TY - GEN A1 - Mehrabi, Pedram A1 - Schulz, Eike A1 - Müller-Werkmeister, Henrike A1 - Persch, Elke A1 - De Gasparo, Raoul A1 - Diederich, Francois A1 - Tellkamp, Friedjof A1 - Pai, Emil F. A1 - Miller, R. J. Dwayne T1 - Time-resolved crystallography via an interlacing approach allows elucidation of milliseconds to seconds time delays T2 - Acta Crystallographica Section A KW - Time-resolved crystallography KW - crystallography KW - enzymology KW - method development Y1 - 2018 U6 - https://doi.org/10.1107/S205327331809321X SN - 2053-2733 VL - 74 SP - E138 EP - E138 PB - International Union of Crystallography CY - Chester ER - TY - JOUR A1 - Holland-Moritz, Henry A1 - Graupner, Julia A1 - Möller, Wolfhard A1 - Pacholski, Claudia A1 - Ronning, Carsten T1 - Dynamics of nanoparticle morphology under low energy ion irradiation JF - Nanotechnology N2 - If nanostructures are irradiated with energetic ions, the mechanism of sputtering becomes important when the ion range matches about the size of the nanoparticle. Gold nanoparticles with diameters of similar to 50 nm on top of silicon substrates with a native oxide layer were irradiated by gallium ions with energies ranging from 1 to 30 keV in a focused ion beam system. High resolution in situ scanning electron microscopy imaging permits detailed insights in the dynamics of the morphology change and sputter yield. Compared to bulk-like structures or thin films, a pronounced shaping and enhanced sputtering in the nanostructures occurs, which enables a specific shaping of these structures using ion beams. This effect depends on the ratio of nanoparticle size and ion energy. In the investigated energy regime, the sputter yield increases at increasing ion energy and shows a distinct dependence on the nanoparticle size. The experimental findings are directly compared to Monte Carlo simulations obtained from iradina and TRI3DYN, where the latter takes into account dynamic morphological and compositional changes of the target. KW - ion beam KW - nanoparticles KW - sputtering KW - Monte Carlo KW - in situ Y1 - 2018 U6 - https://doi.org/10.1088/1361-6528/aac36c SN - 0957-4484 SN - 1361-6528 VL - 29 IS - 31 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Mertens, Monique A1 - Hilsch, Malte A1 - Haralampiev, Ivan A1 - Volkmer, Rudolf A1 - Wessig, Pablo A1 - Müller, Peter T1 - Synthesis and characterization of a new Bifunctionalized, Fluorescent, and Amphiphilic molecule for recruiting SH-Containing molecules to membranes JF - ChemBioChem N2 - This study describes the synthesis and characterization of an amphiphilic construct intended to recruit SH-containing molecules to membranes. The construct consists of 1)an aliphatic chain to enable anchoring within membranes, 2)a maleimide moiety to react with the sulfhydryl group of a soluble (bio)molecule, and 3)a fluorescence moiety to allow the construct to be followed by fluorescence spectroscopy and microscopy. It is shown that the construct can be incorporated into preformed membranes, thus allowing application of the approach with biological membranes. The close proximity between the fluorophore and the maleimide moiety within the construct causes fluorescence quenching. This allows monitoring of the reaction with SH-containing molecules by measurement of increases in fluorescence intensity and lifetime. Notably, the construct distributes into laterally ordered membrane domains of lipid vesicles, which is probably triggered by the length of its membrane anchor. The advantages of the new construct can be employed for several biological, biotechnological, and medicinal applications. KW - DBD dyes KW - fatty acids KW - liposomes KW - maleimide KW - membranes KW - palmitoylation Y1 - 2018 U6 - https://doi.org/10.1002/cbic.201800268 SN - 1439-4227 SN - 1439-7633 VL - 19 IS - 15 SP - 1643 EP - 1647 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Shainyan, Bagrat A. A1 - Suslova, Elena N. A1 - Tran Dinh Phien, A1 - Shlykov, Sergey A. A1 - Kleinpeter, Erich T1 - Synthesis, conformational preferences in gas and solution, and molecular gear rotation in 1-(dimethylamino)-1-phenyl-1-silacyclohexane by gas phase electron diffraction (GED), LT NMR and theoretical calculations JF - Tetrahedron N2 - 1-(Dimethylamino)-1-phenyl-1-silacyclohexane 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED), low temperature C-13 NMR spectroscopy and quantum-chemical calculations. The predominance of the 1-Ph-ax conformer (1-Ph-eq:1-Ph-ax ratio of 20:80%, Delta G degrees (317 K) = -0.87 kcal/mol) in the gas phase is close to the theoretically estimated conformational equilibrium. In solution, low temperature NMR spectroscopy showed analyzable decoalescence of C-ipso and C(1,5) carbon signals in C-13 NMR spectra at 103 K. Opposite to the gas state in the freon solution employed (CD2Cl2/CHFCl2/CHFCl2 = 1:1:3), which is still liquid at 100 K, the 1-Ph-eq conformer was found to be the preferred one [(1-Ph-eq: 1-Ph-ax = 77%: 23%, K = 77/23 = 2.8; -Delta G degrees = -RT In K (at 103 K) = 0.44 +/- 0.1 kcal/mol]. When comparing 1 with 1-phenyl-1-(X)silacylohexanes (X = H, Me, OMe, F, Cl), studied so far, the trend of predominance of the Ph-ax conformer in the gas phase and of the Ph-eq conformer in solution is confirmed. KW - 1-(Dimethylamino)-1-phenyl-1-silacyclohexane KW - Conformational analysis KW - Gas phase electron diffraction KW - Low-temperature d-NMR KW - DFT KW - MP2 KW - M062X/6-311G** calculations Y1 - 2018 U6 - https://doi.org/10.1016/j.tet.2018.06.023 SN - 0040-4020 VL - 74 IS - 32 SP - 4299 EP - 4307 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kretzschmar, Jerome A1 - Haubitz, Toni A1 - Huebner, Rene A1 - Weiss, Stephan A1 - Husar, Richard A1 - Brendler, Vinzenz A1 - Stumpf, Thorsten T1 - Network-like arrangement of mixed-valence uranium oxide nanoparticles after glutathione-induced reduction of uranium(VI) JF - Chemical communications N2 - Glutathione (GSH), a ubiquitous intracellular reducing tripeptide, is able to reduce hexavalent uranium, U(VI), to its tetravalent form, U(IV), in aqueous media in vitro, inducing the formation of nanocrystalline mixed-valence uranium oxide particles. After the initial reduction to U(V) and subsequent dismutation, the yielded U(IV) rapidly hydrolyses under near-neutral conditions forming 2-5 nm sized nanoparticles. The latter further aggregate to 20-40 nm chain-like building blocks that finally arrange as network-like structures. Y1 - 2018 U6 - https://doi.org/10.1039/c8cc02070a SN - 1359-7345 SN - 1364-548X VL - 54 IS - 63 SP - 8697 EP - 8700 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Klopsch, Rebecca A1 - Baldermann, Susanne A1 - Voss, Alexander A1 - Rohn, Sascha A1 - Schreiner, Monika A1 - Neugart, Susanne T1 - Bread enriched with legume microgreens and leaves BT - ontogenetic and baking-driven changes in the profile of secondary plant metabolites JF - Frontiers in chemistry N2 - Flavonoids, carotenoids, and chlorophylls were characterized in microgreens and leaves of pea (Pisum sativum) and lupin (Lupinus angustifolius) as these metabolites change during ontogeny. All metabolites were higher in the leaves for both species. Acylated quercetin and kaempferol sophorotrioses were predominant in pea. Genistein and malonylated chrysoeriol were predominant in lupin. Further, the impact of breadmaking on these metabolites using pea and lupin material of two ontogenetic stages as an added ingredient in wheat-based bread was assessed. In "pea microgreen bread" no decrease of quercetin was found with regard to the non-processed plant material. However kaempferol glycosides showed slight decreases induced by the breadmaking process in "pea microgreen bread" and "pea leaf bread." In "lupin microgreen bread" no decrease of genistein compared to the non-processed plant material was found. Chrysoeriol glycosides showed slight decreases induced by the breadmaking process in "lupin microgreen bread" and "lupin leaf bread." In all breads, carotenoids and chlorophylls were depleted however pheophytin formation was caused. Thus, pea and lupin microgreens and leaves are suitable, natural ingredients for enhancing health-promoting secondary plant metabolites in bread and may even be used to tailor bread for specific consumer health needs. KW - ontogeny KW - microgreen KW - pea KW - lupin KW - flavonoid KW - carotenoid KW - thermal processing of food Y1 - 2018 U6 - https://doi.org/10.3389/fchem.2018.00322 SN - 2296-2646 VL - 6 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Fang, Liang A1 - Gould, Oliver E. C. A1 - Lysyakova, Liudmila A1 - Jiang, Yi A1 - Sauter, Tilman A1 - Frank, Oliver A1 - Becker, Tino A1 - Schossig, Michael A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Implementing and quantifying the shape-memory effect of single polymeric micro/nanowires with an atomic force microscope JF - ChemPhysChem : a European journal of chemical physics and physical chemistry N2 - The implementation of shape-memory effects (SME) in polymeric micro- or nano-objects currently relies on the application of indirect macroscopic manipulation techniques, for example, stretchable molds or phantoms, to ensembles of small objects. Here, we introduce a method capable of the controlled manipulation and SME quantification of individual micro- and nano-objects in analogy to macroscopic thermomechanical test procedures. An atomic force microscope was utilized to address individual electro-spun poly(ether urethane) (PEU) micro- or nanowires freely suspended between two micropillars on a micro-structured silicon substrate. In this way, programming strains of 10 +/- 1% or 21 +/- 1% were realized, which could be successfully fixed. An almost complete restoration of the original free-suspended shape during heating confirmed the excellent shape-memory performance of the PEU wires. Apparent recovery stresses of sigma(max,app)=1.2 +/- 0.1 and 33.3 +/- 0.1MPa were obtained for a single microwire and nanowire, respectively. The universal AFM test platform described here enables the implementation and quantification of a thermomechanically induced function for individual polymeric micro- and nanosystems. KW - cyclic thermomechanical testing KW - atomic force microscopy KW - soft matter micro- and nanowires KW - shape-memory effect KW - materials science Y1 - 2018 U6 - https://doi.org/10.1002/cphc.201701362 SN - 1439-4235 SN - 1439-7641 VL - 19 IS - 16 SP - 2078 EP - 2084 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Dani, Alessandro A1 - Taeuber, Karoline A1 - Zhang, Weiyi A1 - Schlaad, Helmut A1 - Yuan, Jiayin T1 - Stable covalently photo-cross-linked porous poly(ionic liquid) membrane with gradient pore size T2 - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS N2 - Porous polyelectrolyte membranes stable in a highly ionic environment are obtained by covalent crosslinking of an imidazolium-based poly(ionic liquid). The crosslinking reaction involves the UV light-induced thiol-ene (click) chemistry, and the phase separation, occurring during the crosslinking step, generates a fully interconnected porous structure in the membrane. The porosity is on the order of the micrometer scale and the membrane shows a gradient of pore size across the membrane cross-section. The membrane can separate polystyrene latex particles of different size and undergoes actuation in contact with acetone due to the asymmetric porous structure. Y1 - 2018 SN - 0065-7727 VL - 256 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zhong, Qi A1 - Mi, Lei A1 - Metwalli, Ezzeldin A1 - Biessmann, Lorenz A1 - Philipp, Martine A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Cubitt, Robert A1 - Schwartzkopf, Matthias A1 - Roth, Stephan V. A1 - Wang, Jiping A1 - Müller-Buschbaum, Peter T1 - Effect of chain architecture on the swelling and thermal response of star-shaped thermo-responsive (poly(methoxy diethylene glycol acrylate)-block-polystyrene)(3) block copolymer films JF - Soft matter N2 - The effect of chain architecture on the swelling and thermal response of thin films obtained from an amphiphilic three-arm star-shaped thermo-responsive block copolymer poly(methoxy diethylene glycol acrylate)-block-polystyrene ((PMDEGA-b-PS)(3)) is investigated by in situ neutron reflectivity (NR) measurements. The PMDEGA and PS blocks are micro-phase separated with randomly distributed PS nanodomains. The (PMDEGA-b-PS)(3) films show a transition temperature (TT) at 33 degrees C in white light interferometry. The swelling capability of the (PMDEGA-b-PS)(3) films in a D2O vapor atmosphere is better than that of films from linear PS-b-PMDEGA-b-PS triblock copolymers, which can be attributed to the hydrophilic end groups and limited size of the PS blocks in (PMDEGA-b-PS)(3). However, the swelling kinetics of the as-prepared (PMDEGA-b-PS)(3) films and the response of the swollen film to a temperature change above the TT are significantly slower than that in the PS-b-PMDEGA-b-PS films, which may be related to the conformation restriction by the star-shape. Unlike in the PS-b-PMDEGA-b-PS films, the amount of residual D2O in the collapsed (PMDEGA-b-PS)(3) films depends on the final temperature. It decreases from (9.7 +/- 0.3)% to (7.0 +/- 0.3)% or (6.0 +/- 0.3)% when the final temperatures are set to 35 degrees C, 45 degrees C and 50 degrees C, respectively. This temperature-dependent reduction of embedded D2O originates from the hindrance of chain conformation from the star-shaped chain architecture. Y1 - 2018 U6 - https://doi.org/10.1039/c8sm00965a SN - 1744-683X SN - 1744-6848 VL - 14 IS - 31 SP - 6582 EP - 6594 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Tuncaboylu, Deniz Ceylan A1 - Friess, Fabian A1 - Wischke, Christian A1 - Lendlein, Andreas T1 - A multifunctional multimaterial system for on-demand protein release JF - Journal of controlled release N2 - In order to provide best control of the regeneration process for each individual patient, the release of protein drugs administered during surgery may need to be timely adapted and/or delayed according to the progress of healing/regeneration. This study aims to establish a multifunctional implant system for a local on-demand release, which is applicable for various types of proteins. It was hypothesized that a tubular multimaterial container kit, which hosts the protein of interest as a solution or gel formulation, would enable on-demand release if equipped with the capacity of diameter reduction upon external stimulation. Using devices from poly(epsilon-caprolactone) networks, it could be demonstrated that a shape-memory effect activated by heat or NIR light enabled on-demand tube shrinkage. The decrease of diameter of these shape-memory tubes (SMT) allowed expelling the payload as demonstrated for several proteins including SDF-1 alpha, a therapeutically relevant chemotactic protein, to achieve e.g. continuous release with a triggered add-on dosing (open tube) or an on-demand onset of bolus or sustained release (sealed tube). Considering the clinical relevance of protein factors in (stem) cell attraction to lesions and the progress in monitoring biomarkers in body fluids, such on-demand release systems may be further explored e.g. in heart, nerve, or bone regeneration in the future. KW - Shape-memory polymer KW - On-demand release KW - Proteins KW - Poly(epsilon-caprolactone) networks KW - Near infrared light triggered shape-recovery Y1 - 2018 U6 - https://doi.org/10.1016/j.jconrel.2018.06.022 SN - 0168-3659 SN - 1873-4995 VL - 284 SP - 240 EP - 247 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wang, Li A1 - Razzaq, Muhammad Yasar A1 - Rudolph, Tobias A1 - Heuchel, Matthias A1 - Nöchel, Ulrich A1 - Mansfeld, Ulrich A1 - Jiang, Yi A1 - Gould, Oliver E. C. A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Reprogrammable, magnetically controlled polymeric nanocomposite actuators JF - Material horizons N2 - Soft robots and devices with the advanced capability to perform adaptive motions similar to that of human beings often have stimuli-sensitive polymeric materials as the key actuating component. The external signals triggering the smart polymers’ actuations can be transmitted either via a direct physical connection between actuator and controlling unit (tethered) or remotely without a connecting wire. However, the vast majority of such polymeric actuator materials are limited to one specific type of motion as their geometrical information is chemically fixed. Here, we present magnetically driven nanocomposite actuators, which can be reversibly reprogrammed to different actuation geometries by a solely physical procedure. Our approach is based on nanocomposite materials comprising spatially segregated crystallizable actuation and geometry determining units. Upon exposure to a specific magnetic field strength the actuators’ geometric memory is erased by the melting of the geometry determining units allowing the implementation of a new actuator shape. The actuation performance of the nanocomposites can be tuned and the technical significance was demonstrated in a multi-cyclic experiment with several hundreds of repetitive free-standing shape shifts without losing performance. Y1 - 2018 U6 - https://doi.org/10.1039/c8mh00266e SN - 2051-6347 SN - 2051-6355 VL - 5 IS - 5 SP - 861 EP - 867 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Yang, Guang A1 - Hu, Rongting A1 - Ding, Hong-ming A1 - Kochovski, Zdravko A1 - Mei, Shilin A1 - Lu, Yan A1 - Ma, Yu-qiang A1 - Chen, Guosong A1 - Jiang, Ming T1 - CO2-switchable response of protein microtubules BT - behaviour and mechanism JF - Materials chemistry frontiers N2 - Recently, we proposed a small molecular inducing ligand strategy to assemble proteins into highly-ordered structures via dual non-covalent interactions, i.e. carbohydrate-protein interaction and dimerization of Rhodamine B. Using this approach, artificial protein microtubules were successfully constructed. In this study, we find that these microtubules exhibit a perfect CO2 responsiveness; assembly and disassembly of these microtubules were nicely controlled by the alternative passage of CO2 and N-2. Upon the injection of CO2, a negative net-charged SBA turns into a neutral or positive net-charged SBA, which elongated, to some extent, the effective distance between SBA and Rhodamine B, resulting in the disassociation of the Rhodamine B dimer. Further experimental and simulation results reveal that the CO2-responsive mechanism differs from that of solubility change of the previously reported CO2-responsive synthetic materials. Y1 - 2018 U6 - https://doi.org/10.1039/c8qm00245b SN - 2052-1537 VL - 2 IS - 9 SP - 1642 EP - 1646 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Hoang, Hoa T. A1 - Haubitz, Toni A1 - Kumke, Michael Uwe T1 - Photophysics of "Floppy" Dyadsas Potential Biomembrane Probes JF - Journal of fluorescence N2 - In the study a dyad (C6 probe), constructed of two dyes with highly different hydrophobicities, was investigated by steady-state and time-resolved spectroscopic techniques in chloroform, methanol, and in phospholipid vesicles, respectively. The dyad was built on two dyes: the lipophilic benzo[a]pyrene (BaP) and the hydrophilic sulforhodamine B (SRB). The dyes were linked via a short, but flexible alkyl chain (six C-atoms). Based on their spectroscopic properties, BaP and SRB showed a very efficient non-radiative resonance energy transfer in solution. Incorporation into a lipid bilayer limited the relative flexibility (degree of freedom) between donor and acceptor and was used for the investigation of fundamental photophysical aspects (especially of FRET) as well as to elucidate the potential of the dyad to probe the interface of vesicles (or cells). The location of the two dyes in vesicles and their respective accessibility for interactions with dye-specific antibodies was investigated. Based on the alteration of the anisotropy, on the rotational correlation time as well as on the diffusion coefficient the incorporation of the C6 probe into the vesicles was evaluated. Especially the limitation in the relative movements of the two dyes was considered and used to differentiate between potential parameters, that influence the energy transfer in the dyad. Transient absorption spectroscopy (TAS) and pulsed-interleave single molecule fluorescence experiments were performed to better understand the intramolecular interactions in the dyad. Finally, in a showcase for a biosensing application of the dyads, the binding of an SRB-specific antibody was investigated when the dyad was incorporated in vesicles. KW - Forster resonance energy transfer(FRET) KW - Antibody binding KW - Vesicles KW - Anisotropy KW - Fluorescence correlation KW - Single molecule fluorescence KW - Transient absorption KW - Pulsed interleaved excitation Y1 - 2018 U6 - https://doi.org/10.1007/s10895-018-2286-4 SN - 1053-0509 SN - 1573-4994 VL - 28 IS - 5 SP - 1225 EP - 1237 PB - Springer CY - New York ER - TY - JOUR A1 - Schulze, Sven A1 - Wehrhold, Michel A1 - Hille, Carsten T1 - Femtosecond-Pulsed laser written and etched fiber bragg gratings for fiber-optical biosensing JF - Sensors N2 - We present the development of a label-free, highly sensitive fiber-optical biosensor for online detection and quantification of biomolecules. Here, the advantages of etched fiber Bragg gratings (eFBG) were used, since they induce a narrowband Bragg wavelength peak in the reflection operation mode. The gratings were fabricated point-by-point via a nonlinear absorption process of a highly focused femtosecond-pulsed laser, without the need of prior coating removal or specific fiber doping. The sensitivity of the Bragg wavelength peak to the surrounding refractive index (SRI), as needed for biochemical sensing, was realized by fiber cladding removal using hydrofluoric acid etching. For evaluation of biosensing capabilities, eFBG fibers were biofunctionalized with a single-stranded DNA aptamer specific for binding the C-reactive protein (CRP). Thus, the CRP-sensitive eFBG fiber-optical biosensor showed a very low limit of detection of 0.82 pg/L, with a dynamic range of CRP detection from approximately 0.8 pg/L to 1.2 mu g/L. The biosensor showed a high specificity to CRP even in the presence of interfering substances. These results suggest that the proposed biosensor is capable for quantification of CRP from trace amounts of clinical samples. In addition, the adaption of this eFBG fiber-optical biosensor for detection of other relevant analytes can be easily realized. KW - fiber Bragg gratings KW - ultra-fast laser inscription KW - fiber etching KW - nanostructure fabrication KW - fiber-optical sensors KW - aptamers KW - C-reactive protein KW - biomarker Y1 - 2018 U6 - https://doi.org/10.3390/s18092844 SN - 1424-8220 VL - 18 IS - 9 PB - MDPI CY - Basel ER - TY - JOUR A1 - Pereira, Rui F. P. A1 - Zehbe, Kerstin A1 - Günter, Christina A1 - dos Santos, Tiago A1 - Nunes, Silvia C. A1 - Almeida Paz, Filipe A. A1 - Silva, Maria M. A1 - Granja, Pedro L. A1 - Taubert, Andreas A1 - de Zea Bermudez, Verónica T1 - Ionic liquid-assisted synthesis of mesoporous silk fibroin/silica hybrids for biomedical applications JF - ACS Omega N2 - New mesoporous silk fibroin (SF)/silica hybrids were processed via a one-pot soft and energy-efficient sol-gel chemistry and self-assembly from a silica precursor, an acidic or basic catalyst, and the ionic liquid 1-butyl-3-methylimidazolium chloride, acting as both solvent and mesoporosity-inducer. The as-prepared materials were obtained as slightly transparent-opaque, amorphous monoliths, easily transformed into powders, and stable up to ca. 300 degrees C. Structural data suggest the formation of a hexagonal mesostructure with low range order and apparent surface areas, pore volumes, and pore radii of 205-263 m(2) g(-1), 0.16-0.19 cm(3) g(-1), and 1.2-1.6 nm, respectively. In all samples, the dominating conformation of the SF chains is the beta-sheet. Cytotoxicity/bioactivity resazurin assays and fluorescence microscopy demonstrate the high viability of MC3T3 pre-osteoblasts to indirect (>= 99 +/- 9%) and direct (78 +/- 2 to 99 +/- 13%) contact with the SF/silica materials. Considering their properties and further improvements, these systems are promising candidates to be explored in bone tissue engineering. They also offer excellent prospects as electrolytes for solid-state electrochemical devices, in particular for fuel cells. Y1 - 2018 U6 - https://doi.org/10.1021/acsomega.8b02051 SN - 2470-1343 VL - 3 IS - 9 SP - 10811 EP - 10822 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Haubitz, Toni A1 - Tsushima, Satoru A1 - Steudtner, Robin A1 - Drobot, Björn A1 - Geipel, Gerhard A1 - Stumpf, Thorsten A1 - Kumke, Michael Uwe T1 - Ultrafast Transient Absorption Spectroscopy of UO(2)(2+)and [UO2Cl](+) JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - For the only water coordinated "free" uranyl (VI) aquo ion in perchlorate solution we identified and assigned several different excited states and showed that the (3)Delta state is the luminescent triplet state from transient absorption spectroscopy. With additional data from other spectroscopic methods (TRLFS, UV/vis) we generated a detailed Jablonski diagram and determined rate constants for several state transitions, like the inner conversion rate constant from the (3)Phi state to the (3)Delta state transition to be 0.35 ps(-1). In contrast to luminescence measurements, it was possible to observe the highly quenched uranyl(VI) ion in highly concentrated chloride solution by TAS and we were able to propose a dynamic quenching mechanism, where chloride complexation is followed by the charge transfer from the excited state uranyl(VI) to chloride. This proposed quenching route is supported by TD-DFT calculations. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpca.8b05567 SN - 1089-5639 VL - 122 IS - 35 SP - 6970 EP - 6977 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Senf, Deborah A1 - Ruprecht, Colin A1 - Kishani, Saina A1 - Matic, Aleksandar A1 - Toriz, Guillermo A1 - Gatenholm, Paul A1 - Wagberg, Lars A1 - Pfrengle, Fabian T1 - Tailormade polysaccharides with defined branching patterns BT - Enzymatic polymerization of arabinoxylan oligosaccharides JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - The heterogeneous nature of non-cellulosic polysaccharides, such as arabinoxylan, makes it difficult to correlate molecular structure with macroscopic properties. To study the impact of specific structural features of the polysaccharides on crystallinity or affinity to other cell wall components, collections of polysaccharides with defined repeating units are required. Herein, a chemoenzymatic approach to artificial arabinoxylan polysaccharides with systematically altered branching patterns is described. The polysaccharides were obtained by glycosynthase-catalyzed polymerization of glycosyl fluorides derived from arabinoxylan oligosaccharides. X-ray diffraction and adsorption experiments on cellulosic surfaces revealed that the physicochemical properties of the synthetic polysaccharides strongly depend on the specific nature of their substitution patterns. The artificial polysaccharides allow structure-property relationship studies that are not accessible by other means. KW - carbohydrates KW - enzymes KW - glycosynthases KW - structure elucidation KW - synthetic methods Y1 - 2018 U6 - https://doi.org/10.1002/anie.201806871 SN - 1433-7851 SN - 1521-3773 VL - 57 IS - 37 SP - 11987 EP - 11992 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Uchida, Ryusuke A1 - Binet, Silvia A1 - Arora, Neha A1 - Jacopin, Gwenole A1 - Alotaibi, Mohammad Hayal A1 - Taubert, Andreas A1 - Zakeeruddin, Shaik Mohammed A1 - Dar, M. Ibrahim A1 - Graetzel, Michael T1 - Insights about the Absence of Rb Cation from the 3D Perovskite Lattice BT - Effect on the Structural, Morphological, and Photophysical Properties and Photovoltaic Performance JF - Small N2 - Efficiencies >20% are obtained from the perovskite solar cells (PSCs) employing Cs+ and Rb+ based perovskite compositions; therefore, it is important to understand the effect of these inorganic cations specifically Rb+ on the properties of perovskite structures. Here the influence of Cs+ and Rb+ is elucidated on the structural, morphological, and photophysical properties of perovskite structures and the photovoltaic performances of resulting PSCs. Structural, photoluminescence (PL), and external quantum efficiency studies establish the incorporation of Cs+ (x < 10%) but amply rule out the possibility of Rb-incorporation into the MAPbI(3) (MA = CH3NH3+) lattice. Moreover, morphological studies and time-resolved PL show that both Cs+ and Rb+ detrimentally affect the surface coverage of MAPbI(3) layers and charge-carrier dynamics, respectively, by influencing nucleation density and by inducing nonradiative recombination. In addition, differential scanning calorimetry shows that the transition from orthorhombic to tetragonal phase occurring around 160 K requires more thermal energy for the Cs-containing MAPbI(3) systems compared to the pristine MAPbI(3). Investigation including mixed halide (I/Br) and mixed cation A-cation based compositions further confirms the absence of Rb+ from the 3D-perovskite lattice. The fundamental insights gained through this work will be of great significance to further understand highly promising perovskite compositions. KW - cation miscibility KW - cesium cation KW - perovskite solar cells KW - rubidium cation KW - X-ray diffraction Y1 - 2018 U6 - https://doi.org/10.1002/smll.201802033 SN - 1613-6810 SN - 1613-6829 VL - 14 IS - 36 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Vacogne, Charlotte Dominique A1 - Wei, Chunxiang A1 - Tauer, Klaus A1 - Schlaad, Helmut T1 - Self-assembly of alpha-helical polypeptides into microscopic and enantiomorphic spirals JF - Journal of the american chemical society N2 - Helical structures are ubiquitous in biological materials and often serve a structural purpose. Bioinspired helical materials can be challenging to synthesize and rarely reach the degree of hierarchy of their natural counterparts. Here we report the first example of particles synthesized by direct emulsification of polypeptides found to display spiral morphologies in the dry state. The polypeptides were alpha-helical homo- and copolypeptides of gamma-benzyl glutamate and allylglycine. The chirality of the spirals was controlled by the chirality of the alpha-helices. Notably, right-handed alpha-helical polypeptides (rich in 1, residues) produced clockwise spirals, whereas left-handed alpha-helical polypeptides (rich in D residues) produced the enantiomorphs, i.e., counterclockwise spirals. The disruption of the alpha-helical conformation by the introduction of chiral defects led to less regular spirals and in some cases their suppression. A hypothesis for the transmission of helicity and chirality from a molecular to a higher hierarchical level, involving fibril bundling of coiled alpha-helices, is proposed. Y1 - 2018 U6 - https://doi.org/10.1021/jacs.8b06503 SN - 0002-7863 VL - 140 IS - 36 SP - 11387 EP - 11394 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Tan, Li A1 - Liu, Bing A1 - Siemensmeyer, Konrad A1 - Glebe, Ulrich A1 - Böker, Alexander T1 - Synthesis of thermo-responsive nanocomposites of superparamagnetic cobalt nanoparticlesipoly(N-isopropylacrylamide) JF - Journal of colloid and interface science N2 - Novel nanocomposites of superparamagnetic cobalt nanoparticles (Co NPs) and poly(N-isopropylacrylamide) (PNIPAM) were fabricated through surface-initiated atom-transfer radical polymerization (SI-ATRP). We firstly synthesized a functional ATRP initiator, containing an amine (as anchoring group) and a 2-bromopropionate group (SI-ATRP initiator). Oleic acid- and trioctylphosphine oxide-coated Co NPs were then modified with the initiator via ligand exchange. The process is facile and rapid for efficient surface functionalization and afterwards the Co NPs can be dispersed into polar solvent DMF without aggregation. Transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and dynamic light scattering measurements confirmed the success of ligand exchange. The following polymerization of NIPAM was conducted on the surface of Co NPs. Temperature-dependent dynamic light scattering study showed the responsive behavior of PNIPAM-coated Co NPs. The combination of superparamagnetic and thermo-responsive properties in these hybrid nanoparticles is promising for future applications e.g. in biomedicine. (C) 2018 Elsevier Inc. All rights reserved. KW - Nanoparticles KW - Superparamagnetic KW - Surface-initiated atom-transfer radical KW - polymerization KW - Responsivity Y1 - 2018 U6 - https://doi.org/10.1016/j.jcis.2018.04.074 SN - 0021-9797 SN - 1095-7103 VL - 526 SP - 124 EP - 134 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Nagel, Oliver A1 - Beta, Carsten A1 - Metzler, Ralf T1 - Non-Gaussianity, population heterogeneity, and transient superdiffusion in the spreading dynamics of amoeboid cells JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - What is the underlying diffusion process governing the spreading dynamics and search strategies employed by amoeboid cells? Based on the statistical analysis of experimental single-cell tracking data of the two-dimensional motion of the Dictyostelium discoideum amoeboid cells, we quantify their diffusive behaviour based on a number of standard and complementary statistical indicators. We compute the ensemble- and time-averaged mean-squared displacements (MSDs) of the diffusing amoebae cells and observe a pronounced spread of short-time diffusion coefficients and anomalous MSD-scaling exponents for individual cells. The distribution functions of the cell displacements, the long-tailed distribution of instantaneous speeds, and the velocity autocorrelations are also computed. In particular, we observe a systematic superdiffusive short-time behaviour for the ensemble- and time-averaged MSDs of the amoeboid cells. Also, a clear anti-correlation of scaling exponents and generalised diffusivity values for different cells is detected. Most significantly, we demonstrate that the distribution function of the cell displacements has a strongly non-Gaussian shape andusing a rescaled spatio-temporal variablethe cell-displacement data collapse onto a universal master curve. The current analysis of single-cell motions can be implemented for quantifying diffusive behaviours in other living-matter systems, in particular, when effects of active transport, non-Gaussian displacements, and heterogeneity of the population are involved in the dynamics. Y1 - 2018 U6 - https://doi.org/10.1039/c8cp04254c SN - 1463-9076 SN - 1463-9084 VL - 20 IS - 35 SP - 23034 EP - 23054 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Fudickar, Werner A1 - Linker, Torsten T1 - Release of Singlet Oxygen from Aromatic Endoperoxides by Chemical Triggers JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - The generation of reactive singlet oxygen under mild conditions is of current interest in chemistry, biology, and medicine. We were able to release oxygen from dipyridylanthracene endoperoxides (EPOs) by using a simple chemical trigger at low temperature. Protonation and methylation of such EPOs strongly accelerated these reactions. Furthermore, the methyl pyridinium derivatives are water soluble and therefore serve as oxygen carriers in aqueous media. Methylation of the EPO of the ortho isomer affords the parent form directly without increasing the temperature under very mild conditions. This exceptional behavior is ascribed to the close contact between the nitrogen atom and the peroxo group. Singlet oxygen is released upon this reaction, and can be used to oxygenate an acceptor such as tetramethylethylene in the dark with no heating. Thus, a new chemical source of singlet oxygen has been found, which is triggered by a simple stimulus. KW - anthracenes KW - donor-acceptor systems KW - mild reaction conditions KW - selective oxidations KW - singlet oxygen Y1 - 2018 U6 - https://doi.org/10.1002/anie.201806881 SN - 1433-7851 SN - 1521-3773 VL - 57 IS - 39 SP - 12971 EP - 12975 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Franz, Alexandra A1 - Többens, Daniel M. A1 - Steckhan, Julia A1 - Schorr, Susan T1 - Determination of the miscibility gap in the solid solutions series of methylammonium lead iodide/chloride JF - Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials N2 - Perovskites are widely known for their enormous possibility of elemental substitution, which leads to a large variety of physical properties. Hybrid perovskites such as CH3NH3PbI3 (MAPbI(3)) and CH3NH3PbCl3 (MAPbCl(3)) are perovskites with an A([XII])B([VI)X(-)([II)(])structure, where A is an organic molecule, B is a lead(II) cation and X is a halide anion of iodine or chlorine. Whereas MAPbCl(3) crystallizes in the cubic space group Pm (3) over barm, MAPbI(3) is in the tetragonal space group I4/mcm. The substitution of I by Cl leads to an increased tolerance against humidity but is challenging or even impossible due to their large difference in ionic radii. Here, the influence of an increasing Cl content in the reaction solution on the miscibility of the solid solution members is examined systematically. Powders were synthesized by two different routes depending on the I:Cl ratio. High-resolution synchrotron X-ray data are used to establish values for the limits of the miscibility gap which are 3.1 (1.1) mol% MAPbCl(3) in MAPI(3) and 1.0 (1) mol% MAPbI(3) in MAPCl. The establishment of relations between average pseudo-cubic lattice parameters for both phases allows a determination of the degree of substitution from the observed lattice parameters. KW - powder diffraction KW - hybrid perovskites KW - miscibility gap KW - MAPbX3 Y1 - 2018 U6 - https://doi.org/10.1107/S2052520618010764 SN - 2052-5206 VL - 74 SP - 445 EP - 449 PB - International Union of Crystallography CY - Chester ER - TY - JOUR A1 - Frede, Katja A1 - Schreiner, Monika A1 - Zrenner, R. A1 - Graefe, Jan A1 - Baldermann, Susanne T1 - Carotenoid biosynthesis of pak choi (Brassica rapa ssp chinensis) sprouts grown under different light-emitting diodes during the diurnal course JF - Photochemical & photobiological sciences N2 - Light-emitting diodes (LEDs) are considered the future of greenhouse lighting. This study investigates the carotenoid concentrations of pak choi sprouts after growth under blue, red and white LEDs at six different time points. Furthermore, the diurnal changes of RNA transcripts of key genes of the carotenoid biosynthesis pathway as well as of the carotenoid cleavage dioxygenase 4 (CCD4) gene and of the transcription factor genes elongated hypocotyl 5 (HY5) and circadian clock associated 1 (CCA1) were investigated. The carotenoid concentrations were steady throughout the day, but showed a small maximum in the afternoon. An average total carotenoid concentration of 536 +/- 29 ng mg(-1) DM produced under white LEDs was measured, which is comparable to previously described field-grown levels. The carotenoid concentrations were slightly lower under blue or red LEDs. Moreover, the diurnal RNA transcript rhythms of most of the carotenoid biosynthesis genes showed an increase during the light period, which can be correlated to the carotenoid maxima in the afternoon. Blue LEDs caused the highest transcriptional induction of biosynthetic genes as well as of CCD4, thereby indicating an increased flux through the pathway. In addition, the highest levels of HY5 transcripts and CCA1 transcripts were determined under blue LEDs. Y1 - 2018 U6 - https://doi.org/10.1039/c8pp00136g SN - 1474-905X SN - 1474-9092 VL - 17 IS - 10 SP - 1289 EP - 1300 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Erler, Alexander A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Grothusheitkamp, Daniela A1 - Kunz, T. A1 - Methner, Frank-Jürgen T1 - Detection of volatile organic compounds in the headspace above mold fungi by GC-soft X-radiation-based APCI-MS JF - Journal of mass spectrometr N2 - Mold fungi on malting barley grains cause major economic loss in malting and brewery facilities. Possible proxies for their detection are volatile and semivolatile metabolites. Among those substances, characteristic marker compounds have to be identified for a confident detection of mold fungi in varying surroundings. The analytical determination is usually performed through passive sampling with solid phase microextraction, gas chromatographic separation, and detection by electron ionization mass spectrometry (EI-MS), which often does not allow a confident determination due to the absence of molecular ions. An alternative is GC-APCI-MS, generally, allowing the determination of protonated molecular ions. Commercial atmospheric pressure chemical ionization (APCI) sources are based on corona discharges, which are often unspecific due to the occurrence of several side reactions and produce complex product ion spectra. To overcome this issue, an APCI source based on soft X-radiation is used here. This source facilitates a more specific ionization by proton transfer reactions only. In the first part, the APCI source is characterized with representative volatile fungus metabolites. Depending on the proton affinity of the metabolites, the limits of detection are up to 2 orders of magnitude below those of EI-MS. In the second part, the volatile metabolites of the mold fungus species Aspergillus, Alternaria, Fusarium, and Penicillium are investigated. In total, 86 compounds were found with GC-EI/APCI-MS. The metabolites identified belong to the substance classes of alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, terpenes, and sesquiterpenes. In addition to substances unspecific for the individual fungus species, characteristic patterns of metabolites, allowing their confident discrimination, were found for each of the 4 fungus species. Sixty-seven of the 86 metabolites are detected by X-ray-based APCI-MS alone. The discrimination of the fungus species based on these metabolites alone was possible. Therefore, APCI-MS in combination with collision induced dissociation alone could be used as a supervision method for the detection of mold fungi. KW - APCI KW - gas chromatography KW - mass spectrometry KW - mold fungi KW - soft X-radiation KW - volatile organic compounds Y1 - 2018 U6 - https://doi.org/10.1002/jms.4210 SN - 1076-5174 SN - 1096-9888 VL - 53 IS - 10 SP - 911 EP - 920 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Plötz, Per-Arno A1 - Megow, Jörg A1 - Niehaus, Thomas A1 - Kühn, Oliver T1 - All-DFTB Approach to the Parametrization of the System-Bath Hamiltonian Describing Exciton-Vibrational Dynamics of Molecular Assemblies JF - Journal of chemical theory and computation N2 - Spectral density functions are central to the simulation of complex many body systems. Their determination requires making approximations not only to the dynamics but also to the underlying electronic structure theory. Here, blending different methods bears the danger of an inconsistent description. To solve this issue we propose an all-DFTB approach to determine spectral densities for the description of Frenkel excitons in molecular assemblies. The protocol is illustrated for a model of a PTCDI crystal, which involves the calculation of monomeric excitation energies and Coulomb couplings between monomer transitions, as well as their spectral distributions due to thermal fluctuations of the nuclei. Using dynamically defined normal modes, a mapping onto the standard harmonic oscillator spectral densities is achieved. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jctc.8b00493 SN - 1549-9618 SN - 1549-9626 VL - 14 IS - 10 SP - 5001 EP - 5010 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Tan, Li A1 - Liu, Bing A1 - Siemensmeyer, Konrad A1 - Glebe, Ulrich A1 - Böker, Alexander T1 - Synthesis of Polystyrene-Coated Superparamagnetic and Ferromagnetic Cobalt Nanoparticles JF - Polymers N2 - Polystyrene-coated cobalt nanoparticles (NPs) were synthesized through a dual-stage thermolysis of cobalt carbonyl (Co-2(CO)(8)). The amine end-functionalized polystyrene surfactants with varying molecular weight were prepared via atom-transfer radical polymerization technique. By changing the concentration of these polymeric surfactants, Co NPs with different size, size distribution, and magnetic properties were obtained. Transmission electron microscopy characterization showed that the size of Co NPs stabilized with lower molecular weight polystyrene surfactants (M-n = 2300 g/mol) varied from 12-22 nm, while the size of Co NPs coated with polystyrene of middle (M-n = 4500 g/mol) and higher molecular weight (M-n = 10,500 g/mol) showed little change around 20 nm. Magnetic measurements revealed that the small cobalt particles were superparamagnetic, while larger particles were ferromagnetic and self-assembled into 1-D chain structures. Thermogravimetric analysis revealed that the grafting density of polystyrene with lower molecular weight is high. To the best of our knowledge, this is the first study to obtain both superparamagnetic and ferromagnetic Co NPs by changing the molecular weight and concentration of polystyrene through the dual-stage decomposition method. KW - cobalt nanoparticles KW - polystyrene KW - superparamagnetic KW - ferromagnetic KW - molecular weight Y1 - 2018 U6 - https://doi.org/10.3390/polym10101053 SN - 2073-4360 VL - 10 IS - 10 PB - MDPI CY - Basel ER - TY - JOUR A1 - Wolff, Christian Michael A1 - Frischmann, Peter D. A1 - Schulze, Marcus A1 - Bohn, Bernhard J. A1 - Wein, Robin A1 - Livadas, Panajotis A1 - Carlson, Michael T. A1 - Jäckel, Frank A1 - Feldmann, Jochen A1 - Würthner, Frank A1 - Stolarczyk, Jacek K. T1 - All-in-one visible-light-driven water splitting by combining nanoparticulate and molecular co-catalysts on CdS nanorods JF - Nature Energy N2 - Full water splitting into hydrogen and oxygen on semiconductor nanocrystals is a challenging task; overpotentials must be overcome for both half-reactions and different catalytic sites are needed to facilitate them. Additionally, efficient charge separation and prevention of back reactions are necessary. Here, we report simultaneous H-2 and O-2 evolution by CdS nanorods decorated with nanoparticulate reduction and molecular oxidation co-catalysts. The process proceeds entirely without sacrificial agents and relies on the nanorod morphology of CdS to spatially separate the reduction and oxidation sites. Hydrogen is generated on Pt nanoparticles grown at the nanorod tips, while Ru(tpy)(bpy)Cl-2-based oxidation catalysts are anchored through dithiocarbamate bonds onto the sides of the nanorod. O-2 generation from water was verified by O-18 isotope labelling experiments, and time-resolved spectroscopic results confirmed efficient charge separation and ultrafast electron and hole transfer to the reaction sites. The system demonstrates that combining nanoparticulate and molecular catalysts on anisotropic nanocrystals provides an effective pathway for visible-light-driven photocatalytic water splitting. Y1 - 2018 U6 - https://doi.org/10.1038/s41560-018-0229-6 SN - 2058-7546 VL - 3 IS - 10 SP - 862 EP - 869 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Qi, Wenjing A1 - Zhang, Yufei A1 - Kochovski, Zdravko A1 - Wang, Jue A1 - Lu, Yan A1 - Chen, Guosong A1 - Jiang, Ming T1 - Self-assembly of Human Galectin-1 via dual supramolecular interactions and its inhibition of T-cell agglutination and apoptosis JF - Nano Research N2 - Recently, we proposed a new strategy to construct artificial plant protein assemblies, which were induced by adding a small molecule, based on dual supramolecular interactions. In this paper, we further explored this method by employing Human Galectin-1 (Gal-1) as a building block to form self-assembled microribbons. Two non-covalent interactions, including lactose-lectin binding and dimerization of Rhodamine B (RhB), induced by the small molecule ligand addition, were involved in the crosslinking of the animal protein, resulting in the formation of assemblies. By using transmission electron microscopy (TEM), cryo-electron microscopy (cryo-EM), and three-dimensional (3D) tomographic analysis, we arrived at a possible mechanistic model for the microribbon formation. Furthermore, the morphology of protein assemblies could be fine-timed by varying the incubation time, the protein/ligand ratio, and the chemical structures of ligands. Interestingly, the formation of protein microribbons successfully inhibited Gal-1 induced T-cell agglutination and apoptosis. This is because the multivalent and dynamic interactions in protein assemblies compete with the binding between Gal-1 and the glycans on cell surfaces, which suppresses the function of Gal-1 in promotion of tumor progression and metastasis. KW - protein self-assembly KW - supramolecular interactions KW - galectin KW - cell agglutination Y1 - 2018 U6 - https://doi.org/10.1007/s12274-018-2169-7 SN - 1998-0124 SN - 1998-0000 VL - 11 IS - 10 SP - 5566 EP - 5572 PB - Tsinghua Univ Press CY - Beijing ER - TY - JOUR A1 - Duydu, Yalcin A1 - Basaran, Nursen A1 - Aydin, Sevtap A1 - Ustundag, Aylin A1 - Yalcin, Can Özgür A1 - Anlar, Hatice Gul A1 - Bacanli, Merve A1 - Aydos, Kaan A1 - Atabekoglu, Cem Somer A1 - Golka, Klaus A1 - Ickstadt, Katja A1 - Schwerdtle, Tanja A1 - Werner, Matthias A1 - Meyer, Sören A1 - Bolt, Hermann M. T1 - Evaluation of FSH, LH, testosterone levels and semen parameters in male boron workers under extreme exposure conditions JF - Archives of toxicology : official journal of EUROTOX N2 - Boric acid and sodium borates are currently classified in the EU-CLP regulation as "toxic to reproduction" under "Category 1B", with hazard statement of H360FD. However, so far field studies on male reproduction in China and in Turkey could not confirm such boron-associated toxic effects. As validation by another independent study is still required, the present study has investigated possible boron-associated effects on male reproduction in workers (n = 212) under different boron exposure conditions. The mean daily boron exposure (DBE) and blood boron concentration of workers in the extreme exposure group (n = 98) were 47.17 +/- 17.47 (7.95-106.8) mg B/day and 570.6 +/- 160.1 (402.6-1100) ng B/g blood, respectively. Nevertheless, boron-associated adverse effects on semen parameters, as well as on FSH, LH and total testosterone levels were not seen, even within the extreme exposure group. With this study, a total body of evidence has accumulated that allows to conclude that male reproductive effects are not relevant to humans, under any feasible and realistic conditions of exposure to inorganic boron compounds. KW - Boron exposure KW - Boric acid KW - Reproductive toxicity KW - FSH KW - LH KW - Testosterone KW - Semen parameters Y1 - 2018 U6 - https://doi.org/10.1007/s00204-018-2296-7 SN - 0340-5761 SN - 1432-0738 VL - 92 IS - 10 SP - 3051 EP - 3059 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Goldhahn, Christian A1 - Schubert, Jonas A1 - Schlaad, Helmut A1 - Ferri, James K. A1 - Fery, Andreas A1 - Chanana, Munish T1 - Synthesis of Metal@Protein@Polymer Nanoparticles with Distinct Interfacial and Phase Transfer Behavior JF - Chemistry of materials : a publication of the American Chemical Society N2 - In this study, we present a novel and facile method for the synthesis of multiresponsive plasmonic nanoparticles with an interesting interfacial behavior. We used thiol-initiated photopolymerization technique to graft poly(N-isopropylacrylamide) onto the surface of protein-coated gold nanoparticles. The combination of the protein bovine serum albumin with the thermoresponsive polymer leads to smart hybrid nanoparticles, which show a stimuli-responsive behavior of their aggregation and a precisely controllable phase transfer behavior. Three interconnected stimuli, namely, temperature, ionic strength, and pH, were identified as property tuning switches. The aggregation was completely reversible and was quantified by determining Smoluchowski’s instability ratios with time-resolved dynamic light scattering. The tunable hydrophobicity via the three stimuli was used to study interfacial activity and phase transfer behavior of the nanoparticles at an octanol/water interface. Depending on the type of coating (i.e., protein or protein/polymer) as well as the three external stimuli, the nanoparticles either remained in the aqueous phase (aggregated or nonaggregated), accumulated at the oil/water interface, wet the glass wall between the glass vial and the octanol phase, or even crossed the oil/water interface. Such smart and interfacially active nanoparticles with external triggers that are capable of crossing oil/water interfaces under physiological conditions open up new avenues for a variety of applications ranging from the development of drug-delivery nanosystems across biological barriers to the preparation of new catalytic materials. Y1 - 2018 U6 - https://doi.org/10.1021/acs.chemmater.8b02314 SN - 0897-4756 SN - 1520-5002 VL - 30 IS - 19 SP - 6717 EP - 6727 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Ehlert, Christopher A1 - Gühr, Markus A1 - Saalfrank, Peter T1 - An efficient first principles method for molecular pump-probe NEXAFS spectra BT - application to thymine and azobenzene JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Pump-probe near edge X-ray absorption fine structure (PP-NEXAFS) spectra of molecules offer insight into valence-excited states, even if optically dark. In PP-NEXAFS spectroscopy, the molecule is "pumped" by UV or visible light enforcing a valence excitation, followed by an X-ray "probe" exciting core electrons into (now) partially empty valence orbitals. Calculations of PP-NEXAFS have so far been done by costly, correlated wavefunction methods which are not easily applicable to medium-sized or large molecules. Here we propose an efficient, first principles method based on density functional theory in combination with the transition potential and Delta SCF methodology (TP-DFT/Delta SCF) to compute molecular ground state and PP-NEXAFS spectra. We apply the method to n ->pi* pump/O-K-edge NEXAFS probe spectroscopy of thymine (for which both experimental and other theoretical data exist) and to n -> pi* or pi -> pi* pump/N-K-edge NEXAFS probe spectroscopies of trans-and cis-azobenzene. Published by AIP Publishing. Y1 - 2018 U6 - https://doi.org/10.1063/1.5050488 SN - 0021-9606 SN - 1089-7690 VL - 149 IS - 14 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Sun, Zhiyong A1 - Glebe, Ulrich A1 - Charan, Himanshu A1 - Böker, Alexander A1 - Wu, Changzhu T1 - Enzyme-Polymer Conjugates as Robust Pickering Interfacial Biocatalysts for Efficient Biotransformations and One-Pot Cascade Reactions JF - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition N2 - Despite the rapid development of Pickering interfacial catalysis (PIC) at liquid-liquid interfaces with chemocatalysts, the use of unstable biocatalysts at emulsion interfaces remains a technical challenge. Herein, we present a Pickering interfacial biocatalysis (PIB) platform based on robust and recyclable enzyme-polymer conjugates that act as both catalytic sites and stabilizers at the interface of Pickering emulsions. The conjugates were prepared by growing poly(N-isopropylacrylamide) on a fragile enzyme, benzaldehyde lyase, under physiological conditions. The mild in situ conjugation process preserved the enzyme structure, and the conjugates were used to emulsify a water-organic two-phase system into a stable Pickering emulsion, leading to a significantly larger interfacial area and a 270-fold improvement in catalytic performance as compared to the unemulsified two-phase system. The PIB system could be reused multiple times. Conjugates of other enzymes were also fabricated and applied for cascade reactions. KW - biphasic catalysis KW - cascade reactions KW - enzyme catalysis KW - enzyme-polymer conjugates KW - Pickering interfacial catalysis Y1 - 2018 U6 - https://doi.org/10.1002/anie.201806049 SN - 1433-7851 SN - 1521-3773 VL - 57 IS - 42 SP - 13810 EP - 13814 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Turrini, Nikolaus G. A1 - Kroepfl, Nina A1 - Jensen, Kenneth Bendix A1 - Reiter, Tamara C. A1 - Francesconi, Kevin A. A1 - Schwerdtle, Tanja A1 - Kroutil, Wolfgang A1 - Kuehnelt, Doris T1 - Biosynthesis and isolation of selenoneine from genetically modified fission yeast JF - Metallomics : integrated biometal science N2 - Selenoneine, a naturally occurring form of selenium, is the selenium analogue of ergothioneine, a sulfur species with health relevance not only as a purported antioxidant but likely also beyond. Selenoneine has been speculated to exhibit similar effects. To study selenoneine's health properties as well as its metabolic transformation, the pure compound is required. Chemical synthesis of selenoneine, however, is challenging and biosynthetic approaches have been sought. We herein report the biosynthesis and isolation of selenoneine from genetically modified fission yeast Schizosaccharomyces pombe grown in a medium containing sodium selenate. After cell lysis and extraction with methanol, selenoneine was purified by three consecutive preparative reversed-phase HPLC steps. The product obtained at the mg level was characterised by high resolution mass spectrometry, NMR and HPLC/ICPMS. Biosynthesis was found to be a promising alternative to chemical synthesis, and should be suitable for upscaling to produce higher amounts of this important selenium species in the future. Y1 - 2018 U6 - https://doi.org/10.1039/c8mt00200b SN - 1756-5901 SN - 1756-591X VL - 10 IS - 10 SP - 1532 EP - 1538 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Tadjoung Waffo, Armel Franklin A1 - Yesildag, Cigdem A1 - Caserta, Giorgio A1 - Katz, Sagie A1 - Zebger, Ingo A1 - Lensen, Marga C. A1 - Wollenberger, Ulla A1 - Scheller, Frieder W. A1 - Altintas, Zeynep T1 - Fully electrochemical MIP sensor for artemisinin JF - Sensors and actuators : B, Chemical N2 - This study aims to develop a rapid, sensitive and cost-effective biomimetic electrochemical sensor for artemisinin determination in plant extracts and for pharmacokinetic studies. A novel molecularly imprinted polymer (MIP)based electrochemical sensor was developed by electropolymerization of o-phenylenediamine (o-PD) in the presence of artemisinin on gold wire surface for sensitive detection of artemisinin. The experimental parameters, including selection of functional monomer, polymerization conditions, template extraction after polymerization, influence of pH and buffer were all optimized. Every step of imprinted film synthesis were evaluated by employing voltammetry techniques, surface-enhanced infrared absorption spectroscopy (SEIRAS) and atomic force microscopy (AFM). The specificity was further evaluated by investigating non-specific artemisinin binding on non-imprinted polymer (NIP) surfaces and an imprinting factor of 6.8 was achieved. The artemisinin imprinted polymers using o-PD as functional monomer have provided highly stable and effective binding cavities for artemisinin. Cross-reactivity studies with drug molecules showed that the MIPs are highly specific for artemisinin. The influence of matrix effect was further investigated both in artificial plant matrix and diluted human serum. The results revealed a high affinity of artemisinin-MIP with dissociation constant of 7.3 x 10(-9) M and with a detection limit of 0.01 mu M and 0.02 mu M in buffer and plant matrix, respectively. KW - Electro-synthesized molecularly imprinted polymer KW - o-Phenylenediamine KW - Artemisinin KW - Antimalarial drug detection KW - Electrochemical sensor Y1 - 2018 U6 - https://doi.org/10.1016/j.snb.2018.08.018 SN - 0925-4005 VL - 275 SP - 163 EP - 173 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Büchner, Dörthe A1 - John, Leonard A1 - Mertens, Monique A1 - Wessig, Pablo T1 - Detection of dsDNA with [1,3]Dioxolo[4,5-f]benzodioxol (DBD) Dyes JF - Chemistry - a European journal N2 - DBD fluorescent dyes have proven to be useful in numerous applications. To widen the range of biological applications, we propose three different types of DBD molecules that have been modified in such a way that DNA interaction becomes probable. After the successful synthesis of all three compounds, we tested their fluorescent properties and their DNA binding abilities. Two of the three probes exhibit an interaction with dsDNA with subsequent fluorescence enhancement. The determined binding constants of the two new DNA dyes are comparable to other minorgroove-binding dyes. Their large Stokes shifts and their long fluorescent lifetimes are outstanding features of these dyes. KW - DNA recognition KW - dyes/pigments KW - fluorescent probes KW - heterocycles KW - scatchard plot Y1 - 2018 U6 - https://doi.org/10.1002/chem.201804057 SN - 0947-6539 SN - 1521-3765 VL - 24 IS - 60 SP - 16183 EP - 16190 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schulz, Eike C. A1 - Mehrabi, Pedram A1 - Müller-Werkmeister, Henrike A1 - Tellkamp, Friedjof A1 - Jha, Ajay A1 - Stuart, William A1 - Persch, Elke A1 - De Gasparo, Raoul A1 - Diederich, François A1 - Pai, Emil F. A1 - Miller, R. J. Dwayne T1 - The hit-and-return system enables efficient time-resolved serial synchrotron crystallography JF - Nature methods : techniques for life scientists and chemists N2 - We present a ‘hit-and-return’ (HARE) method for time-resolved serial synchrotron crystallography with time resolution from milliseconds to seconds or longer. Timing delays are set mechanically, using the regular pattern in fixed-target crystallography chips and a translation stage system. Optical pump-probe experiments to capture intermediate structures of fluoroacetate dehalogenase binding to its ligand demonstrated that data can be collected at short (30 ms), medium (752 ms) and long (2,052 ms) intervals. KW - Biophysical chemistry KW - Enzymes KW - Molecular biophysics KW - X-ray crystallography Y1 - 2018 U6 - https://doi.org/10.1038/s41592-018-0180-2 SN - 1548-7091 SN - 1548-7105 VL - 15 IS - 11 SP - 901 EP - 904 PB - Nature Publishing Group (London) CY - London ER - TY - JOUR A1 - Riemer, Nastja A1 - Coswig, Christin A1 - Shipman, Michael A1 - Schmidt, Bernd T1 - Palladium-catalyzed cross-coupling of arenediazonium salts with organoindium or organobismuth reagents JF - Synlett : accounts and rapid communications in synthetic organic chemistry N2 - Arylindium and isolated triarylbismuth compounds generated in situ react as nucleophiles with arenediazonium salts in palladium-catalyzed cross-coupling reactions to give substituted biphenyls. KW - Palladium-catalyzed cross-coupling of arenediazonium salts with organoindium or organobismuth reagents Y1 - 2018 U6 - https://doi.org/10.1055/s-0037-1611001 SN - 0936-5214 SN - 1437-2096 VL - 29 IS - 18 SP - 2427 EP - 2431 PB - Georg Thieme Verlag KG CY - Stuttgart ER - TY - JOUR A1 - Hardy, John G. A1 - Bertin, Annabelle A1 - Torres-Rendon, Jose Guillermo A1 - Leal-Egana, Aldo A1 - Humenik, Martin A1 - Bauer, Felix A1 - Walther, Andreas A1 - Cölfen, Helmut A1 - Schlaad, Helmut A1 - Scheibel, Thomas R. T1 - Facile photochemical modification of silk protein-based biomaterials JF - Macromolecular bioscience N2 - Silk protein-based materials show promise for application as biomaterials for tissue engineering. The simple and rapid photochemical modification of silk protein-based materials composed of either Bombyx mori silkworm silk or engineered spider silk proteins (eADF4(C16)) is reported. Radicals formed on the silk-based materials initiate the polymerization of monomers (acrylic acid, methacrylic acid, or allylamine) which functionalize the surface of the silk materials with poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), or poly(allylamine) (PAAm). To demonstrate potential applications of this type of modification, the polymer-modified silks are mineralized. The PAA- and PMAA-functionalized silks are mineralized with calcium carbonate, whereas the PAAm-functionalized silks are mineralized with silica, both of which provide a coating on the materials that may be useful for bone tissue engineering, which will be the subject of future investigations. KW - biomaterials KW - chemical modification KW - photochemistry KW - silkworm silk KW - spider silk Y1 - 2018 U6 - https://doi.org/10.1002/mabi.201800216 SN - 1616-5187 SN - 1616-5195 VL - 18 IS - 11 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zheng, Botuo A1 - Bai, Tianwen A1 - Tao, Xinfeng A1 - Schlaad, Helmut A1 - Ling, Jun T1 - Identifying the Hydrolysis of Carbonyl Sulfide as a Side Reaction Impeding the Polymerization of N-Substituted Glycine N-Thiocarboxyanhydride JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences N2 - Polypeptoids are noticeable biological materials due to their versatile properties and various applications in drug delivery, surface modification, self-assembly, etc. N-Substituted glycine N-thiocarboxyanhydrides (NNTAs) are more stable monomers than the corresponding N-carboxyanhydrides (NNCAs) and enable one to prepare polypeptoids via ring-opening polymerization even in the presence of water. However, larger amounts of water (>10,000 ppm) cause inhibition of the polymerization. Herein, we discover that during polymerization hydrogen sulfide evolves from the hydrolysis of carbonyl sulfide, which is the byproduct of ring-opening reaction, and reacts with NNTA to produce cyclic oligopeptoids. The capture of N-ethylethanethioic acid as an intermediate product confirms the reaction mechanism together with density functional theory quantum computational results. By bubbling the polymerization solution with argon, the side reaction can be suppressed to allow the synthesis of polysarcosine with high molar mass (M-n = 11,200 g/mol, D = 1.25) even in the presence of similar to 10,000 ppm of water. Y1 - 2018 U6 - https://doi.org/10.1021/acs.biomac.8b01119 SN - 1525-7797 SN - 1526-4602 VL - 19 IS - 11 SP - 4263 EP - 4269 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Kutlug, Oezgür A1 - Hass, Roland A1 - Reck, Stephan A1 - Hartwig, Andreas T1 - Inline characterization of dispersion formation of a solvent-borne acrylic copolymer by Photon Density Wave spectroscopy JF - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects N2 - Most investigations on phase inversion (PI) of resins upon addition of water have been carried out by dynamic light scattering (DLS), torque, and viscosity measurements. The main problem, however, is analytic discontinuity due to sample removal and a changing matrix due to dilution during the preparation of the aqueous resin dispersions. This work presents Photon Density Wave (PDW) spectroscopy as a tool for the inline characterization of the acetone process for an acrylic copolymer with high acrylic acid (AA) content. PDW spectroscopy revealed different trends for optical properties compared to torque during water feed. Also the absence of PI due to dissolution of copolymer in the solvent/water mixture is observed by PDW spectroscopy. PI for the investigated copolymer did not occour during water feed but during removal of solvent. Different feeding rates of water gave similar trends while a change in temperature and degree of AA neutralization led to changes in optical properties and torque. Thermal processing showed that the optical properties of mixtures prior and after removal of solvent were completely different caused by changes of solubility. KW - Acetone process KW - Dispersion KW - Photon Density Wave spectroscopy KW - Radical polymerization KW - Torque KW - Turbid media Y1 - 2018 U6 - https://doi.org/10.1016/j.colsurfa.2018.08.011 SN - 0927-7757 SN - 1873-4359 VL - 556 SP - 113 EP - 119 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Burek, Katja A1 - Krause, Felix A1 - Schwotzer, Matthias A1 - Nefedov, Alexei A1 - Süssmuth, Julia A1 - Haubitz, Toni A1 - Kumke, Michael Uwe A1 - Thissen, Peter T1 - Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements JF - ACS sustainable chemistry & engineering N2 - In this study, the apparent relationship between the transport process and the surface chemistry of the Calcium-Silicate Hydrate (CSH) phases was investigated. For this purpose, a method was developed to synthesize ultrathin CSH phases to be used as a model substrate with the specific modification of their structure by introducing europium (Eu(III)). The structural and chemical changes during this Eu(III)-doping were observed by means of infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and time-resolved laser fluorescence spectroscopy (TRLFS). These alterations of the CSH phases led to significant changes in the surface chemistry and consequently to considerable variations in the interaction with water, as evidenced by measurements of the contact angles on the modified model substrates. Our results provide the basis for a more profound molecular understanding of reactive transport processes in cement-based systems. Furthermore, these results broaden the perspective of improving the stability of cement-based materials, which are subjected to the impact of aggressive aqueous environments through targeted modifications of the CSH phases. KW - Rare-earth elements KW - Europium KW - Luminescence KW - Metal-proton exchange reaction KW - Contact angle KW - Infrared spectroscopy KW - X-ray photoelectron spectroscopy Y1 - 2018 U6 - https://doi.org/10.1021/acssuschemeng.8b03244 SN - 2168-0485 VL - 6 IS - 11 SP - 14669 EP - 14678 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Hänsel, Marc A1 - Barta, Christoph A1 - Rietze, Clemens A1 - Utecht, Manuel Martin A1 - Rueck-Braun, Karola A1 - Saalfrank, Peter A1 - Tegeder, Petra T1 - Two-Dimensional Nonlinear Optical Switching Materials BT - Molecular Engineering toward High Nonlinear Optical Contrasts JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Combining photochromism and nonlinear optical (NLO) properties of molecular switches-functionalized self-assembled monolayers (SAMs) represents a promising concept toward novel photonic and optoelectronic devices. Using second harmonic generation, density functional theory, and correlated wave function methods, we studied the switching abilities as well as the NLO contrasts between different molecular states of various fulgimide-containing SAMs on Si(111). Controlled variations of the linker systems as well as of the fulgimides enabled us to demonstrate very efficient reversible photoinduced ring-opening/closure reactions between the open and closed forms of the fulgimides. Thus, effective cross sections on the order of 10(-18) cm(-2) are observed. Moreover, the reversible switching is accompanied by pronounced NLO contrasts up to 32%. Further molecular engineering of the photochromic switches and the linker systems may even increase the NLO contrast upon switching. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcc.8b08212 SN - 1932-7447 SN - 1932-7455 VL - 122 IS - 44 SP - 25555 EP - 25564 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Xiong, Tao A1 - Wlodarczyk, Radoslaw A1 - Saalfrank, Peter T1 - Vibrationally resolved absorption and fluorescence spectra of perylene and N-substituted derivatives from autocorrelation function approaches JF - Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature N2 - Vibrationally resolved absorption and emission (fluorescence) spectra of perylene and its N-derivatives in gas phase and in solution (acetonitrile) were simulated using a time-dependent approach based on correlation functions determined by density functional theory. By systematically varying the number and position of N atoms, it is shown that the presence of nitrogen heteroatoms has a negligible effect on the molecular structure and geometric distortions upon electronic transitions, while spectral properties change: in particular the number of N atoms is important while their position is less decisive. Thus, the N-substitution can be used to fine-tune the optical properties of perylene-based molecules. KW - Perylene KW - Vibronic spectrum KW - Correlation function KW - Dimer KW - Excimer KW - PCM Y1 - 2018 U6 - https://doi.org/10.1016/j.chemphys.2018.06.011 SN - 0301-0104 SN - 1873-4421 VL - 515 SP - 728 EP - 736 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Utecht, Manuel Martin A1 - Gaebel, Tina A1 - Klamroth, Tillmann T1 - Desorption induced by low energy charge carriers on Si(111)-7 x 7 BT - first principles molecular dynamics for benzene derivates JF - Journal of computational chemistry : organic, inorganic, physical, biological N2 - We use clusters for the modeling of local ion resonances caused by low energy charge carriers in STM-induced desorption of benzene derivates from Si(111)-7 x 7. We perform Born-Oppenheimer molecular dynamics for the charged systems assuming vertical transitions to the charged states at zero temperature, to rationalize the low temperature activation energies, which are found in experiment for chlorobenzene. Our calculations suggest very similar low temperature activation energies for toluene and benzene. For the cationic resonance transitions to physisorption are found even at 0 K, while the anion remains chemisorbed during the propagations. Further, we also extend our previous static quantum chemical investigations to toluene and benzene. In addition, an in depth analysis of the ionization potentials and electron affinities, which are used to estimate resonance energies, is given. KW - Born-Oppenheimer MD KW - STM-induced reactions KW - cluster models KW - Si(111)-7x7 Y1 - 2018 U6 - https://doi.org/10.1002/jcc.25607 SN - 0192-8651 SN - 1096-987X VL - 39 IS - 30 SP - 2517 EP - 2525 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Tan, Li A1 - Liu, Bing A1 - Glebe, Ulrich A1 - Böker, Alexander T1 - Magnetic Field-Induced Assembly of Superparamagnetic Cobalt Nanoparticles on Substrates and at Liquid-Air Interface JF - Langmuir N2 - Superparamagnetic cobalt nanoparticles (Co NPs) are an interesting material for self-assembly processes because of their magnetic properties. We investigated the magnetic field-induced assembly of superparamagnetic cobalt nanoparticles and compared three different approaches, namely, the assembly on solid substrates, at water-air, and ethylene glycol-air interfaces. Oleic acid- and trioctylphosphine oxide-coated Co NPs were synthesized via a thermolysis of cobalt carbonyl and dispersed into either hexane or toluene. The Co NP dispersion was dropped onto different substrates (e.g., transmission electron microscopy (TEM) grid, silicon wafer) and onto liquid surfaces. Transmission electron microscopy (TEM), scanning force microscopy, optical microscopy, as well as scanning electron microscopy showed that superparamagnetic Co NPs assembled into one-dimensional chains in an external magnetic field. By varying the concentration of the Co NP dispersion (1-5 mg/mL) and the strength of the magnetic field (4-54 mT), the morphology of the chains changed. Short, thin, and flexible chain structures were obtained at low NP concentration and low strength of magnetic field, whereas they became long, thick and straight when the NP concentration and the magnetic field strength increased. In comparison, the assembly of Co NPs from hexane dispersion at ethylene glycol-air interface showed the most regular and homogeneous alignment, since a more efficient spreading could be achieved on ethylene glycol than on water and solid substrates. Y1 - 2018 U6 - https://doi.org/10.1021/acs.langmuir.8b02673 SN - 0743-7463 VL - 34 IS - 46 SP - 13993 EP - 14002 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Yalcinkaya, Hacer A1 - Bressel, Katharina A1 - Lindner, Peter A1 - Gradzielski, Michael T1 - Controlled formation of vesicles with added styrene and their fixation by polymerization JF - Journal of colloid and interface science N2 - Hypothesis: An effective way for fixating vesicle structures is the insertion of monomers and cross-linking agents into their bilayer, and their subsequent polymerization can lead to the formation of polymeric nanocapsules. Particularly attractive here are vesicle systems that form spontaneously well-defined small vesicles, as obtaining such small nanocapsules with sizes below 100 nm is still challenging. Experiments: A spontaneously forming well-defined vesicle system composed of the surfactants TDMAO (tetradecyldimethylamine oxide), Pluronic L35, and LiPFOS (lithium perfluorooctylsulfonate) mixture was used as template for fixation by polymerization. Therefore, styrene monomer was incorporated into the vesicle bilayer and ultimately these structures were fixated by UV induced radical polymerization. Structural alteration of the vesicles upon loading with monomer and the cross-linker as well as the effect of subsequent polymerization in the membrane were investigated in detail by turbidity measurements, dynamic and static light scattering, (DLS, SLS), and small angle neutron scattering (SANS). Findings: The analysis showed the changes on vesicle structures due to the monomer loading, and that these structures can become permanently fixed by the polymerization process. The potential of this approach to produce well-defined nanocapsules starting from a self-assembled system and following polymerization is critically evaluated. (C) 2018 Elsevier Inc. All rights reserved. KW - Template reaction KW - Zwitterionic surfactant KW - Anionic surfactant KW - Styrene KW - Vesicle KW - Small angle neutron scattering KW - Polymerization Y1 - 2018 U6 - https://doi.org/10.1016/j.jcis.2018.07.097 SN - 0021-9797 SN - 1095-7103 VL - 531 SP - 672 EP - 680 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Peng, Xingzhou A1 - Behl, Marc A1 - Zhang, Pengfei A1 - Mazurek-Budzynska, Magdalena A1 - Feng, Yakai A1 - Lendlein, Andreas T1 - Synthesis of Well-Defined Dihydroxy Telechelics by (Co)polymerization of Morpholine-2,5-Diones Catalyzed by Sn(IV) Alkoxide JF - Macromolecular bioscience N2 - Well-defined dihydroxy telechelic oligodepsipeptides (oDPs), which have a high application potential as building blocks for scaffold materials for tissue engineering applications or particulate carrier systems for drug delivery applications are synthesized by ring-opening polymerization (ROP) of morpholine-2,5-diones (MDs) catalyzed by 1,1,6,6-tetra-n-butyl-1,6-distanna-2,5,7,10-tetraoxacyclodecane (Sn(IV) alkoxide). In contrast to ROP catalyzed by Sn(Oct)(2), the usage of Sn(IV) alkoxide leads to oDPs, with less side products and well-defined end groups, which is crucial for potential pharmaceutical applications. A slightly faster reaction of the ROP catalyzed by Sn(IV) alkoxide compared to the ROP initiated by Sn(Oct)(2)/EG is found. Copolymerization of different MDs resulted in amorphous copolymers with T(g)s between 44 and 54 degrees C depending on the molar comonomer ratios in the range from 25% to 75%. Based on the well-defined telechelic character of the Sn(IV) alkoxide synthesized oDPs as determined by matrix-assisted laser desorption/ionization time of flight measurements, they resemble interesting building blocks for subsequent postfunctionalization or multifunctional materials based on multiblock copolymer systems whereas the amorphous oDP-based copolymers are interesting building blocks for matrices of drug delivery systems. KW - oligodepsipeptides KW - ring-opening polymerization KW - Sn(IV) alkoxide KW - telechelics KW - tin(II) 2-ethylhexanoate Y1 - 2018 U6 - https://doi.org/10.1002/mabi.201800257 SN - 1616-5187 SN - 1616-5195 VL - 18 IS - 12 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Hermanns, Jolanda A1 - Schmidt, Bernd T1 - Developing and Applying Stepped Supporting Tools in Organic Chemistry To Promote Students’ Self-Regulated Learning JF - Journal of chemical education N2 - Stepped supporting tools were developed and used in the university seminar Organic Chemistry taken by nonmajor chemistry students, which supported self-regulated learning. These supporting tools were also used for accompanying homework, which included a QR code that led to additional supporting tools. The application of stepped supporting tools in the seminars was evaluated by a four-item Likert scale. The students assessed the tools as a helpful instrument for solving tasks in chemistry. KW - High School/Introductory Chemistry KW - Organic Chemistry Y1 - 2018 U6 - https://doi.org/10.1021/acs.jchemed.8b00565 SN - 0021-9584 SN - 1938-1328 VL - 96 IS - 1 SP - 47 EP - 52 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Noack, Sebastian A1 - Schanzenbach, Dirk A1 - Koetz, Joachim A1 - Schlaad, Helmut T1 - Polylactide-based amphiphilic block copolymers BT - Crystallization-Induced Self-Assembly and Stereocomplexation JF - Macromolecular rapid communications N2 - The aqueous self-assembly behavior of a series of poly(ethylene glycol)-poly(l-/d-lactide) block copolymers and corresponding stereocomplexes is examined by differential scanning calorimetry, dynamic light scattering, and transmission electron microscopy. Block copolymers assemble into spherical micelles and worm-like aggregates at room temperature, whereby the fraction of the latter seemingly increases with decreasing lactide weight fraction or hydrophobicity. The formation of the worm-like aggregates arises from the crystallization of the polylactide by which the spherical micelles become colloidally unstable and fuse epitaxically with other micelles. The self-assembly behavior of the stereocomplex aggregates is found to be different from that of the block copolymers, resulting in rather irregular-shaped clusters of spherical micelles and pearl-necklace-like structures. KW - crystallization KW - polylactide KW - self-assembly KW - stereocomplexation Y1 - 2018 U6 - https://doi.org/10.1002/marc.201800639 SN - 1022-1336 SN - 1521-3927 VL - 40 IS - 1 PB - Wiley-VCH CY - Weinheim ER -