structure of the Cu(II) complex is planar and forms strong p-p aggregates with very small lateral shifts. Macroscopically, the packing is similar to that of porphyrin sponges of the 5,10,15,20-tetraphenylporphyrin type. KW - conformational analysis KW - crystal structure KW - porphyrins KW - tetrapyrroles Y1 - 2015 U6 - https://doi.org/10.1515/znb-2014-0217 SN - 0932-0776 SN - 1865-7117 VL - 70 IS - 2 SP - 119 EP - 123 PB - De Gruyter CY - Tübingen ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Chipanina, Nina N. A1 - Oznobikhina, Larisa P. A1 - Kleinpeter, Erich A1 - Shlykov, Sergey A. A1 - Osadchiy, Dmitriy Yu. T1 - Synthesis and Conformational Analysis of 3-Methyl-3-silatetrahydropyran by GED, FTIR, NMR, and Theoretical Calculations: Comparative Analysis of 1-Hetero-3-methyl-3-silacyclohexanes JF - The journal of organic chemistry N2 - 3-Methyl-3-silatetrahydropyran 1 was synthesized and its molecular structure and conformational behavior was studied by gas-phase electron diffraction (GED), FTIR, low temperature H-1 and C-13 NMR spectroscopy, and by theoretical calculations (DFT, MP2). Two conformers; 1-ax and 1-eq; were located on the potential energy Surface. In the gas phase; a slight predominance of the axial conformer was determined, with the ratio 1-ax:1-eq = 54(9):46(9) (from GED) or 53:47 or 61;39 (from IR). In solution, LT NMR spectroscopy at 103 K gives the ratio 1-ax:1-eq = 35:65 (-Delta G(103)degrees = 0.13 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the corresponding solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of 3-methyl-3-silatettahydropyran in the gas phase and in solution. Comparative analysis of the effect of heteroatom in 1-hetero-3-methyl-3-silacyclohexanes on the structure, stereoelectronic interactions, and relative energies of the conformers is done. Y1 - 2015 U6 - https://doi.org/10.1021/acs.joc.5b02355 SN - 0022-3263 VL - 80 IS - 24 SP - 12492 EP - 12500 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich T1 - Stereochemistry of 3-isopropoxy-3-methyl-1,3-oxasilinane-the first 3-silatetrahydropyran with an exo-cyclic RO-Si bond JF - Tetrahedron N2 - Molecular structure and conformational behavior of 3-isopropoxy-3-methyl-3-oxasilinane is studied by low temperature C-13 NMR spectroscopy and theoretical calculations (DFT, MP2). Two conformers, 1-ROax and 1-ROeq, were found experimentally and located on the potential energy surface. LT C-13 NMR spectroscopy gives almost equal population of the two conformers at 98 K with Delta G(98K)degrees=0.02 kcal/mol in favor of 1-ROax and Delta G(98K)(#)=4.5 kcal/mol. The corresponding DFT calculated values (Delta G(98K)degrees=0.03 kcal/mol, Delta G(98K)(#)=5.1 kcal/mol) are in excellent agreement with the experiment. Detailed DFT and MP2 calculations of the solvent effect on the conformational equilibrium were performed and highlighted the leveling out of the two conformers when transferred from gas to solution. (C) 2015 Published by Elsevier Ltd. KW - 1,3-Oxasilinanes KW - Conformational equilibrium KW - Barrier to ring inversion KW - Solvent effects KW - Assignment of stereochemistry Y1 - 2015 U6 - https://doi.org/10.1016/j.tet.2015.07.047 SN - 0040-4020 VL - 71 IS - 38 SP - 6720 EP - 6726 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Kirpichenko, Svetlana V. A1 - Kleinpeter, Erich A1 - Shlykov, Sergey A. A1 - Osadchiy, Dmitriy Yu. T1 - Molecular structure and conformational analysis of 3-methyl-3-phenyl-3-silatetrahydropyran. Gas-phase electron diffraction, low temperature NMR and quantum chemical calculations JF - Tetrahedron N2 - The molecular structure and conformational behavior of 3-methyl-3-phenyl-3-silatetrahydropyran 1 was studied by gas-phase electron diffraction (GED-MS), low temperature C-13 NMR spectroscopy (LT NMR) and theoretical calculations. The 1-Ph-eq and 1-Ph-ax conformers were located on the potential energy surface. Rotation about the Si-C-ph bond revealed the phenyl ring orthogonal to the averaged plane of the silatetrahydropyran ring for 1-Ph-eq and a twisted orientation for 1-Ph-ax. Theoretical calculations and GED analysis indicate the predominance of 1-Ph-ax in the gas phase with the ratio of conformers (GED) 1-Ph-eq:1-Ph-ax=38:62 (Delta G degrees(307)=-0.29 kcal/mol). In solution, LT NMR spectroscopy gives almost the opposite ratio Ph-eq:1-Ph-ax=68:32 (Delta G degrees(103)=0.16 kcal/mol). Simulation of solvent effects using the PCM continuum model or by calculation of the solvent-solute complexes allowed us to rationalize the experimentally observed opposite conformational predominance of the conformers of compound 1 in the gas phase and in solution. (C) 2015 Elsevier Ltd. All rights reserved. KW - 3-Silatetrahydropyrans KW - Conformational analysis KW - Low temperature NMR spectroscopy KW - Gas-phase electron diffraction KW - Quantum chemical calculations Y1 - 2015 U6 - https://doi.org/10.1016/j.tet.2015.03.117 SN - 0040-4020 VL - 71 IS - 23 SP - 3810 EP - 3818 PB - Elsevier CY - Oxford ER - TY - THES A1 - Soulié, Virginie T1 - Sessile droplets of salt solutions on inert and metallic surfaces T1 - Gouttes sessiles de solutions salines sur des surfaces inertes et métalliques BT - influence of salt concentration gradients on evaporation and corrosion behaviour BT - influence des gradients de concentration en sel sur la dynamique d’Evaporation et le processus de corrosion N2 - In this thesis we investigate the evaporation behaviour of sessile droplets of aqueous saline solutions on planar inert and metallic surfaces and characterise the corrosion phenomenon for iron surfaces. First we study the evaporation behaviour of sessile salty droplets on inert surfaces for a wide range of salt concentrations, relative humidities, droplet sizes and contact angles. Our study reveals the range of validity of the well-accepted diffusion-controlled evaporation model and highlights the impact of salt concentration (surface tension) gradients driven Marangoni flows on the evaporation behaviour and the subsequent salty deposit patterns. Furthermore we study the spatial-temporal evolution of sessile droplets from saline solutions on metallic surfaces. In contrast to the simple, generally accepted Evans droplet model, we show that the corrosion spreads ahead of the macroscopic contact line with a peripheral film. The three-phase contact line is destabilized by surface tension gradients induced by ionic composition changes during the course of the corrosion process and migration of cations towards the droplet perimeter. Finally we investigate the corrosion behaviour under drying salty sessile droplets on metallic surfaces. The corrosion process, in particular the location of anodic and cathodic activities over the footprint droplet area is correlated to the spatial distribution of the salt inside the drying droplet. N2 - Dans cette thèse, la dynamique d’évaporation de gouttes sessiles de solutions salines sur des surfaces planes inertes et métalliques a été étudiée et le phénomène de corrosion pour les surfaces ferriques caractérisé. En premier lieu, nous nous sommes intéressés à la dynamique d’évaporation de gouttes sessiles salées sur des surfaces inertes pour une large gamme de concentrations en sel, d’humidité relatives, de tailles de goutte et d’angles de contact. Notre étude révèle les domaines de validité du modèle classique d’évaporation, processus contrôlé par la diffusion de la vapeur dans l’air et met en évidence l’impact de flux (de Marangoni) induits par des gradients de concentration (tension de surface) en sel sur la dynamique d’évaporation et les dépôts salins obtenus après évaporation de la goutte. De plus, nous nous sommes consacrés à l’évolution spatio-temporelle de gouttes sessiles de solutions salines sur des surfaces métalliques. Contrairement au modèle simplifié de la goutte d’Evans, nous avons montré que le processus de corrosion s’étend aux abords de la ligne de contact, avec la formation d’un film périphérique. La ligne triple est déstabilisée par des gradients de tension de surface induits par des variations de composition ionique au cours du processus de corrosion et la migration des cations vers la périphérie de la goutte. Enfin nous avons étudié le phénomène de corrosion du métal induit par l’évaporation de gouttes sessiles salées. Le processus de corrosion, en particulier la localisation des réactions anodiques et cathodiques sur la surface métallique en contact avec la goutte est corrélée à la distribution spatiale du sel au sein de la goutte s’évaporant. KW - sessile droplet KW - salt KW - evaporation KW - corrosion KW - liegende Tropfen KW - Salz KW - Verdunstung KW - Korrosion KW - gouttes sessiles KW - sel KW - evaporation KW - corrosion Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-90329 ER - TY - JOUR A1 - Strauch, Peter A1 - Neumann, Mike A1 - Kelling, Alexandra A1 - Schilde, Uwe T1 - Bis(1,2-dithiosquarato)nickelates(II): Synthesis, Structure, EPR and Thermal Behavior JF - Acta chimica Slovenica N2 - 1,2-Dithiosquaratonickelates are available by direct synthesis from metal salts with dipotassium-1,2-dithiosquarate and the appropriate counter cations. The synthesis and characterization, including mass spectrometry, of a series 1,2-dithiosquaratonickelates(II), [Ni(dtsq)(2)](2-), with several "onium" cations is reported and the X-ray structures of two diamagnetic complexes, (HexPh(3)P)(2)[Ni(dtsq)(2)] and (BuPh3P)(2)[Ni(dtsq)(2)] with sterically demanding counter ions are presented. The diamagnetic nickel complexes have been doped as host lattices with traces of Cu(II) to measure EPR for additional structural information. The thermal behavior of this series is studied by thermogravimetry and differential thermal analysis (TG/DTA). The thermolysis in air as well as under nitrogen atmosphere of these complexes results in nickel oxide nano-particles in all cases, which are characterized by X-ray powder diffraction. KW - 1,2-Dithiosquarate,1,2-Dithiosquaratonickelate KW - X-ray structure KW - TG/DTA KW - Nickel oxide KW - EPR spectroscopy Y1 - 2015 SN - 1318-0207 SN - 1580-3155 VL - 62 IS - 2 SP - 288 EP - 296 PB - Drustvo CY - Ljubljana ER - TY - JOUR A1 - Sulyanova, Elena A. A1 - Shabalin, Anatoly A1 - Zozulya, Alexey V. A1 - Meijer, Janne-Mieke A1 - Dzhigaev, Dmitry A1 - Gorobtsov, Oleg A1 - Kurta, Ruslan P. A1 - Lazarev, Sergey A1 - Lorenz, Ulf A1 - Singer, Andrej A1 - Yefanov, Oleksandr A1 - Zaluzhnyy, Ivan A1 - Besedin, Ilya A1 - Sprung, Michael A1 - Petukhov, Andrei V. A1 - Vartanyants, Ivan A. T1 - Structural Evolution of Colloidal Crystal Films in the Process of Melting Revealed by Bragg Peak Analysis JF - Langmuir N2 - In situ X-ray diffraction studies of structural evolution of colloidal crystal films formed by polystyrene spherical particles upon incremental heating are reported. The Bragg peak parameters, such as peak position, integrated intensity, and radial and azimuthal widths were analyzed as a function of temperature. A quantitative study of colloidal crystal lattice distortions and mosaic spread as a function of temperature was carried out using Williamson-Hall plots based on mosaic block model. The temperature dependence of the diameter of polystyrene particles was obtained from the analysis of Bragg peaks, and the form factor contribution extracted from the diffraction patterns. Four stages of structural evolution in a colloidal crystal upon heating were identified. Based on this analysis, a model of the heating and melting process in the colloidal crystal film is suggested. Y1 - 2015 U6 - https://doi.org/10.1021/la504652z SN - 0743-7463 VL - 31 IS - 19 SP - 5274 EP - 5283 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Tasior, Mariusz A1 - Bald, Ilko A1 - Deperasińska, Irena A1 - Cywiński, Piotr J. A1 - Gryko, Daniel T. T1 - An internal charge transfer-dependent solvent effect in V-shaped azacyanines N2 - New V-shaped non-centrosymmetric dyes, possessing a strongly electron-deficient azacyanine core, have been synthesized based on a straightforward two-step approach. The key step in this synthesis involves palladium-catalysed cross-coupling of dibromo-N,N′-methylene-2,2′-azapyridinocyanines with arylacetylenes. The resulting strongly polarized π-expanded heterocycles exhibit green to orange fluorescence and they strongly respond to changes in solvent polarity. We demonstrate that differently electron-donating peripheral groups have a significant influence on the internal charge transfer, hence on the solvent effect and fluorescence quantum yield. TD-DFT calculations confirm that, in contrast to the previously studied bis(styryl)azacyanines, the proximity of S1 and T2 states calculated for compounds bearing two 4-N,N-dimethylaminophenylethynyl moieties establishes good conditions for efficient intersystem crossing and is responsible for its low fluorescence quantum yield. Non-linear properties have also been determined for new azacyanines and the results show that depending on peripheral groups, the synthesized dyes exhibit small to large two-photon absorption cross sections reaching 4000 GM. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 306 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102704 SP - 11714 EP - 11720 ER - TY - JOUR A1 - Taubert, Andreas T1 - Electrospinning of Ionogels: Current Status and Future Perspectives JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - Ionogels (IGs), also termed ion gels, are functional hybrid materials based on an ionic liquid (IL) and a polymeric, hybrid, or inorganic matrix. IGs combine the properties of the matrix such as mechanical strength with IL properties like high ionic conductivity, high thermal stability, or catalytic activity. IGs are thus attractive for many applications, but the vast majority of IGs made and published so far are bulk materials or dense films. Applications like sensing or catalysis, however, would benefit from IGs with high surface areas or defined surface morphologies or architectures. In spite of this, only relatively few examples of high-surface-area IGs have been made so far; this has mostly been achieved by electrospinning, which has proven to be a promising strategy towards advanced IGs. The current review discusses first developments and outlines the future potential of electrospun ionogels, predominantly from a materials and inorganic chemistry perspective. KW - Ionic liquids KW - Ionogels KW - Hybrid materials KW - Electrospinning KW - Heterogeneous catalysis KW - Sensors KW - Energy KW - Health Y1 - 2015 U6 - https://doi.org/10.1002/ejic.201402490 SN - 1434-1948 SN - 1099-0682 IS - 7 SP - 1148 EP - 1159 PB - Wiley-VCH CY - Weinheim ER - TY - THES A1 - Taßler, Stephanie T1 - Physical-Chemical Investigation of newly-synthesised Lysine-Based Amino-Functionalised Lipids for gene transfection in 2D and 3D model systems Y1 - 2015 ER - TY - JOUR A1 - Tong, Yujin A1 - Wirth, Jonas A1 - Kirsch, Harald A1 - Wolf, Martin A1 - Saalfrank, Peter A1 - Campen, Richard Kramer T1 - Optically probing Al-O and O-H vibrations to characterize water adsorption and surface reconstruction on alpha-alumina: An experimental and theoretical study JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Oxide/water interfaces are ubiquitous in a wide variety of applications and the environment. Despite this ubiquity, and attendant decades of study, gaining molecular level insight into water/oxide interaction has proven challenging. In part, this challenge springs from a lack of tools to concurrently characterize changes in surface structure (i.e., water/oxide interaction from the perspective of the solid) and O-H population and local environment (i.e., water/oxide interaction from the water perspective). Here, we demonstrate the application of surface specific vibrational spectroscopy to the characterization of the interaction of the paradigmatic alpha-Al2O3(0001) surface and water. By probing both the interfacial Al-O (surface phonon) and O-H spectral response, we characterize this interaction from both perspectives. Through electronic structure calculation, we assign the interfacial Al-O response and rationalize its changes on surface dehydroxylation and reconstruction. Because our technique is all-optical and interface specific, it is equally applicable to oxide surfaces in vacuum, ambient atmospheres and at the solid/liquid interface. Application of this approach to additional alumina surfaces and other oxides thus seems likely to significantly expand our understanding of how water meets oxide surfaces and thus the wide variety of phenomena this interaction controls. (C) 2015 AIP Publishing LLC. Y1 - 2015 U6 - https://doi.org/10.1063/1.4906346 SN - 0021-9606 SN - 1089-7690 VL - 142 IS - 5 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Trautmann, Michael A1 - Holdt, Hans-Jürgen T1 - Separation of platinum and ruthenium by a sulphoxide modified polystyrene resin in laboratory column systems JF - Separation and purification technology N2 - The present study deals with the adsorption performance of fixed bed columns using powdered sulphoxide modified poly(styrene-co-divinylbenzene) (d(10) < 13 mu m, d(50) < 30 mu m, d(90) < 50 mu m) for the separation of platinum and ruthenium from hydrochloric acidic solutions containing both metals (c(Pt) = 20 mg/L, c(Ru) = 10 mg/L). The influence of hydrochloric acid concentration, temperature, flow rate, flow direction, redox potential and bed height on the breakthrough characteristics was examined. Platinum was separately adsorbed mainly induced by hydrochloric acid concentration and redox potential keeping platinum as Pt-IV and ruthenium as Ru-III. Ruthenium was separately adsorbed to 90% essentially induced by hydrochloric acid concentration, temperature and redox potential keeping platinum as Pt-IV and ruthenium predominantly as Ru-IV. Experimental data at optimised separation conditions were fitted to different kinetic models (Thomas, Yoon-Nelson, Bohart-Adams, Wolborska) to characterise the fixed bed column behaviour. Adsorption of both metals was well described by Thomas and Yoon-Nelson model with correlation coefficients R-2 >= 0.95 whereas Bohart-Adams and Wolborska model were less suitable. (C) 2015 Elsevier B.V. All rights reserved. KW - Solid-phase extraction KW - Platinum group metals KW - Sulphoxide KW - Breakthrough curve KW - Kinetic model Y1 - 2015 U6 - https://doi.org/10.1016/j.seppur.2015.05.013 SN - 1383-5866 SN - 1873-3794 VL - 149 SP - 279 EP - 287 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Tremblay, Jean Christophe A1 - Blanco-Rey, Maria T1 - Manipulating interfacial hydrogens at palladium via STM N2 - In this contribution, we provide a detailed dynamical analysis of the interfacial hydrogen migration mediated by scanning tunneling microscopy (STM). Contributions from the STM-current and from the non-adiabatic couplings are taken into account using only first principle models. The slight asymmetry of the tunnelling rates with respect to the potential bias sign inferred from experimental observations is reproduced by weighting the contributions of the metal acceptor–donor states for the propagation of the impinging electrons. The quasi-thermal inelastic collision mechanism is treated perturbatively. The influence of hydrogen pre-coverage is also investigated using new potential energy surfaces obtained from periodic density functional theory calculations. Fully quantum dynamical simulations of the system evolution are performed by solving the Pauli master equation, providing insight into the reaction mechanism of STM manipulation of subsurface hydrogens. It is observed that the hydrogen impurity favors resurfacing over occupation of the bulk and subsurface sites whenever possible. The present simulations give strong indication that the experimentally observed protuberances after STM-excitation are due to hydrogen accumulating in the vicinity of the surface. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 291 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-99511 ER - TY - JOUR A1 - Tritschler, U. A1 - Beck, F. A1 - Schlaad, Helmut A1 - Cölfen, Helmut T1 - Electrochromic properties of self-organized multifunctional V2O5-polymer hybrid films JF - Journal of materials chemistry : C, Materials for optical and electronic devices N2 - Bio-inspired V2O5-polymer hybrid films were prepared following a one-step self-organization procedure based on liquid crystal formation of organic and inorganic components. These materials were previously reported to exhibit advantageous mechanical properties, comparable to biomaterials, such as human bone and dentin. Here, we show that these hybrid films prepared via a fast and simple synthesis procedure have an additional function as an electrochromic material, exhibiting a long-term cycle stability under alternating potentials. The structures were found to remain intact without visible changes after more than hundred switching cycles and storing the devices for several weeks. Consequently, this multifunctional V2O5-polymer hybrid system shows great promise for various technical applications. Y1 - 2015 U6 - https://doi.org/10.1039/c4tc02138j SN - 2050-7526 SN - 2050-7534 VL - 3 IS - 5 SP - 950 EP - 954 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Umbreen, Sumaira A1 - Linker, Torsten T1 - Simple Synthesis of Conformationally Fixed Glycosamine Analogues by Beckmann Rearrangement at the Carbohydrate Ring JF - Chemistry - a European journal N2 - Conformationally fixed carbohydrate analogues are promising small-molecule inhibitors for hydrolases like O-GlcNAcase (OGA); however, their synthesis usually requires many steps. Herein we describe cycloadditions of dichloroketene to various glycals and subsequent Beckmann rearrangements, which offer an easy and stereoselective entry to glycosamine derivatives in good yields. The reactions are applicable for hexoses, pentoses, and disaccharides, and transformations to the corresponding imidates proceed smoothly. First biological tests reveal that such imidates indeed inhibit human OGA. KW - carbohydrates KW - cycloaddition KW - enzyme inhibitors KW - rearrangement KW - selective syntheses Y1 - 2015 U6 - https://doi.org/10.1002/chem.201406546 SN - 0947-6539 SN - 1521-3765 VL - 21 IS - 20 SP - 7340 EP - 7344 PB - Wiley-VCH CY - Weinheim ER - TY - THES A1 - Utecht, Manuel Martin T1 - Zur Optimierung und dem Auslesen molekularer Schalter BT - quantenchemische Untersuchungen an vier Beispielen Y1 - 2015 ER - TY - GEN A1 - Vacogne, Charlotte D. A1 - Brosnan, Sarah M. A1 - Masic, Admir A1 - Schlaad, Helmut T1 - Fibrillar gels via the self-assembly of poly(L-glutamate)-based statistical copolymers N2 - Polypeptides having secondary structures often undergo self-assembly which can extend over multiple length scales. Poly(γ-benzyl-L-glutamate) (PBLG), for example, folds into α-helices and forms physical organogels, whereas poly(L-glutamic acid) (PLGA at acidic pH) or poly(L-glutamate) (PLG at neutral/basic pH) do not form hydrogels. We explored the gelation of modified PBLG and investigated the deprotection of the carboxylic acid moieties in such gels to yield unique hydrogels. This was accomplished through photo-crosslinking gelation of poly(γ-benzyl-L-glutamate-co-allylglycine) statistical copolymers in toluene, tetrahydrofuran, and 1,4-dioxane. Unlike most polymer-based chemical gels, our gels were prepared from dilute solutions (<20 g L−1, i.e., <2% w/v) of low molar mass polymers. Despite such low concentrations and molar masses, our dioxane gels showed high mechanical stability and little shrinkage; remarkably, they also exhibited a porous fibrillar network. Deprotection of the carboxylic acid moieties in dioxane gels yielded pH responsive and highly absorbent PLGA/PLG-based hydrogels (swelling ratio of up to 87), while preserving the network structure, which is an unprecedented feature in the context of crosslinked PLGA gels. These outstanding properties are highly attractive for biomedical materials. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 301 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102289 SP - 5040 EP - 5052 ER - TY - JOUR A1 - Vacogne, Charlotte D. A1 - Brosnan, Sarah M. A1 - Masic, Admir A1 - Schlaad, Helmut T1 - Fibrillar gels via the self-assembly of poly(L-glutamate)-based statistical copolymers JF - Polymer Chemistry N2 - Polypeptides having secondary structures often undergo self-assembly which can extend over multiple length scales. Poly(gamma-benzyl-L-glutamate) (PBLG), for example, folds into a-helices and forms physical organogels, whereas poly(L-glutamic acid) (PLGA at acidic pH) or poly(L-glutamate) (PLG at neutral/basic pH) do not form hydrogels. We explored the gelation of modified PBLG and investigated the deprotection of the carboxylic acid moieties in such gels to yield unique hydrogels. This was accomplished through photo-crosslinking gelation of poly(gamma-benzyl-L-glutamate-co-allylglycine) statistical copolymers in toluene, tetrahydrofuran, and 1,4-dioxane. Unlike most polymer-based chemical gels, our gels were prepared from dilute solutions (<20 g L-1, i.e., <2% w/v) of low molar mass polymers. Despite such low concentrations and molar masses, our dioxane gels showed high mechanical stability and little shrinkage; remarkably, they also exhibited a porous fibrillar network. Deprotection of the carboxylic acid moieties in dioxane gels yielded pH responsive and highly absorbent PLGA/PLG-based hydrogels (swelling ratio of up to 87), while preserving the network structure, which is an unprecedented feature in the context of crosslinked PLGA gels. These outstanding properties are highly attractive for biomedical materials. Y1 - 2015 U6 - https://doi.org/10.1039/c5py00491h SN - 1759-9954 SN - 1759-9962 VL - 6 IS - 28 SP - 5040 EP - 5052 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Vacogne, Charlotte D. A1 - Schlaad, Helmut T1 - Primary ammonium/tertiary amine-mediated controlled ring opening polymerisation of amino acid N-carboxyanhydrides N2 - Stable commercial primary ammonium chlorides were combined with tertiary amines to initiate the controlled ring opening polymerisation of amino acid N-carboxyanhydrides to yield polypeptides with defined end group structure, predetermined molar mass and narrow molar mass distribution. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 307 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102718 SP - 15645 EP - 15648 ER - TY - JOUR A1 - Vacogne, Charlotte D. A1 - Schlaad, Helmut T1 - Primary ammonium/tertiary amine-mediated controlled ring opening polymerisation of amino acid N-carboxyanhydrides JF - Chemical communications N2 - Stable commercial primary ammonium chlorides were combined with tertiary amines to initiate the controlled ring opening polymerisation of amino acid N-carboxyanhydrides to yield polypeptides with defined end group structure, predetermined molar mass and narrow molar mass distribution. Y1 - 2015 U6 - https://doi.org/10.1039/c5cc06905j SN - 1359-7345 SN - 1364-548X VL - 51 IS - 86 SP - 15645 EP - 15648 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Vankar, Yashwant D. A1 - Linker, Torsten T1 - Recent Developments in the Synthesis of 2-C-Branched and 1,2-Annulated Carbohydrates JF - European journal of organic chemistry N2 - The importance of carbohydrate chemistry in biological and medicinal chemistry has led to enormous developments in the synthesis of carbohydrate mimics. In this context, the synthesis of branched sugars in general and of 2-C-branched carbohydrates in particular, as well as the synthesis of 1,2-annulated sugars, have received immense attention. They serve not only as carbohydrate mimics in the form of stand-alone molecules, but also as useful intermediates in the synthesis of many natural products, their analogues, and glycosidase inhibitors. This microreview covers the recent synthetic efforts in this area and puts the subject matter into proper perspective for future developments. KW - Synthetic methods KW - Annulation KW - Carbohydrates KW - Carbohydrate mimics Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201501176 SN - 1434-193X SN - 1099-0690 IS - 35 SP - 7633 EP - 7642 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Vogel, Stefanie A1 - Rackwitz, Jenny A1 - Schuerman, Robin A1 - Prinz, Julia A1 - Milosavljevic, Aleksandar R. A1 - Refregiers, Matthieu A1 - Giuliani, Alexandre A1 - Bald, Ilko T1 - Using DNA origami nanostructures to determine absolute cross sections for UV photon-induced DNA strand breakage JF - The journal of physical chemistry letters N2 - We have characterized ultraviolet (UV) photon-induced DNA strand break processes by determination of absolute cross sections for photoabsorption and for sequence-specific DNA single strand breakage induced by photons in an energy range from 6.50 to 8.94 eV. These represent the lowest-energy photons able to induce DNA strand breaks. Oligonudeotide targets are immobilized on a UV transparent substrate in controlled quantities through attachment to DNA origami templates. Photon-induced dissociation of single DNA strands is visualized and quantified using atomic force microscopy. The obtained quantum yields for strand breakage vary between 0.06 and 0.5, indicating highly efficient DNA strand breakage by UV photons, which is clearly dependent on the photon energy. Above the ionization threshold strand breakage becomes clearly the dominant form of DNA radiation damage, which is then also dependent on the nucleotide sequence. Y1 - 2015 U6 - https://doi.org/10.1021/acs.jpclett.5b02238 SN - 1948-7185 VL - 6 IS - 22 SP - 4589 EP - 4593 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Vukicevic, Radovan A1 - Neffe, Axel T. A1 - Luetzow, Karola A1 - Pierce, Benjamin F. A1 - Lendlein, Andreas T1 - Conditional Ultrasound Sensitivity of Poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] Microgels for Controlled Lipase Release JF - Macromolecular rapid communications N2 - Triggering the release of cargo from a polymer network by ultrasonication as an external, non-invasive stimulus can be an interesting concept for on-demand release. Here, it is shown that, in pH-and thermosensitive microgels, the ultrasound sensitivity of the polymer network depends on the external conditions. Crosslinked poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] microgels showed a volume phase transition temperature (VPTT) of 25-50 degrees C, which increases with decreasing pH. Above the VPTT the polymer chains are collapsed, while below VPTT they are extended. Only in the case of maximum observed swelling, where the polymer chains are expanded, the microgels are mechanically fragmented through ultrasonication. In contrast, when the polymer chains are partially collapsed it is not possible to manipulate the microgels by ultrasound. Additionally, the ultrasound-induced on-demand release of wheat germ lipase from the microgels could be demonstrated successfully. The principle of conditional ultrasound sensitivity is likely to be general and can be used for selection of matrix-cargo combinations. KW - ultrasound KW - polymers KW - microgels KW - lipase release KW - controlled release KW - thermoresponsive polymers KW - biomaterials Y1 - 2015 U6 - https://doi.org/10.1002/marc.201500311 SN - 1022-1336 SN - 1521-3927 VL - 36 IS - 21 SP - 1891 EP - 1896 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Wang, Li A1 - Baudis, Stefan A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Characterization of bi-layered magnetic nanoparticles synthesized via two-step surface-initiated ring-opening polymerization JF - Pure and applied chemistry : official journal of the International Union of Pure and Applied Chemistry N2 - A versatile strategy to integrate multiple functions in a polymer based material is the formation of polymer networks with defined nanostructures. Here, we present synthesis and comprehensive characterization of covalently surface functionalized magnetic nanoparticles (MNPs) comprising a bi-layer oligomeric shell, using Sn(Oct)(2) as catalyst for a two-step functionalization. These hydroxy-terminated precursors for degradable magneto-and thermo-sensitive polymer networks were prepared via two subsequent surfaceinitiated ring-opening polymerizations (ROPs) with omega-pentadecalactone and e-caprolactone. A two-step mass loss obtained in thermogravimetric analysis and two distinct melting transitions around 50 and 85 degrees C observed in differential scanning calorimetry experiments, which are attributed to the melting of OPDL and OCL crystallites, confirmed a successful preparation of the modified MNPs. The oligomeric coating of the nanoparticles could be visualized by transmission electron microscopy. The investigation of degrafted oligomeric coatings by gel permeation chromatography and H-1-NMR spectroscopy showed an increase in number average molecular weight as well as the presence of signals related to both of oligo(omega-pentadecalactone) (OPDL) and oligo(e-caprolactone) (OCL) after the second ROP. A more detailed analysis of the NMR results revealed that only a few.-pentadecalactone repeating units are present in the degrafted oligomeric bi-layers, whereby a considerable degree of transesterification could be observed when OPDL was polymerized in the 2nd ROP step. These findings are supported by a low degree of crystallinity for OPDL in the degrafted oligomeric bi-layers obtained in wide angle X-ray scattering experiments. Based on these findings it can be concluded that Sn(Oct)(2) was suitable as catalyst for the preparation of nanosized bi-layered coated MNP precursors by a two-step ROP. KW - degradable polyester KW - magnetic nanoparticles KW - nanoparticle characterization KW - NICE-2014 KW - ring opening polymerization KW - surface functionalization Y1 - 2015 U6 - https://doi.org/10.1515/pac-2015-0607 SN - 0033-4545 SN - 1365-3075 VL - 87 IS - 11-12 SP - 1085 EP - 1097 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Wang, Weiwei A1 - Kratz, Karl A1 - Behl, Marc A1 - Yan, Wan A1 - Liu, Yue A1 - Xu, Xun A1 - Baudis, Stefan A1 - Li, Zhengdong A1 - Kurtz, Andreas A1 - Lendlein, Andreas A1 - Ma, Nan T1 - The interaction of adipose-derived human mesenchymal stem cells and polyether ether ketone JF - Clinical hemorheology and microcirculation : blood flow and vessels N2 - Polyether ether ketone (PEEK) as a high-performance, thermoplastic implant material entered the field of medical applications due to its structural function and commercial availability. In bone tissue engineering, the combination of mesenchymal stem cells (MSCs) with PEEK implants may accelerate the bone formation and promote the osseointegration between the implant and the adjacent bone tissue. In this concept the question how PEEK influences the behaviour and functions of MSCs is of great interest. Here the cellular response of human adipose-derived MSCs to PEEK was evaluated and compared to tissue culture plate (TCP) as the reference material. Viability and morphology of cells were not altered when cultured on the PEEK film. The cells on PEEK presented a high proliferation activity in spite of a relatively lower initial cell adhesion rate. There was no significant difference on cell apoptosis and senescence between the cells on PEEK and TCP. The inflammatory cytokines and VEGF secreted by the cells on these two surfaces were at similar levels. The cells on PEEK showed up-regulated BMP2 and down-regulated BMP4 and BMP6 gene expression, whereas no conspicuous differences were observed in the committed osteoblast markers (BGLAP, COL1A1 and Runx2). With osteoinduction the cells on PEEK and TCP exhibited a similar osteogenic differentiation potential. Our results demonstrate the biofunctionality of PEEK for human MSC cultivation and differentiation. Its clinical benefits in bone tissue engineering may be achieved by combining MSCs with PEEK implants. These data may also provide useful information for further modification of PEEK with chemical or physical methods to regulate the cellular processes of MSCs and to consequently improve the efficacy of MSC-PEEK based therapies. KW - Polyether ether ketone KW - mesenchymal stem cells KW - biocompatibility KW - cell-material interaction KW - osteogenic differentiation Y1 - 2015 U6 - https://doi.org/10.3233/CH-152001 SN - 1386-0291 SN - 1875-8622 VL - 61 IS - 2 SP - 301 EP - 321 PB - IOS Press CY - Amsterdam ER - TY - JOUR A1 - Wang, Xuebin A1 - Wang, Xiaoli A1 - Hu, Jing A1 - Wang, Zhaoya A1 - Pimpalpalle, Tukaram M. A1 - Linker, Torsten A1 - Yin, Jian T1 - Study on the Synthesis of Novel Sugar Amino Acids T1 - 新型糖氨基酸类化合物的合成研究 JF - Acta chimica Sinica = Huaxue-xuebao N2 - Sugar amino acids (SAAs) are carbohydrate derivatives bearing both amino and carboxylic acid functional groups. SAAs represent an important class of multifunctional building blocks, which are amenable to serve as glycomimetics or peptidomimetics with well-defined structures and useful properties. Because SAAs exist in nature in many forms with various biological activities, recently, many unnatural SAAs, as the demand for finding new molecules to discover new drugs and new materials, have been designed and synthesized by a number of research groups. In this paper, we have developed a convenient method for the synthesis of novel SAAs gluco-7 and galacto-7 for the first time. The structure of gluco-7 was similar to the natural SAA glucosaminuronic acid that was a component of many typical bacterial cell walls and could be used for the preparation of type D flu vaccine; while galacto-7 was similar to the natural SAA galactosaminuronic acid that was one of bacterial Vi-antigen components of Escherichia coli. Starting from unexpensive and commercially available 3,4,6-tri-O-acetyl-D-glucal and 3,4,6-tri-O-acetyl-D-galactal, two novel SAAs gluco-7 and galacto-7 were achieved in the linear 6 steps with 34% overall yield and 19% overall yield, respectively. The key reactions included radical addition, decarboxylation, iodine generation reaction, azide reaction and reductive amination reaction. The crucial step was the synthesis of the target compound gluco-7 from gluco-6. By using method A, the target compound gluco-7 was obtained in 4 steps with 63% overall yield. To optimize the transformation from gluco-6 to gluco-7, method B was developed to generate gluco-7 by using one-pot reaction successfully with 76% yield only in one step. It proved that method B was superior to method A with shorter steps and higher yields. All the new compounds were characterized by IR, H-1 NMR, C-13 NMR and HRMS data. Study on the synthesis and biological evaluation of linear and cyclic oligomers derived from gluco-7 and galacto-7 are currently in progress. KW - sugar amino acids KW - glycal KW - radical addition KW - one-pot reaction KW - synthesis Y1 - 2015 U6 - https://doi.org/10.6023/A15030205 SN - 0567-7351 VL - 73 IS - 7 SP - 699 EP - 704 PB - Science China Press CY - Beijing ER -