TY - GEN A1 - Kort, C. A. D. de A1 - Peter, Martin G. A1 - Koopmanschap, A. B. T1 - Binding and degradation of juvenile hormone III by haemolymph proteins of the Colorado potato beetle: a re-examination N2 - The haemolymph of the adult Colorado potato beetle, Lepinotarsa decemlineata Say, contains a high molecular weight (MW > 200,000) JH-III specific binding protein. The Kd value of the protein for racemic JH-III is 1.3 ± 0.2 × 10−7 M. It has a lower affinity for racemic JH-I and it does not bind JH-III-diol or JH-III-acid. The binding protein does discriminate between the enantiomers of synthetic, racemic JH-III as was determined by stereochemical anaysis of the bound and the free JH-III. Incubation of racemic JH-III with crude haemolymph results in preferential formation of (10S)-JH-III-acid, the unnatural configuration. The JH-esterase present in L. decemlineata haemolymph is not enantioselective. It is concluded that the most important function of the binding protein is that of a specific carrier, protecting the natural hormone against degradation by esterases. The carrier does not protect JH-I as efficiently as the lower homologue. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 068 KW - Juvenile hormone KW - Leptinotarsa decemlineata KW - JH-III-specific carrier protein KW - enantioselectivity Y1 - 1983 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16777 ER - TY - GEN A1 - Erdelen, C. A1 - Laschewsky, André A1 - Ringsdorf, H. A1 - Schneider, J. A1 - Schuster, A. T1 - Thermal behaviour of polymeric Langmuir-Blodgett multilayers N2 - Langmuir-Blodgett multilayers of hydrocarbon and fluorocarbon polymers with hydrophilic spacer, lipid-polyelectrolyte complexes and mesogenic polymers have been prepared. The thermal behaviour of the multilayers was studied by small angle X-ray scattering, IR and UV—visible spectroscopy. Good thermal stabilities were found for the various classes of polymers. In addition, for both complexed multilayers and mesogenic polymer films, reorientation processes were observed. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 080 Y1 - 1989 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17378 ER - TY - GEN A1 - Peter, Martin G. A1 - Boldt, Peter C. A1 - Niederstein, Yvonne A1 - Peter-Katalinić, Jasna T1 - Synthesen von Galactose-Cluster-haltigen Steroid-Derivaten N2 - The synthesis of galactose clusters that are linked to a steroid moiety by a peptide-like spacer unit is described. The galactose cluster is obtained by Koenigs-Knorr glycosylation of TRIS-Gly-Fmoc (2b) under Helferich conditions. Peptide and ester bonds are formed after activation of carboxylic acids as diphenylthiophene dioxide (TDO) esters. 6a is synthesized in a convergent way by coupling of (Ac4Gal)3-TRIS-Gly (3e) with cholesteryl TDO succinate (5b). Coupling of (Ac4Gal)3-TRIS-Gly hydrogen succinate (3f) with Gly-O-Chol (5d) by means of EEDQ yields 6d. Reaction of (Ac4Gal)3-TRIS-Gly-SUCC-O-TDO (3g) with 25-hydroxycholesterol leads in a linear sequence to the oxysterol derivative 6f. Selective cleavage of the acetyl groups from galactose units yields the known compound 6b and the new derivatives 6e and 6g. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 042 KW - Glycoconjugates KW - Galactosides KW - Steroid esters KW - Amphiphiles KW - Glycopeptides Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16783 ER - TY - JOUR A1 - Griel, C. A1 - Ströhl, D. A1 - Jeschkeit, H. A1 - Kleinpeter, Erich T1 - Synthetische und NMR-spektroskopische Untersuchungen der Benzzyl-aminaddition an N-Maleyl- aminosäurederivaten Y1 - 1992 ER - TY - JOUR A1 - Janiak, Chr. A1 - Scharmann, T. G. A1 - Green, J. C. A1 - Parkin, R. P. G. A1 - Kolm, M. J. A1 - Riedel, E. A1 - Mickler, Wulfhard A1 - Elguero, J. A1 - Claramunt, R. M. A1 - Sanz, D. T1 - Effects of nitrogen substitution in Poly(pyrazolyl)borato Ligands : from orbital energy levels to C-H...O Hydrogen Bonding Y1 - 1996 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Koch, Andreas A1 - Fischer, G. A1 - Askolin, C.-P. T1 - 13 C NMR, 15 N NMR and quantum-chemical study of the tautomerism of 2-substituted 5-ME-7-OH-1,2,4-triazolo[1,5- a]pyrimidines Y1 - 1997 ER - TY - JOUR A1 - Letzel, Matthias C. A1 - Synstad, Bjoenar A1 - Eijsink, Vincent G. H. A1 - Peter-Katalinic, Jasna A1 - Peter, Martin G. T1 - Libraries of chito-oligosaccharides of mixed acetylation patterns and their interactions with chitinases Y1 - 1999 SN - 3-9806494-5-8 ER - TY - JOUR A1 - Schwarz, W. H. Eugen A1 - Andrae, Dirk A1 - Arnold, S. R. A1 - Heidberg, Joachim A1 - Hellmann jr., H. A1 - Hinze, J. A1 - Karachalios, A. A1 - Kovner, M. A. A1 - Schmidt, P. C. A1 - Zülicke, Lutz T1 - Hans G. Hellmann (1903 - 1938) : ein deutscher Pionier der Quantenchemie in Moskau Y1 - 1999 ER - TY - JOUR A1 - Schwarz, W. H. Eugen A1 - Andrae, Dirk A1 - Arnold, S. R. A1 - Heidberg, Joachim A1 - Hellmann jr., H. A1 - Hinze, J. A1 - Karachalios, A. A1 - Kovner, M. A. A1 - Schmidt, P. C. A1 - Zülicke, Lutz T1 - Hans G. Hellmann (1903 - 1938) : ein Pionier der Quantenchemie Y1 - 1999 ER - TY - JOUR A1 - Kumke, Michael Uwe A1 - Specht, C. H. A1 - Frimmel, Fritz Hartmann T1 - Characterization of NOM adsorption to clay minerals by sizs exclusion chromatography Y1 - 2000 ER - TY - JOUR A1 - Benassi, Rois A1 - Bertarini, C. A1 - Kleinpeter, Erich A1 - Taddei, F. A1 - Thomas, Steffen T1 - Exocyclic push-pull conjugated compounds : Part 1 ; theoretical study of the effect of ring size on the structure, electronic properties and rotational barriers of cyclic analogoues of 1,1-diamino-2.2-dicyanoethylene Y1 - 2000 ER - TY - JOUR A1 - Benassi, Rois A1 - Bertarini, C. A1 - Kleinpeter, Erich A1 - Taddei, F. T1 - Exocyclic push-pull conjugated compounds, Part 2 : the effect of donor and acceptor substituents on the rotational barrier of push-pull ethylenes Y1 - 2000 ER - TY - JOUR A1 - Benassi, Rois A1 - Bertarini, C. A1 - Hilfert, Liane A1 - Kempter, Gerhard A1 - Kleinpeter, Erich A1 - Spindler, Jürgen A1 - Taddei, F. A1 - Thomas, Steffen T1 - Exocyclic push-pull conjugated compounds : Part 3 Y1 - 2000 ER - TY - JOUR A1 - Letzel, Matthias C. A1 - Peter-Katalinic, Jasna A1 - Peter, Martin G. T1 - Mass spectrometry of chitin and chitosan oligosaccharides Y1 - 2001 ER - TY - JOUR A1 - Illenseer, C. T1 - Investigation of ion-molecule collisions with laser-based ion mobility spectrometry Y1 - 2001 ER - TY - JOUR A1 - Strehmel, Bernd A1 - Henbest, K. B. A1 - Sarker, A. M. A1 - Malpert, J. H. A1 - Chen, D. Y. A1 - Rodgers, M. A. J. A1 - Neckers, D. C. T1 - Ion induced man ipulation of photochemical pathways in crown ether compounends based on fluorinated oligophenylenevinylenes Y1 - 2001 PB - Journal of nanoscience and nanotechnology. - 1 (2001), 1, S. 107 - 124 ER - TY - JOUR A1 - Jansen, K. A1 - Buschmann, Hans-Jürgen A1 - Wego, A. A1 - Dopp, D. A1 - Mayer, C. A1 - Holdt, Hans-Joachim A1 - Schollmeyer, E. T1 - Curcubit[5]uril, decamethylcururbit[5]uril and curcurbit[6]uril : synthesis, solubility and amin complex formation N2 - A simple way to prepare cucurbit[5]uril is described. The macrocycles of the cucurbituril type are nearly insoluble in water. The solubilities of cucurbit[5]uril, decamethylcucurbit[5]uril and cucurbit[6]uril in hydrochloric acid, formic acid and acetic acid of different concentrations have been investigated. Due to the formation of complexes between cucurbit[n]urils and protons the solubility increases in aqueous acids. The macrocyclic ligands are able to form complexes with several organic compounds. Thus, the complex formation of the cucurbituril macrocycles with different amines has beenstudied by means of calorimetric titrations. The reaction enthalpy gives noevidence of the formation of inclusion or exclusion complexes. 1H-NMR measurements show that in the case of cucurbit[5]uril and cucurbit[6]uril the organic guest compound is included within the hydrophobic cavity. Decamethylcucurbit[5]uril forms only exclusion complexes with organicamines. This was confirmed by the crystal structure of the decamethylcucurbit[5]uril-1,6- diaminohexane complex. complex formation - cucurbit[5]uril - cucurbit[6]uril - decamethylcucurbit[5]uril - solubility - synthesis Y1 - 2001 ER - TY - GEN A1 - Dosche, Carsten A1 - Löhmannsröben, Hans-Gerd A1 - Bieser, A. A1 - Dosa, P. I. A1 - Han, S. A1 - Iwamoto, M. A1 - Schleifenbaum, A. A1 - Vollhardt, K. Peter C. T1 - Photophysical properties of [N]phenylenes N2 - In the present study, photophysical properties of [N]phenylenes were studied by means of stationary and time-resolved absorption and fluorescence spectroscopy (in THF at room temperature). For biphenylene (1) and linear [3]phenylene (2a), internal conversion (IC) with quantum yields ΦIC > 0.99 is by far the dominant mechanism of S1 state deactivation. Angular [3]phenylene (3a), the zig-zag [4]- and [5]phenylenes (3b), (3c), and the triangular [4]phenylene (4) show fluorescence emission with fluorescence quantum yieds and lifetimes between ΦF = 0.07 for (3a) and 0.21 for (3c) and τF = 20 ns for (3a) and 81 ns for (4). Also, compounds (3) and (4) exhibit triplet formation upon photoexcitation with quantum yields as high as ΦISC = 0.45 for (3c). The strong differences in the fluorescence properties and in the triplet fromation efficiencies between (1) and (2a) on one hand and (3) and (4) on the other are related to the remarkable variation of the internal conversion (IC) rate constants kIC. A tentative classification of (1) and (2a) as “fast IC compounds”, with kIC > 109 s-1, and of (3) and (4) as “slow IC compounds”, with kIC ≈ 107 s-1, is suggested. This classification cannot simply be related to Hückel’s rule-type concepts of aromaticity, because the group of “fast IC compounds” consists of “antiaromatic” (1) and “aromatic” (2a), and the group of “slow IC compounds” consists of “antiaromatic” (3b), (4) and “aromatic” (3a), (3c). The IC in the [N]phenylenes is discussed within the framework of the so-called energy gap law established for non-radiative processes in benzenoid hydrocarbons. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 001 Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11936 ER - TY - GEN A1 - Kaafarani, Bilal R. A1 - Wex, Brigitte A1 - Strehmel, Bernd A1 - Neckers, Douglas C. T1 - Structural concept for fluorinated Y-enynes with solvatochromic properties N2 - An approach to the development of fluorescent probes to follow polymerizations in situ using fluorinated cross-conjugated enediynes (Y-enynes) is reported. Different substitution patterns in the Y-enynes result in distinct solvatochromic behavior. β,β-Bis(phenylethynyl)pentafluorostyrene 7, which bears no donor substituents and only fluorine at the styrene moiety, shows no solvatochromism. Donor substituted β,β-bis(3,4,5-trimethoxyphenylethynyl) pentafluorostyrene 8 and β,β-bis(4-butyl-2,3,5,6-tetrafluorophenylethynyl)-3,4,5-trimethoxystyrene 9 exhibit solvatochromism upon change of solvent polarity. Y-enyne 8 showed the largest solvatochromic shift (94 nm bathochromic shift) upon changing solvent from cyclohexane to acetonitrile. A smaller solvatochromic response (44 nm bathochromic shift) was observed for 9. Lippert–Mataga treatment of 8 and 9 yields slopes of -10,800 and -6,400 cm -1, respectively. This corresponds to a change in dipole moment of 9.6 and 6.9 D, respectively. The solvatochromic behavior in 8 and 9 supports the formation of an intramolecular charge transfer (ICT) state. The low fluorescence quantum yields are caused by competitive double bond rotation. The fluorescence decay time of 9 decreases in methyltetrahydrofuran from 2.1 ns at 77 K to 0.11 ns at 200 K. Efficient single bond rotation in 9 was frozen at -50 °C in a configuration in which the trimethoxyphenyl ring is perpendicular to the fluorinated rings. 7–9 are photostable compounds. The X-ray structure of 7 shows it is not planar and that its conjugation is distorted. Y-enyne 7 stacks in the solid state showing coulombic, actetylene–arene, and fluorine–π interactions. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 027 Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13168 ER - TY - JOUR A1 - Dosche, Carsten A1 - Löhmannsröben, Hans-Gerd A1 - Bieser, A. A1 - Dosa, P. I. A1 - Han, S. A1 - Iwamoto, M. A1 - Schleifenbaum, A. A1 - Vollhardt, K. Peter C. T1 - Photophysical properties of [N]phenylenes Y1 - 2002 ER - TY - JOUR A1 - Bahrke, Sven A1 - Einarsson, Jon M. A1 - Gislason, Johannes A1 - Haebel, Sophie A1 - Letzel, Matthias C. A1 - Peter-Katalinic, Jasna A1 - Peter, Martin G. T1 - Sequence analysis of chitooligosaccharides by matrix-assisted laser desorption ionization postsource decay mass spectrometry N2 - Oligosaccharides composed of 2-acetamido-2-deoxy-D-glucopyranose (GlcNAc) and/or 2-amino-2-deoxy-D- glucopyranose (GlcN) were prepd. by chem. degrdn. of chitin or chitosan and sepd. by gel permeation chromatog. Oligosaccharides obtained after enzymic hydrolysis of chitosan [FA 0.19] with a fungal chitinase were derivatized by reductive amination with 2-aminoacridone and sequenced by matrix-assisted laser desorption ionization time-of-flight postsource decay (PSD) mass spectrometry (MS). The sequence of a trimer, D1A2, was established as D-A-A. The compn. of a hexamer D3A3 was .apprx.65% D-A-D-D-A-A and 35% D-D-A-D-A-A. The PSD MS of a nonamer D5A4-amac revealed four isobaric species D-X-Y-D-X-Y-D-A-A, where A is GlcNAc, D is GlcN, and X and Y (X ¹ Y) are mutually either D or A. This structure motif was also obsd. in a dodecamer D7A5 which was composed of eight isobaric sequences of the general formula (D-X-Y)3- D-A-A. Y1 - 2002 ER - TY - JOUR A1 - Rath, Harapriya A1 - Anand, V. G. A1 - Sankar, J. A1 - Venkatraman, S. A1 - Chandrashekar, T. K. A1 - Joshi, Bhawani S. A1 - Khetrapal, C. L. A1 - Schilde, Uwe A1 - Senge, Mathias O. T1 - Core-Modified Hexaphyrins; Characterization of Two- and Four-Ring Inverted 26 ô Aromatic Macrocycles Y1 - 2003 UR - http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/ol035408q ER - TY - GEN A1 - Dosche, Carsten A1 - Kumke, Michael Uwe A1 - Ariese, F. A1 - Bader, Arjen N. A1 - Gooijer, C. A1 - Dosa, P. I. A1 - Han, S. A1 - Miljanic, O. S. A1 - Vollhardt, K. Peter C. A1 - Puchta, R. A1 - Eikema Hommes, N. J. R. van T1 - Shpol’skii spectroscopy and vibrational analysis of [N]phenylenes N2 - Vibrationally resolved fluorescence spectra of four angular [N]phenylenes were recorded with laser excited Shpol’skii spectroscopy (LESS) in an n-octane matrix at 10 K. In general, the same vibrational frequencies were observed in the fluorescence excitation and emission spectra, indicating that the geometries of ground and electronically excited state are very similar. Because of intensity borrowing from the S2 state, vibrations of two different symmetries were observed in the fluorescence excitation spectra of angular [3]phenylene and zig-zag[5]phenylene. This finding allowed the location of the S2 state for these compounds. DFT calculations(RB3LYP/6-31G*) of the ground state vibrational frequencies were made. The calculated vibrational modes were in reasonably good agreement with the experimental data. A new very low-frequency vibration of approximately 100 cm-1 was predicted and experimentally confirmed for all [N]phenylenes investigated. This vibration seems to be unique for [N]phenylenes and is attributed to an in-plane movement of the carbon backbone. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 024 Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13075 ER - TY - JOUR A1 - Dosche, Carsten A1 - Kumke, Michael Uwe A1 - Ariese, Freek A1 - Bader, Arjen N. A1 - Gooijer, Cees A1 - Dosa, P. I. A1 - Han, S. A1 - Miljanic, Ognjen S. A1 - Vollhardt, K. Peter C. A1 - Puchta, Ralph A1 - Hommes, N. J. R. V. T1 - Shpol'skii spectroscopy and vibrational analysis of [N]phenylenes Y1 - 2003 ER - TY - JOUR A1 - Ryppa, C. A1 - Senge, Mathias O. T1 - Dodecasubstituted porphyrins : an easily accessible type of dendritic porphyrins with tunable properties N2 - Dodecasubstituted dendritic porphyrins with nonplanar macrocycles were synthesized by a convergent approach via Lindsey condensation reactions in good yields Y1 - 2004 SN - 0385-5414 ER - TY - JOUR A1 - Goldmann, Daniela A1 - Janietz, Dietmar A1 - Schmidt, C. A1 - Wendorff, Joachim Heinz T1 - Columnar liquid crystalline phases through hydrogen bonding and nanoscale segregation N2 - Two columnar phases forming 2,4,6-triarylamino-1,3,5-triazines have been investigated in binary mixtures with calamitic and non-liquid crystalline benzoic acids carrying one or two alkoxy chains at the aromatic core. The triazines form hydrogen bonded aggregates with the complementary acids. Each investigated equimolar mixture exhibits a columnar mesophase due to segregation of the H-bonded polar core region from the lipophilic aliphatic molecular segments. The cross sectional shape of cylindrical aggregates and, therefore, the two-dimensional lattice symmetries, hexagonal or rectangular, are defined by the number of alkoxy chains of the benzoic acid component Y1 - 2004 SN - 0959-9428 ER - TY - JOUR A1 - Goldmann, Daniela A1 - Nordsieck, A. A1 - Janietz, Dietmar A1 - Frese, T. A1 - Schmidt, C. A1 - Wendorff, Joachim Heinz T1 - Smectic and columnar liquid crystalline phases through charge-transfer interactions N2 - New heterocyclic electron donors based on. a 1,3,5-triazine nucleus are presented. Three phenyl rings are grafted to the triazine core either via secondary amino groups or by a direct C,C-linkage and a specific number of decyloxy chains is attached to the molecular periphery. The compounds are non-liquid crystalline in their pure states. Lamellar or columnar mesophases are induced by attractive interactions with electron acceptors Y1 - 2004 SN - 1058-725X ER - TY - JOUR A1 - Dosche, Carsten A1 - Kumke, Michael Uwe A1 - Löhmannsröben, Hans-Gerd A1 - Ariese, Freek A1 - Bader, Arjen N. A1 - Gooijer, Cees A1 - Miljanic, Ognjen S. A1 - Iwamoto, M. A1 - Vollhardt, K. Peter C. A1 - Puchta, Ralph A1 - Hommes, N. J. R. V. T1 - Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]phenylene N2 - Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [ 4] phenylene (D-3h [4]phenylene) were studied using laser-excited Shpol'skii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31G*). CH vibrations were identified by their characteristic isotopic shifts in the spectra of deuterated triangular [4]phenylenes. Two CC stretching modes, at 100 cm(-1) and 1176 cm(-1), suitable as probes for bond strength changes in the excited state, were identified. The isotope effect on the internal conversion rates of triangular [4] phenylene was evaluated from measurements of temperature dependent lifetime. Isotope dependency and the magnitude of the internal conversion rates indicate that internal conversion in triangular [4] phenylene is most likely induced by CH vibrations. The results obtained by LESS and lifetime measurements were compared with PM3 PECI calculations of the excited state structure. The theoretical results and the relation between ground and excited state vibration energies of the 1176 cm(-1) probe vibration indicate a reduction of bond alternation of the central cyclohexatriene ring in the excited state Y1 - 2004 SN - 1463-9076 ER - TY - JOUR A1 - Vaaje-Kolstad, G. A1 - Vasella, A. A1 - Peter, Martin G. A1 - Netter, C. A1 - Houston, Douglas R. A1 - Westereng, B. A1 - Synstad, Bjoenar A1 - Eijsink, Vincent G. H. A1 - van Aalten, Daan M. F. T1 - Interactions of a family 18 chitinase with the designed inhibitor HM508 and its degradation product, chitobiono- delta-lactone N2 - We describe enzymological and structural analyses of the interaction between the family 18 chitinase ChiB from Serratia marcescens and the designed inhibitor N,N'-diacetylchitobionoxime-N-phenylcarbamate (HM508). HM508 acts as a competitive inhibitor of this enzyme with a K-i in the 50 muM range. Active site mutants of ChiB show K-i values ranging from 1 to 200 muM, providing insight into some of the interactions that determine inhibitor affinity. Interestingly, the wild type enzyme slowly degrades HM508, but the inhibitor is essentially stable in the presence of the moderately active D142N mutant of ChiB. The crystal structure of the D142N-HM508 complex revealed that the two sugar moieties bind to the -2 and -1 subsites, whereas the phenyl group interacts with aromatic side chains that line the +1 and +2 subsites. Enzymatic degradation of HM508, as well as a Trp-->Ala mutation in the +2 subsite of ChiB, led to reduced affinity for the inhibitor, showing that interactions between the phenyl group and the enzyme contribute to binding. Interestingly, a complex of enzymatically degraded HM508 with the wild type enzyme showed a chitobiono-delta- lactone bound in the -2 and -1 subsites, despite the fact that the equilibrium between the lactone and the hydroxy acid forms in solution lies far toward the latter. This shows that the active site preferentially binds the E-4 conformation of the -1 sugar, which resembles the proposed transition state of the reaction Y1 - 2004 SN - 0021-9258 ER - TY - JOUR A1 - Venkatraman, S. A1 - Kumar, R. A1 - Sankar, J. A1 - Chandrashekar, T. K. A1 - Sendhil, K. A1 - Vijayan, C. A1 - Kelling, Alexandra A1 - Senge, Mathias O. T1 - Oxasmaragdyrin-ferrocene and oxacorrole-ferrocene conjugates : Synthesis, structure, and nonlinear optical properties N2 - Ferrocenyl macrocyclic conjugates involving 22pi oxasmaragdyrins and 18pi oxacorroles have been synthesized and characterized. The direct covalent linkage of the ferrocenyl moiety to the meso position of the macrocycle is achieved by simple oxidative coupling of appropriate precursors with trifluoroacetic acid as catalyst. The electronic coupling between the ferrocenyl moiety and the macrocyclic pi system is apparent from: a) the red shifts (293-718 cm(-1)) of the Soret and Q-bands in the electronic absorption spectra of ferrocenyl conjugates; b) the shift of oxidation potentials (50 130 mV) of both the ferrocene and the corrole rings to the positive potentials; and c) considerable shortening of the C-C bond which connects the ferrocene and the meso-carbon atom of the macrocycle. The single-crystal X-ray structure of oxasmaragdyrin-ferrocene conjugate 9 reveals the planarity of the 22pi skeleton with very small deviations of the meso-carbon atoms. The meso-ferrocenyl substituent has a small dihedral angle of 38degrees, making way for mixing of the molecular orbitals of the ferrocene and the macrocycle. However, the other two meso substituents are almost perpendicular to the mean plane, defined by the three meso carbon atoms. Classical C-(HO)-O-... and nonclassical C- H(...)pi interactions lead to a two-dimensional supramolecular network. Ferrocene-smaragdyrin conjugate 9 bonds to a chloride ion in the protonated form and a rhodium(i) ion in the free base form. Nonlinear optical measurements reveal a larger nonlinear refractive index (-5.83 x 10(-8) cm(2) W-1) and figure of merit (2.28 x 10(-8) cm(3)W(-1)) for the rhodium smaragdyrin-ferrocene conjugate 19 than for the others, suggesting its possible application in optical devices Y1 - 2004 SN - 0947-6539 ER - TY - GEN A1 - Dosche, Carsten A1 - Kumke, Michael Uwe A1 - Löhmannsröben, Hans-Gerd A1 - Ariese, F. A1 - Bader, Arjen N. A1 - Gooijer, C. A1 - Miljanic, O. S. A1 - Iwamoto, M. A1 - Vollhardt, K. Peter C. A1 - Puchta, R. ; van Eikema Hommes, N. J. R. T1 - Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]Phenylene N2 - Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [4]phenylene (D3h[4]phenylene) were studied using laser-excited Shpolskii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31G*). CH vibrations were identified by their characteristic isotopic shifts in the spectra of deuterated triangular [4]phenylenes. Two CC stretching modes, at 100 cm–1 and 1176 cm–1, suitable as probes for bond strength changes in the excited state, were identified. The isotope effect on the internal conversion rates of triangular [4]phenylene was evaluated from measurements of temperature dependent lifetime. Isotope dependency and the magnitude of the internal conversion rates indicate that internal conversion in triangular [4]phenylene is most likely induced by CH vibrations. The results obtained by LESS and lifetime measurements were compared with PM3 PECI calculations of the excited state structure. The theoretical results and the relation between ground and excited state vibration energies of the 1176 cm–1 probe vibration indicate a reduction of bond alternation of the central cyclohexatriene ring in the excited state. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 002 Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11881 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Induli, M. A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Heydenreich, Matthias A1 - Peter, Martin G. A1 - Akala, Hoseah M. A1 - Wangui, Julia A1 - Liyala, Pamela A1 - Waters, Norman C. T1 - Anti-plasmodial flavonoids from the stem bark of Erythrina abyssinica N2 - The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC50 values of 7.9 +/- 1.1 and 5.3 +/- 0.7 mug/ml, respectively. From this extract, a new chalcone, 2,3,4,4'-tetrahydroxy-5- prenylchalcone (trivial name 5-prenylbutein) and a new flavanone, 4',7-dihydroxy-3'-methoxy-5'- prenylflavanone (trivial name, 5-deoxyabyssinin II) along with known flavonoids have been isolated as the anti- plasmodial principles. The structures were determined on the basis of spectroscopic evidence. (C) 2004 Elsevier Ltd. All rights reserved Y1 - 2004 SN - 0031-9422 ER - TY - JOUR A1 - Mertoglu, Murat A1 - Laschewsky, André A1 - Skrabania, Katja A1 - Wieland, C. T1 - New water soluble agents for reversible addition-fragmentation chain transfer polymerization and their application in aqueous solutions N2 - A series of nonionic, anionic, and cationic water-soluble monomers bearing the (meth)acrylate, (meth)acrylamide, or styrene moiety were polymerized in water by free-radical polymerization via reversible addition- fragmentation chain transfer (RAFT). Several new water-soluble RAFT agents based on dithiobenzoate were employed that are water soluble independently of the pH. One of them bears a fluorophore, enabling unsymmetrical double end-group labeling as well as the preparation of fluorescent-labeled polymers. The temperature-dependent stability of the new RAFT agents against hydrolysis was studied. Controlled polymerization in aqueous solution was possible with styrenic, acrylic, and methacrylic monomers; molar masses increase with conversion, and polydispersities are relatively low. But RAFT polymerization failed for an anionic itaconate. Whereas polymerizations of methacrylamides were slow at temperatures below 60 degrees C, such conditions proved favorable for the RAFT polymerization of acrylates and methacrylates, to minimize hydrolysis of the dithioester end-group functionality, and to improve the preparation of block copolymers Y1 - 2005 SN - 0024-9297 ER - TY - JOUR A1 - Wiehe, A. A1 - Shaker, Y. M. A1 - Brandt, J. C. A1 - Mebs, S. A1 - Senge, Mathias O. T1 - Lead structures for applications in photodynamic therapy : Part 1: Synthesis and variation of m-THPC (Temoporfin) related amphiphilic A(2)BC-type porphyrins N2 - Photodynamic therapy (PDT) is a developing modality for the treatment of certain tumorous and other diseases. Considerable progress has been made in recent years in the search for new photosensitizers, in particular elucidating the role of localization of the photosensitizer. Known successful photosensitizers of the tetrapyrrole type are amphiphilic molecules, preferably localizing in cellular membrane structures. Thus, the quest for new photosensitizers requires the synthesis of unsymmetrically Substituted (amphiphilic) tetrapyrroles. In this article. we describe strategies for the de novo synthesis of amphiphilic tetrapyrroles using a 3-hydroxyphenyl substituted tetrapyrrolic system (Temoporfin) as the lead structure. From an applied science-oriented approach, such a set of amphiphilic porphyrins is best synthesized by combining well-developed condensation methods with subsequent functionalization via organolithium compound or transition metal catalyzed coupling protocols. Starting from simple A(2)- or AB-porphyrins, the synthesis of A(2)B-, A(3)-, A(3)B-, and A(2)BC-porphyrins with a mixed hydrophilic/hydrophobic substitution pattern is described. Because of the versatility of this approach to unsymmetrically Substituted porphyrins it is also applicable to other areas where porphyryns with a tailor-made substitution patterns are needed. for example. catalysts or molecular electronic devices based on tetrapyrroles. (c) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0040-4020 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Bii, Christine C. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Antimicrobial flavonoids from the stem bark of Erythrina burttii N2 - The chloroform extract of the stem bark of Erythrina burttii showed antifungal and antibacterial activities using the disk diffusion method. Flavonoids were identified as the active principles. Activities were observed against fungi and Gram(+) bacteria, but the Gram(-) bacteria Escherichia coli was resistant. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0367-326X ER - TY - JOUR A1 - Rusu, Viorel Marin A1 - Ng, C. H. A1 - Wilke, Max A1 - Tiersch, Brigitte A1 - Fratzl, Peter A1 - Peter, Martin G. T1 - Size-controlled hydroxyapatite nanoparticles as self-organized organic-in organic composite materials N2 - This paper presents some results concerning the size-controlled hydroxyapatite nanoparticles obtained in aqueous media in a biopolymer matrix from soluble precursors salts. Taking the inspiration from nature, where composite materials made of a polymer matrix and inorganic fillers are often found, e.g. bone, shell of crustaceans, shell of eggs, etc., the feasibility on making composite materials containing chitosan and nanosized hydroxyapatite was investigated. A stepwise co-precipitation approach was used to obtain different types of composites by means of different ratio between components. The synthesis of hydroxyapatite was carried out in the chitosan matrix from calcium chloride and sodium dihydrogenphosphate in alkaline solutions at moderate pH of 10-11 for 24 h. Our research is focused on studying and understanding the structure of this class of composites, aiming at the development of novel materials, controlled at the nanolevel scale. The X-ray diffraction technique was employed in order to study the kinetic of hydroxyapatite formation in the chitosan matrix as well as to determine the HAp crystallite sizes in the composite samples. The hydroxyapatite synthesized using this route was found to be nano-sized (15-50nm). Moreover, applying an original approach to analyze the (002) XRD diffraction peak profile of hydroxyapatite by using a sum of two Gauss functions, the bimodal distribution of nanosized hydroxyapatite within the chitosan matrix was revealed. Two types of size distribution domains such as cluster-like (between 200 and 400 nm), which are the habitat of "small" hydroxyapatite nanocrystallites and scattered-like, which are the habitat of "large" hydroxyapatite nanocrystallites was probed by TEM and CSLM. The structural features of composites suggest that self-assembly processes might be involved. The composites contain nanosized hydroxyapatite with structural features close to those of biological apatites that make them attractive for bone tissue engineering applications. (c) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0142-9612 ER - TY - JOUR A1 - Zhang, T. A1 - Spitz, Christian A1 - Antonietti, Markus A1 - Faul, C. F. T1 - Highly photoluminescent polyoxometaloeuropate-surfactant complexes by ionic self-assembly N2 - Facile organization of the inorganic sandwiched heteropolytungstomolybdate K-13[Eu(SiW9Mo2O39)(2)] (E) into highly ordered supramolecular nanostructured materials by complexation with a series of cationic surfactants is achieved by the ionic self-assembly (ISA) route. The structure and phase behavior of the complexes were examined by IR spectroscopy, differential scanning calorimetry, optical microscopy, and small- and wide-angle X-ray scattering. This class of materials shows a number of interesting physicochemical properties, namely liquid-crystalline phases (both thermotropic and lyotropic) and strong photoluminescence. The photophysical behavior (fluorescence spectra, fluorescence lifetimes, fluorescence quantum yield) of the complexes differs widely in solid powders, films, and solutions. The amphiphilic cationic surfactants not only play a structural role but also have a strong influence on the photophysical properties of E. The photophysical behavior of E can in this way be easily modified by its organizational motifs Y1 - 2005 ER - TY - JOUR A1 - Saalfrank, Peter A1 - Klamroth, Tillmann A1 - Huber, C. A1 - Krause, Pascal T1 - Laser-driven electron dynamics at interfaces N2 - In this paper we present time-dependent, quantum-dynamical simulations of photoinduced processes at solid surfaces involving nonadiabatic transitions of electrons to and from short-lived intermediate excited states. In particular, two-photon photoemission (2PPE) spectra of naked metal surfaces and free-standing metal films are considered. One major problem in both cases is the presence of electron-electron scattering, which is treated here in various ways. The first way is to adopt an open-system density matrix approach, in which a single electron is weakly coupled to a "bath" of other electrons. The second approach is based on a many-electron Schrodinger equation, which is solved with the help of a time-dependent configuration interactions singles (TD-CIS) method Y1 - 2005 SN - 0021-2148 ER - TY - JOUR A1 - Ryppa, C. A1 - Senge, Mathias O. A1 - Hatscher, S. S. A1 - Kleinpeter, Erich A1 - Wacker, Philipp A1 - Schilde, Uwe A1 - Wiehe, A. T1 - Synthesis of mono- and disubstituted porphyrins : A- and 5,10-A(2)-type systems N2 - General syntheses have been developed for meso-substituted porphyrins with one or two substituents in the 5,10- positions and no beta substituents. 5-Substituted porphyrins with only one meso substituent are easily prepared by an acid-catalyzed condensation of dipyrromethane, pyrrole-2-carbaldehyde. and an appropriate aldehyde using a "[2+1+1]" approach. Similarly, 5,10-disubstituted porphyrins are accessible by simple condensation of unsubstituted tripyrrane with pyrrole and various aldehydes using a "[3+1]" approach. The yields for these reactions are low to moderate and additional formation of either di- or mono-substituted porphyrins due to scrambling of the intermediates is observed. However, the reactions can be performed quite easily and the desired target compounds are easily removed due to large differences in solubility. A complementary and more selective synthesis involves the use of organolithium reagents for SNAr reactions. Reaction of in situ generated porphyrin (porphine) with 1.1-8 equivalents of RLi gave the monosubstituted porphyrins, while reaction with 3-6 equivalents of RLi gave the 5,10-disubstituted porphyrins in yields ranging from 43 to 90%. These hitherto almost inaccessible compounds complete the series of different homologues of A-, 5,15-A(2)-, 5,10-A(2)-, A(3)-, and A(4)-type porphyrin's and allow an investigation of the gradual influence of type, number, and regiochemical arrangement of substituents on the properties of meso-substituted porphyrins. They also present important starting materials for the synthesis of ABCD porphyrins and are potential synthons for supramolecular materials requiring specific substituent orientations Y1 - 2005 SN - 0947-6539 ER - TY - JOUR A1 - Teixeira, C. V. A1 - Blanzat, Muriel A1 - Koetz, Joachim A1 - Rico-Lattes, I. A1 - Brezesinski, Gerald T1 - In-plane miscibility and mixed bilayer microstructure in mixtures of catanionic glycolipids and zwitterionic phospholipids JF - Biochimica et biophysica acta : Biomembranes N2 - SAXS/WAXS studies were performed in combination with freeze fracture electron microscopy using mixtures of a new Gemini catanionic surfactant (Gem 16-12, formed by two sugar groups bound by a hydrocarbon spacer with 12 carbons and two 16-carbon chains) and the zwitterionic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC) to establish the phase diagram. Gem 16-12 in water forms bilayers with the same amount of hydration water as DPPC. A frozen interdigitated phase with a low hydration number is observed below room temperature. The kinetics of the formation of this crystalline phase is very slow. Above the chain melting temperature, multilayered vesicles are formed. Mixing with DPPC produces mixed bilayers above the corresponding chain melting temperature. At room temperature, partially lamellar aggregates with local nematic order are observed. Splitting of infinite lamellae into discs is linked to immiscibility in frozen state. The ordering process is always accompanied by dehydration of the system. As a consequence, an unusual order-disorder phase transition upon cooling is observed. KW - SAXS KW - bilayer KW - gemini surfactant KW - ordering process KW - Anti-HIV KW - miscibility Y1 - 2006 U6 - https://doi.org/10.1016/j.bbamem.2006.05.025 SN - 0005-2736 VL - 1758 SP - 1797 EP - 1808 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Andayi, Andrew W. A1 - Yenesew, Abiy A1 - Derese, Solomon A1 - Midiwo, Jacob O. A1 - Gitu, Peter M. A1 - Jondiko, Ogoche J. I. A1 - Akala, Hoseah M. A1 - Liyala, Pamela A1 - Wangui, Julia A1 - Waters, Norman C. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Antiplasmodial flavonoids from Erythrina sacleuxii N2 - The acetone extracts of the root bark and stem bark of Erythrina sacleuxii showed antiplasmodial activities against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the acetone extract of the root bark afforded a new isoflavone, 7-hydroxy-4 -methoxy-3'- prenylisoflavone (trivial name 5-deoxy-3' - prenylbiochanin A) along with known isoflavonoids as the antiplasmodial principles. Flavonoids and isoflavonoids isolated from the stem bark of E. sucleuxii were also tested and showed antiplasmodial activities. The structures were determined on the basis of spectroscopic evidence Y1 - 2006 UR - http://www.thieme-connect.com/ejournals/toc/plantamedica U6 - https://doi.org/10.1055/s-2005-873200 SN - 0032-0943 ER - TY - GEN A1 - Dosche, Carsten A1 - Mickler, Wulfhard A1 - Löhmannsröben, Hans-Gerd A1 - Agenet, Nicolas A1 - Vollhardt, K. Peter C. T1 - Photoinduced electron transfer in [N]phenylenes N2 - First studies of electron transfer in [N]phenylenes were performed in bimolecular quenching reactions of angular [3]- and triangular [4]phenylene with various electron acceptors. The relation between the quenching rate constants kq and the free energy change of the electron transfer (ΔG0CS ) could be described by the Rehm-Weller equation. From the experimental results, a reorganization energy λ of 0.7 eV was derived. Intramolecular electron transfer reactions were studied in an [N]phenylene bichomophore and a corresponding reference compound. Fluorescence lifetime and quantum yield of the bichromophor display a characteristic dependence on the solvent polarity, whereas the corresponding values of the reference compound remain constant. From the results, a nearly isoenergonic ΔG0CS can be determined. As the triplet quantum yield is nearly independent of the polarity, charge recombination leads to the population of the triplet state. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 23 KW - [N]phenylenes KW - photoinduced electron transfer KW - [N]phenylene dyads Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12463 ER - TY - JOUR A1 - Dosche, Carsten A1 - Mickler, Wulfhard A1 - Löhmannsröben, Hans-Gerd A1 - Agenet, Nicolas A1 - Vollhardt, K. Peter C. T1 - Photoinduced electron transfer in [N]phenylenes N2 - First studies of electron transfer in [N]phenylenes were performed in bimolecular quenching reactions of angular [3]- and triangular [4]phenylene with various electron acceptors. The relation between the quenching rate constants k(q) and the free energy change of the electron transfer (Delta G(CS)(0)) could be described by the Rehm- Weller equation. From the experimental results, a reorganization energy lambda of 0.7 eV was derived. Intramolecular electron transfer reactions were studied in an [N]phenylene bichomophore and a corresponding reference compound. Fluorescence lifetime and quantum yield of the bichromophor display a characteristic dependence on the solvent polarity, whereas the corresponding values of the reference compound remain constant. From the results, a nearly isoenergonic charge separation process can be determined. As the triplet quantum yield is nearly independent of the polarity, charge recombination leads to the population of the triplet state. Y1 - 2007 UR - http://www.sciencedirect.com/science/journal/10106030 U6 - https://doi.org/10.1016/j.jphotochem.2006.12.038 SN - 1010-6030 ER - TY - JOUR A1 - Rukunga, G. M. A1 - Muregi, F. W. A1 - Omar, S. A. A1 - Gathirwa, J. W. A1 - Muthaura, C. N. A1 - Peter, Martin G. T1 - Anti-plasmodial activity of the extracts and two sesquiterpenes from Cyperus articulatus N2 - Two sesquiterpenes, corymbolone and mustakone, isolated from the chloroform extract of the rhizomes of Cyperus articulatus, exhibited significant anti-plasmodial properties. Mustakone was approximately ten times more active than corymbolone against the sensitive strains of the Plasmodium falciparum. Y1 - 2008 SN - 0367-326X ER - TY - JOUR A1 - Kraus, Florian A1 - Aschenbrenner, Jürgen C. A1 - Klamroth, Tillmann A1 - Korber, Nikolaus T1 - Hydrogen polyphosphides P3H23- and P3H32- : synthesis and crystal structure of K3(P3H2)·2.3NH3, Rb3(P3H2)·NH3, [Rb(18-crown-6)]2(P3H3)·7.5NH3, and [Cs(18-crown-6)]2(P3H3)·7NH3 N2 - The incongruous solvation of polyphosphides and phosphanes or the direct reduction of white phosphorus in liquid ammonia leads to the hydrogen polyphosphides catena-dihydrogen triphosphide, P3H23-, and catena-trihydrogen triphosphide, P3H32-, in the crystalline compounds K-3(P3H2)center dot 2.3NH(3) (1), Rb-3(P3H2)center dot NH3 (2), [Rb(18-crown-6)](2)(P3H3)center dot 7.5NH(3) (3), and [Cs(18-crown-6)](2)(P3H3)center dot 7NH(3) (4). Y1 - 2009 UR - http://pubs.acs.org/journal/inocaj U6 - https://doi.org/10.1021/Ic8014546 SN - 0020-1669 ER - TY - GEN A1 - Peter, Martin G. A1 - Yenesew, Abiy A1 - Twinomuhwezi, Hannington A1 - Kabaru, Jacques M. A1 - Akala, Hoseah M. A1 - Kiremire, Bernard T. A1 - Heydenreich, Matthias A1 - Eyase, Fredrick A1 - Waters, Norman C. A1 - Walsh, Douglas S. T1 - Antiplasmodial and larvicidal flavonoids from Derris trifoliata N2 - From the dichloromethane-methanol (1:1) extract of the seed pods of Derris trifoliata, a new flavanone derivative (S)-lupinifolin 4´-methyl ether was isolated. In addition, the known flavonoids lupinifolin and rotenone were identified. The structures were determined on the basis of spectroscopic evidence. Lupinfolin showed moderate in vitro antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquineresistant) strains of Plasmodium falciparum. The different parts of this plant showed larvicidal activities against Aedes aegypti and rotenoids were identified as the active principles. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 121 KW - Derris trifoliata KW - Leguminosae KW - Flavanone KW - (S)-Lupinifolin 4´-methyl ether KW - Lupinifolin Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-44614 ER - TY - GEN A1 - Peter, Martin G. A1 - Muiva, Lois M. A1 - Yenesew, Abiy A1 - Derese, Solomon A1 - Heydenreich, Matthias A1 - Akala, Hoseah M. A1 - Eyase, Fredrick A1 - Waters, Norman C. A1 - Mutai, Charles A1 - Keriko, Joseph M. A1 - Walsh, Douglas S. T1 - Antiplasmodial β-hydroxydihydrochalcone from seedpods of Tephrosia elata N2 - From the seedpods of Tephrosia elata, a new β-hydroxydihydrochalcone named (S)-elatadihydrochalcone was isolated. In addition, the known flavonoids obovatachalcone, obovatin, obovatin methyl ether and deguelin were identified. The structures were determined on the basis of spectroscopic evidence. The crude extract and the flavonoids obtained from the seedpods of this plant showed antiplasmodial activities. The literature NMR data on β-hydroxydihydrochalcones is reviewed and the identity of some of the compounds assigned β-hydroxydihydrochalcone skeleton is questioned. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 118 KW - Tephrosia elata KW - Leguminosae KW - Seedpods KW - (S)-Elatadihydrochalcone KW - β-Hydroxydihydrochalcone Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-44437 ER - TY - JOUR A1 - Kihampa, Charles A1 - Nkunya, Mayunga H. H. A1 - Joseph, Cosam C. A1 - Magesa, Stephen M. A1 - Hassanali, Ahmed A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich T1 - Anti-mosquito and antimicrobial nor-halimanoids, isocoumarins and an anilinoid from Tessmannia densiflora N2 - The nor-halimane diterpenoid tessmannic acid and its methyl, 2-methylisopropyl and 1-methylbutyl esters, the unusual isocoumarins 8-hydroxy-6-methoxy-3-pentylisocoumarin and 7-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin, and 5- pentyl-3-methoxy-N-butylaniline were isolated from the stem and root bark extracts of Tessmannia densiflora Harms (Caesalpiniaceae) that showed mosquito larvicidal activity. The structures were determined on interpretation of spectroscopic data. Tessmannic acid and its methyl ester exhibited antibacterial and antifungal activity. The compounds also caused high larvae and adult Anopheles gambiae mosquitoe mortality effects, and stronger mosquito repellency than that shown by the standard repellent DEET, hence indicating Tessmannia species to be potential sources of bioactive natural products. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00319422 U6 - https://doi.org/10.1016/j.phytochem.2009.07.024 SN - 0031-9422 ER - TY - JOUR A1 - Kihampa, Charles A1 - Joseph, Cosam C. A1 - Nkunya, Mayunga H. H. A1 - Magesa, Stephen M. T1 - Larvicidal and IGR activity of extract of Tanzanian plants against malaria vector mosquitoes N2 - Background & objectives: This paper reports the larvicidal activity of seventeen Tanzanian plant species against the malaria vector, Anopheles gambiae s.s. Giles larvae. Some of the plants are used traditionally as sources of insecticidal materials. Methods: The crude extracts from the leaves, stem and root barks of the investigated plants were obtained by solvent extraction and then bio-assayed following WHO protocols showed LC50 values 10 to 400 ppm after 24 h exposure. The structures were determined on interpretation of spectroscopic data. Results: The most active extracts were those from the stem and root barks of Annona squamosa, Uvaria faulknerae, U. kirkii and Uvariodendron pycnophyllum, all of which had LC50 values between 10 and 100 ppm. Long-term exposure beyond 24 h also showed more susceptibility of the larvae to the extracts. Larvae deformities by forming tail-like structures were observed for the methanol extracts of Tessmannia martiniana var pauloi. Interpretation & conclusion: The results suggest that the investigated plant extracts are promising as larvicides against An. gambiae s.s. Giles mosquitoes and could be useful leads in the search for new and biodegradable plant derived larvicide products. Y1 - 2009 UR - http://www.mrcindia.org/journal/ SN - 0972-9062 ER - TY - JOUR A1 - Webster, Dean C. A1 - Meier, Michael A. R. T1 - Polymer libraries : preparation and applications N2 - Polymer libraries offer straightforward opportunities for the investigation of structure property relationships and for a more thorough understanding of certain research problems. Furthermore, if combined with high-throughput methods for their preparation as well as screening, they offer the additional advantage of time savings and/or the reduction of experimental efforts. Thus, the herein discussed methods of polymer library preparation and selected literature examples of polymer libraries describe efficient and state-of-the-art methods to tackle difficult research challenges in polymer and materials science. Y1 - 2010 UR - http://www.springerlink.com/content/tk40663747722833/ U6 - https://doi.org/10.1007/12_2009_15 SN - 0065-3195 ER - TY - JOUR A1 - de Espinosa, Lucas Montero A1 - Meier, Michael A. R. A1 - Ronda, Juan C. A1 - Galiß, Marina A1 - Cßdiz, Virginia T1 - Phosphorus-containing renewable polyester-polyols via ADMET polymerization : synthesis, functionalization, and radical crosslinking N2 - An alpha,omega-diene containing hydroxyl groups was prepared from plant oil-derived platform chemicals. The acyclic diene metathesis copolymerization (ADMET) of this monomer with a phosphorus-containing alpha,omega-cliene (DOPO II), also plant oil derived, afforded a series of phosphorus containing linear polyesters, which have been fully characterized. The backbone hydroxyls of these polyesters have been acrylated and radically polymerized to produce crosslinked polymers. The thermomechanical and mechanical properties, the thermal stability, and the flame retardancy of these phosphorus-based thermosets have been studied. Moreover, methyl 10-undecenoate has been used as chain stopper in selected ADMET polymerizations to study the effect of the prepolymers' molecular weights on the different properties of the final materials. Y1 - 2010 UR - http://www3.interscience.wiley.com/journal/117932467/tocgroup U6 - https://doi.org/10.1002/Pola.23887 SN - 0887-624X ER - TY - JOUR A1 - Bouakline, Foudhil A1 - Althorpe, Stuart C. A1 - Larregaray, Pascal A1 - Bonnet, Laurent T1 - Strong geometric-phase effects in the hydrogen-exchange reaction at high collision energies : II. quasiclassical trajectory analysis N2 - Recent calculations on the hydrogen-exchange reaction [Bouakline et al., J. Chem. Phys. 128, 124322 (2008)], have found strong geometric phase (GP) effects in the state-to-state differential cross-sections (DCS), at energies above the energetic minimum of the conical intersection (CI) seam, which cancel out in the integral cross-sections (ICS). In this article, we explain the origin of this cancellation and make other predictions about the nature of the reaction mechanisms at these high energies by carrying out quasiclassical trajectory (QCT) calculations. Detailed comparisons are made with the quantum results by splitting the quantum and the QCT cross-sections into contributions from reaction paths that wind in different senses around the CI and that scatter the products in the nearside and farside directions. Reaction paths that traverse one transition state (1-TS) scatter their products in just the nearside direction, whereas paths that traverse two transition states (2-TS) scatter in both the nearside and farside directions. However, the nearside 2-TS products scatter into a different region of angular phase-space than the 1-TS products, which explains why the GP effects cancel out in the ICS. Analysis of the QCT results also suggests that two separate reaction mechanisms may be responsible for the 2-TS scattering at high energies. Y1 - 2010 UR - http://www.informaworld.com/openurl?genre=journal&issn=0026-8976 U6 - https://doi.org/10.1080/00268971003610218 SN - 0026-8976 ER - TY - JOUR A1 - Kihampa, Charles A1 - Nkunya, Mayunga H. H. A1 - Joseph, Cosam C. A1 - Magesa, Stephen M. A1 - Hassanali, Ahmed A1 - Heydenreich, Matthias A1 - Kleinpeter, Erich T1 - Antimosquito and antimicrobial clerodanoids and a chlorobenzoid from Tessmannia species N2 - The clerodane diterpenoids trans-kolavenolic acid, 18-oxocleroda-3,13(E)-dien-15-oic acid, ent-(18- hydroxycarbonyl)-cleroda- 3,13(E)-dien-15-oate, 2-oxo-ent-cleroda-3,13(Z)-dien-15-oic acid and trans-2-oxo-ent-cleroda- 13(Z)-en-15-oic acid, and the chlorobenzenoid O-(3-hydroxy-4-hydroxycarbonyl-5-pentylphenyl)-3-chloro-4-methoxy-6-pentyl- 2-oxybenzoic acid were isolated from Tessmannia martiniana var pauloi and T. martiniana var matiniana. Structures were established based on interpretation of spectroscopic data. Some of the compounds exhibited significant antimosquito, antifungal and antibacterial activities. Y1 - 2010 UR - http://www.naturalproduct.us/ SN - 1934-578X ER - TY - CHAP A1 - Prokop, A. A1 - Zadolinnaya, S. A1 - Abduvaliev, A. A1 - Frias, C. A1 - Hagenow, K. A1 - Voigt, A. A1 - Tatarskiy, V. T1 - Novel copper complexes with potent/synergistic antitumor activity in vivo and promising clinical activity T2 - Journal of clinical oncology Y1 - 2011 SN - 0732-183X SN - 1527-7755 VL - 29 IS - 15 PB - American Society of Clinical Oncology CY - Alexandria ER - TY - JOUR A1 - Bland-Hawthorn, Joss A1 - Ellis, S. C. A1 - Leon-Saval, S. G. A1 - Haynes, R. A1 - Roth, Martin M. A1 - Löhmannsröben, Hans-Gerd A1 - Horton, A. J. A1 - Cuby, J. -G. A1 - Birks, T. A. A1 - Lawrence, J. S. A1 - Gillingham, P. A1 - Ryder, S. D. A1 - Trinh, C. T1 - A complex multi-notch astronomical filter to suppress the bright infrared sky JF - Nature Communications N2 - A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations due to the extreme brightness and variability of the night sky at these wavelengths. A solution to this problem is crucial if we are to obtain the deepest possible observations of the early Universe, as redshifted starlight from distant galaxies appears at these wavelengths. The atmospheric emission between 1,000 and 1,800 nm arises almost entirely from a forest of extremely bright, very narrow hydroxyl emission lines that varies on timescales of minutes. The astronomical community has long envisaged the prospect of selectively removing these lines, while retaining high throughput between them. Here we demonstrate such a filter for the first time, presenting results from the first on-sky tests. Its use on current 8 m telescopes and future 30 m telescopes will open up many new research avenues in the years to come. Y1 - 2011 U6 - https://doi.org/10.1038/ncomms1584 SN - 2041-1723 VL - 2 IS - 50 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Reznichenko, Alexander L. A1 - Emge, Thomas J. A1 - Audoersch, Stephan A1 - Klauber, Eric G. A1 - Hultzsch, Kai C. A1 - Schmidt, Bernd T1 - Group 5 metal binaphtholate complexes for catalytic asymmetric hydroaminoalkylation and hydroamination/cyclization JF - Organometallics N2 - 3,3'-Silylated binaphtholate tantalum and niobium complexes were shown to be efficient catalysts for the asymmetric hydroaminoalkylation of N-methylaniline derivatives and N-benzylmethylamine with simple alkenes in enantioselectivities of up to 80% ee. No hydroaminoalkylation was observed with aminoalkenes; rather, exclusive asymmetric hydroamination/cyclization took place in up to 81% ee. Y1 - 2011 U6 - https://doi.org/10.1021/om1011006 SN - 0276-7333 VL - 30 IS - 5 SP - 921 EP - 924 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Bartlett, Nate C. -M. A1 - Jankunas, Justin A1 - Goswami, Tapas A1 - Zare, Richard N. A1 - Bouakline, Foudhil A1 - Althorpe, Stuart C. T1 - Differential cross sections for H + D-2 -> HD(v '=2, j '=0,3,6,9) + D at center-of-mass collision energies of 1.25, 1.61, and 1.97 eV JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - We have measured differential cross sections (DCSs) for the reaction H + D-2 -> HD- (v' = 2, j' = 0,3,6,9) + D at center-of-mass collision energies E-coll of 1.25, 1.61, and 1.97 eV using the photoloc technique. The DCSs show a strong dependence on the product rotational quantum number. For the HD(v' = 2, j' = 0) product, the DCS is bimodal but becomes oscillatory as the collision energy is increased. For the other product states, they are dominated by a single peak, which shifts from back to sideward scattering as j' increases, and they are in general less sensitive to changes in the collision energy. The experimental results are compared to quantum mechanical calculations and show good, but not fully quantitative agreement. Y1 - 2011 U6 - https://doi.org/10.1039/c0cp02460k SN - 1463-9076 VL - 13 IS - 18 SP - 8175 EP - 8179 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Troll, K. A1 - Kulkarni, Amit A1 - Wang, W. A1 - Darko, C. A1 - Koumba, A. M. Bivigou A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - The collapse transition of poly(styrene-b-(N-isopropyl acrylamide)) diblock copolymers in aqueous solution and in thin films T2 - Colloid and polymer science : official journal of the Kolloid-Gesellschaft Y1 - 2011 U6 - https://doi.org/10.1007/s00396-010-2344-1 SN - 0303-402X VL - 289 IS - 2 SP - 227 EP - 227 PB - Springer CY - New York ER - TY - JOUR A1 - Zakrevskyy, Y. A1 - Ritschel, T. A1 - Dosche, C. A1 - Löhmannsröben, Hans-Gerd T1 - Quantitative calibration - and reference-free wavelength modulation spectroscopy JF - Infrared physics & technology N2 - A unified model for quantitative description of harmonic spectra of gases obtained by wavelength modulation spectroscopy (WMS) technique is presented. In the model, both intensity modulation (IM) and frequency modulation (FM) of the laser emission are taken into account using minimum number of parameters. For the first time, the static behavior of a laser is described as a limiting case of its dynamic response. Laser and its driver are considered as a single device converting applied bias to laser emission. This allows application of the model to any type of laser and the introduced parameters can be assigned to the corresponding laser and/or driver properties. The approach was tested using a distributed feedback (DFB) laser spectrometer. Correctness of the proposed model is justified by very good agreement between the measured and modeled/fitted spectra, which allowed evaluation of the setup performance and assessment of modulation parameters of the DFB laser. An algorithm to minimize the time of numerical calculation of harmonic spectra using numerically approximated Voigt lineshape function was developed. Absolute values of the absorption line parameters (line strength and line width) were obtained from a single calibration- and reference-free spectrum scan with accuracy better than 0.1%. KW - Wavelength modulation gas spectroscopy KW - Diode laser KW - Isotope detection Y1 - 2012 U6 - https://doi.org/10.1016/j.infrared.2011.12.001 SN - 1350-4495 VL - 55 IS - 2-3 SP - 183 EP - 190 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ellis, S. C. A1 - Bland-Hawthorn, Joss A1 - Lawrence, J. A1 - Horton, A. J. A1 - Trinh, C. A1 - Leon-Saval, S. G. A1 - Shortridge, K. A1 - Bryant, J. A1 - Case, S. A1 - Colless, M. A1 - Couch, W. A1 - Freeman, K. A1 - Gers, L. A1 - Glazebrook, K. A1 - Haynes, R. A1 - Lee, S. A1 - Löhmannsröben, Hans-Gerd A1 - O'Byrne, J. A1 - Miziarski, S. A1 - Roth, M. A1 - Schmidt, B. A1 - Tinney, C. G. A1 - Zheng, J. T1 - Suppression of the near-infrared OH night-sky lines with fibre Bragg gratings - first results JF - Monthly notices of the Royal Astronomical Society N2 - The background noise between 1 and 1.8 ?mu m in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, the Gemini Near-infrared OH Suppression Integral Field Unit (IFU) System (GNOSIS), which suppresses 103 OH doublets between 1.47 and 1.7?mu m by a factor of 1000 with a resolving power of 10?000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the Anglo-Australian Telescope. We present measurements of sensitivity, background and throughput. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is 36?per cent, but this could be improved to 46?per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low-resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 mu m is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low-resolution OH-suppressed spectroscopy is illustrated with example observations of Seyfert galaxies and a low-mass star. The GNOSIS background is dominated by detector dark current below 1.67 mu m and by thermal emission above 1.67 mu m. After subtracting these, we detect an unidentified residual interline component of 860 +/- 210 photons s-1 m-2?arcsec-2?mu m-1, comparable to previous measurements. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artefact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimized OH suppression spectrographs. The next-generation OH suppression spectrograph will be focused on resolving the source of the interline component, taking advantage of better optimization for a fibre Bragg grating feed incorporating refinements of design based on our findings from GNOSIS. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design. KW - atmospheric effects KW - instrumentation: miscellaneous KW - infrared: general Y1 - 2012 U6 - https://doi.org/10.1111/j.1365-2966.2012.21602.x SN - 0035-8711 VL - 425 IS - 3 SP - 1682 EP - 1695 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Körzdörfer, Thomas A1 - Parrish, Robert M. A1 - Sears, John S. A1 - Sherrill, C. David A1 - Bredas, Jean-Luc T1 - On the relationship between bond-length alternation and many-electron self-interaction error JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Predicting accurate bond-length alternations (BLAs) in long conjugated molecular chains has been a major challenge for electronic-structure theory for many decades. While Hartree-Fock (HF) overestimates BLA significantly, second-order perturbation theory and commonly used density functional theory (DFT) approaches typically underestimate it. Here, we discuss how this failure is related to the many-electron self-interaction error (MSIE), which is inherent to both HF and DFT approaches. We use tuned long-range corrected hybrids to minimize the MSIE for a series of polyenes. The key result is that the minimization of the MSIE alone does not yield accurate BLAs. On the other hand, if the range-separation parameter is tuned to yield accurate BLAs, we obtain a significant MSIE that grows with chain length. Our findings demonstrate that reducing the MSIE is one but not the only important aspect necessary to obtain accurate BLAs from density functional theory. Y1 - 2012 U6 - https://doi.org/10.1063/1.4752431 SN - 0021-9606 VL - 137 IS - 12 PB - American Institute of Physics CY - Melville ER - TY - THES A1 - Grothe, Dorian C. T1 - Entwicklung und Synthese von Materialien für Polyelektrolytmembranen mit ionischen Flüssigkeiten zum Einsatz in Lithium-Ionen-Batterien T1 - Development and synthesis of materials for poly electrolyte membranes with ionic liquids for application in Lithium-ion batteries N2 - Für den Einsatz in Autobatterien gibt es besondere Anforderungen an den Elektrolyten im Bereich der Energie- und Leistungsdichten, um beispielsweise thermische Verluste gering zu halten. Hochleitfähige Elektrolyte mit Leitfähigkeiten im Millisiemensbereich sind hier ebenso notwendig wie auch sichere, d.h. möglichst nicht brennbare und einen niedrigen Dampfdruck besitzende Materialien. Um diese Vorgaben zu erreichen, ist es notwendig, einen polymeren Separator zu entwickeln, welcher auf brennbare organische Lösungsmittel verzichtet und damit eine drastische Steigerung der Sicherheit gewährleistet. Gleichzeitig müssen hierbei die Leistungsvorgaben bezüglich der Leitfähigkeit erfüllt werden. Zu diesem Zweck wurde ein Konzept basierend auf der Kombination von einer polymeren sauerstoffreichen Matrix und einer ionischen Flüssigkeit entwickelt und verifiziert. Dabei wurden folgende Erkenntnisse gewonnen: 1. Es wurden neuartige diacrylierte sauerstoffreiche Matrixkomponenten mit vielen Carbonylfunktionen, für eine gute Lithiumleitfähigkeit, synthetisiert. 2. Es wurden mehrere neue ionische Flüssigkeiten sowohl auf Imidazolbasis als auch auf Ammoniumbasis synthetisiert und charakterisiert. 3. Die Einflüsse der Kationenstruktur und der Einfluss der Gegenionen im Bezug auf Schmelzpunkte und Leitfähigkeiten wurden untersucht. 4. Aus den entwickelten Materialien wurden Blendsysteme hergestellt und mittels Impedanzspektrometrie untersucht: Leitfähigkeiten von 10-4S/cm bei Raumtemperatur sind realisierbar. 5. Die Blendsysteme wurden auf ihre thermische Stabilität hin untersucht: Stabilitäten bis 250°C sind erreichbar. Dabei wird keine kristalline Struktur beobachtet. N2 - Within the field of energy storage and charge transfer, the lithium polymer batteries are one of the leading technologies, due to their low manufacture cost and their possible variety of packaging shapes. Despite their good thermal stability and very good weight to energy ratio, lithium ion batteries use as a electrolyte system a mixture of ethylene carbonate and diethyl carbonate as solvent which have a high risk of deflagration when they come in contact with water. Thus the developement of new materials for lithium-ion-batteries are necessary. For the electrolyte there are special requirements in terms of energy- and power density e.g. in order to minimize thermal loss. High conductivity electrolytes with conductivities in the range of milisiemens are as essential as safe materials, like non flammable non-volatile materials. To fulfill these requirements it is important to develop a polymeric lithium ion conductor, which is free of flammable organic solvents in order to ensure safety. Simultaneously it is also ,mandatory to achieve high performances in terms of ion-conductivity. Therefore a concept based on a combination of an oxygen rich polymeric matrix and ionic liquids was developed and verified. Following results were achieved . 1. Synthesis of new diacryalted oxygen rich matrix components with many carbonylfunctions for a good lithium ion transport. 2. Synthesis and characterization of new ionic liquids based on imidazol or ammonium compounds. 3. Investigation of the influences of the cation structure and counter ions for melting points and ion conductivity. 4. Creation of Blendsystems with the developed materials 5. Thermal investigations of these solid-state-electrolytes with DSC and TGA measurements, resulting in thermal stabilities up to 250°C.No crystallization were observed. 6. investigation of these solid-state-electrolytes via AC-impedance spectrometry, resulting in conductivities of 10-4S/cm at room temperature. KW - Lithium-Ionen-Batterie KW - ionische Flüssigkeiten KW - Festelektrolyten KW - AC Impedanz KW - Lithium ion battery KW - ionic liquids KW - solid-state-electrolyte KW - AC -Impedance Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-63690 ER - TY - JOUR A1 - Jankunas, Justin A1 - Zare, Richard N. A1 - Bouakline, Foudhil A1 - Althorpe, Stuart C. A1 - Herraez-Aguilar, Diego A1 - Aoiz, F. Javier T1 - Seemingly anomalous angular distributions in H+D-2 reactive scattering JF - Science N2 - When a hydrogen (H) atom approaches a deuterium (D-2) molecule, the minimum-energy path is for the three nuclei to line up. Consequently, nearly collinear collisions cause HD reaction products to be backscattered with low rotational excitation, whereas more glancing collisions yield sideways-scattered HD products with higher rotational excitation. Here we report that measured cross sections for the H + D-2 -> HD(v' = 4, j') + D reaction at a collision energy of 1.97 electron volts contradict this behavior. The anomalous angular distributions match closely fully quantum mechanical calculations, and for the most part quasiclassical trajectory calculations. As the energy available in product recoil is reduced, a rotational barrier to reaction cuts off contributions from glancing collisions, causing high-j' HD products to become backward scattered. Y1 - 2012 U6 - https://doi.org/10.1126/science.1221329 SN - 0036-8075 VL - 336 IS - 6089 SP - 1687 EP - 1690 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Bronner, C. A1 - Leyssner, F. A1 - Stremlau, S. A1 - Utecht, Manuel Martin A1 - Saalfrank, Peter A1 - Klamroth, Tillmann A1 - Tegeder, P. T1 - Electronic structure of a subnanometer wide bottom-up fabricated graphene nanoribbon: End states, band gap, and dispersion JF - Physical review : B, Condensed matter and materials physics N2 - Angle-resolved two-photon photoemission and high-resolution electron energy loss spectroscopy are employed to derive the electronic structure of a subnanometer atomically precise quasi-one-dimensional graphene nanoribbon (GNR) on Au(111). We resolved occupied and unoccupied electronic bands including their dispersion and determined the band gap, which possesses an unexpectedly large value of 5.1 eV. Supported by density functional theory calculations for the idealized infinite polymer and finite size oligomers, an unoccupied nondispersive electronic state with an energetic position in the middle of the band gap of the GNR could be identified. This state resides at both ends of the ribbon (end state) and is only found in the finite sized systems, i.e., the oligomers. Y1 - 2012 U6 - https://doi.org/10.1103/PhysRevB.86.085444 SN - 1098-0121 VL - 86 IS - 8 PB - American Physical Society CY - College Park ER - TY - THES A1 - Wawrzinek, Robert C. W. T1 - Fluoreszenzfarbstoffe mit Dioxolobenzodioxol-Grundgerüst: Synthese, Untersuchungen und Anwendungen Y1 - 2013 CY - Potsdam ER - TY - JOUR A1 - Kerubo, Leonidah Omosa A1 - Midiwo, Jacob Ogweno A1 - Derese, Solomon A1 - Langat, Moses K. A1 - Akala, Hoseah M. A1 - Waters, Norman C. A1 - Peter, Martin A1 - Heydenreich, Matthias T1 - Antiplasmodial activity of compounds from the surface exudates of senecio roseiflorus JF - Natural product communications : an international journal for communications and reviews N2 - From the surface exudates of Senecio roseiflorus fourteen known methylated flavonoids and one phenol were isolated and characterized. The structures of these compounds were determined on the basis of their spectroscopic analysis. The surface exudate and the flavonoids isolated showed moderate to good antiplasmodial activity with 5,4'-dihydroxy-7-dimethoxyflavanone having the highest activity against chloroquine-sensitive (D6) and resistant (W2) strains of Plasmodium falciparum, with IC50 values of 3.2 +/- 0.8 and 4.4 +/- 0.01 mu g/mL respectively. KW - Senecio roseiflorus KW - Asteraceae KW - Surface exudates KW - Antiplasmodial activity Y1 - 2013 SN - 1934-578X VL - 8 IS - 2 SP - 175 EP - 176 PB - NPC CY - Westerville ER - TY - JOUR A1 - Sangoro, Joshia R. A1 - Iacob, C. A1 - Agapov, A. L. A1 - Wang, Yangyang A1 - Berdzinski, Stefan A1 - Rexhausen, Hans A1 - Strehmel, Veronika A1 - Friedrich, C. A1 - Sokolov, A. P. A1 - Kremer, F. T1 - Decoupling of ionic conductivity from structural dynamics in polymerized ionic liquids JF - Soft matter N2 - Charge transport and structural dynamics in low molecular weight and polymerized 1-vinyl-3-pentylimidazolium bis(trifluoromethylsulfonyl) imide ionic liquids (ILs) are investigated by a combination of broadband dielectric spectroscopy, dynamic mechanical spectroscopy and differential scanning calorimetry. While the dc conductivity and fluidity exhibit practically identical temperature dependence for the non-polymerized IL, a significant decoupling of ionic conduction from structural dynamics is observed for the polymerized IL. In addition, the dc conductivity of the polymerized IL exceeds that of its molecular counterpart by four orders of magnitude at their respective calorimetric glass transition temperatures. This is attributed to the unusually high mobility of the anions especially at lower temperatures when the structural dynamics is significantly slowed down. A simple physical explanation of the possible origin of the remarkable decoupling of ionic conductivity from structural dynamics is proposed. Y1 - 2014 U6 - https://doi.org/10.1039/c3sm53202j SN - 1744-683X SN - 1744-6848 VL - 10 IS - 20 SP - 3536 EP - 3540 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Tsendra, Oksana A1 - Scott, Andrea Michalkova A1 - Gorb, Leonid A1 - Boese, Adrian Daniel A1 - Hill, Frances C. A1 - Ilchenko, Mykola M. A1 - Leszczynska, Danuta A1 - Leszczynski, Jerzy T1 - Adsorption of Nitrogen-Containing Compounds on the (100) alpha-Quartz Surface: Ab Initio Cluster Approach JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - A cluster approach extended to the ONIOM methodology has been applied using several density functionals and Moller-Plesset perturbation theory (MP2) to simulate the adsorption of selected nitrogen-containing compounds [NCCs, 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4-dinitroanisole (DNAN), and 3-nitro-1,2,4-triazole-5-one (NTO)] on the hydroxyated (100) surface of a-quartz. The structural properties were calculated using the M06-2X functional and 6-31G(d,p) basis set. The M06-2X-D3, PBE-D3, and MP2 methods were used to calculate the adsorption energies. Results have been compared with the data from other studies of adsorption of compounds of similar nature on silica. Effect of deformation of the silica surface and adsorbates on the binding energy values was also studied. The atoms in molecules (AIM) analysis was employed to characterize the adsorbate-adsorbent binding and to calculate the bond energies. The silica surface shows different sorption affinity toward the chemicals considered depending on their electronic structure. All target NCCs are physisorbed on the modeled silica surface. Adsorption occurs due to the formation of multiple hydrogen bonds between the functional groups of NCCs and surface silanol groups. Parallel orientation of NCCs interacting with the silica surface was found to be favorable when compared with perpendicularly oriented NCCs. NTO was found to be the most strongly adsorbed on the silica surface among all of the considered compounds. Dispersion correction was shown to play an important role in the DFT calculations of the adsorption energies of silica-NCC systems. Y1 - 2014 U6 - https://doi.org/10.1021/jp406827h SN - 1932-7447 VL - 118 IS - 6 SP - 3023 EP - 3034 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Sutton, Christopher A1 - Körzdörfer, Thomas A1 - Gray, Matthew T. A1 - Brunsfeld, Max A1 - Parrish, Robert M. A1 - Sherrill, C. David A1 - Sears, John S. A1 - Bredas, Jean-Luc T1 - Accurate description of torsion potentials in conjugated polymers using density functionals with reduced self-interaction error JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - We investigate the torsion potentials in two prototypical pi-conjugated polymers, polyacetylene and polydiacetylene, as a function of chain length using different flavors of density functional theory. Our study provides a quantitative analysis of the delocalization error in standard semilocal and hybrid density functionals and demonstrates how it can influence structural and thermodynamic properties. The delocalization error is quantified by evaluating the many-electron self-interaction error (MESIE) for fractional electron numbers, which allows us to establish a direct connection between the MESIE and the error in the torsion barriers. The use of non-empirically tuned long-range corrected hybrid functionals results in a very significant reduction of the MESIE and leads to an improved description of torsion barrier heights. In addition, we demonstrate how our analysis allows the determination of the effective conjugation length in polyacetylene and polydiacetylene chains. Y1 - 2014 U6 - https://doi.org/10.1063/1.4863218 SN - 0021-9606 SN - 1089-7690 VL - 140 IS - 5 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Stumpe, Joachim A1 - Sakhno, O. A1 - Gritsai, Y. A1 - Rosenhauer, R. A1 - Fischer, Th. A1 - Rutloh, Michael A1 - Schaal, F. A1 - Weidenfeld, S. A1 - Jetter, M. A1 - Michler, P. A1 - Pruss, C. A1 - Osten, W. T1 - Active and passive LC based polarization elements JF - Molecular crystals and liquid crystals N2 - Passive and active polarization elements were created by surface and bulk photo-alignment of LCs, reactive LCs, photo-sensitive LCP and photo-curable monomer/LC composites. The use of different photo-sensitive liquid crystalline materials for the development of highly anisotropic elements with high spatial resolution and stability or, alternatively, fast switch ability will be discussed. Photo-active and voltage tunable polarization and diffraction elements are presented. For active micro-optic application a photo-addressed patterned retarder was created. Electrically switchable diffraction gratings were generated by interference exposure of photo-curable LC composites at room temperature characterized by droplet free morphology. These polarization sensitive diffraction elements are characterized be excellent optical properties and low switching times. KW - electrically switchable gratings. KW - diffractive elements KW - polymer/LC composites KW - switchable retarder KW - polarization gratings KW - Polarization elements Y1 - 2014 U6 - https://doi.org/10.1080/15421406.2014.917503 SN - 1542-1406 SN - 1563-5287 VL - 594 IS - 1 SP - 140 EP - 149 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Guha, S. A1 - Warsinke, A. A1 - Tientcheu, Ch. M. A1 - Schmalz, K. A1 - Meliani, C. A1 - Wenger, Ch. T1 - Label free sensing of creatinine using a 6 GHz CMOS near-field dielectric immunosensor JF - The analyst : the analytical journal of the Royal Society of Chemistry N2 - In this work we present a CMOS high frequency direct immunosensor operating at 6 GHz (C-band) for label free determination of creatinine. The sensor is fabricated in standard 0.13 μm SiGe:C BiCMOS process. The report also demonstrates the ability to immobilize creatinine molecules on a Si3N4 passivation layer of the standard BiCMOS/CMOS process, therefore, evading any further need of cumbersome post processing of the fabricated sensor chip. The sensor is based on capacitive detection of the amount of non-creatinine bound antibodies binding to an immobilized creatinine layer on the passivated sensor. The chip bound antibody amount in turn corresponds indirectly to the creatinine concentration used in the incubation phase. The determination of creatinine in the concentration range of 0.88–880 μM is successfully demonstrated in this work. A sensitivity of 35 MHz/10 fold increase in creatinine concentration (during incubation) at the centre frequency of 6 GHz is gained by the immunosensor. The results are compared with a standard optical measurement technique and the dynamic range and sensitivity is of the order of the established optical indication technique. The C-band immunosensor chip comprising an area of 0.3 mm2 reduces the sensing area considerably, therefore, requiring a sample volume as low as 2 μl. The small analyte sample volume and label free approach also reduce the experimental costs in addition to the low fabrication costs offered by the batch fabrication technique of CMOS/BiCMOS process. Y1 - 2015 U6 - https://doi.org/10.1039/c4an02194k SN - 0003-2654 SN - 1364-5528 VL - 9 IS - 140 SP - 3019 EP - 3027 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Guha, S. A1 - Warsinke, A. A1 - Tientcheu, Ch. M. A1 - Schmalz, K. A1 - Meliani, C. A1 - Wenger, Ch. T1 - Label free sensing of creatinine using a 6 GHz CMOS near-field dielectric immunosensor N2 - In this work we present a CMOS high frequency direct immunosensor operating at 6 GHz (C-band) for label free determination of creatinine. The sensor is fabricated in standard 0.13 μm SiGe:C BiCMOS process. The report also demonstrates the ability to immobilize creatinine molecules on a Si3N4 passivation layer of the standard BiCMOS/CMOS process, therefore, evading any further need of cumbersome post processing of the fabricated sensor chip. The sensor is based on capacitive detection of the amount of non-creatinine bound antibodies binding to an immobilized creatinine layer on the passivated sensor. The chip bound antibody amount in turn corresponds indirectly to the creatinine concentration used in the incubation phase. The determination of creatinine in the concentration range of 0.88–880 μM is successfully demonstrated in this work. A sensitivity of 35 MHz/10 fold increase in creatinine concentration (during incubation) at the centre frequency of 6 GHz is gained by the immunosensor. The results are compared with a standard optical measurement technique and the dynamic range and sensitivity is of the order of the established optical indication technique. The C-band immunosensor chip comprising an area of 0.3 mm2 reduces the sensing area considerably, therefore, requiring a sample volume as low as 2 μl. The small analyte sample volume and label free approach also reduce the experimental costs in addition to the low fabrication costs offered by the batch fabrication technique of CMOS/BiCMOS process. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 195 Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-81177 ER - TY - JOUR A1 - Kathrein, Christine C. A1 - Bai, Wubin A1 - Currivan-Incorvia, Jean Anne A1 - Liontos, George A1 - Ntetsikas, Konstantinos A1 - Avgeropoulos, Apostolos A1 - Böker, Alexander A1 - Tsarkova, Larisa A1 - Ross, Caroline A. T1 - Combining Graphoepitaxy and Electric Fields toward Uniaxial Alignment of Solvent-Annealed Polystyrene-b-Poly(dimethylsiloxane) Block Copolymers JF - Chemistry of materials : a publication of the American Chemical Society N2 - We report a combined directing effect of the simultaneously applied graphoepitaxy and electric field on the self-assembly of cylinder forming polystyrene-b-poly(dimethylsiloxane) block copolymer in thin films. A correlation length of up to 20 mu m of uniaxial ordered striped patterns is an order of magnitude greater than that produced by either graphoepitaxy or electric field alignment alone and is achieved at reduced annealing times. The angle between the electric field direction and the topographic guides as well as the dimensions of the trenches affected both the quality of the ordering and the direction of the orientation of cylindrical domains: parallel or perpendicular to the topographic features. We quantified the interplay between the electric field and the geometry of the topographic structures by constructing the phase diagram of microdomain orientation. This combined approach allows the fabrication of highly ordered block copolymer structures using macroscopically prepatterned photolithographic substrates. Y1 - 2015 U6 - https://doi.org/10.1021/acs.chemmater.5b03354 SN - 0897-4756 SN - 1520-5002 VL - 27 IS - 19 SP - 6890 EP - 6898 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Bader, Denise A1 - Klier, Dennis Tobias A1 - Hettrich, C. A1 - Bier, Frank Fabian A1 - Wessig, Pablo T1 - Detecting carbohydrate-lectin interactions using a fluorescent probe based on DBD dyes JF - Analytical methods : advancing methods and applications N2 - Herein we present an efficient synthesis of a biomimetic probe with modular construction that can be specifically bound by the mannose binding FimH protein - a surface adhesion protein of E. coli bacteria. The synthesis combines the new and interesting DBD dye with the carbohydrate ligand mannose via a Click reaction. We demonstrate the binding to E. coli bacteria over a large concentration range and also present some special characteristics of those molecules that are of particular interest for the application as a biosensor. In particular, the mix-and-measure ability and the very good photo-stability should be highlighted here. Y1 - 2016 U6 - https://doi.org/10.1039/c5ay02991k SN - 1759-9660 SN - 1759-9679 VL - 8 SP - 1235 EP - 1238 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Dzhigaev, D. A1 - Shabalin, A. A1 - Stankevic, T. A1 - Lorenz, Ulf A1 - Kurta, R. P. A1 - Seiboth, F. A1 - Wallentin, J. A1 - Singer, A. A1 - Lazarev, S. A1 - Yefanov, O. M. A1 - Borgstrom, M. A1 - Strikhanov, M. N. A1 - Samuelson, L. A1 - Falkenberg, G. A1 - Schroer, C. G. A1 - Mikkelsen, A. A1 - Vartanyants, I. A. T1 - Bragg coherent x-ray diffractive imaging of a single indium phosphide nanowire JF - Journal of optics N2 - Three-dimensional (3D) Bragg coherent x-ray diffractive imaging (CXDI) with a nanofocused beam was applied to quantitatively map the internal strain field of a single indium phosphide nanowire. The quantitative values of the strain were obtained by pre-characterization of the beam profile with transmission ptychography on a test sample. Our measurements revealed the 3D strain distribution in a region of 150 nm below the catalyst Au particle. We observed a slight gradient of the strain in the range of +/- 0.6% along the [111] growth direction of the nanowire. We also determined the spatial resolution in our measurements to be about 10 nm in the direction perpendicular to the facets of the nanowire. The CXDI measurements were compared with the finite element method simulations and show a good agreement with our experimental results. The proposed approach can become an effective tool for in operando studies of the nanowires. KW - Bragg coherent x-ray diffractive imaging KW - InP nanowires KW - strain field Y1 - 2016 U6 - https://doi.org/10.1088/2040-8978/18/6/064007 SN - 2040-8978 SN - 2040-8986 VL - 18 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Braune, Steffen A1 - Gross, M. A1 - Walter, M. A1 - Zhou, Shengqiang A1 - Dietze, Siegfried A1 - Rutschow, S. A1 - Lendlein, Andreas A1 - Tschoepe, C. A1 - Jung, Friedrich T1 - Adhesion and activation of platelets from subjects with coronary artery disease and apparently healthy individuals on biomaterials JF - Journal of biomedical materials research : an official journal of the Society for Biomaterials, the Japanese Society for Biomaterials; the Australian Society for Biomaterials N2 - On the basis of the clinical studies in patients with coronary artery disease (CAD) presenting an increased percentage of activated platelets, we hypothesized that hemocompatibility testing utilizing platelets from healthy individuals may result in an underestimation of the materials' thrombogenicity. Therefore, we investigated the interaction of polymer-based biomaterials with platelets from CAD patients in comparison to platelets from apparently healthy individuals. In vitro static thrombogenicity tests revealed that adherent platelet densities and total platelet covered areas were significantly increased for the low (polydimethylsiloxane, PDMS) and medium (Collagen) thrombogenic surfaces in the CAD group compared to the healthy subjects group. The area per single platelet—indicating the spreading and activation of the platelets—was markedly increased on PDMS treated with PRP from CAD subjects. This could not be observed for collagen or polytetrafluoroethylene (PTFE). For the latter material, platelet adhesion and surface coverage did not differ between the two groups. Irrespective of the substrate, the variability of these parameters was increased for CAD patients compared to healthy subjects. This indicates a higher reactivity of platelets from CAD patients compared to the healthy individuals. Our results revealed, for the first time, that utilizing platelets from apparently healthy donors bears the risk of underestimating the thrombogenicity of polymer-based biomaterials. KW - platelets KW - biomaterials KW - hemocompatibility KW - cardiovascular disease KW - cardiovascular implant Y1 - 2016 U6 - https://doi.org/10.1002/jbm.b.33366 SN - 1552-4973 SN - 1552-4981 VL - 104 SP - 210 EP - 217 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Kathrein, Christine C. A1 - Bai, Wubin A1 - Nunns, Adam A1 - Gwyther, Jessica A1 - Manners, Ian A1 - Böker, Alexander A1 - Tsarkova, Larisa A1 - Ross, Caroline A. T1 - Electric field manipulated nanopatterns in thin films of metalorganic 3-miktoarm star terpolymers JF - Soft matter N2 - We report the effect of electric field on the morphological transitions and ordering behavior of polyferrocenylethylmethylsilane block (PFEMS)-containing copolymers. By analyzing structures in solvent-annealed films of metalorganic sphere-and cylinder-forming diblock copolymers, as well as of 3-miktoarm polyisoprene-arm-polystyrene-arm-PFEMS (3 mu-ISF) terpolymers, we decouple two types of responses to the electric field: morphological transformations as a result of an increase in the volume fraction of the PFEMS block by oxidation of the ferrocenyl groups, and the orientation of the dielectric interfaces of microdomains parallel to the electric field vector. In the case of 3m-ISF, the former effect dominates at high electric field strengths which results in an unexpected cylinder-to-sphere transition, leading to a well-ordered hexagonal dot pattern. Our results demonstrate multiple tunability of ordered microdomain morphologies, suggesting future applications in nanofabrication and surface patterning. Y1 - 2016 U6 - https://doi.org/10.1039/c6sm00451b SN - 1744-683X SN - 1744-6848 VL - 12 SP - 4866 EP - 4874 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kathrein, Christine C. A1 - Pester, Christian A1 - Ruppel, Markus A1 - Jung, Maike A1 - Zimmermann, Marc A1 - Böker, Alexander T1 - Reorientation mechanisms of block copolymer/CdSe quantum dot composites under application of an electric field JF - Soft matter N2 - Time- and temperature-resolved in situ birefringence measurements were applied to analyze the effect of nanoparticles on the electric field-induced alignment of a microphase separated solution of poly(styrene)-block-poly(isoprene) in toluene. Through the incorporation of isoprene-confined CdSe quantum dots the reorientation behavior is altered. Particle loading lowers the order-disorder transition temperature, and increases the defect density, favoring nucleation and growth as an alignment mechanism over rotation of grains. The temperature dependent alteration in the reorientation mechanism is analyzed via a combination of birefringence and synchrotron SAXS. The detailed understanding of the effect of nanoparticles on the reorientation mechanism is an important prerequisite for optimization of electricfield-induced alignment of block copolymer/nanoparticle composites where the block copolymer guides the nanoparticle self-assembly into anisotropic structures. Y1 - 2016 U6 - https://doi.org/10.1039/c6sm01073c SN - 1744-683X SN - 1744-6848 VL - 12 SP - 8417 EP - 8424 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Soliveres, Santiago A1 - Manning, Peter A1 - Prati, Daniel A1 - Gossner, Martin M. A1 - Alt, Fabian A1 - Arndt, Hartmut A1 - Baumgartner, Vanessa A1 - Binkenstein, Julia A1 - Birkhofer, Klaus A1 - Blaser, Stefan A1 - Bluethgen, Nico A1 - Boch, Steffen A1 - Boehm, Stefan A1 - Boerschig, Carmen A1 - Buscot, Francois A1 - Diekoetter, Tim A1 - Heinze, Johannes A1 - Hoelzel, Norbert A1 - Jung, Kirsten A1 - Klaus, Valentin H. A1 - Klein, Alexandra-Maria A1 - Kleinebecker, Till A1 - Klemmer, Sandra A1 - Krauss, Jochen A1 - Lange, Markus A1 - Morris, E. Kathryn A1 - Mueller, Joerg A1 - Oelmann, Yvonne A1 - Overmann, Jörg A1 - Pasalic, Esther A1 - Renner, Swen C. A1 - Rillig, Matthias C. A1 - Schaefer, H. Martin A1 - Schloter, Michael A1 - Schmitt, Barbara A1 - Schoening, Ingo A1 - Schrumpf, Marion A1 - Sikorski, Johannes A1 - Socher, Stephanie A. A1 - Solly, Emily F. A1 - Sonnemann, Ilja A1 - Sorkau, Elisabeth A1 - Steckel, Juliane A1 - Steffan-Dewenter, Ingolf A1 - Stempfhuber, Barbara A1 - Tschapka, Marco A1 - Tuerke, Manfred A1 - Venter, Paul A1 - Weiner, Christiane N. A1 - Weisser, Wolfgang W. A1 - Werner, Michael A1 - Westphal, Catrin A1 - Wilcke, Wolfgang A1 - Wolters, Volkmar A1 - Wubet, Tesfaye A1 - Wurst, Susanne A1 - Fischer, Markus A1 - Allan, Eric T1 - Locally rare species influence grassland ecosystem multifunctionality JF - Philosophical transactions of the Royal Society of London : B, Biological sciences N2 - Species diversity promotes the delivery of multiple ecosystem functions (multifunctionality). However, the relative functional importance of rare and common species in driving the biodiversity multifunctionality relationship remains unknown. We studied the relationship between the diversity of rare and common species (according to their local abundances and across nine different trophic groups), and multifunctionality indices derived from 14 ecosystem functions on 150 grasslands across a land use intensity (LUI) gradient. The diversity of above- and below-ground rare species had opposite effects, with rare above-ground species being associated with high levels of multifunctionality, probably because their effects on different functions did not trade off against each other. Conversely, common species were only related to average, not high, levels of multifunctionality, and their functional effects declined with LUI. Apart from the community level effects of diversity, we found significant positive associations between the abundance of individual species and multifunctionality in 6% of the species tested. Species specific functional effects were best predicted by their response to LUI: species that declined in abundance with land use intensification were those associated with higher levels of multifunctionality. Our results highlight the importance of rare species for ecosystem multifunctionality and help guiding future conservation priorities. KW - biodiversity KW - common species KW - ecosystem function KW - identity hypothesis KW - land use KW - multitrophic Y1 - 2016 U6 - https://doi.org/10.1098/rstb.2015.0269 SN - 0962-8436 SN - 1471-2970 VL - 371 SP - 3175 EP - 3185 PB - Royal Society CY - London ER - TY - JOUR A1 - Balci, K. A1 - Akkaya, Y. A1 - Akyuz, S. A1 - Collier, W. B. A1 - Stricker, M. C. A1 - Stover, D. D. A1 - Ritzhaupt, G. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - The effects of conformation and zwitterionic tautomerism on the structural and vibrational spectral data of anserine JF - Vibrational spectroscopy : an international journal devoted to applications of infrared and raman spectroscopy N2 - In this study, the stable conformers of neutral anserine were searched by molecular dynamics simulations and energy minimization calculations using the MM2 force field. Thermochemical calculations at B3LYP/6-31G(d) level of theory followed these preliminary calculations. The results confirmed that neutral anserine has quite a flexible structure and many stable gauche and trans conformers at room temperature. Nevertheless, two are considerably more favourable in energy than the others and expected to dominate the gas-phase and matrix IR spectra of the molecule. The corresponding structural and vibrational spectral data for these two conformers of neutral anserine, whose relative stabilities were also examined by high-accuracy energy calculations carried out using G3MP2B3 method, and for the most stable conformer of anserine in zwitterion form were calculated at B3LYP/6-311++G(d,p) level of theory. The calculated harmonic force constants were refined using the Scaled Quantum Mechanical Force Field (SQM-FF) method and then used to produce the refined wavenumbers, potential energy distributions (PEDs) and IR and Raman intensities. These refined data together with the scaled harmonic wavenumbers obtained using another method, Dual Scale factors (DS), enabled us to correctly analyse the observed IR and Raman spectra of anserine and revealed the effects of conformation and zwitterionic tautomerism on its structural and vibrational spectral data. (C) 2016 Elsevier B.V. All rights reserved. KW - Anserine KW - Matrix IR spectrum KW - Tautomerism KW - SQM-FF KW - Dual scale factors Y1 - 2016 U6 - https://doi.org/10.1016/j.vibspec.2016.08.003 SN - 0924-2031 SN - 1873-3697 VL - 86 SP - 277 EP - 289 PB - Elsevier CY - Amsterdam 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 - Nguyen, Hiep N. A1 - Lee, Hyeunjoo A1 - Audörsch, Stephan A1 - Reznichenko, Alexander L. A1 - Nawara-Hultzsch, Agnieszka J. A1 - Schmidt, Bernd A1 - Hultzsch, Kai C. T1 - Asymmetric Intra- and Intermolecular Hydroamination Catalyzed by 3,3′-Bis(trisarylsilyl)- and 3,3′-Bis(arylalkylsilyl)-Substituted Binaphtholate Rare-Earth-Metal Complexes JF - Organometallics N2 - The series of novel 3,3′-bis(trisarylsilyl)- and 3,3′-bis(arylalkylsilyl)-substituted binaphtholate rare-earth-metal complexes 2a–i (SiR3 = Si(o-biphenylene)Ph (a), SiCyPh2 (b), Si-t-BuPh2 (c), Si(i-Pr)3 (d), SiCy2Ph (e), Si(2-tolyl)Ph2 (f), Si(4-t-Bu-C6H4)3 (g), Si(4-MeO-C6H4)Ph2 (h), SiBnPh2 (i)) have been prepared via arene elimination from [Ln(o-C6H4CH2NMe2)3] (Ln = Y, Lu) and the corresponding 3,3′-bis(silyl)-substituted binaphthol. The complexes exhibit high catalytic activity in the hydroamination/cyclization of aminoalkenes, with activities exceeding 1000 h–1 for (R)-2f-Ln, (R)-2g-Ln, and (R)-2h-Ln in the cyclization of 2,2-diphenylpent-4-enylamine (3a) at 25 °C, while the rigid dibenzosilole-substituted complexes (R)-2a-Ln and the triisopropylsilyl-substituted complexes (R)-2d-Ln exhibited the lowest activity in the range of 150–270 h–1. Catalysts (R)-2b-Lu, (R)-2c-Lu, (R)-2f-Lu, and (R)-2i-Lu provide the highest selectivities for the majority of the substrates, while the yttrium congeners are usually less selective. The highest enantioselectivities of 96% ee were observed using (R)-2a-Lu and (R)-2c-Lu in the cyclization of (4E)-2,2,5-triphenylpent-4-enylamine (9). The reactions show apparently zero-order rate dependence on substrate concentration and first-order rate dependence on catalyst concentration, with some reactions exhibiting a slightly accelerated rate at high conversion due to a shift in the equilibrium between a less active, higher coordinate catalyst species in favor of a more active, lower coordinate species as a result of weaker binding of the hydroamination product in comparison to the aminoalkene substrate. The shift in equilibrium from the higher to the lower coordinate species is also entropically favored at elevated temperatures, which results in an unusual increase in selectivity in the cyclization of 2,2-dimethylpent-4-enylamine (3d), presumably due to a higher selectivity of the lower coordinate catalyst species. All binaphtholate yttrium complexes, except (R)-2a-Y, are catalytically active in the intermolecular hydroamination of benzylamines with terminal alkenes. The highest selectivity of 66% ee was observed for the reaction of benzylamine with 4-phenyl-1-butene using (R)-2h-Y at 110 °C. Y1 - 2018 U6 - https://doi.org/10.1021/acs.organomet.8b00510 SN - 0276-7333 SN - 1520-6041 VL - 37 IS - 23 SP - 4358 EP - 4379 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Ellis, S. C. A1 - Bauer, S. A1 - Bacigalupo, C. A1 - Bland-Hawthorn, J. A1 - Bryant, J. J. A1 - Case, S. A1 - Content, R. A1 - Fechner, T. A1 - Giannone, D. A1 - Haynes, R. A1 - Hernandez, E. A1 - Horton, A. J. A1 - Klauser, U. A1 - Lawrence, J. S. A1 - Leon-Saval, S. G. A1 - Lindley, E. A1 - Löhmannsröben, Hans-Gerd A1 - Min, S. -S. A1 - Pai, N. A1 - Roth, M. A1 - Shortridge, K. A1 - Waller, L. A1 - Xavier, Pascal A1 - Zhelem, Ross T1 - PRAXIS: an OH suppression optimised near infrared spectrograph T2 - Ground-based and Airborne Instrumentation for Astronomy VII N2 - The problem of atmospheric emission from OH molecules is a long standing problem for near-infrared astronomy. PRAXIS is a unique spectrograph which is fed by fibres that remove the OH background and is optimised specifically to benefit from OH-Suppression. The OH suppression is achieved with fibre Bragg gratings, which were tested successfully on the GNOSIS instrument. PRAXIS uses the same fibre Bragg gratings as GNOSIS in its first implementation, and will exploit new, cheaper and more efficient, multicore fibre Bragg gratings in the second implementation. The OH lines are suppressed by a factor of similar to 1000, and the expected increase in the signal-to-noise in the interline regions compared to GNOSIS is a factor of similar to 9 with the GNOSIS gratings and a factor of similar to 17 with the new gratings. PRAXIS will enable the full exploitation of OH suppression for the first time, which was not achieved by GNOSIS (a retrofit to an existing instrument that was not OH-Suppression optimised) due to high thermal emission, low spectrograph transmission and detector noise. PRAXIS has extremely low thermal emission, through the cooling of all significantly emitting parts, including the fore-optics, the fibre Bragg gratings, a long length of fibre, and the fibre slit, and an optical design that minimises leaks of thermal emission from outside the spectrograph. PRAXIS has low detector noise through the use of a Hawaii-2RG detector, and a high throughput through a efficient VPH based spectrograph. PRAXIS will determine the absolute level of the interline continuum and enable observations of individual objects via an IFU. In this paper we give a status update and report on acceptance tests. KW - Near infrared KW - spectroscopy KW - OH suppression KW - astrophotonics KW - fibre Bragg gratings Y1 - 2018 SN - 978-1-5106-1958-6 U6 - https://doi.org/10.1117/12.2311898 SN - 0277-786X SN - 1996-756X VL - 10702 PB - SPIE-INT Soc Optical Engineering CY - Bellingham ER - TY - JOUR A1 - Yan, Wan A1 - Rudolph, Tobias A1 - Nöchel, Ulrich A1 - Gould, Oliver E. C. A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Reversible actuation of thermoplastic multiblock copolymers with overlapping thermal transitions of crystalline and glassy domains JF - Macromolecules : a publication of the American Chemical Society N2 - Polymeric materials possessing specific features like programmability, high deformability, and easy processability are highly desirable for creating modern actuating systems. In this study, thermoplastic shape-memory polymer actuators obtained by combining crystallizable poly(epsilon-caprolactone) (PCL) and poly(3S-isobutylmorpholin-2,5-dione) (PIBMD) segments in multiblock copolymers are described. We designed these materials according to our hypothesis that the confinement of glassy PIBMD domains present at the upper actuation temperature contribute to the stability of the actuator skeleton, especially at large programming strains. The copolymers have a phase-segregated morphology, indicated by the well-separated melting and glass transition temperatures for PIBMD and PCL, but possess a partially overlapping T-m of PCL and T-g of PIBMD in the temperature interval from 40 to 60 degrees C. Crystalline PIBMD hard domains act as strong physical netpoints in the PIBMD-PCL bulk material enabling high deformability (up to 2000%) and good elastic recoverability (up to 80% at 50 degrees C above T-m,T-PCL). In the programmed thermoplastic actuators a high content of crystallizable PCL actuation domains ensures pronounced thermoreversible shape changes upon repetitive cooling and heating. The programmed actuator skeleton, composed of PCL crystals present at the upper actuation temperature T-high and the remaining glassy PIBMD domains, enabled oriented crystallization upon cooling. The actuation performance of PIBMD-PCL could be tailored by balancing the interplay between actuation and skeleton, but also by varying the quantity of crystalline PIBMD hard domains via the copolymer composition, the applied programming strain, and the choice of T-high. The actuator with 17 mol% PIBMD showed the highest reversible elongation of 11.4% when programmed to a strain of 900% at 50 degrees C. It is anticipated that the presented thermoplastic actuator materials can be applied as modern compression textiles. Y1 - 2018 U6 - https://doi.org/10.1021/acs.macromol.8b00322 SN - 0024-9297 SN - 1520-5835 VL - 51 IS - 12 SP - 4624 EP - 4632 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - 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 - 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 - 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 - 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 - Ertan, Emelie A1 - Savchenko, Viktoriia A1 - Ignatova, Nina A1 - Vaz da Cruz, Vinicius A1 - Couto, Rafael C. A1 - Eckert, Sebastian A1 - Fondell, Mattis A1 - Dantz, Marcus A1 - Kennedy, Brian A1 - Schmitt, Thorsten A1 - Pietzsch, Annette A1 - Föhlisch, Alexander A1 - Odelius, Michael A1 - Kimberg, Victor T1 - Ultrafast dissociation features in RIXS spectra of the water molecule JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - In this combined theoretical and experimental study we report on an analysis of the resonant inelastic X-ray scattering (RIXS) spectra of gas phase water via the lowest dissociative core-excited state |1s−1O4a11〉. We focus on the spectral feature near the dissociation limit of the electronic ground state. We show that the narrow atomic-like peak consists of the overlapping contribution from the RIXS channels back to the ground state and to the first valence excited state |1b−114a11〉 of the molecule. The spectral feature has signatures of ultrafast dissociation (UFD) in the core-excited state, as we show by means of ab initio calculations and time-dependent nuclear wave packet simulations. We show that the electronically elastic RIXS channel gives substantial contribution to the atomic-like resonance due to the strong bond length dependence of the magnitude and orientation of the transition dipole moment. By studying the RIXS for an excitation energy scan over the core-excited state resonance, we can understand and single out the molecular and atomic-like contributions in the decay to the lowest valence-excited state. Our study is complemented by a theoretical discussion of RIXS in the case of isotopically substituted water (HDO and D2O) where the nuclear dynamics is significantly affected by the heavier fragments' mass. Y1 - 2018 U6 - https://doi.org/10.1039/c8cp01807c SN - 1463-9076 SN - 1463-9084 VL - 20 IS - 21 SP - 14384 EP - 14397 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Muiva-Mutisya, Lois M. A1 - Atilaw, Yoseph A1 - Heydenreich, Matthias A1 - Koch, Andreas A1 - Akala, Hoseah M. A1 - Cheruiyot, Agnes C. A1 - Brown, Matthew L. A1 - Irungu, Beatrice A1 - Okalebo, Faith A. A1 - Derese, Solomon A1 - Mutai, Charles A1 - Yenesew, Abiy T1 - Antiplasmodial prenylated flavanonols from Tephrosia subtriflora JF - Natural Product Research N2 - The CH2Cl2/MeOH (1:1) extract of the aerial parts of Tephrosia subtriflora afforded a new flavanonol, named subtriflavanonol (1), along with the known flavanone spinoflavanone B, and the known flavanonols MS-II (2) and mundulinol. The structures were elucidated by the use of NMR spectroscopy and mass spectrometry. The absolute configuration of the flavanonols was determined based on quantum chemical ECD calculations. In the antiplasmodial assay, compound 2 showed the highest activity against chloroquine-sensitive Plasmodiumfalciparum reference clones (D6 and 3D7), artemisinin-sensitive isolate (F32-TEM) as well as field isolate (KSM 009) with IC50 values 1.4-4.6M without significant cytotoxicity against Vero and HEp2 cell lines (IC50>100M). The new compound (1) showed weak antiplasmodial activity, IC50 12.5-24.2M, but also showed selective anticancer activity against HEp2 cell line (CC50 16.9M). [GRAPHICS] . KW - Tephrosia subtriflora KW - Leguminosae KW - prenylated flavanonol KW - subtriflavanonol KW - antiplasmodial KW - cytotoxicity Y1 - 2018 U6 - https://doi.org/10.1080/14786419.2017.1353510 SN - 1478-6419 SN - 1478-6427 VL - 32 IS - 12 SP - 1407 EP - 1414 PB - Routledge, Taylor & Francis Group CY - Abingdon 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 - Lendlein, Andreas A1 - Balk, Maria A1 - Tarazona, Natalia A. A1 - Gould, Oliver E. C. T1 - Bioperspectives for Shape-Memory Polymers as Shape Programmable, Active Materials JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences N2 - Within the natural world, organisms use information stored in their material structure to generate a physical response to a wide variety of environmental changes. The ability to program synthetic materials to intrinsically respond to environmental changes in a similar manner has the potential to revolutionize material science. By designing polymeric devices capable of responsively changing shape or behavior based on information encoded into their structure, we can create functional physical behavior, including a shape memory and an actuation capability. Here we highlight the stimuli-responsiveness and shape-changing ability of biological materials and biopolymer-based materials, plus their potential biomedical application, providing a bioperspective on shape-memory materials. We address strategies to incorporate a shape memory (actuation) function in polymeric materials, conceptualized in terms of its relationship with inputs (environmental stimuli) and outputs (shape change). Challenges and opportunities associated with the integration of several functions in a single material body to achieve multifunctionality are discussed. Finally, we describe how elements that sense, convert, and transmit stimuli have been used to create multisensitive materials. Y1 - 2019 U6 - https://doi.org/10.1021/acs.biomac.9b01074 SN - 1525-7797 SN - 1526-4602 VL - 20 IS - 10 SP - 3627 EP - 3640 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Lendlein, Andreas A1 - Gould, Oliver E. C. T1 - Reprogrammable recovery and actuation behaviour of shape-memory polymers JF - Nature reviews. Materials N2 - Shape memory is the capability of a material to be deformed and fixed into a temporary shape. Recovery of the original shape can then be triggered only by an external stimulus. Shape-memory polymers are highly deformable materials that can be programmed to recover a memorized shape in response to a variety of environmental and spatially localized stimuli as a one-way effect. The shape-memory function can also be generated as a reversible effect enabling actuation behaviour through macroscale deformation and processing, specifically by dictating the macromolecular orientation of actuation units and of the skeleton structure of geometry-determining units in the polymers. Shape-memory polymers can be programmed and reprogrammed into arbitrary shapes. Both recovery and actuation behaviour are reprogrammable. In this Review, we outline the common basis and key differences between the two shape-memory behaviours of polymers in terms of mechanism, fabrication schemes and characterization methods. We discuss which combination of macromolecular architecture and macroscale processing is necessary for coordinated, decentralized and responsive physical behaviour. The extraction of relevant thermomechanical information is described, and design criteria are shown for microscale and macroscale morphologies to gain high levels of recovered or actuation strains as well as on-demand 2D-to-3D shape transformations. Finally, real-world applications and key future challenges are highlighted. Y1 - 2019 U6 - https://doi.org/10.1038/s41578-018-0078-8 SN - 2058-8437 VL - 4 IS - 2 SP - 116 EP - 133 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Müller, Katharina A1 - Foerstendorf, Harald A1 - Steudtner, Robin A1 - Tsushima, Satoru A1 - Kumke, Michael Uwe A1 - Lefèvre, Grégory A1 - Rothe, Jörg A1 - Mason, Harris A1 - Szabó, Zoltán A1 - Yang, Ping A1 - Adam, Christian K. R. A1 - André, Rémi A1 - Brennenstuhl, Katlen A1 - Chiorescu, Ion A1 - Cho, Herman M. A1 - Creff, Gaëlle A1 - Coppin, Frédéric A1 - Dardenne, Kathy A1 - Den Auwer, Christophe A1 - Drobot, Björn A1 - Eidner, Sascha A1 - Hess, Nancy J. A1 - Kaden, Peter A1 - Kremleva, Alena A1 - Kretzschmar, Jerome A1 - Krüger, Sven A1 - Platts, James A. A1 - Panak, Petra A1 - Polly, Robert A1 - Powell, Brian A. A1 - Rabung, Thomas A1 - Redon, Roland A1 - Reiller, Pascal E. A1 - Rösch, Notker A1 - Rossberg, André A1 - Scheinost, Andreas C. A1 - Schimmelpfennig, Bernd A1 - Schreckenbach, Georg A1 - Skerencak-Frech, Andrej A1 - Sladkov, Vladimir A1 - Solari, Pier Lorenzo A1 - Wang, Zheming A1 - Washton, Nancy M. A1 - Zhang, Xiaobin T1 - Interdisciplinary Round-Robin Test on molecular spectroscopy of the U(VI) Acetate System JF - ACS omega / American Chemical Society N2 - A comprehensive molecular analysis of a simple aqueous complexing system. U(VI) acetate. selected to be independently investigated by various spectroscopic (vibrational, luminescence, X-ray absorption, and nuclear magnetic resonance spectroscopy) and quantum chemical methods was achieved by an international round-robin test (RRT). Twenty laboratories from six different countries with a focus on actinide or geochemical research participated and contributed to this scientific endeavor. The outcomes of this RRT were considered on two levels of complexity: first, within each technical discipline, conformities as well as discrepancies of the results and their sources were evaluated. The raw data from the different experimental approaches were found to be generally consistent. In particular, for complex setups such as accelerator-based X-ray absorption spectroscopy, the agreement between the raw data was high. By contrast, luminescence spectroscopic data turned out to be strongly related to the chosen acquisition parameters. Second, the potentials and limitations of coupling various spectroscopic and theoretical approaches for the comprehensive study of actinide molecular complexes were assessed. Previous spectroscopic data from the literature were revised and the benchmark data on the U(VI) acetate system provided an unambiguous molecular interpretation based on the correlation of spectroscopic and theoretical results. The multimethodologic approach and the conclusions drawn address not only important aspects of actinide spectroscopy but particularly general aspects of modern molecular analytical chemistry. Y1 - 2019 U6 - https://doi.org/10.1021/acsomega.9b00164 SN - 2470-1343 VL - 4 IS - 5 SP - 8167 EP - 8177 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - da Silva, Filipe Ferreira A1 - Varella, Marcio T. do N. A1 - Jones, Nykola C. A1 - Hoffmann, Soren Vronning A1 - Denifl, Stephan A1 - Bald, Ilko A1 - Kopyra, Janina T1 - Electron-Induced Reactions in 3-Bromopyruvic Acid JF - Chemistry - a European journal N2 - 3-Bromopyruvic acid (3BP) is a potential anticancer drug, the action of which on cellular metabolism is not yet entirely clear. The presence of a bromine atom suggests that it is also reactive towards low-energy electrons, which are produced in large quantities during tumour radiation therapy. Detailed knowledge of the interaction of 3BP with secondary electrons is a prerequisite to gain a complete picture of the effects of 3BP in different forms of cancer therapy. Herein, dissociative electron attachment (DEA) to 3BP in the gas phase has been studied both experimentally by using a crossed-beam setup and theoretically through scattering and quantum chemical calculations. These results are complemented by a vacuum ultraviolet absorption spectrum. The main fragmentation channel is the formation of Br- close to 0 eV and within several resonant features at 1.9 and 3-8 eV. At low electron energies, Br- formation proceeds through sigma* and pi* shape resonances, and at higher energies through core-excited resonances. It is found that the electron-capture cross-section is clearly increased compared with that of non-brominated pyruvic acid, but, at the same time, fragmentation reactions through DEA are significantly altered as well. The 3BP transient negative ion is subject to a lower number of fragmentation reactions than those of pyruvic acid, which indicates that 3BP could indeed act by modifying the electron-transport chains within oxidative phosphorylation. It could also act as a radio-sensitiser. KW - density functional calculations KW - dissociative electron attachment KW - drug discovery KW - gas-phase reactions KW - sensitizers Y1 - 2019 U6 - https://doi.org/10.1002/chem.201806132 SN - 0947-6539 SN - 1521-3765 VL - 25 IS - 21 SP - 5498 EP - 5506 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Zhang, Quanchao A1 - Rudolph, Tobias A1 - Benitez, Alejandro J. A1 - Gould, Oliver E. C. A1 - Behl, Marc A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Temperature-controlled reversible pore size change of electrospun fibrous shape-memory polymer actuator based meshes JF - Smart materials and structures N2 - Fibrous membranes capable of dynamically responding to external stimuli are highly desirable in textiles and biomedical materials, where adaptive behavior is required to accommodate complex environmental changes. For example, the creation of fabrics with temperature-dependent moisture permeability or self-regulating membranes for air filtration is dependent on the development of materials that exhibit a reversible stimuli-responsive pore size change. Here, by imbuing covalently crosslinked poly(ε-caprolactone) (cPCL) fibrous meshes with a reversible bidirectional shape-memory polymer actuation (rbSMPA) we create a material capable of temperature-controlled changes in porosity. Cyclic thermomechanical testing was used to characterize the mechanical properties of the meshes, which were composed of randomly arranged microfibers with diameters of 2.3 ± 0.6 μm giving an average pore size of approx. 10 μm. When subjected to programming strains of εm = 300% and 100% reversible strain changes of εʹrev = 22% ± 1% and 6% ± 1% were measured, with switching temperature ranges of 10 °C–30 °C and 45 °C–60 °C for heating and cooling, respectively. The rbSMPA of cPCL fibrous meshes generated a microscale reversible pore size change of 11% ± 3% (an average of 1.5 ± 0.6 μm), as measured by scanning electron microscopy. The incorporation of a two-way shape-memory actuation capability into fibrous meshes is anticipated to advance the development and application of smart membrane materials, creating commercially viable textiles and devices with enhanced performance and novel functionality. KW - reversible shape-memory effect KW - fiber meshes KW - electrospinning Y1 - 2019 U6 - https://doi.org/10.1088/1361-665X/ab10a1 SN - 0964-1726 SN - 1361-665X VL - 28 IS - 5 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Vishnevetskaya, Natalya S. A1 - Hildebrand, Viet A1 - Nizardo, Noverra Mardhatillah A1 - Ko, Chia-Hsin A1 - Di, Zhenyu A1 - Radulescu, Aurel A1 - Barnsley, Lester C. A1 - Müller-Buschbaum, Peter A1 - Laschewsky, André A1 - Papadakis, Christine M. T1 - All-in-One "Schizophrenic" self-assembly of orthogonally tuned thermoresponsive diblock copolymers JF - Langmuir N2 - Smart, fully orthogonal switching was realized in a highly biocompatible diblock copolymer system with variable trigger-induced aqueous self-assembly. The polymers are composed of nonionic and zwitterionic blocks featuring lower and upper critical solution temperatures (LCSTs and UCSTs). In the system investigated, diblock copolymers from poly(N-isopropyl methacrylamide) (PNIPMAM) and a poly(sulfobetaine methacrylamide), systematic variation of the molar mass of the latter block allowed for shifting the UCST of the latter above the LCST of the PNIPMAM block in a salt-free condition. Thus, successive thermal switching results in "schizophrenic" micellization, in which the roles of the hydrophobic core block and the hydrophilic shell block are interchanged depending on the temperature. Furthermore, by virtue of the strong electrolyte-sensitivity of the zwitterionic polysulfobetaine block, we succeeded to shift its UCST below the LCST of the PNIPMAM block by adding small amounts of an electrolyte, thus inverting the pathway of switching. This superimposed orthogonal switching by electrolyte addition enabled us to control the switching scenarios between the two types of micelles (i) via an insoluble state, if the LCST-type cloud point is below the UCST-type cloud point, which is the case at low salt concentrations or (ii) via a molecularly dissolved state, if the LCST-type cloud point is above the UCST-type cloud point, which is the case at high salt concentrations. Systematic variation of the block lengths allowed for verifying the anticipated behavior and identifying the molecular architecture needed. The versatile and tunable self-assembly offers manifold opportunities, for example, for smart emulsifiers or for sophisticated carrier systems. Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.9b00241 SN - 0743-7463 VL - 35 IS - 19 SP - 6441 EP - 6452 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Liu, Yue A1 - Gould, Oliver E. C. A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Shape-memory actuation of individual micro-/nanofibers JF - MRS Advances N2 - Advances in the fabrication and characterization of polymeric nanomaterials has greatly advanced the miniaturization of soft actuators, creating materials capable of replicating the functional physical behavior previously limited to the macroscale. Here, we demonstrate how a reversible shape-memory polymer actuation can be generated in a single micro/nano object, where the shape change during actuation of an individual fiber can be dictated by programming using an AFM-based method. Electrospinning was used to prepare poly(epsilon-caprolactone) micro-/nanofibers, which were fixed and crosslinked on a structured silicon wafer. The programming as well as the observation of recovery and reversible displacement of the fiber were performed by vertical three point bending, using an AFM testing platform introduced here. A plateau tip was utilized to improve the stability of the fiber contact and working distance, enabling larger deformations and greater rbSMPA performance. Values for the reversible elongation of epsilon(rev)= 3.4 +/- 0.1% and 10.5 +/- 0.1% were obtained for a single micro (d = 1.0 +/- 0.2 mu m) and nanofiber (d = 300 +/- 100 nm) in cyclic testing between the temperatures 10 and 60 degrees C. The reversible actuation of the nanofiber was successfully characterized for 10 cycles. The demonstration and characterization of individual shape-memory nano and microfiber actuators represents an important step in the creation of miniaturized robotic devices capable of performing complex physical functions at the length scale of cells and structural component of the extracellular matrix. Y1 - 2020 U6 - https://doi.org/10.1557/adv.2020.276 SN - 2059-8521 VL - 5 IS - 46-47 SP - 2391 EP - 2399 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Izraylit, Victor A1 - Gould, Oliver E. C. A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Investigating the phase-morphology of PLLA-PCL multiblock copolymer/PDLA blends cross-linked using stereocomplexation JF - MRS advances N2 - The macroscale function of multicomponent polymeric materials is dependent on their phase-morphology. Here, we investigate the morphological structure of a multiblock copolymer consisting of poly(L-lactide) and poly(epsilon-caprolactone) segments (PLLA-PCL), physically cross-linked by stereocomplexation with a low molecular weight poly(D-lactide) oligomer (PDLA). The effects of blend composition and PLLA-PCL molecular structure on the morphology are elucidated by AFM, TEM and SAXS. We identify the formation of a lattice pattern, composed of PLA domains within a PCL matrix, with an average domain spacing d0 = 12 - 19 nm. The size of the PLA domains were found to be proportional to the block length of the PCL segment of the copolymer and inversely proportional to the PDLA content of the blend. Changing the PLLA-PCL / PDLA ratio caused a shift in the melt transition Tm attributed to the PLA stereocomplex crystallites, indicating partial amorphous phase dilution of the PLA and PCL components within the semicrystalline material. By elucidating the phase structure and thermal character of multifunctional PLLA-PCL / PDLA blends, we illustrate how composition affects the internal structure and thermal properties of multicomponent polymeric materials. This study should facilitate the more effective incorporation of a variety of polymeric structural units capable of stimuli responsive phase transitions, where an understanding the phase-morphology of each component will enable the production of multifunctional soft-actuators with enhanced performance. KW - polymer KW - blend KW - nanostructure KW - morphology Y1 - 2020 U6 - https://doi.org/10.1557/adv.2019.465 SN - 2059-8521 VL - 5 IS - 14-15 SP - 699 EP - 707 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Izraylit, Victor A1 - Hommes-Schattmann, Paul Jacob A1 - Neffe, Axel T. A1 - Gould, Oliver E. C. A1 - Lendlein, Andreas T1 - Alkynyl-functionalized chain-extended PCL for coupling to biological molecules JF - European polymer journal N2 - Chemical functionalization of poly(epsilon-caprolactone) (PCL) enables a molecular integration of additional function. Here, we report an approach to incorporate reactive alkynyl side-groups by synthesizing a chain-extended PCL, where the reactive site is introduced through the covalently functionalizable chain extender 3 (prop-2-yn-1-yloxy)propane-1,2-diol (YPD). Chain-extended PCL with M-w of 101 to 385 kg.mol(-1) were successfully synthesized in a one-pot reaction from PCL-diols with various molar masses, L-lysine ethyl ester diisocyanate (LDI) or trimethyl(hexamethylene)diisocyanate (TMDI), and YPD, in which the density of functionalizable groups and spacing between them can be controlled by the composition of the polymer. The employed diisocyanate compounds and YPD possess an asymmetric structure and form a non-crystallizable segment leaving the PCL crystallites to dominate the material's mechanical properties. The mixed glass transition temperature T-g = - 60 to - 46 degrees C of the PCL/polyurethane amorphous phase maintains the synthesized materials in a highly elastic state at ambient and physiological conditions. Reaction conditions for covalent attachment in copper(I)-catalyzed azide-alkyne-cycloaddition reactions (CuAAC) in solution were optimized in a series of model reactions between the alkyne moieties of the chain-extended PCL and benzyl azide, reaching conversions over 95% of the alkyne moieties and with yields of up to 94% for the purified functionalized PCL. This methodology was applied for reaction with the azide-functionalized cell adhesion peptide GRGDS. The required modification of the peptide provides selectivity in the coupling reactions. The obtained results suggest that YPD could potentially be employed as versatile molecular unit for the creation of a variety of functionalizable polyesters as well as polyurethanes and polycarbonates offering efficient and selective click-reactions. KW - copper-catalyzed alkyne-azide cycloaddition KW - chain-extended KW - polycaprolactone KW - RGD-peptide KW - side-chains functionalization Y1 - 2020 U6 - https://doi.org/10.1016/j.eurpolymj.2020.109908 SN - 0014-3057 SN - 1873-1945 VL - 136 PB - Elsevier CY - Oxford ER -