TY - JOUR A1 - Abbas, Ioana M. A1 - Vranic, Marija A1 - Hoffmann, Holger A1 - El-Khatib, Ahmed H. A1 - Montes-Bayón, María A1 - Möller, Heiko Michael A1 - Weller, Michael G. T1 - Investigations of the Copper Peptide Hepcidin-25 by LC-MS/MS and NMR⁺ JF - International Journal of Molecular Sciences N2 - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others. KW - hepcidin-25 KW - copper KW - nickel KW - copper complex KW - ATCUN motif KW - metal complex KW - MS KW - NMR structure KW - metal peptide KW - metalloprotein KW - metallopeptide KW - isomerization KW - racemization KW - purity KW - reference material Y1 - 2018 U6 - https://doi.org/10.3390/ijms19082271 SN - 1422-0067 SN - 1661-6596 VL - 19 IS - 8 PB - Molecular Diversity Preservation International CY - Basel ER - TY - GEN A1 - Abbas, Ioana M. A1 - Vranic, Marija A1 - Hoffmann, Holger A1 - El-Khatib, Ahmed H. A1 - Montes-Bayón, María A1 - Möller, Heiko Michael A1 - Weller, Michael G. T1 - Investigations of the Copper Peptide Hepcidin-25 by LC-MS/MS and NMR⁺ T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 701 KW - hepcidin-25 KW - copper KW - nickel KW - copper complex KW - ATCUN motif KW - metal complex KW - MS KW - NMR structure KW - metal peptide KW - metalloprotein KW - metallopeptide KW - isomerization KW - racemization KW - purity KW - reference material Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-427926 SN - 1866-8372 IS - 701 ER - TY - JOUR A1 - Abbasi, Ali A1 - Xu, Yaolin A1 - Khezri, Ramin A1 - Etesami, Mohammad A1 - Lin, C. A1 - Kheawhom, Soorathep A1 - Lu, Yan T1 - Advances in characteristics improvement of polymeric membranes/separators for zinc-air batteries JF - Materials Today Sustainability N2 - Zinc-air batteries (ZABs) are gaining popularity for a wide range of applications due to their high energy density, excellent safety, and environmental friendliness. A membrane/separator is a critical component of ZABs, with substantial implications for battery performance and stability, particularly in the case of a battery in solid state format, which has captured increased attention in recent years. In this review, recent advances as well as insight into the architecture of polymeric membrane/separators for ZABs including porous polymer separators (PPSs), gel polymer electrolytes (GPEs), solid polymer electrolytes (SPEs) and anion exchange membranes (AEMs) are discussed. The paper puts forward strategies to enhance stability, ionic conductivity, ionic selectivity, electrolyte storage capacity and mechanical properties for each type of polymeric membrane. In addition, the remaining major obstacles as well as the most potential avenues for future research are examined in detail. KW - Ionic selectivity KW - Ionic conductivity KW - Gel polymer KW - Ion exchange KW - Porous KW - polymer Y1 - 2022 U6 - https://doi.org/10.1016/j.mtsust.2022.100126 SN - 2589-2347 VL - 18 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Abdissa, Negera A1 - Heydenreich, Matthias A1 - Midiwo, Jacob O. A1 - Ndakala, Albert A1 - Majer, Zsuzsanna A1 - Neumann, Beate A1 - Stammler, Hans-Georg A1 - Sewald, Norbert A1 - Yenesew, Abiy T1 - A xanthone and a phenylanthraquinone from the roots of Bulbine frutescens, and the revision of six seco-anthraquinones into xanthones JF - Phytochemistry letters N2 - Phytochemical investigation of the dichloromethane/methanol (1:1) extract of the roots of Bulbine frutescens led to the isolation of a new xanthone, 8-hydroxy-6-methylxanthone-1-carboxylic acid (1) and a new phenylanthraquinone, 6',8-O-dimethylknipholone (2) along with six known compounds. The structures were elucidated on the basis of NMR and MS spectral data analyses. The structure of compound 1 was confirmed through X-ray crystallography which was then used as a reference to propose the revision of the structures of six seco-anthraquinones into xanthones. The isolated compounds were evaluated for cytotoxicity against human cervix carcinoma KB-3-1 cells with the phenylanthraquinone knipholone being the most active (IC50 = 0.43 mu M). Two semi-synthetic knipholone derivatives, knipholone Mannich base and knipholone-1,3-oxazine, were prepared and tested for cytotoxic activity; both showed moderate activities (IC50 value of 1.89 and 2.50 mu M, respectively). (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. KW - Bulbine frutescens KW - Xanthone KW - seco-Anthraquinone KW - Phenylanthraquinone KW - Cytotoxicity KW - Structure revision Y1 - 2014 U6 - https://doi.org/10.1016/j.phytol.2014.04.004 SN - 1874-3900 SN - 1876-7486 VL - 9 SP - 67 EP - 73 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Abdissa, Negera A1 - Induli, Martha A1 - Akala, Hoseah M. A1 - Heydenreich, Matthias A1 - Midiwo, Jacob O. A1 - Ndakala, Albert A1 - Yenesew, Abiy T1 - Knipholone cyclooxanthrone and an anthraquinone dimer with antiplasmodial activities from the roots of Kniphofia foliosa JF - Phytochemistry letters N2 - A new phenylanthrone, named knipholone cyclooxanthrone and a dimeric anthraquinone, 10-methoxy-10,7'-(chrysophanol anthrone)-chrysophanol were isolated from the roots of Kniphofia foliosa together with the rare naphthalene glycoside, dianellin. The structures were determined by NMR and mass spectroscopic techniques. The compounds showed antiplasmodial activities against the chloroquine-resistant (W2) and chloroquine-sensitive (D6) strains of Plasmodium falciparum with 10-methoxy-10,7'-(chrysophanol anthrone)-chrysophanol being the most active with IC50 values of 1.17 +/- 0.12 and 4.07 +/- 1.54 mu g/ml, respectively. KW - Kniphofia foliosa KW - Asphodelaceae KW - Roots KW - Anthraquinone KW - Knipholone cyclooxanthrone KW - 10-Methoxy-10,7 '-(chrysophanol anthrone)-chrysophanol KW - Dianellin KW - Malaria Y1 - 2013 U6 - https://doi.org/10.1016/j.phytol.2013.02.005 SN - 1874-3900 VL - 6 IS - 2 SP - 241 EP - 245 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Abdou, Nicole A1 - Alonso, Bruno A1 - Brun, Nicolas A1 - Landois, Perine A1 - Taubert, Andreas A1 - Hesemann, Peter A1 - Mehdi, Ahmad T1 - Ionic guest in ionic host BT - ionosilica ionogel composites via ionic liquid confinement in ionosilica supports JF - Materials chemistry frontiers N2 - Ionosilica ionogels, i.e. composites consisting of an ionic liquid (IL) guest confined in an ionosilica host matrix, were synthesized via a non-hydrolytic sol-gel procedure from a tris-trialcoxysilylated amine precursor using the IL [BMIM]NTf2 as solvent. Various ionosilica ionogels were prepared starting from variable volumes of IL in the presence of formic acid. The resulting brittle and nearly colourless monoliths are composed of different amounts of IL guests confined in an ionosilica host as evidenced via thermogravimetric analysis, FT-IR, and C-13 CP-MAS solid-state NMR spectroscopy. In the following, we focused on confinement effects between the ionic host and guest. Special host-guest interactions between the IL guest and the ionosilica host were evidenced by H-1 solid-state NMR, Raman spectroscopy, and broadband dielectric spectroscopy (BDS) measurements. The three techniques indicate a strongly reduced ion mobility in the ionosilica ionogel composites containing small volume fractions of confined IL, compared to conventional silica-based ionogels. We conclude that the ionic ionosilica host stabilizes an IL layer on the host surface; this then results in a strongly reduced ion mobility compared to conventional silica hosts. The ion mobility progressively increases for systems containing higher volume fractions of IL and finally reaches the values observed in conventional silica based ionogels. These results therefore point towards strong interactions and confinement effects between the ionic host and the ionic guest on the ionosilica surface. Furthermore, this approach allows confining high volume fractions of IL into self-standing monoliths while preserving high ionic conductivity. These effects may be of interest in domains where IL phases must be anchored on solid supports to avoid leaching or IL spilling, e.g., in catalysis, in gas separation/sequestration devices or for the elaboration of solid electrolytes for (lithium-ion) batteries and supercapacitors. Y1 - 2022 U6 - https://doi.org/10.1039/d2qm00021k SN - 2052-1537 VL - 6 IS - 7 SP - 939 EP - 947 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Abegaz, Berhanu M. A1 - Peter, Martin G. T1 - Emodine and emodinanthrone rhamnoside acetates from fruits of rhamnus prinoides Y1 - 1995 SN - 0031-9422 ER - TY - THES A1 - Abouserie, Ahed T1 - Ionic liquid precursors for multicomponent inorganic nanomaterials T1 - Ionische Flüssigkeiten als Vorstufe für anorganische Mehrkomponenten-Nanomaterialien N2 - Health effects, attributed to the environmental pollution resulted from using solvents such as benzene, are relatively unexplored among petroleum workers, personal use, and laboratory researchers. Solvents can cause various health problems, such as neurotoxicity, immunotoxicity, and carcinogenicity. As such it can be absorbed via epidermal or respiratory into the human body resulting in interacting with molecules that are responsible for biochemical and physiological processes of the brain. Owing to the ever-growing demand for finding a solution, an Ionic liquid can use as an alternative solvent. Ionic liquids are salts in a liquid state at low temperature (below 100 C), or even at room temperature. Ionic liquids impart a unique architectural platform, which has been interesting because of their unusual properties that can be tuned by simple ways such as mixing two ionic liquids. Ionic liquids not only used as reaction solvents but they became a key developing for novel applications based on their thermal stability, electric conductivity with very low vapor pressure in contrast to the conventional solvents. In this study, ionic liquids were used as a solvent and reactant at the same time for the novel nanomaterials synthesis for different applications including solar cells, gas sensors, and water splitting. The field of ionic liquids continues to grow, and become one of the most important branches of science. It appears to be at a point where research and industry can work together in a new way of thinking for green chemistry and sustainable production. N2 - Der Einfluss von kommerziellen organischen Lösungsmitteln auf den menschlichen Körper ist bekannt, jedoch nicht ausreichend untersucht worden. Spezielle Lösungsmittel wie Benzol, welche auch vermehrt in der Petrolchemie genutzt werden, zeigen akute Toxizität auf den biologischen Organismus. Daher ist der Bedarf der Verwendung eines alternativen Lösungsmittel groß. Ionische Flüssigkeiten können hier potentiell eine Alternative sein. Als Ionische Flüssigkeiten (ILs) werden Salze in flüssigem Zustand bei niedriger Temperatur (unter 100 °C) oder sogar bei Raumtemperatur definiert. Aufgrund ihrer Variabilität in der Zusammensetzung der strukturellen ionischen Moleküle ergeben sich ungewöhnliche Eigenschaften, welche auf einfachste Weise durch Mischen zweier ionischer Flüssigkeiten beliebig angepasst werden können. ILs werden sowohl als gewöhnliche Lösungsmittel verwendet, jedoch entwickelten sie sich aufgrund ihrer besonderen Eigenschaften vermehrt zu Reaktionsagenzien. Dies ist zurückzuführen auf ihre gute thermische Stabilität, elektrische Leitfähigkeit und ihrem geringen Dampfdruck. In dieser Arbeit wurden nun spezielle Ionische Flüssigkeiten speziell auf ihr Verhalten in chemischen Reaktionen als Reagenz untersucht. Als Ausgangsreaktion diente hierbei eine neuartige Synthese von Nanomaterialen, welche speziell in Solarzellen, Gassensoren und auch in der katalytischen Wasserspaltung genutzt werden. Das Anwendungspotenzial der ILs gewinnt immer mehr an Bedeutung und führt in der Forschung sowie auch in der Industrie zu neuen Denkweisen für nachhaltige Produktionen und auch Entwicklungen. KW - ionic liquids KW - Alkylpyridinium salts KW - Structure elucidation KW - Phase transitions KW - Nanoparticles KW - Metal Chalcogenides KW - Organic photovoltaic Cell KW - Ionische Flüssigkeiten KW - Alkylpyridinium-Salze KW - Strukturaufklärung KW - Phasenübergänge KW - Nanopartikel KW - Metallchalkogenide KW - Organische Photovoltaikzelle Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-418950 ER - TY - JOUR A1 - Abouserie, Ahed A1 - Zehbe, Kerstin A1 - Metzner, Philipp A1 - Kelling, Alexandra A1 - Günter, Christina A1 - Schilde, Uwe A1 - Strauch, Peter A1 - Körzdörfer, Thomas A1 - Taubert, Andreas T1 - Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - Six N-alkylpyridinium salts [CnPy](2)[MCl4] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C4Py](2)[MCl4] compounds are monoclinic and crystallize in the space group P2(1)/n. The crystals of the longer chain analogues [C12Py](2)[MCl4] are triclinic and crystallize in the space group P (1) over bar. Above the melting temperature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl4](2-) ions in the Cu-based ILs have a distorted tetrahedral geometry. KW - Ionic liquids KW - Alkylpyridinium salts KW - Structure elucidation KW - Phase transitions Y1 - 2017 U6 - https://doi.org/10.1002/ejic.201700826 SN - 1434-1948 SN - 1099-0682 SP - 5640 EP - 5649 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Abouserie, Ahed A1 - Zehbe, Kerstin A1 - Metzner, Philipp A1 - Kelling, Alexandra A1 - Günter, Christina A1 - Schilde, Uwe A1 - Strauch, Peter A1 - Körzdörfer, Thomas A1 - Taubert, Andreas T1 - Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - Six N-alkylpyridinium salts [CnPy](2)[MCl4] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C4Py](2)[MCl4] compounds are monoclinic and crystallize in the space group P2(1)/n. The crystals of the longer chain analogues [C12Py](2)[MCl4] are triclinic and crystallize in the space group P (1) over bar. Above the melting temperature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl4](2-) ions in the Cu-based ILs have a distorted tetrahedral geometry. KW - Ionic liquids KW - Alkylpyridinium salts KW - Structure elucidation KW - Phase transitions Y1 - 2017 U6 - https://doi.org/10.1002/ejic.201700826 SN - 1434-1948 SN - 1099-0682 SP - 5640 EP - 5649 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Adamovich, Sergey N. A1 - Mirskova, Anna N. A1 - Mirskov, Rudolf G. A1 - Schilde, Uwe T1 - Synthesis and crystal structure of 1,4,10,13-tetraoxa-7,16-diazoniumcyclo-octadecane bis(4-chloro-2-methyl-phenoxyacetate) JF - Chemistry central journal N2 - The title compound was prepared by the reaction of 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane with 4-chloro-2-methyl-phenoxyacetic acid in a ratio of 1:2. The structure has been proved by the data of elemental analysis, IR spectroscopy, NMR ((1)H, (13)C) technique and by X-ray diffraction analysis. Intermolecular hydrogen bonds between the azonium protons and oxygen atoms of the carboxylate groups were found. Immunoactive properties of the title compound have been screened. The compound has the ability to suppress spontaneous and Con A-stimulated cell proliferation in vitro and therefore can be considered as immunodepressant. Y1 - 2011 U6 - https://doi.org/10.1186/1752-153X-5-23 SN - 1752-153X VL - 5 IS - 17 PB - BioMed Central CY - London ER - TY - GEN A1 - Adamovich, Sergey N. A1 - Mirskova, Anna N. A1 - Mirskov, Rudolf G. A1 - Schilde, Uwe T1 - Synthesis and crystal structure of 1,4,10,13-tetraoxa-7,16-diazoniumcyclo-octadecane bis(4-chloro-2-methyl-phenoxyacetate) N2 - The title compound was prepared by the reaction of 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane with 4-chloro-2-methyl-phenoxyacetic acid in a ratio of 1:2. The structure has been proved by the data of elemental analysis, IR spectroscopy, NMR ( 1 H, 13 C) technique and by X-ray diffraction analysis. Intermolecular hydrogen bonds between the azonium protons and oxygen atoms of the carboxylate groups were found. Immunoactive properties of the title compound have been screened. The compound has the ability to suppress spontaneous and Con A-stimulated cell proliferation in vitro and therefore can be considered as immunodepressant. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 369 KW - salts Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400905 ER - TY - JOUR A1 - Adebayo, Segun Emmanuel A1 - Hashim, Norhashila A1 - Hass, Roland A1 - Reich, Oliver A1 - Regen, Christian A1 - Münzberg, Marvin A1 - Abdan, Khalina A1 - Hanafi, Marsyita A1 - Zude-Sasse, Manuela T1 - Using absorption and reduced scattering coefficients for non-destructive analyses of fruit flesh firmness and soluble solids content in pear JF - Postharvest Biology and Technology N2 - Quality attributes of fruit determine its acceptability by the retailer and consumer. The objective of this work was to investigate the potential of absorption (μa) and reduced scattering (μs’) coefficients of European pear to analyze its fruit flesh firmness and soluble solids content (SSC). The absolute reference values, μa* (cm−1) and μs’* (cm−1), of pear were invasively measured, employing multi-spectral photon density wave (PDW) spectroscopy at preselected wavelengths of 515, 690, and 940 nm considering two batches of unripe and overripe fruit. On eight measuring dates during fruit development, μa and μs’ were analyzed non-destructively by means of laser light backscattering imaging (LLBI) at similar wavelengths of 532, 660, and 830 nm by means of fitting according to Farrell’s diffusion theory, using fix reference values of either μa* or μs’*. Both, the μa* and the μa as well as μs’* and μs’ showed similar trends. Considering the non-destructively measured data during fruit development, μa at 660 nm decreased 91 till 141 days after full bloom (dafb) from 1.49 cm−1 to 0.74 cm−1 due to chlorophyll degradation. At 830 nm, μa only slightly decreased from 0.41 cm−1 to 0.35 cm−1. The μs’ at all wavelengths revealed a decreasing trend as the fruit developed. The difference measured at 532 nm was most pronounced decreasing from 24 cm−1 to 10 cm−1, while at 660 nm and 830 nm values decreased from 15 cm−1 to 13 cm−1 and from 10 cm−1 to 8 cm−1, respectively. When building calibration models with partial least-squares regression analysis on the optical properties for non-destructive analysis of the fruit SSC, μa at 532 nm and 830 nm resulted in a correlation coefficient of R = 0.66, however, showing high measuring uncertainty. The combination of all three wavelengths gave an enhanced, encouraging R = 0.89 for firmness analysis using μs’ in the freshly picked fruit. KW - Absorption KW - Non-destructive KW - Pear KW - Quality KW - Scattering Y1 - 2017 U6 - https://doi.org/10.1016/j.postharvbio.2017.04.004 SN - 0925-5214 SN - 1873-2356 VL - 130 SP - 56 EP - 63 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - Adelhelm, Philipp T1 - Novel carbon materials with hierarchical porosity : templating strategies and advanced characterization T1 - Neue Kohlenstoffmaterialien mit hierarchischer Porosität : Strategien der Templatierung und erweiterte Charakterisierung N2 - The aim of this work was the generation of carbon materials with high surface area, exhibiting a hierarchical pore system in the macro- and mesorange. Such a pore system facilitates the transport through the material and enhances the interaction with the carbon matrix (macropores are pores with diameters > 50 nm, mesopores between 2 – 50 nm). Thereto, new strategies for the synthesis of novel carbon materials with designed porosity were developed that are in particular useful for the storage of energy. Besides the porosity, it is the graphene structure itself that determines the properties of a carbon material. Non-graphitic carbon materials usually exhibit a quite large degree of disorder with many defects in the graphene structure, and thus exhibit inherent microporosity (d < 2nm). These pores are traps and oppose reversible interaction with the carbon matrix. Furthermore they reduce the stability and conductivity of the carbon material, which was undesired for the proposed applications. As one part of this work, the graphene structures of different non-graphitic carbon materials were studied in detail using a novel wide-angle x-ray scattering model that allowed precise information about the nature of the carbon building units (graphene stacks). Different carbon precursors were evaluated regarding their potential use for the synthesis shown in this work, whereas mesophase pitch proved to be advantageous when a less disordered carbon microstructure is desired. By using mesophase pitch as carbon precursor, two templating strategies were developed using the nanocasting approach. The synthesized (monolithic) materials combined for the first time the advantages of a hierarchical interconnected pore system in the macro- and mesorange with the advantages of mesophase pitch as carbon precursor. In the first case, hierarchical macro- / mesoporous carbon monoliths were synthesized by replication of hard (silica) templates. Thus, a suitable synthesis procedure was developed that allowed the infiltration of the template with the hardly soluble carbon precursor. In the second case, hierarchical macro- / mesoporous carbon materials were synthesized by a novel soft-templating technique, taking advantage of the phase separation (spinodal decomposition) between mesophase pitch and polystyrene. The synthesis also allowed the generation of monolithic samples and incorporation of functional nanoparticles into the material. The synthesized materials showed excellent properties as an anode material in lithium batteries and support material for supercapacitors. N2 - Kohlenstoffmaterialien finden aufgrund ihrer Vielseitigkeit heute in den unterschiedlichsten Bereichen des täglichen Lebens ihren Einsatz. Bekannte Beispiele sind Kohlenstofffasern in Verbundwerkstoffen, Graphit als trockenes Schmiermittel, oder Aktivkohlen in Filtersystemen. Ferner wird Graphit als Elektrodenmaterial auch in Lithium-Ionen-Batterien verwendet. Wegen knapper werdender Ressourcen von Öl und Gas wurde in den letzten Jahren verstärkt an der Entwicklung neuer Materialien für die Speicherung von Wasserstoff und elektrischer Energie gearbeitet. Die Nanotechnologie ist dabei auch für neue Kohlenstoffmaterialien zukunftsweisend, denn sie stellt weitere Anwendungsmöglichkeiten in Aussicht. In dieser Arbeit wurden hierzu mittels des sogenannten Nanocastings neue Kohlenstoffmaterialien für Energieanwendungen, insbesondere zur Speicherung von elektrischer Energie entwickelt. Die Eigenschaften eines Kohlenstoffmaterials beruhen im Wesentlichen auf der Struktur des Kohlenstoffs im molekularen Bereich. Die in dieser Arbeit hergestellten Materialen bestehen aus nichtgraphitischem Kohlenstoff und wurden im ersten Teil der Arbeit mit den Methoden der Röntgenstreuung genau untersucht. Eine speziell für diese Art von Kohlenstoffen kürzlich entwickelte Modellfunktion wurde dazu an die experimentellen Streubilder angepasst. Das verwendete Modell basiert dabei auf den wesentlichen Strukturmerkmalen von nichtgraphitischem Kohlenstoff und ermöglichte von daher eine detaillierte Beschreibung der Materialien. Im Gegensatz zu den meisten nichtgraphitischen Kohlenstoffen konnte gezeigt werden, dass die Verwendung von Mesophasen-Pech als Vorläufersubstanz (Precursor) ein Material mit vergleichsweise geringem Grad an Unordnung ermöglicht. Solch ein Material erlaubt eine ähnlich reversible Einlagerung von Lithium-Ionen wie Graphit, weist aber gleichzeitig wegen des nichtgraphitischen Charakters eine deutlich höhere Speicherfähigkeit auf. Zur Beschreibung der Porosität eines Materials verwendet man die Begriffe der Makro-, Meso-, und Mikroporen. Die Aktivität eines Materials kann durch die Erhöhung der Oberfläche noch erheblich gesteigert werden. Hohe Oberflächen können insbesondere durch die Schaffung von Poren im Nanometerbereich erzielt werden. Um die Zugänglichkeit zu diesen Poren zu steigern, weist ein Material idealerweise zusätzlich ein kontinuierliches makroporöses Transportsystem (Porendurchmesser d > 50 nm) auf. Solch eine Art von Porosität über mehrere Größenordnungen wird allgemein als „hierarchische Porosität“ bezeichnet. Für elektrochemische Anwendungen sind sogenannte Mesoporen (d = 2 – 50 nm) relevant, da noch kleinere Poren (Mikroporen, d < 2 nm) z.B. zu einer irreversiblen Bindung von Lithium- Ionen führen können. Wird Mesophasen-Pech als Kohlenstoffprekursor verwendet, kann die Entstehung dieser Mikroporen verhindert werden. Im zweiten und dritten Teil der Arbeit konnte mit den Methoden des „Nanocastings“ zum ersten Mal die spezielle Struktur des Mesophasen-Pech basierenden Kohlenstoffmaterials mit den Vorteilen einer hierarchischen (makro- / meso-) Porosität kombiniert werden. Im ersten Syntheseverfahren wurde dazu ein sogenanntes „hartes Templat“ mit entsprechender Porosität aus Siliziumdioxid repliziert. Aufgrund der hohen Viskosität des Pechs und der geringen Löslichkeit wurde dazu ein Verfahren entwickelt, das die Infiltration des Templates auch auf der Nanometerebene ermöglicht. Das Material konnte in Form größerer Körper (Monolithen) hergestellt werden, die im Vergleich zu Pulvern eine bessere technische Verwendung ermöglichen. Im zweiten Syntheseverfahren konnte die Herstellung eines hierarchisch makro- / mesoporösen Kohlenstoffmaterials erstmals mittels eines weichen Templates (organisches Polymer) erreicht werden. Die einfache Entfernung von weichen Templaten durch eine geeignete Temperaturbehandlung, macht dieses Verfahren im Vergleich zu hart templatierten Materialien kostengünstiger und stellt eine technische Umsetzung in Aussicht. Desweiteren erlaubt das Syntheseverfahren die Herstellung von monolithischen Körpern und die Einbindung funktionaler Nanopartikel. Die hergestellten Materialien zeigen exzellente Eigenschaften als Elektrodenmaterial in Lithium-Ionen-Batterien und als Trägermaterial für Superkondensatoren. KW - Mesoporosität KW - hierarchische Porosität KW - weiche und harte Templatierung KW - Kohlenstoffmaterialien KW - Weitwinkelröntgenstreuung KW - Mesoporosity KW - hierarchical porosity KW - soft and hard templating KW - carbon materials KW - wide-angle x-ray scattering Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15053 ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Bivigou Koumba, Achille Mayelle A1 - Miasnikova, Anna A1 - Busch, Peter A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Polystyrene-block-poly (methoxy diethylene glycol acrylate)-block-polystyrene triblock copolymers in aqueous solution-a SANS study of the temperature-induced switching behavior JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - A concentrated solution of a symmetric triblock copolymer with a thermoresponsive poly(methoxy diethylene glycol acrylate) (PMDEGA) middle block and short hydrophobic, fully deuterated polystyrene end blocks is investigated in D2O where it undergoes a lower critical solution temperature-type phase transition at ca. 36 A degrees C. Small-angle neutron scattering (SANS) in a wide temperature range (15-50 A degrees C) is used to characterize the size and inner structure of the micelles as well as the correlation between the micelles and the formation of aggregates by the micelles above the cloud point (CP). A model featuring spherical core-shell micelles, which are correlated by a hard-sphere potential or a sticky hard-sphere potential together with a Guinier form factor describing aggregates formed by the micelles above the CP, fits the SANS curves well in the entire temperature range. The thickness of the thermoresponsive micellar PMDEGA shell as well as the hard-sphere radius increase slightly already below the cloud point. Whereas the thickness of the thermoresponsive micellar shell hardly shrinks when heating through the CP and up to 50 A degrees C, the hard-sphere radius decreases within 3.5 K at the CP. The volume fraction decreases already significantly below the CP, which may be at the origin of the previously observed gel-sol transition far below the CP (Miasnikova et al., Langmuir 28: 4479-4490, 2012). Above the CP, small, and at higher temperatures, large aggregates are formed by the micelles. KW - Hydrogel KW - Thermoresponsive KW - LCST behavior KW - SANS Y1 - 2015 U6 - https://doi.org/10.1007/s00396-015-3535-6 SN - 0303-402X SN - 1435-1536 VL - 293 IS - 5 SP - 1515 EP - 1523 PB - Springer CY - New York ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Grillo, Isabelle A1 - Kulkarni, Amit A1 - Sharp, Melissa A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Kinetics of aggregation in micellar solutions of thermoresponsive triblock copolymers - influence of concentration, start and target temperatures JF - Soft matter N2 - In aqueous solution, symmetric triblock copolymers with a thermoresponsive middle block and hydrophobic end blocks form flower-like core-shell micelles which collapse and aggregate upon heating through the cloud point (CP). The collapse of the micellar shell and the intermicellar aggregation are followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while heating micellar solutions of a poly((styrene-d(8))-b-(N-isopropyl acrylamide)-b-(styrene-d(8))) triblock copolymer in D2O rapidly through their CP. The influence of polymer concentration as well as of the start and target temperatures is addressed. In all cases, the micellar collapse is very fast. The collapsed micelles immediately form small clusters which contain voids. They densify which slows down or even stops their growth. For low concentrations and target temperatures just above the CP, i.e. shallow temperature jumps, the subsequent growth of the clusters is described by diffusion-limited aggregation. In contrast, for higher concentrations and/or higher target temperatures, i.e. deep temperature jumps, intermicellar bridges dominate the growth. Eventually, in all cases, the clusters coagulate which results in macroscopic phase separation. For shallow temperature jumps, the cluster surfaces stay rough; whereas for deep temperature jumps, a concentration gradient develops at late stages. These results are important for the development of conditions for thermal switching in applications, e.g. for the use of thermoresponsive micellar systems for transport and delivery purposes. Y1 - 2013 U6 - https://doi.org/10.1039/c2sm27152d SN - 1744-683X VL - 9 IS - 5 SP - 1685 EP - 1699 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Kulkarni, Amit A1 - Jain, Abhinav A1 - Wang, Weinan A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Pipich, Vitaliy A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Thermoresponsive PS-b-PNIPAM-b-PS micelles : aggregation behavior, segmental dynamics, and thermal response N2 - We have studied I lie thermal behavior of amphiphilic, symmetric triblock copolymers having short, deuterated polystyrene (PS) end blocks and a large poly(N-isopropylacrylarnicle) (PNIPAM) middle block exhibiting a lower critical solution temperature (LCST) in aqueous solution. A wide range of concentrations (0.1-300 mg/mL) is investigated using it number of analytical methods such as fluorescence correlation spectroscopy (FCS), turbidimetry, dynamic light scattering (DLS), small-angle neutron scattering (SANS), and neutron spin-echo spectroscopy (NSE). The critical micelle concentration is determined using FCS to be 1 mu M or less. The collapse of the micelles at the LCST is investigated using turbidimetry and DLS and shows a weak dependence on the degree of polymerization of the PNIPAM block. SANS with contrast matching allows its to reveal the core-shell Structure of the micelles as well as their correlation as a function of temperature. The segmental dynamics of the PNIPAM shell are studied as a function of temperature and arc found to be faster in the collapsed state than in the swollen state. The mode detected has a linear dispersion in q(2) and is found to be faster in the collapsed state as compared to the swollen state. We attribute this result to the averaging over mobile and immobilized segments. Y1 - 2010 UR - http://pubs.acs.org/journal/mamobx U6 - https://doi.org/10.1021/Ma902714p SN - 0024-9297 ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Meier-Koll, Andreas A1 - Bivigou Koumba, Achille Mayelle A1 - Busch, Peter A1 - Holderer, Olaf A1 - Hellweg, Thomas A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - The collapse transition and the segmental dynamics in concentrated micellar solutions of P(S-b-NIPAM) diblock copolymers JF - Colloid and polymer science : official journal of the Kolloid-Gesellschaft N2 - We investigate concentrated solutions of poly(styrene-b-N-isopropyl acrylamide) (P(S-b-NIPAM)) diblock copolymers in deuterated water (D2O). Both structural changes and the changes of the segmental dynamics occurring upon heating through the lower critical solution temperature (LCST) of PNIPAM are studied using small-angle neutron scattering and neutron spin-echo spectroscopy. The collapse of the micellar shell and the cluster formation of collapsed micelles at the LCST as well as an increase of the segmental diffusion coefficient after crossing the LCST are detected. Comparing to our recent results on a triblock copolymer P(S-b-NIPAM-b-S) [25], we observe that the collapse transition of P(S-b-NIPAM) is more complex and that the PNIPAM segmental dynamics are faster than in P(S-b-NIPAM-b-S). KW - Block copolymers KW - Responsive polymers KW - Small-angle neutron scattering KW - Neutron spin-echo spectroscopy Y1 - 2011 U6 - https://doi.org/10.1007/s00396-011-2382-3 SN - 0303-402X VL - 289 IS - 5-6 SP - 711 EP - 720 PB - Springer CY - New York ER - TY - JOUR A1 - Adelsberger, Joseph A1 - Metwalli, Ezzeldin A1 - Diethert, Alexander A1 - Grillo, Isabelle A1 - Bivigou Koumba, Achille Mayelle A1 - Laschewsky, André A1 - Müller-Buschbaum, Peter A1 - Papadakis, Christine M. T1 - Kinetics of collapse transition and cluster formation in a thermoresponsive micellar solution of P(S-b-NIPAM-b-S) induced by a temperature jump JF - Macromolecular rapid communications N2 - Structural changes at the intra- as well as intermicellar level were induced by the LCST-type collapse transition of poly(N-isopropyl acrylamide) in ABA triblock copolymer micelles in water. The distinct process kinetics was followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while a micellar solution of a triblock copolymer, consisting of two short deuterated polystyrene endblocks and a long thermoresponsive poly(N-isopropyl acrylamide) middle block, was heated rapidly above its cloud point. A very fast collapse together with a multistep aggregation behavior is observed. The findings of the transition occurring at several size and time levels may have implications for the design and application of such thermoresponsive self-assembled systems. KW - polymer physics KW - thermoresponsive polymers KW - small-angle neutron scattering KW - time-resolved measurements Y1 - 2012 U6 - https://doi.org/10.1002/marc.201100631 SN - 1022-1336 VL - 33 IS - 3 SP - 254 EP - 259 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Adem, Fozia A. A1 - Mbaveng, Armelle T. A1 - Kuete, Victor A1 - Heydenreich, Matthias A1 - Ndakala, Albert A1 - Irungu, Beatrice A1 - Yenesew, Abiy A1 - Efferth, Thomas T1 - Cytotoxicity of isoflavones and biflavonoids from Ormocarpum kirkii towards multi-factorial drug resistant cancer JF - Phytomedicine : international journal of phytotherapy and phytopharmacology N2 - Background: While incidences of cancer are continuously increasing, drug resistance of malignant cells is observed towards almost all pharmaceuticals. Several isoflavonoids and flavonoids are known for their cytotoxicity towards various cancer cells. Methods: The cytotoxicity of compounds was determined based on the resazurin reduction assay. Caspases activation was evaluated using the caspase-Glo assay. Flow cytometry was used to analyze the cell cycle (propodium iodide (PI) staining), apoptosis (annexin V/PI staining), mitochondrial membrane potential (MMP) (JC-1) and reactive oxygen species (ROS) (H2DCFH-DA). CCRF-CEM leukemia cells were used as model cells for mechanistic studies. Results: Compounds 1, 2 and 4 displayed IC50 values below 20 mu M towards CCRF-CEM and CEM/ADR5000 leukemia cells, and were further tested towards a panel of 7 carcinoma cells. The IC50 values of the compounds against carcinoma cells varied from 16.90 mu M (in resistant U87MG.Delta EGFR glioblastoma cells) to 48.67 mu M (against HepG2 hepatocarcinoma cells) for 1, from 7.85 mu M (in U87MG.Delta EGFR cells) to 14.44 mu M (in resistant MDA-MB231/BCRP breast adenocarcinoma cells) for 2, from 4.96 mu M (towards U87MG.Delta EGFRcells) to 7.76 mu M (against MDA-MB231/BCRP cells) for 4, and from 0.07 mu M (against MDA-MB231 cells) to 2.15 mu M (against HepG2 cells) for doxorubicin. Compounds 2 and 4 induced apoptosis in CCRF-CEM cells mediated by MMP alteration and increased ROS production. Conclusion: The present report indicates that isoflavones and biflavonoids from Ormocarpum kirkii are cytotoxic compounds with the potential of being exploited in cancer chemotherapy. Compounds 2 and 4 deserve further studies to develop new anticancer drugs to fight sensitive and resistant cancer cell lines. KW - Apoptosis KW - Cancer KW - Ormocarpum kirkii KW - Isoflavone KW - Biflavonoid KW - Multi-drug resistance Y1 - 2019 U6 - https://doi.org/10.1016/j.phymed.2019.152853 SN - 0944-7113 SN - 1618-095X VL - 58 PB - Elsevier CY - München ER - TY - JOUR A1 - Ahnert, Karsten A1 - Abel, Markus A1 - Kollosche, Matthias A1 - Jorgensen, Per Jorgen A1 - Kofod, Guggi T1 - Soft capacitors for wave energy harvesting JF - Journal of materials chemistry N2 - Wave energy harvesting could be a substantial renewable energy source without impact on the global climate and ecology, yet practical attempts have struggled with the problems of wear and catastrophic failure. An innovative technology for ocean wave energy harvesting was recently proposed, based on the use of soft capacitors. This study presents a realistic theoretical and numerical model for the quantitative characterization of this harvesting method. Parameter regions with optimal behavior are found, and novel material descriptors are determined, which dramatically simplify analysis. The characteristics of currently available materials are evaluated, and found to merit a very conservative estimate of 10 years for raw material cost recovery. Y1 - 2011 U6 - https://doi.org/10.1039/c1jm12454d SN - 0959-9428 SN - 1364-5501 VL - 21 IS - 38 SP - 14492 EP - 14497 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Akampurira, Denis A1 - Akala, Hoseah M. A1 - Derese, Solomon A1 - Heydenreich, Matthias A1 - Yenesew, Abiy T1 - A new C-C linked benzophenathridine-2-quinoline dimer, and the antiplasmodial activity of alkaloids from Zanthoxylum holstzianum JF - Natural product research N2 - The CH2Cl2/MeOH (1:1) extract of Zanthoxylum holstzianum stem bark showed good antiplasmodial activity (IC50 2.5 +/- 0.3 and 2.6 +/- 0.3 mu g/mL against the W2 and D6 strains of Plasmodium falciparum, respectively). From the extract five benzophenanthridine alkaloids [8-acetonyldihydrochelerythrine (1), nitidine (2), dihydrochelerythine (3), norchelerythrine (5), arnottianamide (8)]; a 2-quinolone alkaloid [N-methylflindersine (4)]; a lignan [4,4 '-dihydroxy-3,3 '-dimethoxylignan-9,9 '-diyl diacetate (7)] and a dimer of a benzophenanthridine and 2-quinoline [holstzianoquinoline (6)] were isolated. The CH2Cl2/MeOH (1:1) extract of the root bark afforded 1, 3-6, 8, chelerythridimerine (9) and 9-demethyloxychelerythrine (10). Holstzianoquinoline (6) is new, and is the second dimer linked by a C-C bond of a benzophenanthridine and a 2-quinoline reported thus far. The compounds were identified based on spectroscopic evidence. Amongst five compounds (1-5) tested against two strains of P. falciparum, nitidine (IC50 0.11 +/- 0.01 mu g/mL against W2 and D6 strains) and norchelerythrine (IC50 value of 0.15 +/- 0.01 mu g/mL against D6 strain) were the most active. KW - Antiplasmodial KW - benzophenanthridine alkaloid KW - holstzianoquinoline; KW - rutaceae KW - Zanthoxylum holstzianum Y1 - 2022 U6 - https://doi.org/10.1080/14786419.2022.2034810 SN - 1478-6419 SN - 1478-6427 VL - 37 IS - 13 SP - 2161 EP - 2171 PB - Taylor & Francis CY - London [u.a.] ER - TY - JOUR A1 - Akarsu, Pinar A1 - Grobe, Richard A1 - Nowaczyk, Julius A1 - Hartlieb, Matthias A1 - Reinicke, Stefan A1 - Böker, Alexander A1 - Sperling, Marcel A1 - Reifarth, Martin T1 - Solid-phase microcontact printing for precise patterning of rough surfaces BT - using polymer-tethered elastomeric stamps for the transfer of reactive silanes JF - ACS applied polymer materials N2 - We present a microcontact printing (mu CP) routine suitable to introduce defined (sub-) microscale patterns on surface substrates exhibiting a high capillary activity and receptive to a silane-based chemistry. This is achieved by transferring functional trivalent alkoxysilanes, such as (3-aminopropyl)-triethoxysilane (APTES) as a low-molecular weight ink via reversible covalent attachment to polymer brushes grafted from elastomeric polydimethylsiloxane (PDMS) stamps. The brushes consist of poly{N-[tris(hydroxymethyl)-methyl]acrylamide} (PTrisAAm) synthesized by reversible addition-fragmentation chain-transfer (RAFT)-polymerization and used for immobilization of the alkoxysilane-based ink by substituting the alkoxy moieties with polymer-bound hydroxyl groups. Upon physical contact of the silane-carrying polymers with surfaces, the conjugated silane transfers to the substrate, thus completely suppressing ink-flow and, in turn, maximizing printing accuracy even for otherwise not addressable substrate topographies. We provide a concisely conducted investigation on polymer brush formation using atomic force microscopy (AFM) and ellipsometry as well as ink immobilization utilizing two-dimensional proton nuclear Overhauser enhancement spectroscopy (H-1-H-1-NOESY-NMR). We analyze the mu CP process by printing onto Si-wafers and show how even distinctively rough surfaces can be addressed, which otherwise represent particularly challenging substrates. KW - microcontact printing KW - capillary-active substrates KW - silane chemistry KW - PDMS surface grafting KW - surface patterning KW - shuttled RAFT-polymerization Y1 - 2021 U6 - https://doi.org/10.1021/acsapm.1c00024 SN - 2637-6105 VL - 3 IS - 5 SP - 2420 EP - 2431 PB - American Chemical Society CY - Washington ER - TY - THES A1 - Akdemir, Özgür T1 - Synthesis of novel non-viral gene carriers via atom transfer radical polymerization and click chemistry Y1 - 2009 CY - Potsdam ER - TY - THES A1 - Al Nakeeb, Noah T1 - Self-assembly and crosslinking approaches of double hydrophilic linear-brush block copolymers BT - a biocompatible platform for the next generation of nanoreactors Y1 - 2019 ER - TY - JOUR A1 - Al Nakeeb, Noah A1 - Kochovski, Zdravko A1 - Li, Tingting A1 - Zhang, Youjia A1 - Lu, Yan A1 - Schmidt, Bernhard V. K. J. T1 - Poly(ethylene glycol) brush-b-poly(N-vinylpyrrolidone)-based double hydrophilic block copolymer particles crosslinked via crystalline alpha-cyclodextrin domains JF - RSC Advances N2 - Self-assembly of block copolymers is a significant area of polymer science. The self-assembly of completely water-soluble block copolymers is of particular interest, albeit a challenging task. In the present work the self-assembly of a linear-brush architecture block copolymer, namely poly(N-vinylpyrrolidone)-b-poly(oligoethylene glycol methacrylate) (PVP-b-POEGMA), in water is studied. Moreover, the assembled structures are crosslinked via alpha-CD host/guest complexation in a supramolecular way. The crosslinking shifts the equilibrium toward aggregate formation without switching off the dynamic equilibrium of double hydrophilic block copolymer (DHBC). As a consequence, the self-assembly efficiency is improved without extinguishing the unique DHBC self-assembly behavior. In addition, decrosslinking could be induced without a change in concentration by adding a competing complexation agent for alpha-CD. The self-assembly behavior was followed by DLS measurement, while the presence of the particles could be observed via cryo-TEM before and after crosslinking. Y1 - 2019 U6 - https://doi.org/10.1039/c8ra10672j SN - 2046-2069 VL - 9 IS - 9 SP - 4993 EP - 5001 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Al-Naji, Majd A1 - Schlaad, Helmut A1 - Antonietti, Markus T1 - New (and old) monomers from biorefineries to make polymer chemistry more sustainable JF - Macromolecular rapid communications N2 - This opinion article describes recent approaches to use the "biorefinery" concept to lower the carbon footprint of typical mass polymers, by replacing parts of the fossil monomers with similar or even the same monomer made from regrowing dendritic biomass. Herein, the new and green catalytic synthetic routes are for lactic acid (LA), isosorbide (IS), 2,5-furandicarboxylic acid (FDCA), and p-xylene (pXL). Furthermore, the synthesis of two unconventional lignocellulosic biomass derivable monomers, i.e., alpha-methylene-gamma-valerolactone (MeGVL) and levoglucosenol (LG), are presented. All those have the potential to enter in a cost-effective way, also the mass market and thereby recover lost areas for polymer materials. The differences of catalytic unit operations of the biorefinery are also discussed and the challenges that must be addressed along the synthesis path of each monomers. KW - biodegradable polymers KW - biorefineries KW - carbohydrate‐ based KW - monomers KW - green polymers KW - lignocellulosic biomass Y1 - 2020 U6 - https://doi.org/10.1002/marc.202000485 SN - 1022-1336 SN - 1521-3927 VL - 42 IS - 3 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Al-Naji, Majd A1 - Schlaad, Helmut A1 - Antonietti, Markus T1 - New (and old) monomers from biorefineries to make polymer chemistry more sustainable T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - This opinion article describes recent approaches to use the "biorefinery" concept to lower the carbon footprint of typical mass polymers, by replacing parts of the fossil monomers with similar or even the same monomer made from regrowing dendritic biomass. Herein, the new and green catalytic synthetic routes are for lactic acid (LA), isosorbide (IS), 2,5-furandicarboxylic acid (FDCA), and p-xylene (pXL). Furthermore, the synthesis of two unconventional lignocellulosic biomass derivable monomers, i.e., alpha-methylene-gamma-valerolactone (MeGVL) and levoglucosenol (LG), are presented. All those have the potential to enter in a cost-effective way, also the mass market and thereby recover lost areas for polymer materials. The differences of catalytic unit operations of the biorefinery are also discussed and the challenges that must be addressed along the synthesis path of each monomers. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1385 KW - biodegradable polymers KW - biorefineries KW - carbohydrate‐ based KW - monomers KW - green polymers KW - lignocellulosic biomass Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-570614 SN - 1866-8372 IS - 3 ER - TY - THES A1 - Alahverdjieva, Veneta T1 - Experimental study of mixed protein/surfactant systems at the aqueous solution/air interface Y1 - 2007 CY - Potsdam ER - TY - JOUR A1 - Alarcon, Julio A1 - Alderete, Joel B. A1 - Aguila, Sergio A1 - Peter, Martin G. T1 - Regio and stereoselective hydroxylation of alpha-agarofuran by biotransformation of rhizopus nigricans N2 - A new synthesis of 9 alpha-hydroxy-alpha-agarofuran (6 alpha) is described, using a microbiological hydroxylation alpha-agarofuran (5) as the key reaction. The stereochemistry of the biohydroxylation was determined on the basis of a NOESY-experiment and GIAO calculations at the B3LYP/cc-pVDZ level. A strong gamma-effect was observed at C15 of the agarofuran ring which was correctly predicted by the GIAO-B3LYP calculations Y1 - 2005 ER - TY - JOUR A1 - Alarcon, Julio A1 - Alderete, Joel B. A1 - Peter, Martin G. A1 - Becerra, Juan J. A1 - Silva, M. T1 - Study on synthesis of 3 alpha,4 alpha-dihydroxy-dihydro-beta-agarofuran Y1 - 1998 ER - TY - GEN A1 - Albrecht, O. A1 - Cumming, W. A1 - Kreuder, W. A1 - Laschewsky, André A1 - Ringsdorf, Helmut T1 - Monolayers of rod-shaped and disc-shaped liquid crystalline compounds at the air-water interface N2 - Calamitic (rod-shaped) and discotic (disc-shaped) thermotropic liquid crystalline (LC) compounds were spread at the air-water interface, and their ability to form monolayers was studied. The calamitic LCs investigated were found to form monolayers which behave analogously to conventional amphiphiles such as fatty acids. The spreading of the discotic LCs produced monolayers as well, but with a behaviour different from classical amphiphiles. The areas occupied per molecule are too small to allow the contact of all hydrophilic groups with the water surface and the packing of all hydrophobic chains. Various molecular arrangements of the discotics at the water surface to fit the spreading data are discussed. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 079 KW - Monolayers KW - liquid crystals KW - discotics Y1 - 1986 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17124 ER - TY - THES A1 - Ali, Abu Md. Imroz T1 - Morphology control in nanoscopic composite polymer particles Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Ali, Mostafa A1 - Homann, Thomas A1 - Khalil, Mahmoud A1 - Kruse, Hans-Peter A1 - Rawel, Harshadrai Manilal T1 - Milk whey protein modification by coffee-specific phenolics effect on structural and functional properties JF - Journal of agricultural and food chemistry : a publication of the American Chemical Society N2 - A suitable vehicle for integration of bioactive plant constituents is proposed. It involves modification of proteins using phenolics and applying these for protection of labile constituents. It dissects the noncovalent and covalent interactions of beta-lactoglobulin with coffee-specific phenolics. Alkaline and polyphenol oxidase modulated covalent reactions were compared. Tryptic digestion combined with MALDI-TOF-MS provided tentative allocation of the modification type and site in the protein, and an in silico modeling of modified beta-lactoglobulin is proposed. The modification delivers proteins with enhanced antioxidative properties. Changed structural properties and differences in solubility, surface hydrophobicity, and emulsification were observed. The polyphenol oxidase modulated reaction provides a modified beta-lactoglobulin with a high antioxidative power, is thermally more stable, requires less energy to unfold, and, when emulsified with lutein esters, exhibits their higher stability against UV light. Thus, adaptation of this modification provides an innovative approach for functionalizing proteins and their uses in the food industry. KW - coffee phenolic compounds KW - whey proteins KW - antioxidants KW - protein-phenol interactions KW - modeling KW - functionalizing proteins Y1 - 2013 U6 - https://doi.org/10.1021/jf402221m SN - 0021-8561 VL - 61 IS - 28 SP - 6911 EP - 6920 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Ali, Mostafa A1 - Homann, Thomas A1 - Kreisel, Janka A1 - Khalil, Mahmoud A1 - Puhlmann, Ralf A1 - Kruse, Hans-Peter A1 - Rawel, Harshadrai Manilal T1 - Characterization and modeling of the interactions between coffee storage proteins and phenolic compounds JF - Journal of agricultural and food chemistry : a publication of the American Chemical Society N2 - This study addresses the interactions of coffee storage proteins with coffee-specific phenolic compounds. Protein profiles, of Coffea arabica and Coffea canephora (var robusta) were compared. Major Phenolic compounds were extracted and analyzed with appropriate methods. The polyphenol-protein interactions during protein extraction have been addressed by different analytical setups [reversed-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), and Trolox equivalent antioxidant capacity (TEAC) assays], with focus directed toward identification of covalent adduct formation. The results indicate that C. arabica proteins are more susceptible to these interactions and the polyphenol oxidase activity seems to be a crucial factor for the formation of these addition products. A tentative allocation of the modification type and site in the protein has been attempted. Thus, the first available in silico modeling of modified coffee proteins is reported. The extent of these modifications may contribute to the structure and function of "coffee melanoidins" and are discussed in the context of coffee flavor formation. KW - Coffee beans KW - storage proteins KW - phenolic compounds KW - antioxidants KW - protein-phenol interactions KW - modeling Y1 - 2012 U6 - https://doi.org/10.1021/jf303372a SN - 0021-8561 VL - 60 IS - 46 SP - 11601 EP - 11608 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Aloni, Sapir Shekef A1 - Perovic, Milena A1 - Weitman, Michal A1 - Cohen, Reut A1 - Oschatz, Martin A1 - Mastai, Yitzhak T1 - Amino acid-based ionic liquids as precursors for the synthesis of chiral nanoporous carbons JF - Nanoscale Advances N2 - The synthesis of chiral nanoporous carbons based on chiral ionic liquids (CILs) of amino acids as precursors is described. Such unique precursors for the carbonization of CILs yield chiral carbonaceous materials with high surface area (approximate to 620 m(2) g(-1)). The enantioselectivities of the porous carbons are examined by advanced techniques such as selective adsorption of enantiomers using cyclic voltammetry, isothermal titration calorimetry, and mass spectrometry. These techniques demonstrate the chiral nature and high enantioselectivity of the chiral carbon materials. Overall, we believe that the novel approach presented here can contribute significantly to the development of new chiral carbon materials that will find important applications in chiral chemistry, such as in chiral catalysis and separation and in chiral sensors. From a scientific point of view, the approach and results reported here can significantly deepen our understanding of chirality at the nanoscale and of the structure and nature of chiral nonporous materials and surfaces. Y1 - 2019 U6 - https://doi.org/10.1039/c9na00520j SN - 2516-0230 VL - 1 IS - 12 SP - 4981 EP - 4988 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Alrefai, Anas A1 - Mondal, Suvendu Sekhar A1 - Wruck, Alexander A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Brandt, Philipp A1 - Janiak, Christoph A1 - Schoenfeld, Sophie A1 - Weber, Birgit A1 - Rybakowski, Lawrence A1 - Herrman, Carmen A1 - Brennenstuhl, Katlen A1 - Eidner, Sascha A1 - Kumke, Michael Uwe A1 - Behrens, Karsten A1 - Günter, Christina A1 - Müller, Holger A1 - Holdt, Hans-Jürgen T1 - Hydrogen-bonded supramolecular metal-imidazolate frameworks: gas sorption, magnetic and UV/Vis spectroscopic properties JF - Journal of Inclusion Phenomena and Macrocyclic Chemistry N2 - By varying reaction parameters for the syntheses of the hydrogen-bonded metal-imidazolate frameworks (HIF) HIF-1 and HIF-2 (featuring 14 Zn and 14 Co atoms, respectively) to increase their yields and crystallinity, we found that HIF-1 is generated in two different frameworks, named as HIF-1a and HIF-1b. HIF-1b is isostructural to HIF-2. We determined the gas sorption and magnetic properties of HIF-2. In comparison to HIF-1a (Brunauer-Emmett-Teller (BET) surface area of 471m(2) g(-1)), HIF-2 possesses overall very low gas sorption uptake capacities [BET(CO2) surface area=85m(2) g(-1)]. Variable temperature magnetic susceptibility measurement of HIF-2 showed antiferromagnetic exchange interactions between the cobalt(II) high-spin centres at lower temperature. Theoretical analysis by density functional theory confirmed this finding. The UV/Vis-reflection spectra of HIF-1 (mixture of HIF-1a and b), HIF-2 and HIF-3 (with 14 Cd atoms) were measured and showed a characteristic absorption band centered at 340nm, which was indicative for differences in the imidazolate framework. KW - Gas-sorption KW - Ligand design KW - Magnetic properties KW - Supramolecular chemistry KW - Solvothermal synthesis Y1 - 2019 U6 - https://doi.org/10.1007/s10847-019-00926-6 SN - 1388-3127 SN - 1573-1111 VL - 94 IS - 3-4 SP - 155 EP - 165 PB - Springer CY - Dordrecht ER - TY - THES A1 - Altabal, Osamah T1 - Design and fabrication of geometry-assisted on-demand dosing systems N2 - The controlled dosage of substances from a device to its environment, such as a tissue or an organ in medical applications or a reactor, room, machinery or ecosystem in technical, should ideally match the requirements of the applications, e.g. in terms of the time point at which the cargo is released. On-demand dosage systems may enable such a desired release pattern, if the device contain suitable features that can translate external signals into a release function. This study is motivated by the opportunities arising from microsystems capable of an on-demand release and the contributions that geometrical design may have in realizing such features. The goals of this work included the design, fabrication, characterization and experimental proof-of-concept of geometry-assisted triggerable dosing effect (a) with a sequential dosing release and (b) in a self-sufficient dosage system. Structure-function relationships were addressed on the molecular, morphological and, with a particular attention, the device design level, which is on the micrometer scale. Models and/or computational tools were used to screen the parameter space and provide guidance for experiments. N2 - Die kontrollierte Freisetzung von Substanzen aus einem Device in seine Umgebung, wie ein Gewebe oder Organ in medizinischen Anwendungen oder ein Reaktor, ein Raum, ein Gerät oder ein Ökosystem in technischer Nutzung sollte idealerweise den Anforderungen des Einsatzzweckes entsprechen, beispielsweise hinsichtlich des Zeitpunktes an dem die Freisetzung erfolgt. On-demand Freisetzungssysteme könnten eine derartiges gewünschtes Verhalten zeigen, wenn das System die Befähigung besitzt, externe Signale in eine Freisetzungsfunktion zu überführen. Diese Arbeit greift die Möglichkeiten auf, die sich durch den Einsatz und ein gezieltes Design von mikrostrukturierten Systemen für die Realisierung einer on-demand Freisetzung ergeben könnten. Die Ziele der Arbeit umfassen die Konzeptionierung, Herstellung, Charakterisierung sowie den grundsätzlichen Nachweis durch Stimuli induzierten on-demand Freisetzungsfunktion einerseits in Form eines sequentiellen Freigabeverhaltens und anderseits in Form eines autarken (kontaktfrei ausgelösten) Dosiersystems. Struktur-Eigenschafts-Beziehungen wurden auf molekularer, morphologischer und - mit besonderen Augenmerk - auf der Ebene des Device-Designs untersucht. Modelle und/oder Computer-gestützte Verfahren wurden verwendet um geeignete Materialparameter zu identifizieren und einen Leitfaden für die Experimente bereitzustellen. KW - Stress concentration KW - Negative Poisson’s ratio KW - On-demand release KW - Spannungskonzentrationen KW - Negatives Poisson-Verhältnis KW - On-demand Freisetzung Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-532441 ER - TY - THES A1 - Ambrogi, Martina T1 - Application of Poly(Ionic Liquid)s for the synthesis of functional carbons Y1 - 2015 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 - THES A1 - Andersen, Audrée T1 - Surfactant dynamics at interfaces : a series of second harmonic generation experiments T1 - Surfactant Dynamik an Grenzflächen : eine Studie über SHG-Experimente N2 - Adsorption layers of soluble surfactants enable and govern a variety of phenomena in surface and colloidal sciences, such as foams. The ability of a surfactant solution to form wet foam lamellae is governed by the surface dilatational rheology. Only systems having a non-vanishing imaginary part in their surface dilatational modulus, E, are able to form wet foams. The aim of this thesis is to illuminate the dissipative processes that give rise to the imaginary part of the modulus. There are two controversial models discussed in the literature. The reorientation model assumes that the surfactants adsorb in two distinct states, differing in their orientation. This model is able to describe the frequency dependence of the modulus E. However, it assumes reorientation dynamics in the millisecond time regime. In order to assess this model, we designed a SHG pump-probe experiment that addresses the orientation dynamics. Results obtained reveal that the orientation dynamics occur in the picosecond time regime, being in strong contradiction with the two states model. The second model regards the interface as an interphase. The adsorption layer consists of a topmost monolayer and an adjacent sublayer. The dissipative process is due to the molecular exchange between both layers. The assessment of this model required the design of an experiment that discriminates between the surface compositional term and the sublayer contribution. Such an experiment has been successfully designed and results on elastic and viscoelastic surfactant provided evidence for the correctness of the model. Because of its inherent surface specificity, surface SHG is a powerful analytical tool that can be used to gain information on molecular dynamics and reorganization of soluble surfactants. They are central elements of both experiments. However, they impose several structural elements of the model system. During the course of this thesis, a proper model system has been identified and characterized. The combination of several linear and nonlinear optical techniques, allowed for a detailed picture of the interfacial architecture of these surfactants. N2 - Amphiphile vereinen zwei gegensätzliche Strukturelemente in einem Molekül, eine hydrophile Kopfgruppe und ein hydrophobe, meist aliphatische Kette. Aufgrund der molekularen Asymmetrie erfolgt eine spontane Adsorption an der Wasser-Luft Grenzfläche. Die Adsorptionsschicht verändert die makroskopischen Eigenschaften des Materials, z.B. die Grenzflächenspannung wird erniedrigt. Amphiphile sind zentrale Bauelemente der Kolloid- und Grenzflächenforschung, die Phänomene, wie Schäume ermöglichen. Eine Schaumlamelle besteht aus einem dünnen Wasserfilm, der durch zwei Adsorptionsschichten stabilisiert wird. Die Stabilität der Lamelle wird durch die Grenzflächenrheologie entscheidend geprägt. Die wesentliche makroskopische Größe in diesem Zusammenhang ist das so genannte Grenzflächendilatationsmodul E. Es beschreibt die Fähigkeit des Systems die Gleichgewichtsgrenzflächenspannung nach einer Expansion oder Dilatation der Adsorptionschicht wieder herzustellen. Das Modul E ist eine komplexe Größe, in dem der Imaginärteil direkt mit der Schaumstabilität korreliert. Diese Arbeit widmet sich der Grenzflächenrheologie. In der Literatur werden zwei kontroverse Modelle zur Interpretation dieser Größe diskutiert. Diese Modelle werden experimentell in dieser Arbeit überprüft. Dies erfordert die Entwicklung neuer experimenteller Aufbauten basierend auf nichtlinearen, optischen Techniken. Mit diesen Experimenten konnte eines der Modelle bestätigt werden. KW - Tensid KW - Grenzflächenchemie KW - Nichtlineare Spektroskopie KW - Oscillating Bubble KW - surfactants KW - nonlinear optics KW - surface rheology KW - air-water interface KW - oscillating bubble Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-6553 ER - TY - JOUR A1 - Andersen, S. O. A1 - Peter, Martin G. A1 - Roepstorff, Peter T1 - Cuticular sclerotization in insects Y1 - 1996 ER - TY - GEN A1 - Andersen, Svend Olav A1 - Perter, Martin G. A1 - Roepstorff, Peter T1 - Cuticle-catalyzed coupling between N-acetylhistidine and N-acetyldopamine N2 - Several types of insect cuticle contain enzymes catalyzing the formation ofof adducts between N-acetyldopamine (NADA) and N-acetylhistidine (NAH). Two such adducts, NAH-NADA-I and NAH NADA-II, have been isolated and their structures determined. In one of the adducts the link connecting the two residues occurs between the I-position (ß-position) in the NADA side chain and the 1-N atom (τ-N) in the imidazole ring of histidine. Diphenoloxidase activity alone is not sufficient for formation of this adduct, whereas extracts containing both diphenoloxidase and o-quinone-p-quinone methide isomerase activities catalyze the coupling reaction. The adduct consists of a mixture of two diastereomers and they are presumably formed by spontaneous reaction between enzymatically produced NADA-p-quinone methide and N-acetylhistidine. The other adduct has been identified as a ring addition product of N-acetylhistidine and NADA. In contrast to the former adduct it can be formed by incubation of the two substrates with mushroom tyrosinase alone. An adduct between N-acetylhistidine and the benzodioxan-type NADA-dimer is produced in vitro, when the N-acetylhistidine-NADA adduct is incubated with NADA and locust cuticle containing a 1,2-dehydro-NADA generating enzyme system. Trimeric NADA-polymerization products of the substituted benzodioxan-type have been obtained from in vivo sclerotized locust cuticle, confirming the ability of cuticle to produce NADA-oligomers. The results indicate that some insect cuticles contain enzymes promoting linkage of oxidized NADA to histidine residues. It is suggested that histidine residues in the cuticular proteins can serve as acceptors for oxidized NADA and that further addition of NADA-residues to the phenolic groups of bound NADA can occur, resulting in formation of protein-linked NADA-oligomers. The coupling reactions identified may be an important step in natural cuticular sclerotization. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 072 KW - sclerotization KW - quinone KW - quinone methide KW - o-quinone isomerase KW - Hyalophora cecropia KW - Locusta migratoria Y1 - 1992 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16762 ER - TY - JOUR A1 - Andrews, N. L. P. A1 - Ferguson, T. A1 - Rangaswamy, A. M. M. A1 - Bernicky, A. R. A1 - Henning, N. A1 - Dudelzak, A. A1 - Reich, Oliver A1 - Barnes, Jack A. A1 - Loock, Hans-Peter T1 - Hadamard-Transform Fluorescence Excitation-Emission-Matrix Spectroscopy JF - Analytical chemistry N2 - We present a fluorescence excitation-emission-matrix spectrometer with superior data acquisition rates over previous instruments. Light from a white light emitting diode (LED) source is dispersed onto a digital micromirror array (DMA) and encoded using binary n-size Walsh functions ("barcodes"). The encoded excitation light is used to irradiate the liquid sample and its fluorescence is dispersed and detected using a conventional array spectrometer. After exposure to excitation light encoded in n different ways, the 2-dimensional excitation-emission-matrix (EEM) spectrum is obtained by inverse Hadamard transformation. Using this technique we examined the kinetics of the fluorescence of rhodamine B as a function of temperature and the acid-driven demetalation of chlorophyll into pheophytin-a. For these experiments, EEM spectra with 31 excitation channels and 2048 emission channels were recorded every 15 s. In total, data from over 3000 EEM spectra were included in this report. It is shown that the increase in data acquisition rate can be as high as [{n(n + 1)}/2]-fold over conventional EEM spectrometers. Spectral acquisition rates of more than two spectra per second were demonstrated. Y1 - 2017 U6 - https://doi.org/10.1021/acs.analchem.7b02400 SN - 0003-2700 SN - 1520-6882 VL - 89 SP - 8554 EP - 8564 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Andrews, Nicholas L. P. A1 - Ross, Rachel A1 - Munzke, Dorit A1 - van Hoorn, Camiel A1 - Brzezinski, Andrew A1 - Barnes, Jack A. A1 - Reich, Oliver A1 - Loock, Hans-Peter T1 - In-fiber Mach-Zehnder interferometer for gas refractive index measurements based on a hollow-core photonic crystal fiber JF - Optics express : the international electronic journal of optics N2 - We describe an in-fiber interferometer based on a gas-filled hollow-core photonic crystal fiber. Expressions for the sensitivity, figure of merit and refractive index resolution are derived, and values are experimentally measured and theoretically validated using mode field calculations. The refractive indices of nine monoatomic and molecular gases are measured with a resolution of delta(ns) < 10(-6). (C)2016 Optical Society of America Y1 - 2016 U6 - https://doi.org/10.1364/OE.24.014086 SN - 1094-4087 VL - 24 SP - 14086 EP - 14099 PB - Optical Society of America CY - Washington ER - TY - JOUR A1 - Andrianov, Ivan A1 - Saalfrank, Peter T1 - Free vibrational relaxation of H adsorbed on a Si(100) surface investigated with the multi-configurational time-dependent Hartree method JF - Chemical physics letters N2 - The results of a quantum-mechanical study of vibrational relaxation of hydrogen adsorbed on a Si(100) surface with the multi-configurational time-dependent Hartree (MCTDH) method are presented. A two-dimensional subsystem is coupled non-linearly to a bath of harmonic oscillators (phonons of the Si bulk), and the relaxation of subsystem vibrations proceeds primarily via a two-phonon process. Characteristic times of the system evolution agree well with our previous perturbation theory study. The vibrational population decay is non-exponential, exhibiting pronounced recurrences due to finite bath size. The dependence of the lifetimes of the vibrational levels on the bath size and on the coupling details is investigated. Y1 - 2006 U6 - https://doi.org/10.1016/j.cplett.2006.11.067 SN - 0009-2614 VL - 433 SP - 91 EP - 96 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - Antipov, Alexei T1 - Polyelectrolyte multilayer capsules as controlled permeability vehicles and catalyst carriers Y1 - 2003 ER - TY - GEN A1 - Anton, Peter A1 - Köberle, Peter A1 - Laschewsky, André T1 - Recent developments in the field of micellar polymers N2 - This article describes recent achievements in the field of micellar polymers, or polysoaps. Taking advantage of zwitterionic model polymers, systematic variations of the molecular architecture have provided an improved understanding of the relationship between the molecular structure of the polymers and their key properties such as surface activity and solubilization capacity. Useful rules are established, which take into account much of the previous data in the literature. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 090 Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17263 ER - TY - GEN A1 - Anton, Peter A1 - Laschewsky, André T1 - Zwitterionic polysoaps with reduced density of surfactant side groups N2 - Several zwitterionic polymers were prepared by radical homopolymerization of surfactant monomers which bear diallyl, diene or vinylcyclopropane moieties. These polymer systems were complemented by alternating copolymers of appropriate zwitterionic vinyl compounds. Thus, polymers with reduced (as compared with simple vinylic homopolymers, or statistical copolymers) and well defined density of surfactant side groups are obtained. The solubilities found for these polymers are dominated by polymer geometry rather than by the balance of hydrophilic and hydrophobic fragments, thus corroborating a main-chain spacer model proposed recently. All water-soluble polymers exhibit characteristic features of classical polysoaps, as shown by surface tension measurements and by solubilization of hydrophobic dyes. In contrast, the water-insoluble copolymers are capable to form stable monolayers at the air-water interface. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 091 Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17301 ER - TY - GEN A1 - Anton, Peter A1 - Laschewsky, André T1 - Solubilization by polysoaps N2 - The aqueous solubilization power of several series of micellar homopolymers and copolymers (polysoaps) is investigated. Using five insoluble or poorly water-soluble dyes, comparisons of the capacities are made with respect ot the influence of structural variables such as the polymer backbone, the polymer geometry, the comonomer content, and the charge of the hydrophilic group. Some guidelines for polysoap structures suited for efficient solubilization are established. Noteworthy is that the solubilization capacities of the polysoaps are neither linked to the ability to reduce the surface tension of water, nor to the polarity of the solubilization sites deduced from spectroscopic probes. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 083 KW - Micellar polymers KW - polysoaps KW - solubilization Y1 - 1994 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17327 ER - TY - GEN A1 - Anton, Peter A1 - Laschewsky, André T1 - Polysoaps via alternating olefin/SO2 copolymers N2 - Contents: Introduction Results and discussion - Monomers studied - Monomer properties - Polymerization, copolymer composition and general properties - Polymer properties in aqueous solution Conclusion Experimental part - Materials - Copolymerization with S02 (typical procedure) - Methods T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 088 Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17216 ER - TY - GEN A1 - Anton, Peter A1 - Laschewsky, André A1 - Ward, M. D. T1 - Solubilization control by redox-switching of polysoaps N2 - Reversible changes in the self-organization of polysoaps may be induced by controlling their charge numbers via covalently bound redox moieties. This is illustrated with two viologen polysoaps, which in response to an electrochemical stimulus, change their solubility and aggregation in water, leading from homogeneously dissolved and aggregated molecules to collapsed ones and vice verse. Using the electrochemical quartz crystal microbalance (EQCM), it could be shown that the reversibility of this process is better than 95% in 16 cycles. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 084 KW - Quartz Crystal KW - microbalance KW - films KW - Electrochemistry KW - viologen Y1 - 1995 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17336 ER - TY - JOUR A1 - Antoniou, Stella A1 - Pashalidis, I. A1 - Gessner, Andre A1 - Kumke, Michael Uwe T1 - The effect of humic acid on the formation and solubility of secondary solid phases (Nd(OH)CO3 and Sm(OH)CO3) JF - Radiochimica acta : international journal for chemical aspects of nuclear science and technology N2 - The formation of secondary Ln(III) solid phases (e.g. Nd(OH)CO3 and Sm(OH)CO3) has been studied as a function of the humic acid (HA) concentration in 0.1 M NaClO4 aqueous solution and their solubility has been investigated in the neutral pH range (6.5-8) under normal atmospheric conditions. Nd(III) and Sm(III) were selected as analogues for trivalent lanthanide and actinide ions. The solid phases under investigation have been prepared by alkaline precipitation and characterized by TGA, ATR-FTIR, XRD, TRLFS, DR-UV-Vis and Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicate that Nd(OH)CO3 and Sm(OH)CO3 are stable and remain the solubility limiting solid phases even in the presence of increased HA concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurs, the inorganic (Ln(OH)CO3) and the organic phase (HA), which is adsorbed on the particle surface of the former. Nevertheless, HA affects the particle size of the solid phases. Increasing HA concentration results in decreasing crystallite size of the Nd(OH)CO3 and increasing crystallite size of the Sm(OH)CO3 solid phase, and affects inversely the solubility of the solid phases. However, this impact on the solid phase properties is expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere. KW - Lanthanide ions KW - Humic acid KW - Solid phase KW - Solubility KW - Raman KW - TRLFS KW - DR-UV-Vis Y1 - 2011 U6 - https://doi.org/10.1524/ract.2011.1812 SN - 0033-8230 VL - 99 IS - 4 SP - 217 EP - 223 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Antoniou, Stella A1 - Pashalidis, Ioannis A1 - Gessner, Andre A1 - Kumke, Michael Uwe T1 - Spectroscopic investigations on the effect of humic acid on the formation and solubility of secondary solid phases of Ln(2)(CO3)(3) JF - Journal of rare earths N2 - The formation of secondary Ln(III) solid phases (e.g., Nd-2(CO3)(3) and Sm-2(CO3)(3)) was studied as a function of the humic acid concentration in 0.1 mol/L NaClO4 aqueous solution in the neutral pH range (5-6.5). The solid phases under investigation were prepared by alkaline precipitation under 100% CO2 atmosphere and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), time-resolved laser fluorescence spectroscopy (TRLFS), diffuse reflectance ultraviolet-visible (DR-UV-Vis), Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicated that Nd-2(CO3)(3) and Sm-2(CO3)(3) were stable and remained the solubility limiting solid phases even in the presence of increased humic acid concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system, decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurred, the inorganic (Ln(2)(CO3)(3)) and the organic phase (HA), which was adsorbed on the particle surface of the former. Nevertheless, humic acid affected the particle size of the solid phases. Increasing humic acid concentration resulted in decreasing crystallite size of the Nd-2(CO3)(3) and increasing crystallite size of the Sm-2(CO3)(3) solid phase, and affected inversely the solubility of the solid phases. However, this impact on the solid phase properties was expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere. KW - lanthanide ions KW - humic acid KW - solid phase KW - solubility KW - Raman KW - TRLFS KW - DR-UV-Vis KW - rare earths Y1 - 2011 U6 - https://doi.org/10.1016/S1002-0721(10)60490-5 SN - 1002-0721 VL - 29 IS - 6 SP - 516 EP - 521 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Apitz, Sabine E. A1 - Bell, Elanor M. A1 - Damgaard, Lars A1 - Gilbert, Franck A1 - Glud, R A1 - Hall, P. O. J. A1 - Kershaw, P. J. A1 - Nickel, L A1 - Parker, R A1 - Rabouille, Christophe A1 - Shimmield, Grahamm A1 - Solan, Martin A1 - Soltwedel, Thomas A1 - Spagnoli, Federico A1 - Witte, Ursula T1 - Coastal Ocean Benthic Observatories (COBO) : integrated tools for the in situ observation and study of benthic ecosystem biogeochemical processes Y1 - 2005 ER - TY - THES A1 - Appajaiah, Anilkumar T1 - Climatic stability of polymer optical fibers (POF) N2 - Optische Polymerfasern stellen ein relativ neues Medium zur Hochgeschwindigkeitsdatenübertragung mittels moduliertem Licht dar. Sie gestatten die Verbreitung großer Datenmengen über Entfernungen bis zu ca. 100 m, ohne eine Beeinflussung durch externe elektromagnetischen Feldern. Jedoch reagieren die Fasern und somit auch ihre optischen Eigenschaften aufgrund des organischchemischen Faseraufbaus empfindlich auf das Klima ihrer Umgebung. Die Ursachen für die Abnahme der optischen Transmission aufgrund von klimatischen Einflüssen (Alterung, Degradation) werden mittels chemisch analytischer Verfahren wie Chemilumineszenz (CL) und Fourier Transform Infrarot (FTIR) Spektroskopie untersucht. Dabei kommen fünf, von verschiedenen Herstellern bezogene, Multimode- POFs aus PMMA in sieben verschiedenen Klimaten zum Einsatz. Drei dieser fünf POFs werden genauer untersucht, um den Einfluss einzelner Parameter festzustellen und optische Langzeitstabilität aufgrund von Kurzzeittests vorherzusagen. Als erstes erfolgt eine Kennzeichnung unbeanspruchter POF Komponenten (Kern, Mantel und nackte POF als Kombination von Kern und Mantel) über ihre physikalischen und chemischen Eigenschaften. Die Glas- und die Schmelztemperaturen liegen im Bereich von 120 °C bis 140 °C, das Molekulargewicht des Kerns bei größenordnungsmäßig 105 g mol-1 ;. FTIR-Messungen zeigen zwar Unterschiede in der chemischen Zusammensetzung der Mäntel aber keine Unterschiede bei den Kernen. Bei zwei der POF Proben , die als Kabel (Kern, Mantel und Schutzhülle) für 3300 Stunden einem Klima aus 92 °C und 95 % relativer Feuchte (r.F.) ausgesetzt waren, verringern sich daraufhin die optische Transmissionen in unterschiedlicher Weise. Die Untersuchung der zugehörigen nackten POFs mittels CL, FTIR, Thermogravimetrie (TG), UV/VIS und Gel Permeation Chromatographie (GPC) lässt eine stärkere Schädigung der Mäntel als der Kerne vermuten. Wahrscheinlich führt eine starke Manteldegradation zu einer erhöhten Absorption und Fehlstellen im Mantel und damit zu einer Transmissionsabnahme. Daher scheint die optische Stabilität der POF stärker durch die thermo-oxidative Stabilität des Mantels bestimmt zu sein als durch die des Kernes. Drei nackte POFs (Kern und Mantel) sind unterschiedlich lang (30 Stunden bis 3000 Stunden) folgenden Klimaten ausgesetzt: 92 °C / 95 % r.F., 92 °C / 50 % r.F., 50 °C / 95 % r.F., 90 °C / geringe Feuchte, 100 °C / geringe Feuchte, 110 °C / geringe Feuchte and 120 °C / geringe Feuchte. Auch in diesen Klimaten ergaben sich probenbedingte unterschiedliche Transmissionsänderungen. Die Ergebnisse deuten stark darauf hin, dass bei gleichzeitig hoher Temperatur und hoher Feuchte physikalische Änderungen wie die Volumenausdehnung die Hauptursachen für die Abnahme der optischen Transmission bilden. Ein weiterer Einflussfaktor ist die chemische Zusammensetzung der Mäntel. Bei Kombination von hoher Temperatur und geringer Feuchte erzeugen in den Anfangsstadien der Alterung physikalische Änderungen Transmissionsabnahmen, vermutlich entstehen Fehlstellen in der Kern-Mantel-Grenzschicht. Hinzukommen in den späteren Stadien wahrscheinlich zunehmende Lichtabsorption in Kern und Mantel. L. Jankowski (Doktorand in der BAM) bestätigt diese Annahme durch parallel ausgeführte optische Simulationsrechnungen. Auch für nackte POFs scheint also die thermo-oxidative Stabilität die optische Stabilität zu bestimmen. Kurzzeitalterungstests sollen Aufschluss über den Einfluss individueller Klimaparameter auf die POF Eigenschaften geben. Es zeigt sich bei dauerhaft hoher Temperatur und variabler Feuchte aufgrund des physikalisch absorbierten Wassers bis zu einem gewissen Grad ein reversibles Verhalten des Transmissionsverlustes. Dieses Verhalten tritt aber nur kaum merkbar auf, wenn bei konstanter hoher Feuchte die Temperatur variiert wird. Bei Raumtemperatur und variabler Feuchte stellt sich jedoch ein voll reversibles Verhalten des Transmissionsverlustes ein. Die hier beschriebenen Untersuchungen sind als Ausgangspunkt für weitergehende Forschungen zu verstehen. Die begrenzte Zurverfügungstellung von POF Basisdaten durch die Hersteller und der zeitaufwendige klimabedingte Alterungsprozess beschränken die Ergebnisse mehr oder weniger auf die untersuchten Proben. Signifikante allgemeine Aussagen erfordern aber beispielsweise zusätzliche statistische Daten der Produktionsschwankungen von POF Eigenschaften. Dennoch besitzen die hier beschriebenen Tests das Potential für eine Annäherung an die optische Langzeitstabilität und deren Vorhersage. N2 - Polymer optical fibers (POFs) are a rather new tool for high-speed data transfer by modulated light. They allow the transport of high amounts of data over distances up to about 100 m without be influenced by external electromagnetic fields. Due to organic chemical nature of POFs, they are sensitive to the climate of their environment and therefore the optical fiber properties are as well. Hence, the optical stability is a key issue for long-term applications of POFs. The causes for a loss of optical transmission due to climatic exposures (aging/degradation) are researched by means of chemical analytical tools such as chemiluminescence (CL) and Fourier transform infrared (FTIR) spectroscopy for five different (with respect to manufacturers) step-index multimode PMMA based POFs and for seven different climatic conditions. Three of the five POF samples are studied more in detail to realize the effects of individual parameters and for forecasting longterm optical stability by short-term exposure tests. At first, the unexposed POF components (core, cladding, and bare POF as combination of core and cladding) are characterized with respect to important physical and chemical properties. The glass transition temperature Tg, and the melting temperature Tm are in the region of 120 °C to 140 °C, the molecular weight (Mw) of cores is in the order of 105 g mol-1. POFs are found to have different chemical compositions of their claddings as could be detected by FTIR, but identical compositions of their cores. Two of the POFs are exposed as cables (core, cladding and jacket) for about 3300 hours to the climate 92 °C / 95 % relative humidity (RH) resulting in a different transmission decrease. Investigating the related unexposed and exposed bare POFs for degradation using CL, FTIR, thermogravimetry (TG), UV/visible transmittance and gel permeation chromatography (GPC) suggest that claddings of POFs are more affected than cores. Probably the observed loss of transmission is mainly due to increased light absorption and imperfections at the core-cladding boundary caused by a large degradation of claddings. Hence, it is highly possible that the optical transmission stability of POFs is governed mainly by the thermo-oxidative stability of the cladding and minor of the core. Three bare POFs (core and cladding only) are exposed for different duration of exposure time (30 hours to 4500 hours) to 92 °C / 95 %RH, 92 °C / 50 %RH, 50 °C / 95 %RH, 90 °C / low humidity, 100 °C / low humidity, 110 °C / low humidity and 120 °C / low humidity. In these climates their transmission variations are found to be different from each other, too. The outcomes strongly inform that under high temperature and high humid climates physical changes such as volume expansion, are the main sources for the loss of optical transmission. Also, the optical transmission stability of POFs is found to be dependent on chemical compositions of claddings. Under high temperature and low humid conditions, a loss of transmission at the early stages of the exposure is mainly caused by physical changes, presumable by corecladding interface imperfections. For the later stages of exposures it is proposed to an additional increase of light absorption by core and cladding owes to degradation. Optical simulation results obtained parallel by Mr. L. Jankowski (a PhD student of BAM) are found to confirm these results. For bare POFs, too, the optical stability of POFs seems to depend on their thermo-oxidative stability. Some short-term exposure tests are conducted to realize influences of individual climatic parameters on the transmission property of POFs. It is found that at stationary high temperature and variable humidity conditions POFs display to a certain amount a reversible transmission loss due to physically absorbed water. But in the case of varying temperature and constant high humidity such reversibility is hardly noticeable. However, at room temperature and varying humidity, POFs display fully reversible transmission loss. The whole research described above has to be regarded as a starting point for further investigations. The restricted distribution of fundamental POF data by the manufacturers and the time consuming aging by climatic exposures restrict the results more or less to the samples, investigated here. Significant general statements require for example additional information concerning the variation of POF properties due to production. Nevertheless the tests, described here, have the capability for approximating and forecasting the long-term optical transmission stability of POFs. -------------- Auch im Druck erschienen: Appajaiah, Anilkumar: Climatic stability of polymer optical fibers (POF) / Anilkumar Appajaiah. - Bremerhaven : Wirtschaftsverl. NW, Verl. für neue Wiss., 2005. - Getr. Zählung [ca. 175 S.]. : Ill., graph. Darst. - (BAM-Dissertationsreihe ; 9) ISBN 3-86509-302-7 T2 - Climatic stability of polymer optical fibers (POF) KW - POF; Reliabilität; Abbau; Chemilumineszenz KW - POF; reliability; degradation; chemiluminescence Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-0001661 ER - TY - JOUR A1 - Aravopoulou, Dionysia A1 - Kyriakos, Konstantinos A1 - Miasnikova, Anna A1 - Laschewsky, Andre A1 - Papadakis, Christine M. A1 - Kyritsis, Apostolos T1 - Comparative Investigation of the Thermoresponsive Behavior of Two Diblock Copolymers Comprising PNIPAM and PMDEGA Blocks JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - The thermoresponsive behavior of two diblock copolymers PS-b-PNIPAM and PS-b-PMDEGA, which both comprise a hydrophobic polystyrene (PS) block but different thermoresponsive blocks, also differing in length, poly(N-isopropylacrylamide) (PNIPAM) and poly(methoxy diethylene glycol acrylate) (PMDEGA), respectively, was comparatively investigated in a wide temperature range. Concentrated aqueous solutions containing 25 wt % polymer were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and broadband dielectric spectroscopy (BDS). DSC measurements show that, during the demixing phase transition, the hydration number per oligo(ethylene glycol) side chain in the PS-b-PMDEGA solution decreases rather gradually, even up to 20 °C above the onset of the transition, i.e., the cloud point (CP). In contrast, the PS-b-PNIPAM solution exhibits an abrupt, stepwise dehydration behavior at its CP, indicated by the sharp, narrow endothermic peak. BDS measurements suggest that the organization of the expelled water during the phase transition and the subsequent evolution of the micellar aggregates are different for the two copolymers. In the PS-b-PMDEGA solution, the long-range charge transport process changes significantly at its CP and strong interfacial polarization processes appear, probably due to charge accumulation at the interfaces between the micellar aggregates and the aqueous medium. On the contrary, in the PS-b-PNIPAM solution, the phase transition has only a marginal effect on the long-range conduction process and is accompanied by a reduction in the high-frequency (1 MHz) dielectric permittivity, ε′. The latter effect is attributed to the reduced polarization strength of local chain modes due to an enhancement of intra- and interchain hydrogen bonds (HBs) in the polymer-rich phase during the water detaching process. Surprisingly, our BDS measurements indicate that prior to both the demixing and remixing processes the local chain mobility increases temporally. Our dielectric studies suggest that for PS-b-PNIPAM the water detaching process initiates a few degrees below CP and that the local chain mobility and intra- and/or interchain HBs of the PNIPAM blocks may control its thermoresponsive behavior. Dielectric “jump” experiments show that the kinetics of micellar aggregation in the PS-b-PMDEGA solution is slower than that in the PS-b-PNIPAM solution and is independent of the target temperature within the two-phase region. From the experimental point of view, it is shown that the dielectric susceptibility, especially, the dielectric permittivity, ε′, is a well-suited probe for monitoring both the reversible changes in the molecular dipolar bond polarizability and the long-range interfacial polarization at the phase transition. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcb.7b09647 SN - 1520-6106 VL - 122 IS - 9 SP - 2655 EP - 2668 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Arias, Hugo R. A1 - Feuerbach, Dominik A1 - Schmidt, Bernd A1 - Heydenreich, Matthias A1 - Paz, Cristian A1 - Ortells, Marcelo O. T1 - Drimane Sesquiterpenoids Noncompetitively Inhibit Human alpha 4 beta 2 Nicotinic Acetylcholine Receptors with Higher Potency Compared to Human alpha 3 beta 4 and alpha 7 Subtypes JF - Journal of natural products N2 - The drimane sesquiterpenoids drimenin, cinnamolide, dendocarbin A, and polygodial were purified from the Canelo tree (Drimys winteri) and chemically characterized by spectroscopic methods. The pharmacological activity of these natural compounds were determined on hα4β2, hα3β4, and hα7 nicotinic acetylcholine receptors (AChRs) by Ca2+ influx measurements. The results established that drimane sesquiterpenoids inhibit AChRs with the following selectivity: hα4β2 > hα3β4 > hα7. In the case of hα4β2 AChRs, the following potency rank order was determined (IC50’s in μM): drimenin (0.97 ± 0.35) > cinnamolide (1.57 ± 0.36) > polygodial (62.5 ± 19.9) ≫ dendocarbin A (no activity). To determine putative structural features underlying the differences in inhibitory potency at hα4β2 AChRs, additional structure–activity relationship and molecular docking experiments were performed. The Ca2+ influx and structural results supported a noncompetitive mechanism of inhibition, where drimenin interacted with luminal and nonluminal (TMD-β2 intrasubunit) sites. The structure–activity relationship results, i.e., the lower the ligand polarity, the higher the inhibitory potency, supported the nonluminal interaction. Ligand binding to both sites might inhibit the hα4β2 AChR by a cooperative mechanism, as shown experimentally (nH > 1). Drimenin could be used as a molecular scaffold for the development of more potent inhibitors with higher selectivity for the hα4β2 AChR. Y1 - 2018 U6 - https://doi.org/10.1021/acs.jnatprod.7b00893 SN - 0163-3864 SN - 1520-6025 VL - 81 IS - 4 SP - 811 EP - 817 PB - American Chemical Society CY - Washington ER - TY - CHAP A1 - Arlt, Olga A1 - Schwiebs, Anja A1 - Pfarr, Kathrin A1 - Ranglack, Annika A1 - Bouzas, Ferreiros Nerea A1 - Schreiber, Yannick A1 - Neuber, Corinna A1 - Kleuser, Burkhard A1 - Pfeilschifter, Josef M. A1 - Radeke, Heinfried H. T1 - Dynamic interaction between sphingolipid enzymes, S1P and inflammatory cytokine regulation in dendritic cells T2 - NAUNYN-SCHMIEDEBERGS ARCHIVES OF PHARMACOLOGY Y1 - 2014 SN - 0028-1298 SN - 1432-1912 VL - 387 SP - S91 EP - S91 PB - Springer CY - New York ER - TY - JOUR A1 - Armin, Ardalan A1 - Durrant, James R. A1 - Shoaee, Safa T1 - Interplay Between Triplet-, Singlet-Charge Transfer States and Free Charge Carriers Defining Bimolecular Recombination Rate Constant of Organic Solar Cells JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Despite the myriad of organic donor:acceptor materials, only few systems have emerged in the life of organic solar cells to, exhibit considerable reduced bimolecular recombination, with respect to the random encounter rate given by the Langevin equation. Monte Carlo simulations have revealed that the rate constant of the formation of electron-hole bound states depends on the random encounter of opposite charges and is nearly given by the Langevin equation for the domain sizes relevant to efficient bulk heterojunction systems. Recently, three studies :suggested that charge transfer states dissociating much faster than their decay rate to the ground state, can result in reduced bimolecular recombination by lowering the recombination rate to the ground state as a loss pathway. A separate study identified another loss pathway and suggested that forbidden back electron transfer from triplet charge transfer states to triplet excitons is a key to achieving reduced recombination. Herein we further explain the reduced bimolecular recombination by investigating the limitations of these two proposals. By solving kinetic rate equations for a BHJ system with realistic rates, we show that both of these previously presented conditions must only be held at the same time fora system to exhibit non-Langevin behavior. We demonstrate that suppression of both of the parallel loss channels of singlet and triplet states can be achieved through increasing the dissociation rate of the charge transfer states; a crucial requirement to achieve a high charge carrier extraction efficiency. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpcc.7b04825 SN - 1932-7447 VL - 121 SP - 13969 EP - 13976 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Arotcarena, Michel A1 - Heise, Bettina A1 - Ishaya, Sultana A1 - Laschewsky, André T1 - Switching the inside and the outside of aggregates of water-soluble block copolymers with double thermoresponsivity N2 - Water-soluble block copolymers were prepared from the non-ionic monomer N-isopropylacrylamide (NIPA) and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]-ammonio propane sulfonate (SPP) by sequential free radical polymerization via the RAFT process. Such block copolymers with two hydrophilic blocks exhibit double thermo- responsive behavior in water: the poly-NIPA block shows a lower critical solution temperature, whereas the poly-SPP block exhibits an upper critical solution temperature. Appropriate design of the block lengths leads to block copolymers which stay in solution in the full temperature range between 0°C and 100°C. Both blocks of these polymers dissolve in water at intermediate temperatures, whereas at high temperatures, the poly-NIPA block forms colloidal hydrophobic associates that are kept in solution by the poly-SPP block, and at low temperatures, the poly-SPP block forms colloidal polar aggregates that are kept in solution by the poly-NIPA block. In this way, colloidal aggregates can be prepared in water which switch reversibly, and without any additive, their "inside" to the "outside", and vice versa. The aggregates provide microdomains and surfaces of different character, which can be controlled by a simple thermal stimulus. Y1 - 2002 ER - TY - JOUR A1 - Arys, Xavier A1 - Fischer, Peter A1 - Jonas, Alain M. A1 - Koetse, Marc M. A1 - Legras, Roger A1 - Laschewsky, André A1 - Wischerhoff, Erik T1 - Ordered polyelectrolyte multilayers : rules governing layering in organic binary multilayers Y1 - 2003 ER - TY - THES A1 - Asfaw, Mesfin T1 - Adhesion of multi-component membbranes and strings Y1 - 2005 CY - Potsdam ER - TY - THES A1 - Ast, Cindy T1 - Design and photophysical characterization of single fluorophore-based ammonium sensors Y1 - 2013 CY - Potsdam ER - TY - JOUR A1 - Ast, Cindy A1 - Schmälzlin, Elmar A1 - Löhmannsröben, Hans-Gerd A1 - van Dongen, Joost T. T1 - Optical oxygen micro- and nanosensors for plant applications JF - Sensors N2 - Pioneered by Clark's microelectrode more than half a century ago, there has been substantial interest in developing new, miniaturized optical methods to detect molecular oxygen inside cells. While extensively used for animal tissue measurements, applications of intracellular optical oxygen biosensors are still scarce in plant science. A critical aspect is the strong autofluorescence of the green plant tissue that interferes with optical signals of commonly used oxygen probes. A recently developed dual-frequency phase modulation technique can overcome this limitation, offering new perspectives for plant research. This review gives an overview on the latest optical sensing techniques and methods based on phosphorescence quenching in diverse tissues and discusses the potential pitfalls for applications in plants. The most promising oxygen sensitive probes are reviewed plus different oxygen sensing structures ranging from micro-optodes to soluble nanoparticles. Moreover, the applicability of using heterologously expressed oxygen binding proteins and fluorescent proteins to determine changes in the cellular oxygen concentration are discussed as potential non-invasive cellular oxygen reporters. KW - oxygen sensor KW - biosensors KW - microsensors KW - nanosensors KW - endogenous sensor proteins KW - dual-frequency phase-modulation KW - phosphorescence quenching KW - plant science Y1 - 2012 U6 - https://doi.org/10.3390/s120607015 SN - 1424-8220 VL - 12 IS - 6 SP - 7015 EP - 7032 PB - MDPI CY - Basel ER - TY - THES A1 - Ast, Sandra T1 - Integration of the 1,2,3-Triazole "Click" motif as a potent signalling element into metal ion responsive fluorescent probes for physiological cations Y1 - 2012 CY - Potsdam ER - TY - JOUR A1 - Ast, Sandra A1 - Fischer, Tobias A1 - Müller, Holger A1 - Mickler, Wulfhard A1 - Schwichtenberg, Mathias A1 - Rurack, Knut A1 - Holdt, Hans-Jürgen T1 - Integration of the 1,2,3-Triazole "Click" Motif as a potent signalling element in metal ion responsive fluorescent probes JF - Chemistry - a European journal N2 - In a systematic approach we synthesized a new series of fluorescent probes incorporating donoracceptor (D-A) substituted 1,2,3-triazoles as conjugative -linkers between the alkali metal ion receptor N-phenylaza-[18]crown-6 and different fluorophoric groups with different electron-acceptor properties (4-naphthalimide, meso-phenyl-BODIPY and 9-anthracene) and investigated their performance in organic and aqueous environments (physiological conditions). In the charge-transfer (CT) type probes 1, 2 and 7, the fluorescence is almost completely quenched by intramolecular CT (ICT) processes involving charge-separated states. In the presence of Na+ and K+ ICT is interrupted, which resulted in a lighting-up of the fluorescence in acetonitrile. Among the investigated fluoroionophores, compound 7, which contains a 9-anthracenyl moiety as the electron-accepting fluorophore, is the only probe which retains light-up features in water and works as a highly K+/Na+-selective probe under simulated physiological conditions. Virtually decoupled BODIPY-based 6 and photoinduced electron transfer (PET) type probes 35, where the 10-substituted anthracen-9-yl fluorophores are connected to the 1,2,3-triazole through a methylene spacer, show strong ion-induced fluorescence enhancement in acetonitrile, but not under physiological conditions. Electrochemical studies and theoretical calculations were used to assess and support the underlying mechanisms for the new ICT and PET 1,2,3-triazole fluoroionophores. KW - charge transfer KW - click chemistry KW - electron transfer KW - fluorescent probes KW - metal ions Y1 - 2013 U6 - https://doi.org/10.1002/chem.201201575 SN - 0947-6539 VL - 19 IS - 9 SP - 2990 EP - 3005 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Ast, Sandra A1 - Rutledge, Peter J. A1 - Todd, Matthew H. T1 - Reversing the triazole topology in a cyclam-triazole-dye ligand gives a 10-fold brighter signal response to Zn2+ in aqueous solution JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - The fluorescence response of a set of cyclam-triazole-dye ligands is controlled by the appended dye, but simple reversal of the triazole topology affords a novel probe for Zn2+ with a longer fluorescence lifetime and higher fluorescence quantum yield upon Zn2+ binding ( = 2.0 ns, Phi(f) = 0.76). KW - Sensors KW - Zinc KW - Click chemistry KW - Fluorescence KW - Electrochemistry Y1 - 2012 U6 - https://doi.org/10.1002/ejic.201201072 SN - 1434-1948 IS - 34 SP - 5611 EP - 5615 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Ast, Sandra A1 - Schwarze, Thomas A1 - Müller, Holger A1 - Sukhanov, Aleksey A1 - Michaelis, Stefanie A1 - Wegener, Joachim A1 - Wolfbeis, Otto S. A1 - Körzdörfer, Thomas A1 - Dürkop, Axel A1 - Holdt, Hans-Jürgen T1 - A highly K+-Selective Phenylaza-[18]crown-6-Lariat-Ether-Based Fluoroionophore and its application in the sensing of K+ Ions with an optical sensor film and in cells JF - Chemistry - a European journal N2 - Herein, we report the synthesis of two phenylaza-[18]crown-6 lariat ethers with a coumarin fluorophore (1 and 2) and we reveal that compound 1 is an excellent probe for K+ ions under simulated physiological conditions. The presence of a 2-methoxyethoxy lariat group at the ortho position of the anilino moiety is crucial to the substantially increased stability of compounds 1 and 2 over their lariat-free phenylaza-[18] crown-6 ether analogues. Probe 1 shows a high K+/Na+ selectivity and a 2.5-fold fluorescence enhancement was observed in the presence of 100 mm K+ ions. A fluorescent membrane sensor, which was prepared by incorporating probe 1 into a hydrogel, showed a fully reversible response, a response time of 150 s, and a signal change of 7.8% per 1 mm K+ within the range 1-10 mm K+. The membrane was easily fabricated (only a single sensing layer on a solid polyester support), yet no leaching was observed. Moreover, compound 1 rapidly permeated into cells, was cytocompatible, and was suitable for the fluorescent imaging of K+ ions on both the extracellular and intracellular levels. KW - crown compounds KW - fluorescence KW - gels KW - potassium KW - sensors Y1 - 2013 U6 - https://doi.org/10.1002/chem.201302350 SN - 0947-6539 SN - 1521-3765 VL - 19 IS - 44 SP - 14911 EP - 14917 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Atilaw, Yoseph A1 - Duffy, Sandra A1 - Heydenreich, Matthias A1 - Muiva-Mutisya, Lois A1 - Avery, Vicky M. A1 - Erdelyi, Mate A1 - Yenesew, Abiy T1 - Three Chalconoids and a Pterocarpene from the Roots of Tephrosia aequilata JF - Molecules N2 - In our search for new antiplasmodial agents, the CH2Cl2/CH3OH (1:1) extract of the roots of Tephrosia aequilata was investigated, and observed to cause 100% mortality of the chloroquine-sensitive (3D7) strain of Plasmodium falciparum at a 10 mg/mL concentration. From this extract three new chalconoids, E-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (1, aequichalcone A), Z-2,6-dimethoxy-3,4-(2,2-dimethyl)pyranoretrochalcone (2, aequichalcone B), 4-ethoxy-3-hydroxypraecansone B (3, aequichalcone C) and a new pterocarpene, 3,4:8,9-dimethylenedioxy-6a,11a-pterocarpene (4), along with seven known compounds were isolated. The purified compounds were characterized by NMR spectroscopic and mass spectrometric analyses. Compound 1 slowly converts into 2 in solution, and thus the latter may have been enriched, or formed, during the extraction and separation process. The isomeric compounds 1 and 2 were both observed in the crude extract. Some of the isolated constituents showed good to moderate antiplasmodial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum. KW - Tephrosia aequilata KW - chalcone KW - retrochalcone KW - aequichalcone A KW - aequichalcone B KW - aequichalcone C KW - pterocarpene KW - antiplasmodial Y1 - 2017 U6 - https://doi.org/10.3390/molecules22020318 SN - 1420-3049 VL - 22 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Atilaw, Yoseph A1 - Heydenreich, Matthias A1 - Ndakala, Albert A1 - Akala, Hoseah M. A1 - Kamau, Edwin A1 - Yenesew, Abiy T1 - 3-Oxo-14 alpha, 15 alpha-epoxyschizozygine: A new schizozygane indoline alkaloid from Schizozygia coffaeoides JF - Phytochemistry letters N2 - The stem bark extract of Schizozygia coffaeoides (Apocynaceae) showed moderate antiplasmodial activity (IC50 = 8-12 mu g/mL) against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the isolation of a new schizozygane indoline alkaloid, named 3-oxo-14 alpha, 15 alpha-epoxyschizozygine. In addition, two dimeric anthraquinones, cassiamin A and cassiamin B, were identified for the first time in the family Apocynaceae. The structures of the isolated compounds were deduced on the basis of spectroscopic evidence. The schizozygane indole alkaloids showed good to moderate antiplasmodial activities (IC50 = 13-52 mu m). (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. KW - Schizozygia coffaeoides KW - Schizozygane indoline alkaloid KW - 3-Oxo-14 alpha, 15 alpha-epoxyschizozygine KW - Dimeric anthraquinone KW - Cassiamin A KW - Cassiamin B Y1 - 2014 U6 - https://doi.org/10.1016/j.phytol.2014.07.003 SN - 1874-3900 SN - 1876-7486 VL - 10 SP - 28 EP - 31 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Attenberger, Bianca A1 - Moussa, Mehdi El Sayed A1 - Brietzke, Thomas Martin A1 - Vreshch, Volodimir A1 - Holdt, Hans-Jürgen A1 - Lescop, Christophe A1 - Scheer, Manfred T1 - Discrete Polymetallic Arrangements of Ag-I and Cu-I Ions Based on Multiple Bridging Phosphane Ligands and pi-pi Interactions JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - A simple and straightforward approach to new polymetallic Ag-I and Cu-I supramolecules is presented. The reaction of N,P,N,P,N ligand 2 with Ag-I ions affords a trimetallic complex bearing a triangular Ag-3 core; metallophilic interactions are stabilized by ligands that display a multiple bridging coordination mode as 10-electron donors. Heteroleptic polymetallic Ag-I and Cu-I complexes based on ligand 2 and the 1,12-diazaperylene (dape) ligand are obtained by an alternative molecular organization of the polymetallic arrays compared to that in homoleptic complexes of ligand 2. KW - Heterocycles KW - N KW - P ligands KW - Pi interactions KW - Polyaromatic fragments KW - Supramolecular chemistry Y1 - 2015 U6 - https://doi.org/10.1002/ejic.201500445 SN - 1434-1948 SN - 1099-0682 IS - 18 SP - 2934 EP - 2938 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Awad, Duha Jawad A1 - Conrad, Franziska A1 - Koch, Andreas A1 - Schilde, Uwe A1 - Poeppl, Andreas A1 - Strauch, Peter T1 - 1,10-phenanthroline-dithiolate mixed ligand transition metal complexes : synthesis, characterization and EPR spectroscopy N2 - A series of new N2S2 mixed ligand transition metal complexes, where N-2 is phenanthroline and S-2 is 1,2- dithiooxalate (dto) or 1,2-dithiosquarate (dtsq), has been synthesized and characterized. IR spectra reveal that the 1,2- dithiolate ligands are coordinated via the sulfur atoms forming a N2S2 coordination sphere. The copper(II) complex [Cu(phen)(dto)] was studied by EPR spectroscopy as a diamagnetically diluted powder. The diamagnetic dilution resulted from doping of the copper complex into the isostructural host lattice of the nickel complex [Ni(phen)(dto)]. The electronic situation in the frontier orbitals of the copper complex calculated from the experimental data is compared to the results of EHT and DFT calculations. Furthermore, one side product, chlorobis(1,10-phenanthroline)copper(I) ethanol solvate hydrate [(phen)(2)CuCl]center dot C2H5OH center dot H2O, was formed by a reduction process and characterized by X-ray diffraction. In the crystal packing one-dimensional columns of dimers are formed, stabilized by significant pi-pi interactions. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00201693 U6 - https://doi.org/10.1016/j.ica.2010.01.021 SN - 0020-1693 ER - TY - JOUR A1 - Awad, Duha Jawad A1 - Koch, Andreas A1 - Mickler, Wulfhard A1 - Schilde, Uwe A1 - Strauch, Peter T1 - EPR spectroscopy of 4, 4 '-Bis(tert-butyl)-2, 2 '-bipyridine-1, 2-dithiolatocuprates(II) in host lattices with different coordination geometries JF - Zeitschrift für anorganische und allgemeine Chemie N2 - A series of new heteroleptic MN2S2 transition metal complexes with M = Cu2+ for EPR measurements and as diamagnetic hosts Ni2+, Zn2+, and Pd2+ were synthesized and characterized. The ligands are N2 = 4, 4'-bis(tert-butyl)-2, 2'-bipyridine (tBu2bpy) and S2 =1, 2-dithiooxalate, (dto), 1, 2-dithiosquarate, (dtsq), maleonitrile-1, 2-dithiolate, or 1, 2-dicyanoethene-1, 2-dithiolate, (mnt). The CuII complexes were studied by EPR in solution and as powders, diamagnetically diluted in the isostructural planar [NiII(tBu2bpy)(S2)] or[PdII(tBu2bpy)(S2)] as well as in tetrahedrally coordinated[ZnII(tBu2bpy)(S2)] host structures to put steric stress on the coordination geometry of the central CuN2S2 unit. The spin density contributions for different geometries calculated from experimental parameters are compared with the electronic situation in the frontier orbital, namely in the semi-occupied molecular orbital (SOMO) of the copper complex, derived from quantum chemical calculations on different levels (EHT and DFT). One of the hosts, [NiII(tBu2bpy)(mnt)], is characterized by X-ray structure analysis to prove the coordination geometry. The complex crystallizes in a square-planar coordination mode in the monoclinic space group P21/a with Z = 4 and the unit cell parameters a = 10.4508(10) angstrom, b = 18.266(2) angstrom, c = 12.6566(12) angstrom, beta = 112.095(7)degrees. Oxidation and reductions potentials of one of the host complexes, [Ni(tBu2bpy)(mnt)], were obtained by cyclovoltammetric measurements. KW - 1 KW - 2-Dithiosquarate KW - 1 KW - 2-Dithiooxalate KW - 1 KW - 2-Dicyanoethene-1 KW - 2-dithiolate KW - 4 KW - 4'-Bis(tert-butyl)-2 KW - 2'-bipyridine KW - X-ray structure KW - EPR KW - Copper KW - Nickel KW - Zinc Y1 - 2012 U6 - https://doi.org/10.1002/zaac.201100517 SN - 0044-2313 VL - 638 IS - 6 SP - 965 EP - 975 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Awad, Duha Jawad A1 - Schilde, Uwe A1 - Strauch, Peter T1 - 4,4 '-Bis(tert-butyl)-2,2 '-bipyridinedichlorometal(II) - Synthesis, structure and EPR spectroscopy JF - Inorganica chimica acta : the international inorganic chemistry journal N2 - Due to the better solubility of the 4,4'-substituted bipyridine ligand a series of 4,4'0-bis(tert-butyl)-2,2'-bipyridinedichlorometal(II) complexes, [M(tbbpy)Cl(2)], with M = Cu, Ni, Zn, Pd, Pt was synthesised and characterised. The blue copper complex 4,4'-bis(tert-butyl)-2,2'-bipyridinedichlorocopper(II) was isolated in two different polymorphic forms, as prisms 1 with a solvent inclusion and solvent-free as needles 2. Both structures were determined by X-ray structure analysis. They crystallise in the monoclinic space group P2(1)/c with four molecules in the unit cell, but with different unit cells and packing motifs. Whereas in the prisms 1, with the unit cell parameters a = 12.1613(12), b = 10.6363(7), c = 16.3074(15) angstrom, eta = 94.446(8)degrees, the packing is dominated by intra-and intermolecular hydrogen bonds, in the needles 2, with a = 7.738(1), b = 18. 333(2), c = 13.291(3) angstrom, beta = 97.512(15)degrees, only intramolecular hydrogen bonds appear and the complex molecules are arranged in columns which are stabilised by p-p-stacking interactions. In both complexes the copper has a tetrahedrally distorted coordination sphere. These copper complexes were also studied by EPR spectroscopy in solution, as frozen glass and diamagnetically diluted powder with the analogue [Pd(tbbpy)Cl(2)] as host lattice. KW - 4,4 '-Bis(tert-butyl)-2,2 '-bipyridine KW - X-ray structure KW - EPR KW - Copper(II) KW - Transition metals Y1 - 2011 U6 - https://doi.org/10.1016/j.ica.2010.08.035 SN - 0020-1693 VL - 365 IS - 1 SP - 127 EP - 132 PB - Elsevier CY - Lausanne ER - TY - THES A1 - Award, Duhan Jawad T1 - Mixed 1,2-Dümine-1,2-Dithiolate Ligand Complexes : Structure, Proberties and EPR Spectroscopy Y1 - 2009 CY - Potsdam ER - TY - JOUR A1 - Awasthi, Neha A1 - Ritschel, Thomas A1 - Lipowsky, Reinhard A1 - Knecht, Volker T1 - Standard gibbs energies of formation and equilibrium constants from ab-initio calculations covalent dimerization of NO2 and synthesis of NH3 JF - The journal of chemical thermodynamics N2 - Standard quantum chemical methods are used for accurate calculation of thermochemical properties such as enthalpies of formation, entropies and Gibbs energies of formation. Equilibrium reactions are widely investigated and experimental measurements often lead to a range of reaction Gibbs energies and equilibrium constants. It is useful to calculate these equilibrium properties from quantum chemical methods in order to address the experimental differences. Furthermore, most standard calculation methods differ in accuracy and feasibility of the system size. Hence, asystematic comparison of equilibrium properties calculated with different numerical algorithms would provide a useful reference. We select two well-known gas phase equilibrium reactions with small molecules: covalent dimer formation of NO2 (2NO(2) reversible arrow N2O4) and the synthesis of NH3 (N-2 + 3 H-2 reversible arrow 2NH(3)). We test four quantum chemical methods denoted by G3B3, CBS-APNO, W1 and CCSD(T) with aug-cc-pVXZ basis sets (X = 2, 3, and 4), to obtain thermochemical data for NO2, N2O4, and NH3. The calculated standard formation Gibbs energies Delta(f)G degrees are used to calculate standard reaction Gibbs energies Delta(r)G degrees and standard equilibrium constants K-eq for the two reactions. Standard formation enthalpies Delta H-f degrees are calculated in a more reliable way using high-level methods such as W1 and CCSD(T). Standard entropies S degrees for the molecules are calculated well within the range of experiments for all methods, however, the values of standard formation Gibbs energies Delta(f)G degrees show some dependence on the choice of the method. High-level methods perform better for the calculation of molecular energies, however, simpler methods such as G3B3 and CBS-APNO perform quite well in the calculation of total reaction energies and equilibrium constants, provided that the chemical species involved do not exhibit molecular geometries that are difficult to handle by the applied method. The temperature dependence of standard reaction Gibbs energy Delta(r)G degrees for the NH3 reaction is discussed by using the calculated standard formation Gibbs energies Delta(f)G degrees of the reaction species at 298.15 K. The corresponding equilibrium constant K-eq as a function of temperature is found to be close to experimental values. KW - Equilibrium constants KW - Thermochemical properties KW - Ab-initio calculations Y1 - 2013 U6 - https://doi.org/10.1016/j.jct.2013.03.011 SN - 0021-9614 VL - 62 IS - 3 SP - 211 EP - 221 PB - Elsevier CY - London ER - TY - JOUR A1 - Ayi, Ayi A. A1 - Khare, Varsha A1 - Strauch, Peter A1 - Girard, Jèrôme A1 - Fromm, Katharina M. A1 - Taubert, Andreas T1 - On the chemical synthesis of titanium nanoparticles from ionic liquids N2 - We report on attempts towards the synthesis of titanium nanoparticles using a wet chemical approach in imidazolium-based ionic liquids (ILs) under reducing conditions. Transmission electron microscopy finds nanoparticles in all cases. UV/Vis spectroscopy confirms the nanoparticulate nature of the precipitate, as in all cases an absorption band between ca. 280 and 300 nm is visible. IR spectroscopy shows that even after extensive washing and drying, some IL remains adsorbed on the nanoparticles. Raman spectroscopy suggests the formation of anatase nanoparticles, but X-ray diffraction reveals that, possibly, amorphous titania forms or that the nanoparticles are so small that a clear structure assignment is not possible. The report thus shows that (possibly amorphous) titanium oxides even form under reducing conditions and that the chemical synthesis of titanium nanoparticles in ILs remains elusive. Y1 - 2010 UR - http://www.springerlink.com/content/101572 U6 - https://doi.org/10.1007/s00706-010-0403-4 SN - 0026-9247 ER - TY - THES A1 - Ba, Jianhua T1 - Nonaqueous synthesis of metal oxide nanoparticles and their assembly into mesoporous materials T1 - Nichtwässrige Synthese von Metalloxid-Nanopartikeln und deren Anordnung zu mesoporösen Materialien N2 - This thesis mainly consist of two parts, the synthesis of several kinds of technologically interesting crystalline metal oxide nanoparticles via nonaqueous sol-gel process and the formation of mesoporous metal oxides using some of these nanoparticles as building blocks via evaporation induced self-assembly (EISA) technique. In the first part, the experimental procedures and characterization results of successful syntheses of crystalline tin oxide and tin doped indium oxide (ITO) nanoparticles are reported. SnO2 nanoparticles exhibit monodisperse particle size (3.5 nm in average), high crystallinity and particularly high dispersibility in THF, which enable them to become the ideal particulate precursor for the formation of mesoporous SnO2. ITO nanoparticles possess uniform particle morphology, narrow particle size distribution (5-10 nm), high crystallinity as well as high electrical conductivity. The synthesis approaches and characterization of various mesoporous metal oxides, including TiO2, SnO2, mixture of CeO2 and TiO2, mixture of BaTiO3 and SnO2, are reported in the second part of this thesis. Mesoporous TiO2 and SnO2 are presented as highlights of this part. Mesoporous TiO2 was produced in the forms of both films and bulk material. In the case of mesoporous SnO2, the study was focused on the high order of the porous structure. All these mesoporous metal oxides show high crystallinity, high surface area and rather monodisperse pore sizes, which demonstrate the validity of EISA process and the usage of preformed crystalline nanoparticles as nanobuilding blocks (NBBs) to produce mesoporous metal oxides. N2 - Diese Arbeit besteht hauptsächlich aus zwei Teilen. Der erste Teil befasst sich mit der Synthese von mehreren technologisch wichtigen, kristallinen Metalloxid-Nanopartikeln mittels nichtwässriger Sol-Gel Chemie. Der zweite Teil beinhaltet die Herstellung von mesoporösen Metalloxiden. Dabei wurden ausgewählte Nanopartikel als Bausteine verwendet und durch langsames Verdampfen des Lösungsmittels in die entsprechenden porösen Strukturen überführt. Das experimentelle Vorgehen wie auch die Charakterisierung der erfolgreich hergestellten Zinnoxid- und Indiumzinnoxid-Nanopartikel sind im ersten Teil beschrieben. Die Zinnoxid-Nanpartikel zeichnen sich durch einheitliche Partikelgrösse (im Durchschnitt ca. 3.5 nm), hoher Kristallinität, und guter Dispergierbarkeit in Tetrahydrofuran aus. Diese Eigenschaften machen aus den Zinnoxid-Nanopartikeln die perfekten Bausteine für den Aufbau von mesoporösem Zinnoxid. Die Indiumzinnoxid-Nanopartikel haben eine einheitliche Partikelform, eine schmale Grösseverteilung (5-10 nm), hohe Kristallinität wie auch gute elektrische Leitfähigkeit. Die Synthese und Charakterisierung von verschiedenen mesoporösen Metalloxiden wie TiO2, SnO2, Mischungen von CeO2 und TiO2, wie auch Mischungen von BaTiO3 und SnO2 werden im zweiten Teil der Arbeit diskutiert. Mesoporöses TiO2 und SnO2 werden als besonders gelungene Beispiele herausgehoben. Mesoporöses TiO2 wurde in Form von Dünnfilmen wie auch als Bulkmaterial hergestellt. Im Falle von SnO2 galt das Augenmerk vor allem der hohen Ordnung der Mesoporen. Alle diese mesoporösen Materialien zeigen eine hohe Kristallinität, grosse Oberfläche und relativ einheitliche Porengrössen. Diese Eigenschaften unterstreichen, wie wertvoll der Ansatz ist, vorgeformte Nanopartikel als Bausteine für die Synthese von porösen Materialien zu verwenden. KW - Nanopartikel KW - transparent-leitendes Oxid KW - Selbstorganisation KW - nanoparticles KW - oxides KW - assembly KW - mesostructure Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10173 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 - Bagdahn, Christian A1 - Taubert, Andreas T1 - Ionogel fiber mats - functional materials via electrospinning of PMMA and the ionic liquid bis(1-butyl-3-methyl-imidazolium) Tetrachloridocuprate(II), [Bmim](2)[CuCl4] JF - Zeitschrift für Naturforschung : B, Chemical sciences N2 - Ionogel fiber mats were made by electrospinning poly(methylmethacrylate) (PMMA) and the ionic liquid (IL) bis(1-butyl-3-methyl-imidazolium) tetrachloridocupraten, [Bmim](2)[CuCl4], from acetone. The morphology of the electrospun ionogels strongly depends on the spinning parameters. Dense and uniform fiber mats were only obtained at concentrations of 60 to 70 g of polymer and IL mass combined. Lower concentrations led to a low number of poorly defined fibers. High voltages of 20 to 25 kV led to well-defined and uniform fibers; voltages between 15 and 20 kV again led to less uniform and less dense fibers. At 10 kV and lower, no spinning could be induced. Finally, PMMA fibers electrospun without IL show a less well-defined morphology combining fibers and oblong droplets indicating that the IL has a beneficial effect on the electrospinning process. The resulting materials are prototypes for new functional materials, for example in sterile filtration. KW - Ionic Liquid KW - Ionogel KW - Electrospinning KW - Fiber KW - Hydrogen Production KW - Filtration Y1 - 2013 U6 - https://doi.org/10.5560/ZNB.2013-3195 SN - 0932-0776 SN - 1865-7117 VL - 68 IS - 10 SP - 1163 EP - 1171 PB - De Gruyter CY - Tübingen ER - TY - THES A1 - Bahrke, Sven T1 - Mass spectrometric analysis of chitooligosaccharides and their interaction with proteins T1 - Massenspektrometrische Analyse von Chitooligosacchariden und ihre Wechselwirkungen mit Proteinen N2 - Chitooligosaccharides are composed of glycosamin and N-acetylglycisamin residues. Gel permeations chromatography is employed for the separation of oligomers, cation exchange chromatography is used for the separation of homologes and isomers. Trideuterioacetylation of the chitooligosaccharides followed by MALDI-TOF mass spectrometry allowes for the quantitation of mixtures of homologes. vMALDI LTQ multiple-stage MS is employed for quantitative sequencing of complex mixtures of heterochitooligosaccharides. Pure homologes and isomers are applied to biological assays. Chitooligosaccahrides form high-affinity non-covalent complexes with HC gp-39 (human cartilage glycoprotein of 39 kDa). The affinity of the chitooligosaccharides depends on DP, FA and the sequence of glycosamin and N-acetylglycosamin moieties. (+)nanoESI Q TOF MS/MS is used for identification of a high-affinity binding chitooligosaccharide of a non-covalent chitinase B - chitooligosaccharide complex. DADAA is identified as the heterochitoisomer binding with highest affinity and biostability to HC gp-39. Fluorescence based enzyme assays confirm the results. N2 - Chitooligosaccharide sind aus Glycosamin und N-Acetylglycosamun aufgebaut. Gelpermeationschromatographie wird für die Trennung von Oligomeren verwendet, die Kationenaustauschchromatographie wird zur Trennung von homologen- und Isomerengemischen angewendet. Trideuterioacetylierung der Chitooligosaccharide gefolgt von einer Analyse mittels MALDI-TOF MS erlaubt die quantitative Analyse von Homologengemischen. vMALDI LTQ multiple-stage MS wird angewendet zur Sequenzanalyse und Quantifizierung komplexer Gemische von Heterochitooligosacchariden. Reine Homologe und Isomere werden für biologische Assays verwendet. Dabei zeigt sich, dass Chitooligosaccharide mit HC gp-39 hochaffine Komplexe bilden. Die Affinität der Chitooligosaccharide hängt vom DP, FA und der Sequenz der Chitooligosaccharide ab. (+)nanoESI Q TOF MS/MS wird erfolgreich angewendet zur Identifizierung eines Chitooligosaccharides, das mit hoher Affinität an Chitinase B (Serratia marcescens) bindet. DADAA wurde als die Sequenz des Isomers identifiziert, das mit höchster Affinität und Biostabilität an aktive Chitinase B bindet. Fluoreszenz basierte Enzymassays konnten dieses Ergebnis bestätigen. KW - Chitooligosaccharide KW - HPLC KW - Massenspektrometrie KW - Chitolektine KW - Chitinase KW - Chitooligosaccharides KW - HPLC KW - Mass Spectrometry KW - Chitolectins KW - Chitinase Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-20179 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 - Bahrke, Sven A1 - Einarsson, Jon M. A1 - Gislason, Johannes A1 - Haebel, Sophie A1 - Peter-Katalinic, Jasna T1 - Characterization of chitooligosaccharides by mass spectrometry N2 - Heterochitooligosaccharides of DP 6, DP 9, and DP 12 were evaluated using established methods of derivatization and matrix-assisted laser desorption ionization post source decay mass spectrometry. Y1 - 2003 SN - 82-471-5901-5 ER - TY - THES A1 - Bahrke, Sven A1 - Einarsson, Jon M. A1 - Gislason, Johannes A1 - Haebel, Sophie A1 - Peter-Katalinic, Jasna A1 - Peter, Martin G. T1 - Characterization of chitooligosaccharides by mass spectrometry Y1 - 2003 SN - 82-47-15901-5 ER - TY - THES A1 - Bai, Shuo T1 - Active hydrogels with nanocomposites Y1 - 2010 CY - Potsdam ER - TY - JOUR A1 - Baier, Heiko A1 - Kelling, Alexandra A1 - Holdt, Hans-Jürgen T1 - PEPPSI-Effect on Suzuki-Miyaura Reactions Using 4,5-Dicyano-1,3-dimesitylimidazol-2-ylidene-Palladium Complexes: A Comparison between trans-Ligands JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - The PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) complexes 12-15 with the structure [PdCl2{(CN)(2)IMes}(3-R-py)] (12: R = H; 13: R = Cl; 14: R = Br; 15: R = CN) bearing the maleonitrile-based N-heterocyclic carbene (NHC) (CN)(2)IMes ({(CN)(2)IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) were prepared. Solid state structures of 14 and 15 were obtained. Complexes 14 and 15 adopt a slightly distorted square-planar coordination geometry in the solid state with the substituted pyridine ligand trans to the NHC. Catalytic activities of precatalysts 12-15 were studied and subsequently compared to complexes [PdCl2{(CN)(2)IMes}(PPh3)] (4) and [PdCl(dmba){(CN)(2)IMes}] (5) recently reported by our group in the Suzuki-Miyaura reaction of various aryl halides and phenylboronic acid. Reactions using previously reported [PdCl2(IMes)(py)] (IMes: 1,3-dimesitylimidazol-2-ylidene) (1) were also carried out and their results contrasted to those involving 12-15, 4 and 5. Differences in initiation rates and the catalytically active species related to the seven complexes in regards to the throw away ligand were investigated. Poisoning experiments with mercury show that palladium nanoparticles are responsible for the catalytic activity. KW - Carbene ligands KW - Palladium KW - Cross-coupling KW - Arenes Y1 - 2015 U6 - https://doi.org/10.1002/ejic.201500010 SN - 1434-1948 SN - 1099-0682 IS - 11 SP - 1950 EP - 1957 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baier, Heiko A1 - Kelling, Alexandra A1 - Jackstell, Ralf A1 - Holdt, Hans-Jürgen T1 - Rhodium(I) and Silver(I) Complexes of 4,5-Dicyano-1,3-dimesityl- and 4,5-Dicyano-1,3-dineopentylimidazol-2-ylidene JF - Zeitschrift für anorganische und allgemeine Chemie N2 - The new N-heterocyclic carbene (NHC) precursors 4,5-dicyano-1, -dimesityl- (9) and 4, 5-dicyano-1, 3-dineopentyl-2-(pentafluorophenyl)imidazoline (14) were synthesized. 9 could be determined by X-ray crystallography. With the 2-pentafluorophenyl-substituted imidazolines 9 and 14, the [AgCl(NHC)], [RhCl(COD)(NHC)], and [RhCl(CO)(2)(NHC)] complexes [NHC = 4, 5-dicyano-1, 3-dimesitylimidazol-2-ylidene (3) and 4, 5-dicyano-1, 3-dineopentylimidazol-2-ylidene (4)] were obtained. Crystal structures of [AgCl(3)] (15), [RhCl(COD)(3)] (17), [RhCl(COD)(4)] (18), and [RhCl(CO)(2)(3)] (19) were solved and with the crystal data of 19, the percent buried volume (%V-bur) of 31.8(+/- 0.1)% was determined for NHC 3. Infrared spectra of the imidazolines 9 and 14 and of the complexes 15-20 were recorded and the CO stretching frequencies of complexes 19 and 20 were used to determine the 3 ( (-1)) and 4 ( (-1)), thus proving that 1, 3-substitution of maleonitrile-NHCs does not have a significant effect for the high -acceptor strength of these carbenes. KW - Carbenes KW - Rhodium KW - Silver KW - Crystal structure KW - Diaminomaleonitrile Y1 - 2013 U6 - https://doi.org/10.1002/zaac.201300250 SN - 0044-2313 SN - 1521-3749 VL - 639 IS - 10 SP - 1731 EP - 1739 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baier, Heiko A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Holdt, Hans-Jürgen T1 - Investigation of the Catalytic Activity of a 2-Phenylidenepyridine Palladium(II) Complex Bearing 4,5-Dicyano-1,3-bis(mesityl)imidazol-2-ylidene in the Mizoroki-Heck Reaction JF - Zeitschrift für anorganische und allgemeine Chemie N2 - The phenylidenepyridine (ppy) palladacycles [PdCl(ppy)(IMes)] (4) [IMes = 1,3-bis(mesityl) imidazol-2-ylidene] and [PdCl(ppy){(CN)(2)IMes}] (6) [(CN)(2)IMes = 4,5-dicyano-1,3-bis(mesityl) imidazol-2-ylidene] were prepared by facile two step syntheses, starting with the reaction of palladium(II) chloride with 2-phenylpyridine followed by subsequent addition of the NHC ligand to the precatalyst precursor [PdCl(ppy)](2). Suitable crystals for the X-ray analysis of the complexes 4 and 6 were obtained. It was shown that 6 has a shorter NHC-palladium bond than the IMes complex 4. The difference of the palladium carbene bond lengths based on the higher pi-acceptor strength of (CN)(2)IMes in comparison to IMes. Thus, (CN)(2)IMes should stabilize the catalytically active central palladium atom better than IMes. As a measure for the pi-acceptor strength of (CN)(2)IMes compared to IMes, the selone (CN)(2)IMes center dot Se (7) was prepared and characterized by Se-77-NMR spectroscopy. The pi-acceptor strength of 7 was illuminated by the shift of its Se-77-NMR signal. The Se-77-NMR signal of 7 was shifted to much higher frequencies than the Se-77-NMR signal of IMes center dot Se. Catalytic experiments using the Mizoroki-Heck reaction of aryl chlorides with n-butyl acrylate showed that 6 is the superior performer in comparison to 4. Using complex 6, an extensive substrate screening of 26 different aryl bromides with n-butyl acrylate was performed. Complex 6 is a suitable precatalyst for para-substituted aryl bromides. The catalytically active species was identified by mercury poisoning experiments to be palladium nanoparticles. KW - Carbene ligands KW - Heck reaction KW - Palladium KW - Selenium KW - C-C coupling Y1 - 2016 U6 - https://doi.org/10.1002/zaac.201500625 SN - 0044-2313 SN - 1521-3749 VL - 642 SP - 140 EP - 147 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Baier, Heiko A1 - Metzner, Philipp A1 - Körzdörfer, Thomas A1 - Kelling, Alexandra A1 - Holdt, Hans-Jürgen T1 - Efficient palladium(II) precatalysts bearing 4,5-dicyanoimidazol-2-ylidene for the Mizoroki-Heck reaction JF - European journal of inorganic chemistry : a journal of ChemPubSoc Europe N2 - The new N-heterocyclic carbene (NHC) complex [PdCl2{(CN)(2)IMes}(PPh3)] (2) ({(CN)(2)IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) and the NHC palladacycle [PdCl(dmba){(CN)(2)IMes}] (3) (dmba: N,N-dimethylbenzylamine) have been synthesized by thermolysis of 4,5-dicyano-1,3-dimesityl-2-(pentafluorophenyl) imidazoline (1) in the presence of suitable palladium(II) precursors. The acyclic complex 2 was formed by ligand exchange using the mononuclear precursor [PdCl2(PPh3)(2)] and the palladacycle 3 was formed by cleavage of the dinuclear chloro-bridged precursor [Pd(mu-Cl)(dmba)](2). The new NHC precursor 1-benzyl-4,5-dicyano-2-(pentafluorophenyl)-3-picolylimidazoline (5) was formed by condensation of pentafluorobenzaldehyde with N-benzyl-N'-picolyldiaminomaleonitrile (4). The NHC palladacycle [PdCl2{(CN)(2)IBzPic}] (6) ({(CN)(2)IBzPic}: 1-benzyl-4,5-dicyano-3-picolylimidazol-2-ylidene) was prepared by in situ thermolysis of 5 in the presence of [PdCl2(PhCN)(2)]. The three palladium(II) complexes were characterized by NMR and IR spectroscopy, mass spectrometry and elemental analysis. In addition, the molecular structures of 2 and 3 were determined by X-ray diffraction. The pi-acidity of (CN)(2)IBzPic was compared with (CN)(2)IMes and perviously reported pi-acidic imidazol-2-ylidenes by NBO analysis. The Mizoroki-Heck (MH) reactions of various aryl halides with n-butyl acrylate were performed in the presence of complexes 2, 3 and 6. The new precatalysts showed high activity in the MH reactions giving good-to-excellent product yields with 0.1 mol-% pre-catalyst. The nature of the catalytically active species of 2, 3 and 6 was investigated by poisoning experiments with mercury and transmission electron microscopy. It was found that palladium nanoparticles formed from the precatalysts were involved in the catalytic process. KW - Homogeneous catalysis KW - Palladium KW - Cross coupling KW - Carbene ligands Y1 - 2014 U6 - https://doi.org/10.1002/ejic.201402040 SN - 1434-1948 SN - 1099-0682 IS - 18 SP - 2952 EP - 2960 PB - Wiley-VCH CY - Weinheim 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 - Balci, Kubilay A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A theoretical IR spectroscopic study based on DFT calculations for free mn-15S(2)O(3) maleonitrile-dithiacrown ether compound N2 - The theoretically possible stable conformers of free mn-15S2O3 maleonitrile-dithiacrown ether molecule were searched by means of a conformational study which consists of molecular dynamics and energy minimization calculations performed with MM2 force field and successive geometry optimization + frequency calculations performed first at B3LYP/3- 21G and then at B3LYP/6-31G(d) levels of theory. The obtained calculation results have clearly indicated that the free molecule in electronic ground state is very flexible and accordingly has many possible stable conformers of different conformational properties at room temperature; among them, the one having a macrocyclic ring structure in which all of the ether units oriented toward the center of the ring was determined the energetically most preferable conformer. In addition, the equilibrium geometrical parameters, vibrational normal modes and associated IR spectral data of the determined most stable three conformers of the molecule were calculated at B3LYP/6-31+G(d) and B3LYP/6-31++G(d,p) levels of theory. A successful assignment of the fundamental bands observed in the recorded experimental solid phase and solution phase IR spectra of the molecule was achieved in the light of the theoretical data obtained from these DFT calculations. To fit the calculated harmonic wavenumbers to the experimental ones, two different scaling procedures, referred to as "Scaled Quantum Mechanical Force Field (SQM FF) methodology" and "Scaling wavenumbers with empirical dual scale factors", were proceeded independently. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00222860 U6 - https://doi.org/10.1016/j.molstruc.2008.08.027 SN - 0022-2860 ER - TY - JOUR A1 - Balci, Kubilay A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A comparative vibrational spectroscopic investigation of free mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers based on DFT calculations N2 - A successful assignment for the fundamental bands observed in the experimental IR spectra of mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers was achieved by the aid of the density functional theory (DFT) based quantum mechanical calculations carried out at the 133LYP/6-31G(d) and B3LYP/6-31 + G(d) level of theory. Two different scaling approaches, '(i) scaled quantum mechanics force field (SQM FF) methodology', and (ii) the 'scaling frequencies with dual empirical scale factors', were used in order to fit the calculated harmonic frequencies to the experimental ones. Potential energy distribution (PED) calculations were carried out to define the internal coordinate contributions to each normal mode and to define the corresponding normal modes of the molecules. The effects of the conformational differences onto the IR active normal modes of the two isomeric molecules and their corresponding experimental frequencies were discussed in the light of the calculated spectral data. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00222860 U6 - https://doi.org/10.1016/j.molstruc.2005.10.048 SN - 0022-2860 ER - TY - JOUR A1 - Balci, Kubilay A1 - Yapar, G. A1 - Akkaya, Y. A1 - Akyuz, S. A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - A conformational analysis and vibrational spectroscopic investigation on 1,2-bis(o-carboxyphenoxy) ethane molecule JF - Vibrational spectroscopy : an international journal devoted to applications of infrared and raman spectroscopy N2 - The minima on the potential energy surface of 1,2-bis(o-carboxyphenoxy)ethane (CPE) molecule in its electronic ground state were searched by a molecular dynamics simulation performed with MM2 force field. For each of the found minimum-energy conformers, the corresponding equilibrium geometry, charge distribution, HOMO-LUMO energy gap, force field, vibrational normal modes and associated IR and Raman spectral data were determined by means of the density functional theory (DFT) based electronic structure calculations carried out by using B3LYP method and various Pople-style basis sets. The obtained theoretical data confirmed the significant effects of the intra- and inter-molecular hydrogen bonding interactions on the conformational structure, force field, and group vibrations of the molecule. The same data have also revealed that two of the determined stable conformers, both of which exhibit pseudo-crown structure, are considerably more favorable in energy to the others and accordingly provide the major contribution to the experimental spectra of CPE. In the light of the improved vibrational spectral data obtained within the "SQM FF" methodology and "Dual Scale Factors" approach for the monomer and dimer forms of these two conformers, a reliable assignment of the fundamental bands observed in the experimental room-temperature IR and Raman spectra of the molecule was given, and the sensitivities of its group vibrations to conformation, substitution and dimerization were discussed. KW - Glycol podands KW - Salicylic acid KW - IR and Raman spectra KW - SQM FF KW - Dual Scale Factors Y1 - 2012 U6 - https://doi.org/10.1016/j.vibspec.2011.11.011 SN - 0924-2031 VL - 58 IS - 1-2 SP - 27 EP - 43 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bald, Ilko A1 - Keller, Adrian T1 - Molecular processes studied at a single-molecule level using DNA origami nanostructures and atomic force microscopy JF - Molecules N2 - DNA origami nanostructures allow for the arrangement of different functionalities such as proteins, specific DNA structures, nanoparticles, and various chemical modifications with unprecedented precision. The arranged functional entities can be visualized by atomic force microscopy (AFM) which enables the study of molecular processes at a single-molecular level. Examples comprise the investigation of chemical reactions, electron-induced bond breaking, enzymatic binding and cleavage events, and conformational transitions in DNA. In this paper, we provide an overview of the advances achieved in the field of single-molecule investigations by applying atomic force microscopy to functionalized DNA origami substrates. KW - DNA origami KW - atomic force microscopy KW - single-molecule analysis KW - DNA radiation damage KW - protein binding KW - enzyme reactions KW - G quadruplexes Y1 - 2014 U6 - https://doi.org/10.3390/molecules190913803 SN - 1420-3049 VL - 19 IS - 9 SP - 13803 EP - 13823 PB - MDPI CY - Basel ER - TY - GEN A1 - Bald, Ilko A1 - Keller, Adrian T1 - Molecular processes studied at a single-molecule level using DNA origami nanostructures and atomic force microscopy T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - DNA origami nanostructures allow for the arrangement of different functionalities such as proteins, specific DNA structures, nanoparticles, and various chemical modifications with unprecedented precision. The arranged functional entities can be visualized by atomic force microscopy (AFM) which enables the study of molecular processes at a single-molecular level. Examples comprise the investigation of chemical reactions, electron-induced bond breaking, enzymatic binding and cleavage events, and conformational transitions in DNA. In this paper, we provide an overview of the advances achieved in the field of single-molecule investigations by applying atomic force microscopy to functionalized DNA origami substrates. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1146 KW - DNA origami KW - atomic force microscopy KW - single-molecule analysis KW - DNA radiation damage KW - protein binding KW - enzyme reactions KW - G quadruplexes Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-475843 SN - 1866-8372 IS - 9 SP - 13803 EP - 13823 ER - TY - JOUR A1 - Bald, Ilko A1 - Keller, Adrian A1 - Kopyra, Janina T1 - On the role of fluoro-substituted nucleosides in DNA radiosensitization for tumor radiation therapy JF - RSC Advances : an international journal to further the chemical sciences N2 - Gemcitabine (2′,2′-difluorocytidine) is a well-known radiosensitizer routinely applied in concomitant chemoradiotherapy. During irradiation of biological media with high-energy radiation secondary low-energy (<10 eV) electrons are produced that can directly induce chemical bond breakage in DNA by dissociative electron attachment (DEA). Here, we investigate and compare DEA to the three molecules 2′-deoxycytidine, 2′-deoxy-5-fluorocytidine, and gemcitabine. Fluorination at specific molecular sites, i.e., nucleobase or sugar moiety, is found to control electron attachment and subsequent dissociation pathways. The presence of two fluorine atoms at the sugar ring results in more efficient electron attachment to the sugar moiety and subsequent bond cleavage. For the formation of the dehydrogenated nucleobase anion, we obtain an enhancement factor of 2.8 upon fluorination of the sugar, whereas the enhancement factor is 5.5 when the nucleobase is fluorinated. The observed fragmentation reactions suggest enhanced DNA strand breakage induced by secondary electrons when gemcitabine is incorporated into DNA. KW - low-energy electrons KW - single-strand breaks KW - gas-phase KW - chemoradiation therapy KW - molecular-mechanisms KW - resonant formation KW - damage KW - attachment KW - drugs Y1 - 2014 U6 - https://doi.org/10.1039/C3RA46735J SN - 2046-2069 VL - 4 IS - 13 SP - 6825 EP - 6829 PB - Royal Society of Chemistry ER - TY - GEN A1 - Bald, Ilko A1 - Kopyra, Janina A1 - Keller, Adrian T1 - On the role of fluoro-substituted nucleosides in DNA radiosensitization for tumor radiation therapy N2 - Gemcitabine (2′,2′-difluorocytidine) is a well-known radiosensitizer routinely applied in concomitant chemoradiotherapy. During irradiation of biological media with high-energy radiation secondary low-energy (<10 eV) electrons are produced that can directly induce chemical bond breakage in DNA by dissociative electron attachment (DEA). Here, we investigate and compare DEA to the three molecules 2′-deoxycytidine, 2′-deoxy-5-fluorocytidine, and gemcitabine. Fluorination at specific molecular sites, i.e., nucleobase or sugar moiety, is found to control electron attachment and subsequent dissociation pathways. The presence of two fluorine atoms at the sugar ring results in more efficient electron attachment to the sugar moiety and subsequent bond cleavage. For the formation of the dehydrogenated nucleobase anion, we obtain an enhancement factor of 2.8 upon fluorination of the sugar, whereas the enhancement factor is 5.5 when the nucleobase is fluorinated. The observed fragmentation reactions suggest enhanced DNA strand breakage induced by secondary electrons when gemcitabine is incorporated into DNA. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 167 KW - low-energy electrons KW - single-strand breaks KW - gas-phase KW - chemoradiation therapy KW - molecular-mechanisms KW - resonant formation KW - damage KW - attachment KW - drugs Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-73412 SP - 6825 EP - 6829 ER - TY - JOUR A1 - Bald, Ilko A1 - Schürmann, Robin Mathis A1 - Ebel, Kenny A1 - Nicolas, Christophe A1 - Milosavljevic, Aleksandar R. T1 - Role of valence band states and plasmonic enhancement in electron-transfer-induced transformation of nitrothiophenol JF - The Journal of Physical Chemistry Letters N2 - Hot-electron-induced reactions are more and more recognized as a critical and ubiquitous reaction in heterogeneous catalysis. However, the kinetics of these reactions is still poorly understood, which is also due to the complexity of plasmonic nanostructures. We determined the reaction rates of the hot-electron-mediated reaction of 4-nitrothiophenol (NTP) on gold nanoparticles (AuNPs) using fractal kinetics as a function of the laser wavelength and compared them with the plasmonic enhancement of the system. The reaction rates can be only partially explained by the plasmonic response of the NPs. Hence, synchrotron X-ray photoelectron spectroscopy (XPS) measurements of isolated NTP-capped AuNP clusters have been performed for the first time. In this way, it was possible to determine the work function and the accessible valence band states of the NP systems. The results show that besides the plasmonic enhancement, the reaction rates are strongly influenced by the local density of the available electronic states of the system. Y1 - 2019 UR - https://pubs.acs.org/doi/10.1021/acs.jpclett.9b00848 U6 - https://doi.org/10.1021/acs.jpclett.9b00848 SN - 1948-7185 VL - 10 SP - 3153 EP - 3158 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Bald, Ilko A1 - Solov'yov, Ilia A. A1 - Mason, Nigel J. A1 - Solov'yov, Andrey V. T1 - Special issue BT - dynamics of systems on the nanoscale (2018). Editorial JF - The European physical journal. D, Atomic, molecular, optical and plasma physics N2 - The structure, formation and dynamics of both animate and inanimate matter on the nanoscale are a highly interdisciplinary field of rapidly emerging research engaging a broad community encompassing experimentalists, theorists, and technologists. It is relevant for a large variety of molecular and nanosystems of different origin and composition and concerns numerous phenomena originating from physics, chemistry, biology, or materials science. This Topical Issue presents a collection of original research papers devoted to different aspects of structure and dynamics on the nanoscale. Some of the contributions discuss specific applications of the research results in several modern technologies and in next generation medicine. Most of the works of this topical issue were reported at the Fifth International Conference on Dynamics of Systems on the Nanoscale (DySoN) - the premier forum for the presentation of cutting-edge research in this field that was held in Potsdam, Germany in October of 2018. Y1 - 2020 U6 - https://doi.org/10.1140/epjd/e2020-10134-4 SN - 1434-6060 SN - 1434-6079 VL - 74 IS - 4 SP - 75 EP - 82 PB - Springer CY - Berlin ER -