TY  - GEN
A1  - Peter, Martin G.
T1  - Products of in vitro oxidation of N-acetyldopamine as possible components in the sclerotization of insect cuticle
N2  - [1-14C]-N-Acetyldopamine (NADA) was oxidized in the presence of methyl [3-3H]-β-alanate with mushroom tyrosinase. The complex mixture of reaction products was partly resolved by chromatographic procedures and analyzed by spectroscopic methods. Methyl-β-alanate is incorporated to only a small extent into oxidation products of NADA which inter alia are presumed to be oligomeric hydroxyquinones. After oxidation of [1-14C, 2-3H]-NADA with preparations from tanning Manduca sexta pupal cuticle, N-acetylnoradrenalin was identified as one of the products. Binding of radioactivity to melanin-like material was also observed. These results suggest that oxidation products different from those formulated usually for the crosslinkages between protein amino groups and N-acetyldopaquinone are deposited in darkly brown coloured insect cuticles during sclerotization.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 041 
KW  - N-acetyldopamine
KW  - sclerotization
KW  - tyrosinase; o-quinones
KW  - tanning agents
Y1  - 1980
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16759
ER  - 
TY  - GEN
A1  - Ferenz, Hans-Jürgen
A1  - Peter, Martin G.
A1  - Berg, Dieter
T1  - Inhibition of farnesoic acid methyltransferase by sinefungin
N2  - Sinefungin inhibited the S-adenosylmethionine-dependent farnesoic acid methyltransferase in a cell-free system containing a homogenate of corpora allata from female locusts, Locusta migratoria. The enzyme catalyzed the penultimate step of juvenile hormone biosynthesis in the insects. Culturing corpora allata in the presence of sinefungin greatly suppressed juvenile hormone production. The following in vivo effects were visible after injection of the inhibitor: increase in mortality and reduction of total haemolymph protein liter and ovary fresh weight, as well as length of terminal oocytes. Attempts to reverse these effects by topical application of the juvenile hormone analog ZR-515 (methoprene) were only partly successful. Therefore, the in vivo effects may be due to a general inhibition of methyltransferase enzymes in the insect. Sinefungin appeared to be of potential interest as the first representative of a new class of insect growth regulators.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 077 
KW  - Juvenile hormone analogue
KW  - Orthoptera
KW  - Juvenile hormone
KW  - Biosynthesis
KW  - Enzyme
KW  - Corpora allata
KW  - In vitro
KW  - Biological activity
KW  - Enzyme inhibitor
Y1  - 1983
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17016
ER  - 
TY  - GEN
A1  - Kort, C. A. D. de
A1  - Peter, Martin G.
A1  - Koopmanschap, A. B.
T1  - Binding and degradation of juvenile hormone III by haemolymph proteins of the Colorado potato beetle: a re-examination
N2  - The haemolymph of the adult Colorado potato beetle, Lepinotarsa decemlineata Say, contains a high molecular weight (MW > 200,000) JH-III specific binding protein. The Kd value of the protein for racemic JH-III is 1.3 ± 0.2 × 10−7 M. It has a lower affinity for racemic JH-I and it does not bind JH-III-diol or JH-III-acid. The binding protein does discriminate between the enantiomers of synthetic, racemic JH-III as was determined by stereochemical anaysis of the bound and the free JH-III. Incubation of racemic JH-III with crude haemolymph results in preferential formation of (10S)-JH-III-acid, the unnatural configuration. The JH-esterase present in L. decemlineata haemolymph is not enantioselective. It is concluded that the most important function of the binding protein is that of a specific carrier, protecting the natural hormone against degradation by esterases. The carrier does not protect JH-I as efficiently as the lower homologue.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 068 
KW  - Juvenile hormone
KW  - Leptinotarsa decemlineata
KW  - JH-III-specific carrier protein
KW  - enantioselectivity
Y1  - 1983
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16777
ER  - 
TY  - GEN
A1  - Laschewsky, André
A1  - Ringsdorf, H.
A1  - Schmidt, G.
T1  - Polymerization of hydrocarbon and fluorocarbon amphiphiles in Langmuir-Blodgett multilayers
N2  - Langmuir-Blodgett multilayers of polymerizable carboxylic acids with hydrocarbon or fluorocarbon chains were prepared. The multilayers were polymerized by UV light and the reactions were studied by UV/visible spectroscopy. The polyreactions strongly influence the multilayer structures which were investigated by X-ray small-angle scattering and scanning electron microscopy. The spreading behaviour of the monomers, the preparation of multilayers, their reactivities in multilayers and structural effects caused by the polyreactions are discussed with regard to the hydrophilic head groups, the polymerizable groups and the hydrophobic chains.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 055 
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17096
ER  - 
TY  - GEN
A1  - Elbert, R.
A1  - Laschewsky, André
A1  - Ringsdorf, H.
T1  - Hydrophilic spacer groups in polymerizable lipids: formation of biomembrane models from bulk polymerized lipids
N2  - A variety of polymerizable lipids containing a hydrophilic spacer group between the reactive group and the main amphiphilic structure have been synthesized. They were investigated in monolayers, liposomes, and multilayers. When the spacer concept was used, efficient decoupling of the motions of the polymeric chain and the amphiphilic side groups is achieved. Thus, the often found loss of the important fluid phases by polymerization is avoided. Polymeric monolayers of the spacer lipid, prepared either by polymerization in the monolayer or by spreading of prepolymerized lipid, exhibit nearly identical surface pressure-area diagrams. Most distinctly, the successful decoupling of the motions of the polymer main chain and the membrane forming amphiphilic side groups is demonstrated by the self-organization of bulk polymerized spacer lipids to polymeric liposomes. In addition, spacer lipids are able to build polymeric Langmuir-Blodgett multilayers. The decoupling of the polymer main chain and the membrane-forming amphiphilic side groups enables the deposition of already polymeric monolayers onto supports to form defined multilayers. If, alternatively, monomeric monolayers are deposited and polymerized on the support, defects in the layers due to structural changes during the polymerization are avoided by the flexible spacer group.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 095 
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17361
ER  - 
TY  - GEN
A1  - Koch, Horst
A1  - Laschewsky, André
A1  - Ringsdorf, Helmut
A1  - Teng, Kang
T1  - Photodimerization and photopolymerization of amphiphilic cinnamic acid derivatives in oriented monolayers, vesicles and solution
N2  - Cinnamic acid moieties were incorporated into amphiphilic compounds containing one and two alkyl chains. These lipid-like compounds with photoreactive units undergo self-organization to form monolayers at the gas-water interface and bilayer structures (vesicles) in aqueous solutions. The photoreaction of the cinnamic acid moiety induced by 254 nm UV light was investigated in the crystalline state, in monolayers, in vesicles and in solution in organic solvents. The single-chain amphiphiles undergo dimerization to yield photoproducts with twice the molecular weight of the corresponding monomers in organized systems. The photoreaction of amphiphiles containing two cinnamic acid groups occurs via two mechanisms: The intramolecular dimerization produces bicycles, with retention of the molecular weight of the corresponding monomer. The intermolecular reaction leads to oligomeric and polymeric photoproducts. In contrast to the single-chain amphiphiles, photodimerization processes of lipoids containing two cinnamic acid moieties also occur in solution in organic solvents.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 078 
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17111
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  - GEN
A1  - Laschewsky, André
A1  - Ringsdorf, H.
A1  - Schneider, J.
T1  - Oriented supramolecular systems-polymeric monolayers and multilayers from prepolymerized amphiphiles
N2  - Oriented polymeric membranes were originally prepared by polymerization or polycondensation of preoriented monomers. The introduction of hydrophilic spacer groups into the polymeric amphiphiles allowed the formation of highly ordered systems (monolayers, liposomes, multilayers) from prepolymerized amphiphiles: due to the partial decoupling of the different mobilities and orientation tendencies of the polymer chain and the amphiphilic side groups, these polymers are able to self-organize. In monolayer experiments the high order of these membranes could be demonstrated by their surface pressure area-diagrams. In addition the combination of order and mobility of these spacer groups containing polymeric amphiphiles allowed the formation of Langmuir-Blodgett-multilyers with a high layer correlation. Thus, disturbancies in highly oriented layers can be avoided normally taking place during the polymerization reaction (e.g. contractions) or oriented monomeric layers.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 056 
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17131
ER  - 
TY  - GEN
A1  - Laschewsky, André
A1  - Ringsdorf, H.
A1  - Schmidt, G.
A1  - Schneider, J.
T1  - Self-organization of polymeric lipids with hydrophilic spacers in side groups and main chain : investigation in monolayers and multilayers
N2  - Several polymerizable lipids were synthesized and polymerized to amphiphilic homopolymers and to copolymers with the help of hydrophilic comonomers. The self-organization of these polymeric lipids was investigated in monolayers and Langmuir-Blodgett multilayers. The self-organization of these polymers in model membranes is due to hydrophilic spacer groups in the amphiphilic side groups as well as to hydrophilic spacer groups in the polymer backbone. Thus, highly ordered monolayers and LB-multilayers are easily obtained.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 057 
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17147
ER  - 
TY  - GEN
A1  - Ferenz, Hans-Jörg
A1  - Peter, Martin G.
T1  - The inhibitory effect of sinefungin on juvenile hormone biosynthesis and development in locusts
N2  - The antibiotic fungal metabolite sinefungin is a potent inhibitor of S-adenosylmethionine-acceptor methyltransferases. Its effect on insect metabolism and especially on corpora allata farnesoic acid methyltransferase, which catalyzes the penultimate step of juvenile hormone biosynthesis, was investigated in Locusta migratoria. Injection of sinefungin results in a delay of imaginal molt and in suppression of ovary development. Isolated corpora allata are unable to synthesize juvenile hormone III in the presence of more than 1.0 mM sinefungin. In a cell-free system containing the S-adenosylmethionine-dependent farnesoic acid methyltransferase from corpora allata sinefungin is a competitive inhibitor of the synthesis of methylfarnesoate with Ki of 1 μM.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 076 
KW  - Locust
KW  - sinefungin
KW  - O-methyltransferase
KW  - juvenile hormone biosynthesis
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16811
ER  - 
TY  - GEN
A1  - Laschewsky, André
A1  - Ringsdorf, H.
T1  - Polymerization of amphiphilic dienes in Langmuir-Blodgett multilayers
N2  - Amphiphilic derivatives of octadiene and docosadiene were investigated in monolayers and Langmuir-Blodgett multilayers, with respect to their self-organization and their polymerization behavior. All amphiphiles investigated form monolayers. However, only acid and alcohol derivatives were able to build up multilayers. Those multilayers are rapidly photopolymerized in the layers via a two-step process: Irradiation with long-wavelength UV light yields soluble polymers, whereas additional irradiation with sfiort-wavelength UV light produces insoluble and presumably cross-linked polymers. The reaction meclianism is discussed according to the polymer characterization by UV spectroscopy, small-angle X-ray scattering, NMR spectroscopy, and gel permeation chromatography. All multilayers undergo structural changes during the polymerization; substantial changes result in defects in the polymerized layers as observed by scanning electron microscopy. In contrast to the acids and alcohols, the deposition of monolayers of the aldehyde derivatives did not yield well-ordered multilayers, but rather amorphous films. In this different film structure, the photopolymerization process differs from the one observed in multilayers.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 058 
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17176
ER  - 
TY  - GEN
A1  - Lupo, Donald
A1  - Prass, Werner
A1  - Scheunemann, Ude
A1  - Laschewsky, André
A1  - Ringsdorf, Helmut
A1  - Ledoux, Isabelle
T1  - Second-harmonic generation in Langmuir-Blodgett monolayers of stilbazium salt and phenylhydrazone dyes
N2  - Contents: 1. INTRODUCTION 2. SYNTHESIS OF THE COMPOUNDS 3. PREPARATION AND CHARACTERIZATION OF MONOLAYERS A. Monolayer Isotherms B. Langmuir-Blodgett Monolayer Films 4. EXPERIMENTAL SETUP FOR NONLINEAR MEASUREMENTS 5. NONLINEAR OPTICAL PROPERTIES 6. DISCUSSION 7. CONCLUSION
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 094 
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17401
ER  - 
TY  - GEN
A1  - Peter, Martin G.
A1  - Förster, Hans
T1  - On the structure of Eumelanins : identification of constitutional patterns by solid-state NMR spectroscopy
N2  - Aus dem Inhalt: Melanins are complex polyphenolic polymers. They are usually formed in nature by enzyme-catalyzed oxidative polymerization of o-diphenols. The deep black eumelanins, derived from Dopa 1 or dopamine 3, are distinguished from the yellow to brown phaeomelanins obtained from Dopa in the presence of cysteine. Characteristic of eumelanins are the indole units, which are formed from catecholamines by intramolecular addition of the amino groups to the oxidatively generated o-quinones. [...]
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 053 
Y1  - 1989
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17027
ER  - 
TY  - GEN
A1  - Erdelen, C.
A1  - Laschewsky, André
A1  - Ringsdorf, H.
A1  - Schneider, J.
A1  - Schuster, A.
T1  - Thermal behaviour of polymeric Langmuir-Blodgett multilayers
N2  - Langmuir-Blodgett multilayers of hydrocarbon and fluorocarbon polymers with hydrophilic spacer, lipid-polyelectrolyte complexes and mesogenic polymers have been prepared. The thermal behaviour of the multilayers was studied by small angle X-ray scattering, IR and UV—visible spectroscopy. Good thermal stabilities were found for the various classes of polymers. In addition, for both complexed multilayers and mesogenic polymer films, reorientation processes were observed.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 080 
Y1  - 1989
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17378
ER  - 
TY  - GEN
A1  - Laschewsky, André
T1  - Monolayers and Langmuir-Blodgett multilayers of discotic liquid crystals?
N2  - Contents: 1. Discotic Liquid Crystals 2. Monolayers and Langmuir-Blodgett Multilayers 3. Theoretical Considerations on the Molecular Packing of Discotic LCs in Monolayers and Multilayers 4. Spreading Experiments with Discotic LCs 5. LB-Multilayers of Discotic LCs 6. Polymeric Discotic LCs 7. Summary
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 061 
Y1  - 1989
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17396
ER  - 
TY  - GEN
A1  - Biddle, M. B.
A1  - Rickert, S. E.
A1  - Lando, J. B.
A1  - Laschewsky, André
T1  - The use of the Langmuir-Blodgett technique to obtain ultra-thin polar films
N2  - The piezoelectric and pyroelectric properties of oriented films possessing dipole moments are increasingly being used in pressure, acoustic, thermal and optical devices. The performance of these devices in many applications may be enhanced by thin-film technology.The developing Langmuir-Blodgett thin-film deposition technique offers the opportunity to obtain highly oriented and uniform organic-based films in the 10–5000 nm thickness range. Special techniques must be used, however, to assemble these molecules in such a way as to result in polar multilayer films. Several possible deposition techniques are investigated, with one resulting in a polar and pyroelectric film about 50 nm thick.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 098 
Y1  - 1989
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17185
ER  - 
TY  - GEN
A1  - Embs, Frank
A1  - Funhoff, Dirk
A1  - Laschewsky, André
A1  - Licht, Ulrike
A1  - Ohst, Holger
A1  - Prass, Werner
A1  - Ringsdorf, Helmut
A1  - Wegner, Gerhard
A1  - Wehrmann, Rolf
T1  - Preformed polymers for Langmuir-Blodgett films- molecular concepts
N2  - The use of preformed polymers for the preparation of Langmuir-Blodgett (LB) multilayers is reviewed. Principles for polymer self-organization are outlined and the appropriate molecular designs are discussed. Recent developments in the different classes of polymers for LB multilayers are presented, and their outstanding properties highlighted.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 081 
KW  - Amphiphilic Polymers
KW  - Rod-like Polymers
KW  - LCPs
KW  - Stability of LB Films
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17196
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  - Laschewsky, André
T1  - Oligoethyleneoxide spacer groups in polymerizable surfactants
N2  - Cationic and zwitterionic polymerizable surfactants bearing tri- and tetraethyleneglycol spacer groups between the polymerizable moiety and the surfactant structure were prepared and polymerized. Monomers and polymers were investigated with respect to their aggregation behavior in aqueous systems and compared to analogous monomers and polymers lacking spacer groups. In the case of the monomeric surfactants, the spacer groups depress both the Kraffttemperature and the critical micelle concentration. the area occupied per molecule at the air-water interface is substantially enlarged by the spacers, whereas the depression of surface tension is nearly constant. Although the monomers with and without spacers are true surfactants, all the polymers are water-insoluble, but form monomolecular layers at the air-water interface. In analogy to the monomer behavior, the incorporation of the spacer groups increases the area occupied per repeat unit at the air-water interface substantially, but hardly affects the surface activity.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 059 
KW  - Polymerizable surfactant
KW  - polysoap
KW  - sulfobetain
KW  - spacer
KW  - micelle
KW  - monolayer
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17221
ER  - 
TY  - GEN
A1  - Bubeck, Christoph
A1  - Laschewsky, André
A1  - Lupo, Donald
A1  - Neher, Dieter
A1  - Ottenbreit, Petra
A1  - Paulus, Wolfgang
A1  - Prass, Werner
A1  - Ringsdorf, Helmut
A1  - Wegner, Gerhard
T1  - Amphiphilic dyes for nonlinear optics: Dependence of second harmonic generation on functional group substitution
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 082 
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17201
ER  - 
TY  - GEN
A1  - Köberle, Peter
A1  - Laschewsky, André
A1  - Tsukruk, Vladimir
T1  - The structural order of some novel ionic polymers : 1. X-ray scattering studies
N2  - A set of novel zwitterionic side-chain polyacrylates and polymethacrylates is studied by X-ray scattering. The structural order both in the short-range and long-range scale is investigated. The influence of the polymer backbone, of different locations of the ionic groups in isomeric polymers, of bound water and of added inorganic salts on the bulk structures is studied, and the observed rearrangements are analysed.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 089 
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17247
ER  - 
TY  - GEN
A1  - Peter, Martin G.
A1  - Andersen, Svend Olav
A1  - Hartmann, Rudolf
A1  - Miessner, Merle
A1  - Roepstorff, Peter
T1  - Catecholamine-protein conjugates : isolation of 4-phenylphenoxazin-2-ones from oxidative coupling of N-acetyldopamine with alipathic amino acids
N2  - 4-Phenylphenoxazinones were isolated after biomimetic oxidation, using diphenoloxidases of insect cuticle, mushroom tyrosinase, or after autoxidation of N-acetyldopamine (Image ) in the presence of β-alanine, β-alanine methyl ester or N-acetyl-L-lysine. They are formed presumably by addition of 2-aminoalkyl-5-alkylphenols to the o-quinone of biphenyltetrol which, in turn, arises from oxidative coupling of. The structures of present the first examples for the assembly of reasonably stable intermediates in the rather complex process of chemical modifications of aliphatic amino acid residues by o-quinones.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 062 
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17571
ER  - 
TY  - GEN
A1  - Laschewsky, André
A1  - Paulus, Wolfgang
A1  - Ringsdorf, Helmut
A1  - Schuster, A.
A1  - Frick, G.
A1  - Mathy, A.
T1  - Mixed polymeric monolayers and Langmuir-Blodgett multilayers with functional low molecular weight guest compounds
N2  - Mixed monolayers and Langmuir-Blodgett multilayers of functional low molecular weight guest compounds, especially nonlinear optical (NLO) dyes, within the matrix of an amphotropic spacer polymer have been prepared. The polymer matrix enabled the transfer of guest compounds not capable of self-organizing at the air-water interface by themselves. The structure of the LB multilayers and the transfer process were studied by small angle X-ray scattering and UV-visible spectroscopy. Good NLO coefficients were found in the mixed films.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 060 
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17233
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  - GEN
A1  - Tsukruk, Vladimir
A1  - Mischenko, Nikolay
A1  - Köberle, Peter
A1  - Laschewsky, André
T1  - The structural order of some novel ionic polymers; 2. : Models of molecular packing
N2  - The molecular packing and spatial correlations of two isomeric zwitterionic polymethacrylates and one polyacrylate analog are studied by means of X-ray analysis and conformational calculations. The analysis of the correlation functions and density distribution profiles suggest a double-layered molecular packing which is discussed for the three polymers investigated, with respect to their different chemical structures. Whereas the zwitterionic polymethacrylates studied exhibit liquid-like short-range order, the polyacrylate analog exhibits an ordered double-layered superstructure.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 096 
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17256
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  - 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  - Laschewsky, André
A1  - Schulz-Hanke, Wolfgang
T1  - Ring-opening metathesis polymerization of amphiphilic norbornenes functionalized with non-linear optical (NLO) chromophores
N2  - Contents: Potential of amphiphilic NLO polymers Ring-opening metathesis polymerization (ROMP) Properties of the polymers Monolayer properties Experimental part - Methods - Materials - Analytical data - General polymerization procedure Conclusions
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 092 
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-26917
ER  - 
TY  - GEN
A1  - Köberle, Peter
A1  - Laschewsky, André
T1  - Hybrid materials from organic polymers and inorganic salts
N2  - The prepaparation of amorphous, homogeneous blends of zwitterionic polymers and transition metal salts was investigated. Homogeneous miscibility was achieved in many cases up to equimolar amounts of salt, depending on the anion and cation chosen. Various analytical techniques point to a solid state solution of the inorganic ions in the polymer matrix.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 086 
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-26884
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
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  - GEN
A1  - Cochin, Didier
A1  - Hendlinger, P.
A1  - Laschewsky, André
T1  - Polysoaps with fluorocarbon hydrophobic chains
N2  - A series of amphiphilic copolymers is prepared by copolymerization of choline methacrylate with 1,1,2,2-tetrahydroperfluorooctyl methacrylate in varying amounts. The copolymers bearing fluorocarbon chains are studied concerning their effects on viscosity, solubilization and surface activity in aqueous solution, exhibiting a general behavior characteristic for polysoaps. The results are compared with the ones obtained for an analogous series of amphiphilic copolymers bearing hydrocarbon chains.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 085 
KW  - Amphiphilic polymers
KW  - fluorocarbon polymers
KW  - associating polymers
KW  - polysoaps
Y1  - 1995
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17347
ER  - 
TY  - GEN
A1  - Laschewsky, André
T1  - Molecular concepts, self-organisation and properties of polysoaps
N2  - The article reviews water-soluble polymers characterized by surfactant side chains, and related amphiphilic polymers. Various synthetic approaches are presented, and rules for useful molecular architectures are given. Models for the self-organization of such polymers in water are presented comparing them with the micellization of low molecular weight surfactants. Highlighting key properties of aqueous polysoap solutions such as viscosity, surface tension and solubilization power, some structure-property relationships are established. Further, the formation of mesophases and of superstructures in bulk is addressed. Finally, the functionalization of polysoaps, and potential applications are discussed.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 087 
Y1  - 1995
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-26895
ER  - 
TY  - GEN
A1  - Rozanski, Stanislaw A.
A1  - Kremer, Friedrich
A1  - Köberle, Peter
A1  - Laschewsky, André
T1  - Relaxation and charge transport in mixtures of zwitterionic polymers and inorganic salts
N2  - Dielectric spectroscopy is employed to analyze the molecular dynamics and the charge transport in mixtures of zwitterionic polymers of the type poly{3 [N(-methacryloyloxyalkyl)] N, [N-dimethylammonio propanesulfonate] with sodium iodide in the frequency range of 10²Hz-10(up)7 Hz and in the temperature range of 110 K-400 K. The amount of inorganic salt added varies from 0-200 mol-% relative to the number of zwitterionic groups present in the polymer, contributing strongly to the conductivity. One relaxation process is observed whose relaxation rate depends strongly on the length of the aliphatic spacer between the polymethacrylate main chain and the zwitterionic group. Exhibiting an Arrhenius-like temperature depence with activation energy EA = 47 KJ/mol, this relaxation process is assigned to fluctuation of the quaternary ammonium groups in the side chains. At higher temperatures, the dielectric properties and the conductivity are primarily dominated by the mobile inorganic ions: conductivity strongly depends on the salt concentration, showing a pronounced electrode polarization effect. The frequency and salt concentration, dependences of the conductivity can be quantitatively described as hopping of charge carriers being subject to spatially randomly varying energy barriers. For the low-frequency regime and for the critical frequency marking the onset of the conductivity's dispersion, the Barton-Nakajima-Namikawa (BNN) relationship is fulfilled.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 093 
Y1  - 1995
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17438
ER  - 
TY  - GEN
A1  - Kumke, Michael Uwe
A1  - Frimmel, Fritz Hartmann
T1  - Stationary and time-resolved fluorescence for humic substances characterization
N2  - Steady-state and time-resolved fluorescence methods were applied to investigate the fluorescence properties of humic substances of different origins. Using standard 2D emission and total luminescence spectra, fluorescence maxima, the width of the fluorescence band and a relative fluorescence quantum efficiency were determined. Different trends for fulvic acids and humic acids were observed indicating differences in the heterogeneity of the sample fractions. The complexity of the fluorescence decay of humic substances is discussed and compared to simple model compounds. The effect of oxidation of humic substances on their fluorescence properties is discussed as well.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 014 
Y1  - 2002
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12353
ER  - 
TY  - GEN
A1  - Dosche, Carsten
A1  - Löhmannsröben, Hans-Gerd
A1  - Bieser, A.
A1  - Dosa, P. I.
A1  - Han, S.
A1  - Iwamoto, M.
A1  - Schleifenbaum, A.
A1  - Vollhardt, K. Peter C.
T1  - Photophysical properties of [N]phenylenes
N2  - In the present study, photophysical properties of [N]phenylenes were studied by means of stationary and time-resolved absorption and fluorescence spectroscopy (in THF at room temperature). For biphenylene (1) and linear [3]phenylene (2a), internal conversion (IC) with quantum yields ΦIC > 0.99 is by far the dominant mechanism of S1 state deactivation. Angular [3]phenylene (3a), the zig-zag [4]- and [5]phenylenes (3b), (3c), and the triangular [4]phenylene (4) show fluorescence emission with fluorescence quantum yieds and lifetimes between ΦF = 0.07 for (3a) and 0.21 for (3c) and τF = 20 ns for (3a) and 81 ns for (4). Also, compounds (3) and (4) exhibit triplet formation upon photoexcitation with quantum yields as high as ΦISC = 0.45 for (3c). The strong differences in the fluorescence properties and in the triplet fromation efficiencies between (1) and (2a) on one hand and (3) and (4) on the other are related to the remarkable variation of the internal conversion (IC) rate constants kIC. A tentative classification of (1) and (2a) as “fast IC compounds”, with kIC > 109 s-1, and of (3) and (4) as “slow IC compounds”, with kIC ≈ 107 s-1, is suggested. This classification cannot simply be related to Hückel’s rule-type concepts of aromaticity, because the group of “fast IC compounds” consists of “antiaromatic” (1) and “aromatic” (2a), and the group of “slow IC compounds” consists of “antiaromatic” (3b), (4) and “aromatic” (3a), (3c). The IC in the [N]phenylenes is discussed within the framework of the so-called energy gap law established for non-radiative processes in benzenoid hydrocarbons.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 001 
Y1  - 2002
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11936
ER  - 
TY  - GEN
A1  - Kaafarani, Bilal R.
A1  - Wex, Brigitte
A1  - Strehmel, Bernd
A1  - Neckers, Douglas C.
T1  - Structural concept for fluorinated Y-enynes with solvatochromic properties
N2  - An approach to the development of fluorescent probes to follow polymerizations in situ using fluorinated cross-conjugated enediynes (Y-enynes) is reported. Different substitution patterns in the Y-enynes result in distinct solvatochromic behavior. β,β-Bis(phenylethynyl)pentafluorostyrene 7, which bears no donor substituents and only fluorine at the styrene moiety, shows no solvatochromism. Donor substituted β,β-bis(3,4,5-trimethoxyphenylethynyl) pentafluorostyrene 8 and β,β-bis(4-butyl-2,3,5,6-tetrafluorophenylethynyl)-3,4,5-trimethoxystyrene 9 exhibit solvatochromism upon change of solvent polarity. Y-enyne 8 showed the largest solvatochromic shift (94 nm bathochromic shift) upon changing solvent from cyclohexane to acetonitrile. A smaller solvatochromic response (44 nm bathochromic shift) was observed for 9. Lippert–Mataga treatment of 8 and 9 yields slopes of -10,800 and -6,400 cm -1, respectively. This corresponds to a change in dipole moment of 9.6 and 6.9 D, respectively. The solvatochromic behavior in 8 and 9 supports the formation of an intramolecular charge transfer (ICT) state. The low fluorescence quantum yields are caused by competitive double bond rotation. The fluorescence decay time of 9 decreases in methyltetrahydrofuran from 2.1 ns at 77 K to 0.11 ns at 200 K. Efficient single bond rotation in 9 was frozen at -50 °C in a configuration in which the trimethoxyphenyl ring is perpendicular to the fluorinated rings. 7–9 are photostable compounds. The X-ray structure of 7 shows it is not planar and that its conjugation is distorted. Y-enyne 7 stacks in the solid state showing coulombic, actetylene–arene, and fluorine–π interactions.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 027 
Y1  - 2002
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13168
ER  - 
TY  - GEN
A1  - Billard, Isabelle
A1  - Ansoborlo, Eric
A1  - Apperson, Kathleen
A1  - Arpigny, Sylvie
A1  - Azenha, M. Emilia
A1  - Birch, David
A1  - Bros, Pascal
A1  - Burrows, Hugh D.
A1  - Choppin, Gregory
A1  - Kumke, Michael Uwe
T1  - Aqueous solutions of Uranium(VI) as studied by time-resolved emission spectroscopy : a Round-Robin Test
N2  - Results of an inter-laboratory round-robin study of the application of time-resolved emission spectroscopy (TRES) to the speciation of uranium(VI) in aqueous media are presented. The round-robin study involved 13 independent laboratories, using various instrumentation and data analysis methods. Samples were prepared based on appropriate speciation diagrams and, in general, were found to be chemically stable for at least six months. Four different types of aqueous uranyl solutions were studied: (1) acidic medium where UO22+aq is the single emitting species, (2) uranyl in the presence of fluoride ions, (3) uranyl in the presence of sulfate ions, and (4) uranyl in aqueous solutions at different pH, promoting the formation of hydrolyzed species. Results between the laboratories are compared in terms of the number of decay components, luminescence lifetimes, and spectral band positions. The successes and limitations of TRES in uranyl analysis and speciation in aqueous solutions are discussed.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 005 
KW  - uranium (VI)
KW  - intercomparison
KW  - speciation
Y1  - 2003
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12318
ER  - 
TY  - GEN
A1  - Reich, Oliver
A1  - Löhmannsröben, Hans-Gerd
A1  - Schael, Frank
T1  - Optical sensing with photon density waves: investigation of model media
N2  - Investigations with frequency domain photon density waves allow elucidation of absorption and scattering properties of turbid media. The temporal and spatial propagation of intensity modulated light with frequencies up to more than 1 GHz can be described by the P1 approximation to the Boltzmann transport equation. In this study, we establish requirements for the appropriate choice of turbid model media and characterize mixtures of isosulfan blue as absorber and polystyrene beads as scatterer. For these model media, the independent determination of absorption and reduced scattering coefficients over large absorber and scatterer concentration ranges is demonstrated with a frequency domain photon density wave spectrometer employing intensity and phase measurements at various modulation frequencies.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 026 
Y1  - 2003
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13147
ER  - 
TY  - GEN
A1  - Löhmannsröben, Hans-Gerd
A1  - Beitz, Toralf
A1  - Luadien, Robert
A1  - Schultze, Rainer
T1  - Laser-based ion mobility spectrometry for sensing  of aromatic compounds
N2  - The drift time spectra of polycyclic aromatic hydrocarbons (PAH), alkylbenzenes and alkylphenylethers were recorded with a laser-based ion mobility (IM) spectrometer. The ion mobilities of all compounds were determined in helium as drift gas. This allows the calculation of the diffusion cross sections (Omegacalc) on the basis of the exact hard sphere scattering model (EHSSM) and their comparison with the experimentally determined diffusion cross sections (Omegaexp). These Omegaexp/Omegacalc-correlations are presented for molecules with a rigid structure like PAH and prove the reliability of the theoretical model and experimental method. The increase of the selectivity of IM spectrometry is demonstrated using resonance enhanced multiphoton ionisation (REMPI) at atmospheric pressure, realized by tuneable lasers. The REMPI spectra of nine alkylbenzenes and alkylphenylethers are investigated. On the basis of these spectra, the complete qualitative distinction of eight compounds in a mixture is shown. These experiments are extended to alkylbenzene isomer mixtures.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 003 
KW  - Laser
KW  - REMPI
KW  - Ion mobility spectrometry
KW  - PAH
Y1  - 2004
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11892
ER  - 
TY  - GEN
A1  - Hörner, Gerald
A1  - Lau, Steffen
A1  - Löhmannsröben, Hans-Gerd
T1  - NIR-diode laser spectroscopy for isotope-selective sensing of soil-respired carbon dioxide
N2  - The performance of a home-built tunable diode laser (TDL) spectrometer has been optimized regarding multi-line detection of carbon dioxide in natural gases. In the regime of the (30<SUP>0</SUP>1)<SUB>III</SUB> ← (000) band of <SUP>12</SUP>CO<SUB>2</SUB> around 1.6 μm, the dominating isotope species <SUP>12</SUP>CO<SUB>2</SUB>, <SUP>13</SUP>CO<SUB>2</SUB>, and <SUP>12</SUP>C<SUP>18</SUP>O<SUP>16</SUP>O were detected simultaneously. In contrast to most established techniques, selective measurements are performed without any sample preparation. This is possible since the CO<SUB>2</SUB> detection is free of interference from water, ubiquitous in natural gases. Detection limits in the range of a few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. Linear calibration plots cover a dynamic range of four orders of magnitude, allowing for quantitative CO<SUB>2</SUB> detection in various samples, like soil and breath gas. High isotopic resolution enables the excellent selectivity, sensitivity, and stability of the chosen analytical concept. The obtained isotopic resolution of typically ± 1.0 ‰ and ± 1.5 ‰ (for 3 vol. % and 0.7 vol. % of CO<SUB>2</SUB>, respectively) offers a promising analytical tool for isotope-ratio determination of carbon dioxide in soil gas. Preliminary experiments on soil respiration for the first time combine the on-line quantification of the overall carbon dioxide content with an optode sensor and isotopic determination (TDL system) of natural gas species.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 021 
KW  - Kohlendioxid
KW  - Isotopenverhältnis
KW  - Bodengas
KW  - Diodenlaserspektroskopie
KW  - tunable diode laser (TDL)
KW  - carbon dioxide
KW  - isotope ratios
KW  - soil gas
Y1  - 2004
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10148
ER  - 
TY  - GEN
A1  - Hörner, Gerald
A1  - Lau, Steffen
A1  - Kantor, Zoltan
A1  - Löhmannsröben, Hans-Gerd
T1  - Isotope selective analysis of CO2 with tunable diode laser (TDL) spectroscopy in the NIR
N2  - The performance of a home-built tunable diode laser (TDL) spectrometer, aimed at multi-line detection of carbon dioxide, has been evaluated and optimized. In the regime of the (30<SUP>0</SUP>1)<SUB>III</SUB> / (000) band of <SUP>12</SUP>CO<SUB>2</SUB> around 1.6 μm, the dominating isotope species <SUP>12</SUP>CO<SUB>2</SUB>, <SUP>13</SUP>CO<SUB>2</SUB>, and <SUP>12</SUP>C<SUP>18</SUP>O<SUP>16</SUP>O were detected simultaneously without interference by water vapor. Detection limits in the range of few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. High sensitivity in conjunction with high precision —typically ±1‰ and ±6‰ for 3% and 0.7% of CO<SUB>2</SUB>, respectively— renders this experimental approach a promising analytical concept for isotope-ratio determination of carbon dioxide in soil and breath gas. For a moderate <SUP>12</SUP>CO<SUB>2</SUB> line, the pressure dependence of the line profile was characterized in detail, to account for pressure effects on sensitive measurements.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 020 
KW  - Isotopenverhältnis
KW  - Kohlendioxid
KW  - Diodenlaserspektroskopie
KW  - Isotope ratio
KW  - carbon monoxide
KW  - diode laser spectroscopy
Y1  - 2004
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10167
ER  - 
TY  - GEN
A1  - Schuler, Benjamin
A1  - Lipman, Everett A.
A1  - Steinbach, Peter J.
A1  - Kumke, Michael Uwe
A1  - Eaton, William A.
T1  - Polyproline and the "spectroscopic ruler" revisited with single-molecule fluorescence
N2  - To determine whether Förster resonance energy transfer (FRET) measurements can provide quantitative distance information in single-molecule fluorescence experiments on polypeptides, we measured FRET efficiency distributions for donor and acceptor dyes attached to the ends of freely diffusing polyproline molecules of various lengths. The observed mean FRET efficiencies agree with those determined from ensemble lifetime measurements but differ considerably from the values expected from Förster theory, with polyproline treated as a rigid rod. At donor–acceptor distances much less than the Förster radius R0, the observed efficiencies are lower than predicted, whereas at distances comparable to and greater than R0, they are much higher. Two possible contributions to the former are incomplete orientational averaging during the donor lifetime and, because of the large size of the dyes, breakdown of the point-dipole approximation assumed in Förster theory. End-to-end distance distributions and correlation times obtained from Langevin molecular dynamics simulations suggest that the differences for the longer polyproline peptides can be explained by chain bending, which considerably shortens the donor–acceptor distances.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 008 
KW  - Förster resonance energy transfer
KW  - molecular dynamics
KW  - polypeptide
KW  - FRET
Y1  - 2005
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12229
ER  - 
TY  - GEN
A1  - Lemke, Matthias
A1  - Fernández-Trujillo, Rebeca
A1  - Löhmannsröben, Hans-Gerd
T1  - In-situ LIF analysis of biological and petroleum-based hydraulic oils on soil
N2  - Absorption and fluorescence properties of 4 hydraulic oils (3 biological and 1 petroleum-based) were investigated. In-situ LIF (laser-induced fluorescence) analysis of the oils on a brown sandy loam soil was performed. With calibration, quantitative detection was achieved. Estimated limits of detection were below ca. 500 mg/kg for the petroleum-based oil and ca. 2000 mg/kg for one biological oil. A semi-quantitative classification scheme is proposed for monitoring of the biological oils. This approach was applied to investigate the migration of a biological oil in soil-containing compartments, namely a soil column and a soil bed.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 011 
KW  - in-situ
KW  - optical oil sensor
KW  - lubricants
KW  - hydraulic oils
KW  - soil
KW  - laser induced
Y1  - 2005
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12268
ER  - 
TY  - GEN
A1  - Kumke, Michael Uwe
A1  - Eidner, Sascha
T1  - Fluorescence and energy transfer processes of humic substances and related model compounds in terbium complexes
N2  - The fluorescence properties and the fluorescence quenching by Tb3+ of substituted benzoic acid were investigated in solution at different pH. The substituted benzoic acids were used as simple model compounds for chromophores present in humic substances (HS). It is shown that the fluorescence properties of the model compounds resemble fluorescence of HS quite well. A major factor determining the fluorescence of model compounds are proton transfer reactions in the electronically excited state. It is intriguing that the fluorescence of the model compounds was almost not quenched by Tb3+ while the HS fluorescence was decreased very effectively. From our results we concluded that proton transfer reactions as well as conformational reorientation processes play an important role in the fluorescence of HS. The luminescence of bound Tb3+ was sensitized by an energy transfer step upon excitation of the model compounds and of HS, respectively. For HS the observed sensitization was dependent on its origin indicating differences 1) in the connection between chromophores and binding sites and 2) in the energy levels of the chromophore triplet states. Hence, the observed sensitization of the Tb3+ luminescence could be useful to characterize structural differences of HS in solution. Interlanthanide energy transfer between Tb3+ and Nd3+ was used to determine the average distance R between both ions using the well-known formalism of luminescence resonance energy transfer. R was dependent on the origin of the HS reflecting the difference in structure. The value of Rmin seemed to be a unique feature of the HS. It was further found that upon variation of the pH R also changed. This demonstrates that the measurement of interlanthanide energy transfer can be used as a direct method to monitor conformational changes in HS.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 10 
Y1  - 2005
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12255
ER  - 
TY  - GEN
A1  - Schmälzlin, Elmar
A1  - Dongen, Joost T. van
A1  - Klimant, Ingo
A1  - Marmodée, Bettina
A1  - Steup, Martin
A1  - Fishahn, Joachim
A1  - Geigenberger, Peter
A1  - Löhmannsröben, Hans-Gerd
T1  - An optical multifrequency phase-modulation method using microbeads for measuring intracellular oxygen concentrations in plants
N2  - A technique has been developed to measure absolute intracellular oxygen concentrations in green plants. Oxygen-sensitive phosphorescent microbeads were injected into the cells and an optical multifrequency phase-modulation technique was used to discriminate the sensor signal from the strong autofluorescence of the plant tissue. The method was established using photosynthesis-competent cells of the giant algae Chara corallina L., and was validated by application to various cell types of other plant species.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 007 
Y1  - 2005
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12232
ER  - 
TY  - GEN
A1  - Hildebrandt, Nico
A1  - Charbonnière, Loïc J.
A1  - Ziessel, Raymond F.
A1  - Löhmannsröben, Hans-Gerd
T1  - Quantum dots as resonance energy transfer acceptors for monitoring biological interactions
N2  - Quantum dots (QDs) are common as luminescing markers for imaging in biological applications because their optical properties seem to be inert against their surrounding solvent. This, together with broad and strong absorption bands and intense, sharp tuneable luminescence bands, makes them interesting candidates for methods utilizing Forster Resonance Energy Transfer (FRET), e. g. for sensitive homogeneous fluoroimmunoassays (FIA). In this work we demonstrate energy transfer from Eu3+-trisbipyridin (Eu-TBP) donors to CdSe-ZnS-QD acceptors in solutions with and without serum. The QDs are commercially available CdSe-ZnS core-shell particles emitting at 655 nm (QD655). The FRET system was achieved by the binding of the streptavidin conjugated donors with the biotin conjugated acceptors. After excitation of Eu-TBP and as result of the energy transfer, the luminescence of the QD655 acceptors also showed lengthened decay times like the donors. The energy transfer efficiency, as calculated from the decay times of the bound and the unbound components, amounted to 37%. The Forster-radius, estimated from the absorption and emission bands, was ca. 77Å. The effective binding ratio, which not only depends on the ratio of binding pairs but also on unspecific binding, was obtained from the donor emission dependent on the concentration. As serum promotes unspecific binding, the overall FRET efficiency of the assay was reduced. We conclude that QDs are good substitutes for acceptors in FRET if combined with slow decay donors like Europium. The investigation of the influence of the serum provides guidance towards improving binding properties of QD assays.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 012 
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12213
ER  - 
TY  - GEN
A1  - Schmälzlin, Elmar
A1  - Walz, Bernd
A1  - Klimant, Ingo
A1  - Schewe, Bettina
A1  - Löhmannsröben, Hans-Gerd
T1  - Monitoring hormone-induced oxygen consumption in the salivary glands of the blowfly, Calliphora vicina, by use of luminescent microbeads
N2  - The salivary glands of the blowfly were injected with luminescent oxygen-sensitive microbeads. The changes in oxygen content within individual gland tubules during hormone-induced secretory activity were quantified. The measurements are based on an upgraded phase-modulation technique, where the phase shift of the sensor phosphorescence is determined independently from concentration and background signals. We show that the combination of a lock-in amplifier with a fluorescence microscope results in a convenient setup to measure oxygen concentrations within living animal tissues at the cellular level.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 006 
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12206
ER  - 
TY  - GEN
A1  - Engelhard, Sonja
A1  - Kumke, Michael Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - OPQS – optical process and quality sensing : exemplary applications in the beerbrewing and polyurethane foaming processes
N2  - Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near-infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 004 
KW  - process analytical technology
KW  - beer
KW  - biomass
KW  - foam analysis
KW  - NIR spectroscopy
KW  - fluorescence quenching
KW  - photon density wave spectroscopy
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12191
ER  - 
TY  - GEN
A1  - Löhmannsröben, Hans-Gerd
A1  - Beck, Michael
A1  - Hildebrandt, Niko
A1  - Schmälzlin, Elmar
A1  - van Dongen, Joost T.
T1  - New challenges in biophotonics : laser-based fluoroimmuno analysis and in-vivo optical oxygen monitoring
N2  - Two examples of our biophotonic research utilizing nanoparticles are presented, namely laser-based fluoroimmuno analysis and in-vivo optical oxygen monitoring. Results of the work include significantly enhanced sensitivity of a homogeneous fluorescence immunoassay and markedly improved spatial resolution of oxygen gradients in root nodules of a legume species.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 018 
KW  - Sauerstoff
KW  - Quantenpunkt
KW  - Lumineszenz
KW  - Immunoassay
KW  - Energietransfer
KW  - Fluoreszenz-Resonanz-Energie-Transfer
KW  - Nanopartikel
KW  - Lanthanoide
KW  - Optode
KW  - Förster Resonanz Energie Transfer
KW  - Biophotonik
KW  - biophotonics
KW  - nanoparticles
KW  - immunoassay
KW  - oxygen
KW  - optode
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10120
ER  - 
TY  - GEN
A1  - Lau, Steffen
A1  - Salffner, Katharina
A1  - Löhmannsröben, Hans-Gerd
T1  - Isotopic resolution of carbon monoxide and carbon dioxide by NIR diode laser spectroscopy
N2  - Near-infrared (NIR) absorption spectroscopy with tunable diode lasers allows the simultaneous detection of the three most important isotopologues of carbon dioxide (<SUP>12</SUP>CO<SUB>2</SUB>, <SUP>13</SUP>CO<SUB>2</SUB>, <SUP>12</SUP>C<SUP>18</SUP>O<SUP>16</SUP>O) and carbon monoxide (<SUP>12</SUP>CO, <SUP>13</SUP>CO, <SUP>12</SUP>C<SUP>18</SUP>O). The flexible and compact fiber-optic tunable diode laser absorption spectrometer (TDLAS) allows selective measurements of CO<SUB>2</SUB> and CO with high isotopic resolution without sample preparation since there is no interference with water vapour. For each species, linear calibration plots with a dynamic range of four orders of magnitude and detection limits (LOD) in the range of a few ppm were obtained utilizing wavelength modulation spectroscopy (WMS) with balanced detection in a Herriott-type multipass cell. The high performance of the apparatus is illustrated by fill-evacuation-refill cycles.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 017 
KW  - Isotop
KW  - Kohlenmonoxid
KW  - Kohlendioxid
KW  - Diodenlaserspektroskopie
KW  - isotope
KW  - carbon monoxide
KW  - carbon dioxide
KW  - diode laser spectroscopy
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10135
ER  - 
TY  - GEN
A1  - Niederkrüger, Matthias
A1  - Salb, Christian
A1  - Beck, Michael
A1  - Hildebrandt, Niko
A1  - Löhmannsröben, Hans-Gerd
A1  - Marowsky, Gerd
T1  - Improvement of a fluorescence immunoassay with a compact diode-pumped solid state laser at 315 nm
N2  - We demonstrate the improvement of fluorescence immunoassay (FIA) diagnostics in deploying a newly developed compact diode-pumped solid state (DPSS) laser with emission at 315 nm. The laser is based on the quasi-three-level transition in Nd:YAG at 946 nm. The pulsed operation is either realized by an active Q-switch using an electro-optical device or by introduction of a Cr<SUP>4+</SUP>:YAG saturable absorber as passive Q-switch element. By extra-cavity second harmonic generation in different nonlinear crystal media we obtained blue light at 473 nm. Subsequent mixing of the fundamental and the second harmonic in a β-barium-borate crystal provided pulsed emission at 315 nm with up to 20 μJ maximum pulse energy and 17 ns pulse duration. Substitution of a nitrogen laser in a FIA diagnostics system by the DPSS laser succeeded in considerable improvement of the detection limit. Despite significantly lower pulse energies (7 μJ DPSS laser versus 150 μJ nitrogen laser), in preliminary investigations the limit of detection was reduced by a factor of three for a typical FIA.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 016 
KW  - Immunoassay
KW  - Fluoreszenz-Resonanz-Energie-Transfer
KW  - Neodym-YAG-Laser
KW  - 946 nm
KW  - 473 nm
KW  - 315 nm
KW  - gepulster DPSS Laser
KW  - sättigbarer Absorber
KW  - fluorescence immunoassay
KW  - 946 nm
KW  - 473 nm
KW  - 315 nm
KW  - pulsed DPSS laser
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10150
ER  - 
TY  - GEN
A1  - Beck, Michael
A1  - Hildebrandt, Niko
A1  - Löhmannsröben, Hans-Gerd
T1  - Quantum dots as acceptors in FRET-assays containing serum
N2  - Quantum dots (QDs) are common as luminescing markers for imaging in biological applications because their optical properties seem to be inert against their surrounding solvent. This, together with broad and strong absorption bands and intense, sharp tuneable luminescence bands, makes them interesting candidates for methods utilizing Förster Resonance Energy Transfer (FRET), e. g. for sensitive homogeneous fluoroimmunoassays (FIA). In this work we demonstrate energy transfer from Eu<SUP>3+</SUP>-trisbipyridin (Eu-TBP) donors to CdSe-ZnS-QD acceptors in solutions with and without serum. The QDs are commercially available CdSe-ZnS core-shell particles emitting at 655 nm (QD655). The FRET system was achieved by the binding of the streptavidin conjugated donors with the biotin conjugated acceptors. After excitation of Eu-TBP and as result of the energy transfer, the luminescence of the QD655 acceptors also showed lengthened decay times like the donors. The energy transfer efficiency, as calculated from the decay times of the bound and the unbound components, amounted to 37%. The Förster-radius, estimated from the absorption and emission bands, was ca. 77 Å. The effective binding ratio, which not only depends on the ratio of binding pairs but also on unspecific binding, was obtained from the donor emission dependent on the concentration. As serum promotes unspecific binding, the overall FRET efficiency of the assay was reduced. We conclude that QDs are good substitutes for acceptors in FRET if combined with slow decay donors like Europium. The investigation of the influence of the serum provides guidance towards improving binding properties of QD assays.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 019 
KW  - Quantenpunkt
KW  - Lumineszenz
KW  - Serum
KW  - Europium
KW  - Immunoassay
KW  - Energietransfer
KW  - Fluoreszenz-Resonanz-Energie-Transfer
KW  - Förster-Resonanz-Energie-Transfer
KW  - Quantum Dot
KW  - Luminescence
KW  - Serum
KW  - Europium
KW  - Immunoassay
KW  - Energy Transfer
KW  - FRET
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-9504
ER  - 
TY  - GEN
A1  - Dosche, Carsten
A1  - Mickler, Wulfhard
A1  - Löhmannsröben, Hans-Gerd
A1  - Agenet, Nicolas
A1  - Vollhardt, K. Peter C.
T1  - Photoinduced electron transfer in [N]phenylenes
N2  - First studies of electron transfer in [N]phenylenes were performed in bimolecular quenching reactions of angular [3]- and triangular [4]phenylene with various electron acceptors. The relation between the quenching rate constants kq and the free energy change of the electron transfer (ΔG0CS ) could be described by the Rehm-Weller equation. From the experimental results, a reorganization energy λ of 0.7 eV was derived. Intramolecular electron transfer reactions were studied in an [N]phenylene bichomophore and a corresponding reference compound. Fluorescence lifetime and quantum yield of the bichromophor display a characteristic dependence on the solvent polarity, whereas the corresponding values of the reference compound remain constant. From the results, a nearly isoenergonic ΔG0CS can be determined. As the triplet quantum yield is nearly independent of the polarity, charge recombination leads to the population of the triplet state.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 23 
KW  - [N]phenylenes
KW  - photoinduced electron transfer
KW  - [N]phenylene dyads
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12463
ER  - 
TY  - GEN
A1  - Oliveira Jr, E. N.
A1  - Gueddari, Nour E. El
A1  - Moerschbacher, Bruno M.
A1  - Peter, Martin
A1  - Franco, Telma
T1  - Growth of phytopathogenic fungi in the presence of partially acetylated chitooligosaccharides
N2  - Four phytopathogenic fungi were cultivated up to six days in media containing chitooligosaccharide mixtures differing in average DP and FA. The three different mixtures were named Q3 (which contained oligosaccharides ofDP2–DP10, withDP2–DP7 asmain components), Q2 (which contained oligosaccharides of DP2–DP12, with DP2–DP10 as main components) and Q1 (which derived from Q2 and contained oligomers of DP5–DP8 with hexamer and a heptamer as the main components). The novel aspect of this work is the description of the effect of mixtures of oligosaccharides with different and known composition on fungal growth rates. The growth rate of Alternaria alternata and Rhizopus stolonifer was initially inhibited by Q3 and Q2 at higher concentrations. Q1 had a growth stimulating effect on these two fungi. Growth of Botrytis cinerea was inhibited by Q3 and Q2, while Q1 had no effect on the growth of this fungus. Growth of Penicillium expansum was only slightly inhibited by higher concentrations of sample Q3, while Q2 and Q1 had no effect. The inhibition of growth rates or their resistance toward chitooligosaccharides correlated with the absence or presence of chitinolytic enzymes in the culture media, respectively.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 105 
KW  - Chitosan
KW  - Chitinase
KW  - Fungi
KW  - Oligosaccharides
KW  - Phytopathogens
Y1  - 2008
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-42646
ER  - 
TY  - GEN
A1  - Bringmann, Gerhard
A1  - Mutanyatta-Comar, Joan
A1  - Maksimenka, Katja
A1  - Wanjohi, John M.
A1  - Heydenreich, Matthias
A1  - Brun, Reto
A1  - Müller, Werner E. G.
A1  - Peter, Martin
A1  - Midiwo, Jacob O.
A1  - Yenesew, Abiy
T1  - Joziknipholones A and B : the First Dimeric Phenylanthraquinones, from the Roots of Bulbine frutescens
N2  - From the roots of the African plant Bulbine frutescens (Asphodelaceae), two unprecedented novel dimeric phenylanthraquinones, named joziknipholones A and B, possessing axial and centrochirality, were isolated, together with six known compounds. Structural elucidation of the new metabolites was achieved by spectroscopic and chiroptical methods, by reductive cleavage of the central bond between the monomeric phenylanthraquinone and -anthrone portions with sodium dithionite, and by quantum chemical CD calculations. Based on the recently revised absolute axial configuration of the parent phenylanthraquinones, knipholone and knipholone anthrone, the new dimers were attributed to possess the P-configuration (i.e., with the acetyl portions below the anthraquinone plane) at both axes in the case of joziknipholone A, whereas in joziknipholone B, the knipholone part was found to be M-configured. Joziknipholones A and B are active against the chloroquine resistant strain K1 of the malaria pathogen, Plasmodium falciparum, and show moderate activity against murine leukemic lymphoma L5178y cells.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 104 
KW  - antimalarial activity
KW  - chirality
KW  - joziknipholones
KW  - natural products
KW  - structure elucidation
Y1  - 2008
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-42638
ER  - 
TY  - GEN
A1  - Tsukamoto, Junko
A1  - Heabel, Sophie
A1  - Valenca, Gustavo P.
A1  - Peter, Martin
A1  - Franco, Telma
T1  - Enzymatic direct synthesis of acrylic acid esters of mono- and disaccharides
N2  - BACKGROUND: There is an increased need to replace materials derived from fossil sources by renewables. Sugar-cane derived carbohydrates are very abundant in Brazil and are the cheapest sugars available in the market, with more than 400 million tons of sugarcane processed in the year 2007. The objective of this work was to study the preparation of sugar acrylates from free sugars and free acrylic acid, thus avoiding the previous preparation of protected sugar derivatives, such as glycosides, or activated acrylates, such as vinyl acrylate. RESULTS: Lipase catalyzed esterification of three mono- and two disaccharides with acrylic acid, in the presence or absence of molecular sieves was investigated. The reactions were monitored by high-performance liquid chromatography (HPLC) and the products were analyzed by matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry. The main products are mono- and diacrylates, while higher esters are formed as minor products. The highest conversion to sugar acrylates was observed for the D-glucose and D-fructose, followed by D-xylose and D-maltose. Molecular sieves had no pronounced effect on the conversion CONCLUSIONS: A feasible method is described to produce and to characterize sugar acrylates, including those containing more than two acrylate groups. The process for production of these higher esters could potentially be optimized further to produce molecules for cross-linking in acrylate polymerization and other applications. The direct enzymatic esterification of free carbohydrates with acrylic acid is unprecedented.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 106 
KW  - carbohydrate esters
KW  - enzymatic esterification
KW  - acrylic acid esters
KW  - MALDI-TOF mass spectrometry
Y1  - 2008
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-42652
ER  - 
TY  - GEN
A1  - Schäfer-Bung, Boris
A1  - Nest, Mathias
T1  - Correlated dynamics of electrons with reduced two-electron density matrices
N2  - We present an approach to the correlated dynamics of many-electron systems. We show, that the twoelectron reduced density matrix (2RDM) can provide a suitable description of the real time evolution of a system. To achieve this, the hierarchy of equations of motion must be truncated in a practical way. Also, the computational effort, given that the 2RDM is represented by products of two-electron determinants, is discussed, and numerical model calculations are presented.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 100 
Y1  - 2008
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-41774
SN  - 1866-8372
ER  - 
TY  - GEN
A1  - Jeličić, Aleksandra
A1  - Friedrich, Alwin
A1  - Jeremić, Katarina
A1  - Siekmeyer, Gerd
A1  - Taubert, Andreas
T1  - Polymer hydrogel/polybutadiene/iron oxide nanoparticle hybrid actuators for the characterization of NiTi implants
N2  - One of the main issues with the use of nickel titanium alloy (NiTi) implants in cardiovascular implants (stents) is that these devices must be of very high quality in order to avoid subsequent operations due to failing stents. For small stents with diameters below ca. 2 mm, however, stent characterization is not straightforward. One of the main problems is that there are virtually no methods to characterize the interior of the NiTi tubes used for fabrication of these tiny stents. The current paper reports on a robust hybrid actuator for the characterization of NiTi tubes prior to stent fabrication. The method is based on a polymer/hydrogel/magnetic nanoparticle hybrid material and allows for the determination of the inner diameter at virtually all places in the raw NiTi tubes. Knowledge of the inner structure of the raw NiTi tubes is crucial to avoid regions that are not hollow or regions that are likely to fail due to defects inside the raw tube. The actuator enables close contact of a magnetic polymer film with the inner NiTi tube surface. The magnetic signal can be detected from outside and be used for a direct mapping of the tube interior. As a result, it is possible to detect critical regions prior to expensive and slow stent fabrication processes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 161 
KW  - NiTi
KW  - inner surface
KW  - hydrogel
KW  - polybutadiene
KW  - magnetic nanoparticles
Y1  - 2009
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-48589
ER  - 
TY  - GEN
A1  - Li, Zhonghao
A1  - Taubert, Andreas
T1  - Cellulose/gold nanocrystal hybrids via an ionic liquid/aqueous precipitation route
N2  - Injection of a mixture of HAuCl4 and cellulose dissolved in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride [Bmim]Cl into aqueous NaBH4 leads to colloidal gold nanoparticle/cellulose hybrid precipitates. This process is a model example for a very simple and generic approach towards (noble) metal/cellulose hybrids, which could find applications in sensing, sterile filtration, or as biomaterials.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 135 
KW  - Cellulose
KW  - Gold nanoparticles
KW  - Ionic liquid
KW  - Precipitation
KW  - Hybrid material
Y1  - 2009
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-45046
ER  - 
TY  - GEN
A1  - Peter, Martin G.
A1  - Yenesew, Abiy
A1  - Twinomuhwezi, Hannington
A1  - Kabaru, Jacques M.
A1  - Akala, Hoseah M.
A1  - Kiremire, Bernard T.
A1  - Heydenreich, Matthias
A1  - Eyase, Fredrick
A1  - Waters, Norman C.
A1  - Walsh, Douglas S.
T1  - Antiplasmodial and larvicidal flavonoids from Derris trifoliata
N2  - From the dichloromethane-methanol (1:1) extract of the seed pods of Derris trifoliata, a new flavanone derivative (S)-lupinifolin 4´-methyl ether was isolated. In addition, the known flavonoids lupinifolin and rotenone were identified. The structures were determined on the basis of spectroscopic evidence. Lupinfolin showed moderate in vitro antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquineresistant) strains of Plasmodium falciparum. The different parts of this plant showed larvicidal activities against Aedes aegypti and rotenoids were identified as the active principles.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 121 
KW  - Derris trifoliata
KW  - Leguminosae
KW  - Flavanone
KW  - (S)-Lupinifolin 4´-methyl ether
KW  - Lupinifolin
Y1  - 2009
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-44614
ER  - 
TY  - GEN
A1  - Peter, Martin G.
A1  - Muiva, Lois M.
A1  - Yenesew, Abiy
A1  - Derese, Solomon
A1  - Heydenreich, Matthias
A1  - Akala, Hoseah M.
A1  - Eyase, Fredrick
A1  - Waters, Norman C.
A1  - Mutai, Charles
A1  - Keriko, Joseph M.
A1  - Walsh, Douglas S.
T1  - Antiplasmodial β-hydroxydihydrochalcone from seedpods of Tephrosia elata
N2  - From the seedpods of Tephrosia elata, a new β-hydroxydihydrochalcone named (S)-elatadihydrochalcone was isolated. In addition, the known flavonoids obovatachalcone, obovatin, obovatin methyl ether and deguelin were identified. The structures were determined on the basis of spectroscopic evidence. The crude extract and the flavonoids obtained from the seedpods of this plant showed antiplasmodial activities. The literature NMR data on β-hydroxydihydrochalcones is reviewed and the identity of some of the compounds assigned β-hydroxydihydrochalcone skeleton is questioned.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 118 
KW  - Tephrosia elata
KW  - Leguminosae
KW  - Seedpods
KW  - (S)-Elatadihydrochalcone
KW  - β-Hydroxydihydrochalcone
Y1  - 2009
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-44437
ER  - 
TY  - GEN
A1  - Schmidt, Bernd
A1  - Hauke, Sylvia
T1  - Cross metathesis of allyl alcohols
BT  - how to suppress and how to promote double bond isomerization
N2  - Under standard conditions the cross metathesis of allyl alcohols and methyl acrylate is accompanied by the formation of ketones, resulting from uncontrolled and undesired double bond isomerization. By conducting the CM in the presence of phenol, the catalyst loading and the reaction time required for quantiative conversion can be reduced, and isomerization can be suppressed. On the other hand, consecutive isomerization can be deliberately promoted by evaporating excess methyl acrylate after completing cross metathesis and by adding a base or silane as chemical triggers.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 241 
KW  - ring-closing metathesis
KW  - de-novo synthesis
KW  - catalyzed redox isomerization
KW  - carbohydrate-based oxepines
KW  - diels-alder reaction
KW  - olefin-metathesis
KW  - in-situ
KW  - ruthenium carbene
KW  - alkynol cycloisomerization
KW  - carbonyl-compounds
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95037
SP  - 4194
EP  - 4206
ER  - 
TY  - GEN
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Population splitting, trapping, and non-ergodicity in heterogeneous diffusion processes
N2  - We consider diffusion processes with a spatially varying diffusivity giving rise to anomalous diffusion. Such heterogeneous diffusion processes are analysed for the cases of exponential, power-law, and logarithmic dependencies of the diffusion coefficient on the particle position. Combining analytical approaches with stochastic simulations, we show that the functional form of the space-dependent diffusion coefficient and the initial conditions of the diffusing particles are vital for their statistical and ergodic properties. In all three cases a weak ergodicity breaking between the time and ensemble averaged mean squared displacements is observed. We also demonstrate a population splitting of the time averaged traces into fast and slow diffusers for the case of exponential variation of the diffusivity as well as a particle trapping in the case of the logarithmic diffusivity. Our analysis is complemented by the quantitative study of the space coverage, the diffusive spreading of the probability density, as well as the survival probability.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 236 
KW  - anomalous diffusion
KW  - disordered media
KW  - fractional dynamics
KW  - infection pathway
KW  - inhomogeneous-media
KW  - intracellular-transport
KW  - langevin equation
KW  - living cells
KW  - random-walks
KW  - single-particle tracking
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94468
SP  - 20220
EP  - 20235
ER  - 
TY  - GEN
A1  - Schönborn, Jan Boyke
A1  - Hartke, Bernd
T1  - Photochemical dynamics of E-methylfurylfulgide
BT  - kinematic effects on photorelaxation dynamics of furylfulgides
N2  - With the present theoretical study of the photochemical switching of E-methylfurylfulgide we contribute an important step towards the understanding of the photochemical processes in furylfulgide-related molecules. We have carried out large-scale, full-dimensional direct semiempirical configuration-interaction surface-hopping dynamics of the photoinduced ring-closure reaction. Simulated static and dynamical UV/Vis-spectra show good agreement with experimental data of the same molecule. By a careful investigation of our dynamical data, we were able to identify marked differences to the dynamics of the previously studied E-isopropylfurylfulgide. With our simulations we can not only reproduce the experimentally observed quantum yield differences qualitatively but we can also pinpoint two reasons for them: kinematics and pre-orientation. With our analysis, we thus offer straightforward molecular explanations for the high sensitivity of the photodynamics towards seemingly minor changes in molecular constitution. Beyond the realm of furylfulgides, these insights provide additional guidance to the rational design of photochemically switchable molecules.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 237 
KW  - decay dynamics
KW  - fulgides
KW  - implementation
KW  - molecular-dynamics
KW  - photoinduced nonadiabatic dynamics
KW  - photoisomerization
KW  - ring-closure
KW  - semiempirical methods
KW  - spectroscopy
KW  - state
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94516
SP  - 2483
EP  - 2490
ER  - 
TY  - GEN
A1  - McQuade, D. Tyler
A1  - O'Brien, Alexander G.
A1  - Dörr, Markus
A1  - Rajaratnam, Rajathees
A1  - Eisold, Ursula
A1  - Monnanda, Bopanna
A1  - Nobuta, Tomoya
A1  - Löhmannsröben, Hans-Gerd
A1  - Meggers, Eric
A1  - Seeberger, Peter H.
T1  - Continuous synthesis of pyridocarbazoles and initial photophysical and bioprobe characterization
N2  - Pyridocarbazoles when ligated to transition metals yield high affinity kinase inhibitors. While batch photocyclizations enable the synthesis of these heterocycles, the non-oxidative Mallory reaction only provides modest yields and difficult to purify mixtures. We demonstrate here that a flow-based Mallory cyclization provides superior results and enables observation of a clear isobestic point. The flow method allowed us to rapidly synthesize ten pyridocarbazoles and for the first time to document their interesting photophysical attributes. Preliminary characterization reveals that these molecules might be a new class of fluorescent bioprobe.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 246 
KW  - protein-kinase inhibitors
KW  - continuous-flow
KW  - photochemical synthesis
KW  - light
KW  - efficient
KW  - phenanthrenes
KW  - complexes
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95214
SP  - 4067
EP  - 4070
ER  - 
TY  - GEN
A1  - Wessig, Pablo
A1  - Matthes, Annika
T1  - Photochemical synthesis and properties of 1,6- and 1,8-Naphthalenophanes
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Various 1,6- and 1,8-naphthalenophanes were synthesized by using the Photo-Dehydro-Diels-Alder (PDDA) reaction of bis-ynones. These compounds are easily accessible from omega-(3-iodophenyl)carboxylic acids in three steps. The obtained naphthalenophanes are axially chiral and the activation barrier for the atropisomerization could be determined in some cases by means of dynamic NMR (DNMR) and/or dynamic HPLC (DHPLC) experiments.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1042 
KW  - photo-dehydro-Diels-Alder reaction
KW  - naphthalenophanes
KW  - atropisomerism
KW  - dynamic NMR
KW  - dynamic HPLC
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-476675
SN  - 1866-8372
IS  - 1042
ER  - 
TY  - GEN
A1  - Eich, Susanne
A1  - Schmälzlin, Elmar
A1  - Löhmannsröben, Hans-Gerd
T1  - Distributed fiber optical sensing of oxygen with optical time domain reflectometry
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - In many biological and environmental applications spatially resolved sensing of molecular oxygen is desirable. A powerful tool for distributed measurements is optical time domain reflectometry (OTDR) which is often used in the field of telecommunications. We combine this technique with a novel optical oxygen sensor dye, triangular-[4] phenylene (TP), immobilized in a polymer matrix. The TP luminescence decay time is 86 ns. The short decay time of the sensor dye is suitable to achieve a spatial resolution of some meters. In this paper we present the development and characterization of a reflectometer in the UV range of the electromagnetic spectrum as well as optical oxygen sensing with different fiber arrangements.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1085 
KW  - OTDR
KW  - optical sensing
KW  - molecular oxygen
KW  - triangular-[4] phenylene
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-476659
SN  - 1866-8372
IS  - 1085
ER  - 
TY  - GEN
A1  - Men, Yongjun
A1  - Siebenbürger, Miriam
A1  - Qiu, Xunlin
A1  - Antonietti, Markus
A1  - Yuan, Jiayin
T1  - Low fractions of ionic liquid or poly(ionic liquid) can activate polysaccharide biomass into shaped, flexible and fire-retardant porous carbons
N2  - Sugar-based molecules and polysaccharide biomass can be turned into porous functional carbonaceous products at comparably low temperatures of 400 °C under a nitrogen atmosphere in the presence of an ionic liquid (IL) or a poly(ionic liquid) (PIL). The IL and PIL act as “activation agents” with own structural contribution, and effectively promote the conversion and pore generation in the biomaterials even at a rather low doping ratio (7 wt%). In addition, this “induced carbonization” and pore forming phenomenon enables the preservation of the biotemplate shape to the highest extent and was employed to fabricate shaped porous carbonaceous materials from carbohydrate-based biotemplates, exemplified here with cellulose filter membranes, coffee filter paper and natural cotton. These carbonized hybrids exhibit comparably good mechanical properties, such as bendability of membranes or shape recovery of foams. Moreover, the nitrogen atoms incorporated in the final products from the IL/PIL precursors further improve the oxidation stability in the fire-retardant tests.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 248 
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95250
SP  - 11887
EP  - 11887
ER  - 
TY  - GEN
A1  - Mondal, Suvendu Sekhar
A1  - Dey, Subarna
A1  - Baburin, Igor A.
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Seifert, Gotthard
A1  - Janiak, Christoph
A1  - Holdt, Hans-Jürgen
T1  - Syntheses of two imidazolate-4-amide-5-imidate linker-based hexagonal metal–organic frameworks with flexible ethoxy substituent
N2  - A rare example of in situ linker generation with the formation of soft porous Zn- and Co-MOFs (IFP-9 and -10, respectively) is reported. The flexible ethoxy groups of IFP-9 and -10 protrude into the 1D hexagonal channels. The gas-sorption behavior of both materials for H2, CO2 and CH4 showed wide hysteretic isotherms, typical for MOFs having a flexible substituent which can give rise to a gate effect.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 234 
KW  - adsorption
KW  - behavior
KW  - carbon-dioxide
KW  - crystals
KW  - gases
KW  - ligand
KW  - pressure
KW  - selectivity
KW  - temperature
KW  - zinc
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94360
SP  - 9394
EP  - 9399
ER  - 
TY  - GEN
A1  - Mondal, Suvendu Sekhar
A1  - Bhunia, Asamanjoy
A1  - Demeshko, Serhiy
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Janiak, Christoph
A1  - Holdt, Hans-Jürgen
T1  - Synthesis of a Co(II)–imidazolate framework from an anionic linker precursor
BT  - gas-sorption and magnetic properties
N2  - A Co(II)–imidazolate-4-amide-5-imidate based MOF, IFP-5, is synthesized by using an imidazolate anion-based novel ionic liquid as a linker precursor under solvothermal conditions. IFP-5 shows significant amounts of gas (N2, CO2, CH4 and H2) uptake capacities. IFP-5 exhibits an independent high spin Co(II) centre and antiferromagnetic coupling.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 235 
KW  - building-blocks
KW  - carbon-dioxide capture
KW  - exchange
KW  - ionic liquids
KW  - ionothermal synthesis
KW  - ligand
KW  - metal-organic frameworks
KW  - solvent
KW  - surface
KW  - zeolitic imidazolate frameworks
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94424
SP  - 39
EP  - 42
ER  - 
TY  - GEN
A1  - Mondal, Suvendu Sekhar
A1  - Bhunia, Asamanjoy
A1  - Baburin, Igor A.
A1  - Jäger, Christian
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Seifert, Gotthard
A1  - Janiak, Christoph
A1  - Holdt, Hans-Jürgen
T1  - Gate effects in a hexagonal zinc-imidazolate-4-amide-5-imidate framework with flexible methoxy substituents and CO2 selectivity
N2  - A new imidazolate-4-amide-5-imidate based MOF, IFP-7, is generated, having flexible methoxy groups, which act as molecular gates for guest molecules. This allows highly selective CO2 sorption over N2 and CH4 gases.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 233 
KW  - adsorption
KW  - capacity
KW  - carbon-dioxide capture
KW  - coordination polymer
KW  - flexibility
KW  - hydrogen storage
KW  - ligand
KW  - metal-organic frameworks
KW  - mixed-matrix membranes
KW  - separation
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94341
SP  - 7599
EP  - 7601
ER  - 
TY  - GEN
A1  - Winter, Alette
A1  - Thiel, Kerstin
A1  - Zabel, André
A1  - Klamroth, Tillmann
A1  - Pöppl, Andreas
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Taubert, Andreas
A1  - Strauch, Peter
T1  - Tetrahalidocuprates(II) – structure and EPR spectroscopy
BT  - Part 2: tetrachloridocuprates(II)
N2  - We present and discuss the results of crystallographic and electron paramagnetic resonance (EPR) spectroscopic analyses of five tetrachloridocuprate(II) complexes to supply a useful tool for the structural characterisation of the [CuCl4]2− moiety in the liquid state, for example in ionic liquids, or in solution. Bis(benzyltriethylammonium)-, bis(trimethylphenylammonium)-, bis(ethyltriphenylphosphonium)-, bis(benzyltriphenylphosphonium)-, and bis(tetraphenylarsonium)tetrachloridocuprate(II) were synthesised and characterised by elemental, IR, EPR and X-ray analyses. The results of the crystallographic analyses show distorted tetrahedral coordination geometry of all [CuCl4]2− anions in the five complexes and prove that all investigated complexes are stabilised by hydrogen bonds of different intensities. Despite the use of sterically demanding ammonium, phosphonium and arsonium cations to obtain the separation of the paramagnetic Cu(II) centres for EPR spectroscopy no hyperfine structure was observed in the EPR spectra but the principal values of the electron Zeeman tensor, g∥ and g⊥, could be determined. With these EPR data and the crystallographic parameters we were able to carry out a correlation study to anticipate the structural situation of tetrachloridocuprates in different physical states. This correlation is in good agreement with DFT calculations.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 240 
KW  - electron-spin resonance
KW  - liquid-crystal precursors
KW  - copper(II) halide salts
KW  - ionic liquid
KW  - square planar
KW  - tetrachlorocuprate(II) salts
KW  - molecular-structure
KW  - magnetic-properties
KW  - paramagnetic-resonance
KW  - temperature phase
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95012
SP  - 1019
EP  - 1030
ER  - 
TY  - GEN
A1  - Junginger, Mathias
A1  - Kübel, Christian
A1  - Schacher, Felix H.
A1  - Müller, Axel H. E.
A1  - Taubert, Andreas
T1  - Crystal structure and chemical composition of biomimetic calcium phosphate nanofibers
N2  - Calcium phosphate nanofibers with a diameter of only a few nanometers and a cotton-ball-like aggregate morphology have been reported several times in the literature. Although fiber formation seems reproducible in a variety of conditions, the crystal structure and chemical composition of the fibers have been elusive. Using scanning transmission electron microscopy, low dose electron (nano)diffraction, energy-dispersive X-ray spectroscopy, and energy-filtered transmission electron microscopy, we have assigned crystal structures and chemical compositions to the fibers. Moreover, we demonstrate that the mineralization process yields true polymer/calcium phosphate hybrid materials where the block copolymer template is closely associated with the calcium phosphate.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 244 
KW  - air-water-interface
KW  - polycationic monolayer
KW  - mineralization beneath
KW  - block-copolymers
KW  - aqueous-solution
KW  - morphology
KW  - orthophosphates
KW  - biomaterials
KW  - nucleation
KW  - clusters
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95176
SP  - 11301
EP  - 11308
ER  - 
TY  - GEN
A1  - Di Florio, Giuseppe
A1  - Bründermann, Erik
A1  - Yadavalli, Nataraja Sekhar
A1  - Santer, Svetlana
A1  - Havenith, Martina
T1  - Polarized 3D Raman and nanoscale near-field optical microscopy of optically inscribed surface relief gratings
BT  - chromophore orientation in azo-doped polymer films
N2  - We have used polarized confocal Raman microspectroscopy and scanning near-field optical microscopy with a resolution of 60 nm to characterize photoinscribed grating structures of azobenzene doped polymer films on a glass support. Polarized Raman microscopy allowed determining the reorientation of the chromophores as a function of the grating phase and penetration depth of the inscribing laser in three dimensions. We found periodic patterns, which are not restricted to the surface alone, but appear also well below the surface in the bulk of the material. Near-field optical microscopy with nanoscale resolution revealed lateral two-dimensional optical contrast, which is not observable by atomic force and Raman microscopy.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 247 
KW  - glass-transition temperature
KW  - holographic diffraction gratings
KW  - chain azobenzene polymers
KW  - molecular-reorientation
KW  - amorphous polymers
KW  - data-storage
KW  - thin-films
KW  - dye
KW  - photoisomerization
KW  - alignment
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95233
SP  - 1544
EP  - 1554
ER  - 
TY  - GEN
A1  - Banerjee, Shiladitya
A1  - Saalfrank, Peter
T1  - Vibrationally resolved absorption, emission and resonance Raman spectra of diamondoids
BT  - a study based on time-dependent correlation functions
N2  - The time-dependent approach to electronic spectroscopy, as popularized by Heller and coworkers in the 1980's, is applied here in conjunction with linear-response, time-dependent density functional theory to study vibronic absorption, emission and resonance Raman spectra of several diamondoids. Two-state models, the harmonic and the Condon approximations, are used for the calculations, making them easily applicable to larger molecules. The method is applied to nine pristine lower and higher diamondoids: adamantane, diamantane, triamantane, and three isomers each of tetramantane and pentamantane. We also consider a hybrid species “Dia = Dia” – a shorthand notation for a recently synthesized molecule comprising two diamantane units connected by a C[double bond, length as m-dash]C double bond. We resolve and interpret trends in optical and vibrational properties of these molecules as a function of their size, shape, and symmetry, as well as effects of “blending” with sp2-hybridized C-atoms. Time-dependent correlation functions facilitate the computations and shed light on the vibrational dynamics following electronic transitions.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 238 
KW  - adamantane
KW  - models
KW  - molecules
KW  - states
KW  - thermochemistry
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94542
SP  - 144
EP  - 158
ER  - 
TY  - GEN
A1  - Schmidt, Bernd
A1  - Elizarov, Nelli
A1  - Berger, René
A1  - Hölter, Frank
T1  - Scope and limitations of the Heck–Matsuda-coupling of phenol diazonium salts and styrenes
BT  - a protecting-group economic synthesis of phenolic stilbenes
N2  - 4-Phenol diazonium salts undergo Pd-catalyzed Heck reactions with various styrenes to 4’-hydroxy stilbenes. In almost all cases higher yields and fewer side products were observed, compared to the analogous 4-methoxy benzene diazonium salts. In contrast, the reaction fails completely with 2- and 3-phenol diazonium salts. For these substitution patterns the methoxy-substituted derivatives are superior.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 242 
KW  - catalyzed cross metathesis
KW  - o bond formation
KW  - arenediazonium salts
KW  - stereoselective-synthesis
KW  - arylboronic acids
KW  - substituted stilbenes
KW  - aryldiazonium salts
KW  - palladium catalyst
KW  - trans-stilbenes
KW  - boronic acid
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95070
SP  - 3674
EP  - 3691
ER  - 
TY  - GEN
A1  - Thiel, Kerstin
A1  - Zehbe, Rolf
A1  - Roeser, Jerômé
A1  - Strauch, Peter
A1  - Enthaler, Stephan
A1  - Thomas, Arne
T1  - A polymer analogous reaction for the formation of imidazolium and NHC based porous polymer networks
N2  - A polymer analogous reaction was carried out to generate a porous polymeric network with N-heterocyclic carbenes (NHC) in the polymer backbone. Using a stepwise approach, first a polyimine network is formed by polymerization of the tetrafunctional amine tetrakis(4-aminophenyl)methane. This polyimine network is converted in the second step into polyimidazolium chloride and finally to a polyNHC network. Furthermore a porous Cu(II)-coordinated polyNHC network can be generated. Supercritical drying generates polymer networks with high permanent surface areas and porosities which can be applied for different catalytic reactions. The catalytic properties were demonstrated for example in the activation of CO2 or in the deoxygenation of sulfoxides to the corresponding sulfides.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 243 
KW  - covalent organic framework
KW  - n-heterocyclic carbenes
KW  - carbon-dioxide
KW  - intrinsic microporosity
KW  - heterogeneous catalysis
KW  - sulfoxides
KW  - reduction
KW  - complex
KW  - system
KW  - transformation
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95118
SP  - 1848
EP  - 1856
ER  - 
TY  - GEN
A1  - Thete, Aniket
A1  - Rojas, Oscar
A1  - Neumeyer, David
A1  - Koetz, Joachim
A1  - Dujardin, Erik
T1  - Ionic liquid-assisted morphosynthesis of gold nanorods using polyethyleneimine-capped seeds
N2  - Seed-mediated gold nanorods with tunable lengths are prepared using new polyethyleneimine-capped gold nanoparticles synthesized in ionic liquid. The effect of polyethyleneimine and ionic liquid during nanorod growth is investigated and shows a marked effect on their final aspect ratio.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 245 
KW  - aqueous-solution
KW  - aspect-ratio
KW  - cationic surfactants
KW  - chemical-synthesis
KW  - delivery
KW  - metal nanoparticles
KW  - mixtures
KW  - shape
KW  - silver nanowires
KW  - surface-plasmon resonance
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95196
SP  - 14294
EP  - 14298
ER  - 
TY  - GEN
A1  - Li, Hongguang
A1  - Babu, Sukumaran Santhosh
A1  - Turner, Sarah T.
A1  - Neher, Dieter
A1  - Hollamby, Martin J.
A1  - Seki, Tomohiro
A1  - Yagai, Shiki
A1  - Deguchi, Yonekazu
A1  - Möhwald, Helmuth
A1  - Nakanishi, Takashi
T1  - Alkylated-C60 based soft materials
BT  - regulation of selfassembly and optoelectronic properties by chain branching
N2  - Derivatization of fullerene (C60) with branched aliphatic chains softens C60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84 °C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 ± 0.1%) in comparison with another compound, 10 (PCE: 0.5 ± 0.1%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 250 
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95358
SP  - 1943
EP  - 1951
ER  - 
TY  - GEN
A1  - Inal, Sahika
A1  - Kölsch, Jonas D.
A1  - Chiappisi, Leonardo
A1  - Janietz, Dietmar
A1  - Gradzielski, Michael
A1  - Laschewsky, André
A1  - Neher, Dieter
T1  - Structure-related differences in the temperature-regulated fluorescence response of LCST type polymers
N2  - We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 251 
KW  - anionic polymerizations
KW  - dilute aqueous-solutions
KW  - ether methacrylates
KW  - n-isopropylacrylamide
KW  - oligo(ethylene glycol) methacrylate
KW  - phase-transitions
KW  - protein interactions
KW  - solvatochromic fluorophore
KW  - thermoresponsive polymers
KW  - to-coil transition
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95379
SP  - 6603
EP  - 6612
ER  - 
TY  - GEN
A1  - Inal, Sahika
A1  - Kölsch, Jonas D.
A1  - Sellrie, Frank
A1  - Schenk, Jörg A.
A1  - Wischerhoff, Erik
A1  - Laschewsky, André
A1  - Neher, Dieter
T1  - A water soluble fluorescent polymer as a dual colour sensor for temperature and a specific protein
N2  - We present two thermoresponsive water soluble copolymers prepared via free radical statistical copolymerization of N-isopropylacrylamide (NIPAm) and of oligo(ethylene glycol) methacrylates (OEGMAs), respectively, with a solvatochromic 7-(diethylamino)-3-carboxy-coumarin (DEAC)- functionalized monomer. In aqueous solutions, the NIPAm-based copolymer exhibits characteristic changes in its fluorescence profile in response to a change in solution temperature as well as to the presence of a specific protein, namely an anti-DEAC antibody. This polymer emits only weakly at low temperatures, but exhibits a marked fluorescence enhancement accompanied by a change in its emission colour when heated above its cloud point. Such drastic changes in the fluorescence and absorbance spectra are observed also upon injection of the anti-DEAC antibody, attributed to the specific binding of the antibody to DEAC moieties. Importantly, protein binding occurs exclusively when the polymer is in the well hydrated state below the cloud point, enabling a temperature control on the molecular recognition event. On the other hand, heating of the polymer–antibody complexes releases a fraction of the bound antibody. In the presence of the DEAC-functionalized monomer in this mixture, the released antibody competitively binds to the monomer and the antibody-free chains of the polymer undergo a more effective collapse and inter-aggregation. In contrast, the emission properties of the OEGMA-based analogous copolymer are rather insensitive to the thermally induced phase transition or to antibody binding. These opposite behaviours underline the need for a carefully tailored molecular design of responsive polymers aimed at specific applications, such as biosensing.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 249 
KW  - intramolecular charge-transfer
KW  - phase-transitions
KW  - responsive polymers
KW  - sensitivity
KW  - thermometer
KW  - dyes
KW  - modulation
KW  - assemblies
KW  - antibodies
KW  - binding
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95336
SP  - 6373
EP  - 6381
ER  - 
TY  - GEN
A1  - Schott, Juliane
A1  - Kretzschmar, Jerome
A1  - Acker, Margret
A1  - Eidner, Sascha
A1  - Kumke, Michael Uwe
A1  - Drobot, Björn
A1  - Barkleit, Astrid
A1  - Taut, Steffen
A1  - Brendler, Vinzenz
A1  - Stumpf, Thorsten
T1  - Formation of a Eu(III) borate solid species from a weak Eu(III) borate complex in aqueous solution
N2  - In the presence of polyborates (detected by 11B-NMR) the formation of a weak Eu(III) borate complex (lg β11 ∼ 2, estimated) was observed by time-resolved laser-induced fluorescence spectroscopy (TRLFS). This complex is a precursor for the formation of a solid Eu(III) borate species. The formation of this solid in solution was investigated by TRLFS as a function of the total boron concentration: the lower the total boron concentration, the slower is the solid formation. The solid Eu(III) borate was characterized by IR spectroscopy, powder XRD and solid-state TRLFS. The determination of the europium to boron ratio portends the existence of pentaborate units in the amorphous solid.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 277 
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98774
ER  - 
TY  - GEN
A1  - Plehn, Thomas
A1  - Megow, Jörg
A1  - May, Volkhard
T1  - Concerted charge and energy transfer processes in a highly flexible fullerene–dye system
BT  - a mixed quantum–classical study
N2  - Photoinduced excitation energy transfer and accompanying charge separation are elucidated for a supramolecular system of a single fullerene covalently linked to six pyropheophorbide-a dye molecules. Molecular dynamics simulations are performed to gain an atomistic picture of the architecture and the surrounding solvent. Excitation energy transfer among the dye molecules and electron transfer from the excited dyes to the fullerene are described by a mixed quantum–classical version of the Förster rate and the semiclassical Marcus rate, respectively. The mean characteristic time of energy redistribution lies in the range of 10 ps, while electron transfer proceeds within 150 ps. In between, on a 20 to 50 ps time-scale, conformational changes take place in the system. This temporal hierarchy of processes guarantees efficient charge separation, if the structure is exposed to a solvent. The fast energy transfer can adopt the dye excitation to the actual conformation. In this sense, the probability to achieve charge separation is large enough since any dominance of unfavorable conformations that exhibit a large dye–fullerene distance is circumvented. And the slow electron transfer may realize an averaging with respect to different conformations. To confirm the reliability of our computations, ensemble measurements on the charge separation dynamics are simulated and a very good agreement with the experimental data is obtained.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 279 
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98791
ER  - 
TY  - GEN
A1  - Węcławski, Marek K.
A1  - Tasior, Mariusz
A1  - Hammann, Tommy
A1  - Cywiński, Piotr J.
A1  - Gryko, Daniel T.
T1  - From π-expanded coumarins to π-expanded pentacenes
N2  - The synthesis of two novel types of π-expanded coumarins has been developed. Modified Knoevenagel bis-condensation afforded 3,9-dioxa-perylene-2,8-diones. Subsequent oxidative aromatic coupling or light driven electrocyclization reaction led to dibenzo-1,7-dioxacoronene-2,8-dione. Unparalleled synthetic simplicity, straightforward purification and superb optical properties have the potential to bring these perylene and coronene analogs towards various applications.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 280 
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98822
ER  - 
TY  - GEN
A1  - Cywiński, Piotr J.
A1  - Nono, Katia Nchimi
A1  - Charbonnière, Loïc J.
A1  - Hammann, Tommy
A1  - Löhmannsröben, Hans-Gerd
T1  - Photophysical evaluation of a new functional terbium complex in FRET-based time-resolved homogenous fluoroassays
N2  - A new functional luminescent lanthanide complex (LLC) has been synthesized with terbium as a central lanthanide ion and biotin as a functional moiety. Unlike in typical lanthanide complexes assembled via carboxylic moieties, in the presented complex, four phosphate groups are chelating the central lanthanide ion. This special chemical assembly enhances the complex stability in phosphate buffers conventionally used in biochemistry. The complex synthesis strategy and photophysical properties are described as well as the performance in time-resolved Förster Resonance Energy Transfer (FRET) assays. In those assays, this biotin-LLC transferred energy either to acceptor organic dyes (Cy5 or AF680) labelled on streptavidin or to quantum dots (QD655 or QD705) surface-functionalised with streptavidins. The permanent spatial donor–acceptor proximity is assured through strong and stable biotin–streptavidin binding. The energy transfer is evidenced from the quenching observed in donor emission and from a decrease in donor luminescence decay, both associated with simultaneous increase in acceptor intensity and in the decay time. The dye-based assays are realised in TRIS and in PBS, whereas QD-based systems are studied in borate buffer. The delayed emission analysis allows for quantifying the recognition process and for auto-fluorescence-free detection, which is particularly relevant for application in bioanalysis. In accordance with Förster theory, Förster-radii (R0) were found to be around 60 Å for organic dyes and around 105 Å for QDs. The FRET efficiency (η) reached 80% and 25% for dye and QD acceptors, respectively. Physical donor–acceptor distances (r) have been determined in the range 45–60 Å for organic dye acceptors, while for acceptor QDs between 120 Å and 145 Å. This newly synthesised biotin-LLC extends the class of highly sensitive analytical tools to be applied in the bioanalytical methods such as time-resolved fluoroimmunoassays (TR-FIA), luminescent imaging and biosensing.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 252 
KW  - acceptors
KW  - bioanalysis
KW  - contrast agents
KW  - europium
KW  - fluoroimmunoassay
KW  - labels
KW  - lanthanide luminescence
KW  - quantum dots
KW  - resonance energy-transfer
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95390
SP  - 6060
EP  - 6067
ER  - 
TY  - GEN
A1  - Metzler, Ralf
A1  - Jeon, Jae-Hyung
A1  - Cherstvy, Andrey G.
A1  - Barkai, Eli
T1  - Anomalous diffusion models and their properties
BT  - non-stationarity, non-ergodicity, and ageing at the centenary of single particle tracking
N2  - Modern microscopic techniques following the stochastic motion of labelled tracer particles have uncovered significant deviations from the laws of Brownian motion in a variety of animate and inanimate systems. Such anomalous diffusion can have different physical origins, which can be identified from careful data analysis. In particular, single particle tracking provides the entire trajectory of the traced particle, which allows one to evaluate different observables to quantify the dynamics of the system under observation. We here provide an extensive overview over different popular anomalous diffusion models and their properties. We pay special attention to their ergodic properties, highlighting the fact that in several of these models the long time averaged mean squared displacement shows a distinct disparity to the regular, ensemble averaged mean squared displacement. In these cases, data obtained from time averages cannot be interpreted by the standard theoretical results for the ensemble averages. Here we therefore provide a comparison of the main properties of the time averaged mean squared displacement and its statistical behaviour in terms of the scatter of the amplitudes between the time averages obtained from different trajectories. We especially demonstrate how anomalous dynamics may be identified for systems, which, on first sight, appear to be Brownian. Moreover, we discuss the ergodicity breaking parameters for the different anomalous stochastic processes and showcase the physical origins for the various behaviours. This Perspective is intended as a guidebook for both experimentalists and theorists working on systems, which exhibit anomalous diffusion.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 174 
KW  - Fokker-Planck equations
KW  - flight search patterns
KW  - fluctuation-dissipation theorem
KW  - fluorescence photobleaching recovery
KW  - fractional dynamics approach
KW  - intermittent chaotic systems
KW  - levy flights
KW  - photon-counting statistics
KW  - time random-walks
KW  - weak ergodicity breaking
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74448
SP  - 24128
EP  - 24164
ER  - 
TY  - GEN
A1  - Wessig, Pablo
A1  - Gerngroß, Maik
A1  - Pape, Simon
A1  - Bruhns, Philipp
A1  - Weber, Jens
T1  - Novel porous materials based on oligospiroketals (OSK)
N2  - New porous materials based on covalently connected monomers are presented. The key step of the synthesis is an acetalisation reaction. In previous years we used acetalisation reactions extensively to build up various molecular rods. Based on this approach, investigations towards porous polymeric materials were conducted by us. Here we wish to present the results of these studies in the synthesis of 1D polyacetals and porous 3D polyacetals. By scrambling experiments with 1D acetals we could prove that exchange reactions occur between different building blocks (evidenced by MALDI-TOF mass spectrometry). Based on these results we synthesized porous 3D polyacetals under the same mild conditions.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 175 
KW  - construction
KW  - frameworks
KW  - membranes
KW  - microporous organic polymers
KW  - models
KW  - molecular rods
KW  - sorption
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74466
SP  - 31123
EP  - 31129
ER  - 
TY  - GEN
A1  - Zamponi, Flavio
A1  - Penfold, Thomas J.
A1  - Nachtegaal, Maarten
A1  - Lübcke, Andrea
A1  - Rittmann, Jochen
A1  - Milne, Chris J.
A1  - Chergui, Majed
A1  - van Bokhoven, Jeroen A.
T1  - Probing the dynamics of plasmon-excited hexanethiol-capped gold nanoparticles by picosecond X-ray absorption spectroscopy
N2  - Picosecond X-ray absorption spectroscopy (XAS) is used to investigate the electronic and structural dynamics initiated by plasmon excitation of 1.8 nm diameter Au nanoparticles (NPs) functionalised with 1-hexanethiol. We show that 100 ps after photoexcitation the transient XAS spectrum is consistent with an 8% expansion of the Au–Au bond length and a large increase in disorder associated with melting of the NPs. Recovery of the ground state occurs with a time constant of ∼1.8 ns, arising from thermalisation with the environment. Simulations reveal that the transient spectrum exhibits no signature of charge separation at 100 ps and allows us to estimate an upper limit for the quantum yield (QY) of this process to be <0.1.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 176 
KW  - TiO2 nanoparticles
KW  - diimine-complexes
KW  - electron-transfer
KW  - excitation
KW  - nanoclusters
KW  - reactivity
KW  - supported gold
KW  - surface
KW  - visible-light
KW  - water
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74492
SP  - 23157
EP  - 23163
ER  - 
TY  - GEN
A1  - Cherstvy, Andrey G.
A1  - Chechkin, Aleksei V.
A1  - Metzler, Ralf
T1  - Particle invasion, survival, and non-ergodicity in 2D diffusion processes with space-dependent diffusivity
N2  - We study the thermal Markovian diffusion of tracer particles in a 2D medium with spatially varying diffusivity D(r), mimicking recently measured, heterogeneous maps of the apparent diffusion coefficient in biological cells. For this heterogeneous diffusion process (HDP) we analyse the mean squared displacement (MSD) of the tracer particles, the time averaged MSD, the spatial probability density function, and the first passage time dynamics from the cell boundary to the nucleus. Moreover we examine the non-ergodic properties of this process which are important for the correct physical interpretation of time averages of observables obtained from single particle tracking experiments. From extensive computer simulations of the 2D stochastic Langevin equation we present an in-depth study of this HDP. In particular, we find that the MSDs along the radial and azimuthal directions in a circular domain obey anomalous and Brownian scaling, respectively. We demonstrate that the time averaged MSD stays linear as a function of the lag time and the system thus reveals a weak ergodicity breaking. Our results will enable one to rationalise the diffusive motion of larger tracer particles such as viruses or submicron beads in biological cells.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 168 
KW  - adenoassociated virus
KW  - anomalous diffusion
KW  - cytoplasm
KW  - endosomal escape
KW  - escherichia-coli
KW  - infection pathway
KW  - intracellular-transport
KW  - living cells
KW  - models
KW  - trafficking
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74021
IS  - 168
SP  - 1591
EP  - 1601
ER  - 
TY  - GEN
A1  - Meyer, Sören
A1  - Matissek, M.
A1  - Müller, Sandra Marie
A1  - Taleshi, M. S.
A1  - Ebert, Franziska
A1  - Francesconi, Kevin A.
A1  - Schwerdtle, Tanja
T1  - In vitro toxicological characterisation of three arsenic-containing hydrocarbons
N2  - Arsenic-containing hydrocarbons are one group of fat-soluble organic arsenic compounds (arsenolipids) found in marine fish and other seafood. A risk assessment of arsenolipids is urgently needed, but has not been possible because of the total lack of toxicological data. In this study the cellular toxicity of three arsenic-containing hydrocarbons was investigated in cultured human bladder (UROtsa) and liver (HepG2) cells. Cytotoxicity of the arsenic-containing hydrocarbons was comparable to that of arsenite, which was applied as the toxic reference arsenical. A large cellular accumulation of arsenic, as measured by ICP-MS/MS, was observed after incubation of both cell lines with the arsenolipids. Moreover, the toxic mode of action shown by the three arsenic-containing hydrocarbons seemed to differ from that observed for arsenite. Evidence suggests that the high cytotoxic potential of the lipophilic arsenicals results from a decrease in the cellular energy level. This first in vitro based risk assessment cannot exclude a risk to human health related to the presence of arsenolipids in seafood, and indicates the urgent need for further toxicity studies in experimental animals to fully assess this possible risk.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 170 
KW  - cod-liver
KW  - human-cells
KW  - arsenolipids present
KW  - excision-repair
KW  - fatty-acids
KW  - marine oils
KW  - RP-HPLC
KW  - metabolites
KW  - identification
KW  - trivalent
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74201
SP  - 1023
EP  - 1033
ER  - 
TY  - GEN
A1  - Unterberg, Marlies
A1  - Leffers, Larissa
A1  - Hübner, Florian
A1  - Humpf, Hans-Ulrich
A1  - Lepikhov, Konstantin
A1  - Walter, Jörn
A1  - Ebert, Franziska
A1  - Schwerdtle, Tanja
T1  - Toxicity of arsenite and thio-DMAV after long-term (21 days) incubation of human urothelial cells: cytotoxicity, genotoxicity and epigenetics
N2  - This study aims to further mechanistically understand toxic modes of action after chronic inorganic arsenic exposure. Therefore long-term incubation studies in cultured cells were carried out, to display chronically attained changes, which cannot be observed in the generally applied in vitro short-term incubation studies. Particularly, the cytotoxic, genotoxic and epigenetic effects of an up to 21 days incubation of human urothelial (UROtsa) cells with pico- to nanomolar concentrations of iAsIII and its metabolite thio-DMAV were compared. After 21 days of incubation, cytotoxic effects were strongly enhanced in the case of iAsIII and might partly be due to glutathione depletion and genotoxic effects on the chromosomal level. These results are in strong contrast to cells exposed to thio-DMAV. Thus, cells seemed to be able to adapt to this arsenical, as indicated among others by an increase in the cellular glutathione level. Most interestingly, picomolar concentrations of both iAsIII and thio-DMAV caused global DNA hypomethylation in UROtsa cells, which was quantified in parallel by 5-medC immunostaining and a newly established, reliable, high resolution mass spectrometry (HRMS)-based test system. This is the first time that epigenetic effects are reported for thio-DMAV; iAsIII induced epigenetic effects occur in at least 8000 fold lower concentrations as reported in vitro before. The fact that both arsenicals cause DNA hypomethylation at really low, exposure-relevant concentrations in human urothelial cells suggests that this epigenetic effect might contribute to inorganic arsenic induced carcinogenicity, which for sure has to be further investigated in future studies.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 178 
KW  - induced malignant-transformation
KW  - genomic dna methylation
KW  - vitro toxicological characterization
KW  - thio-dimethylarsinic acid
KW  - bladder-cancer
KW  - methyltransferases dnmt3a
KW  - cytosine methylation
KW  - carcinogen exposure
KW  - mass-spectrometry
KW  - gene-expression
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-76239
SP  - 456
EP  - 464
ER  - 
TY  - GEN
A1  - Ghosh, Surya K.
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Non-universal tracer diffusion in crowded media of non-inert obstacles
N2  - We study the diffusion of a tracer particle, which moves in continuum space between a lattice of excluded volume, immobile non-inert obstacles. In particular, we analyse how the strength of the tracer–obstacle interactions and the volume occupancy of the crowders alter the diffusive motion of the tracer. From the details of partitioning of the tracer diffusion modes between trapping states when bound to obstacles and bulk diffusion, we examine the degree of localisation of the tracer in the lattice of crowders. We study the properties of the tracer diffusion in terms of the ensemble and time averaged mean squared displacements, the trapping time distributions, the amplitude variation of the time averaged mean squared displacements, and the non-Gaussianity parameter of the diffusing tracer. We conclude that tracer–obstacle adsorption and binding triggers a transient anomalous diffusion. From a very narrow spread of recorded individual time averaged trajectories we exclude continuous type random walk processes as the underlying physical model of the tracer diffusion in our system. For moderate tracer–crowder attraction the motion is found to be fully ergodic, while at stronger attraction strength a transient disparity between ensemble and time averaged mean squared displacements occurs. We also put our results into perspective with findings from experimental single-particle tracking and simulations of the diffusion of tagged tracers in dense crowded suspensions. Our results have implications for the diffusion, transport, and spreading of chemical components in highly crowded environments inside living cells and other structured liquids.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 186 
KW  - escence correlation spectroscopy
KW  - single-particle tracking
KW  - anomalous diffusion
KW  - living cells
KW  - physiological consequences
KW  - langevin equation
KW  - infection pathway
KW  - excluded volume
KW  - brownian-motion
KW  - random-walks
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-77128
SP  - 1847
EP  - 1858
PB  - The Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Shin, Jaeoh
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Kinetics of polymer looping with macromolecular crowding: effects of volume fraction and crowder size
N2  - The looping of polymers such as DNA is a fundamental process in the molecular biology of living cells, whose interior is characterised by a high degree of molecular crowding. We here investigate in detail the looping dynamics of flexible polymer chains in the presence of different degrees of crowding. From the analysis of the looping–unlooping rates and the looping probabilities of the chain ends we show that the presence of small crowders typically slows down the chain dynamics but larger crowders may in fact facilitate the looping. We rationalise these non-trivial and often counterintuitive effects of the crowder size on the looping kinetics in terms of an effective solution viscosity and standard excluded volume. It is shown that for small crowders the effect of an increased viscosity dominates, while for big crowders we argue that confinement effects (caging) prevail. The tradeoff between both trends can thus result in the impediment or facilitation of polymer looping, depending on the crowder size. We also examine how the crowding volume fraction, chain length, and the attraction strength of the contact groups of the polymer chain affect the looping kinetics and hairpin formation dynamics. Our results are relevant for DNA looping in the absence and presence of protein mediation, DNA hairpin formation, RNA folding, and the folding of polypeptide chains under biologically relevant high-crowding conditions.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 185 
KW  - gene-regulation kinetics
KW  - physiological consequences
KW  - spatial-organization
KW  - anomalous diffusion
KW  - folding kinetics
KW  - living cells
KW  - dna coiling
KW  - in-vitro
KW  - dynamics
KW  - mixtures
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-76961
SP  - 472
EP  - 488
PB  - The Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Morgner, Frank
A1  - Lecointre, Alexandre
A1  - Charbonnière, Loic J.
A1  - Löhmannsröben, Hans-Gerd
T1  - Detecting free hemoglobin in blood plasma and serum with luminescent terbium complexes
N2  - Hemolysis, the rupturing of red blood cells, can result from numerous medical conditions (in vivo) or occur after collecting blood specimen or extracting plasma and serum out of whole blood (in vitro). In clinical laboratory practice, hemolysis can be a serious problem due to its potential to bias detection of various analytes or biomarkers. Here we present the first ‘‘mix-and-measure’’ method to assess the degree of hemolysis in biosamples using luminescence spectroscopy. Luminescent terbium complexes (LTC) were studied in the presence of free hemoglobin (Hb) as indicators for hemolysis in TRIS-buffer, and in fresh human plasma with absorption, excitation and emission measurements. Our findings indicate dynamic as well as resonance energy transfer (FRET) between the LTC and the porphyrin ligand of hemoglobin. This transfer leads to a decrease in luminescence intensity and decay time even at nanomolar hemoglobin concentrations either in buffer or plasma. Luminescent terbium complexes are very sensitive to free hemoglobin in buffer and blood plasma. Due to the instant change in luminescence properties of the LTC in presence of Hb it is possible to access the concentration of hemoglobin via spectroscopic methods without incubation time or further treatment of the sample thus enabling a rapid and sensitive detection of hemolysis in clinical diagnostics.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 288 
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-99485
ER  - 
TY  - GEN
A1  - Laschewsky, André
T1  - Structures and synthesis of zwitterionic polymers
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The structures and synthesis of polyzwitterions ("polybetaines") are reviewed, emphasizing the literature of the past decade. Particular attention is given to the general challenges faced, and to successful strategies to obtain polymers with a true balance of permanent cationic and anionic groups, thus resulting in an overall zero charge. Also, the progress due to applying new methodologies from general polymer synthesis, such as controlled polymerization methods or the use of "click" chemical reactions is presented. Furthermore, the emerging topic of responsive ("smart") polyzwitterions is addressed. The considerations and critical discussions are illustrated by typical examples.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1043 
KW  - review
KW  - polyzwitterion
KW  - polyampholyte
KW  - zwitterionic group
KW  - betaine
KW  - synthesis
KW  - monomer
KW  - polymerization
KW  - post-polymerization modification
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-476167
SN  - 1866-8372
IS  - 1043
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  - GEN
A1  - Schmidt, Christian
A1  - Behl, Marc
A1  - Lendlein, Andreas
A1  - Bauermann, Sabine
T1  - Synthesis of high molecular weight polyglycolide in supercritical carbon dioxide
N2  - Polyglycolide (PGA) is a biodegradable polymer with multiple applications in the medical sector. Here the synthesis of high molecular weight polyglycolide by ring-opening polymerization of diglycolide is reported. For the first time stabilizer free supercritical carbon dioxide (scCO2) was used as a reaction medium. scCO2 allowed for a reduction in reaction temperature compared to conventional processes. Together with the lowering of monomer concentration and consequently reduced heat generation compared to bulk reactions thermal decomposition of the product occurring already during polymerization is strongly reduced. The reaction temperatures and pressures were varied between 120 and 150 °C and 145 to 1400 bar. Tin(II) ethyl hexanoate and 1-dodecanol were used as catalyst and initiator, respectively. The highest number average molecular weight of 31 200 g mol−1 was obtained in 5 hours from polymerization at 120 °C and 530 bar. In all cases the products were obtained as a dry white powder. Remarkably, independent of molecular weight the melting temperatures were always at (219 ± 2) °C.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 284 
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-99439
ER  - 
TY  - GEN
A1  - Schwarze, Thomas
A1  - Müller, Holger
A1  - Ast, Sandra
A1  - Steinbrück, Dörte
A1  - Eidner, Sascha
A1  - Geißler, Felix
A1  - Kumke, Michael Uwe
A1  - Holdt, Hans-Jürgen
T1  - Fluorescence lifetime-based sensing of sodium by an optode
N2  - We report a 1,2,3-triazol fluoroionophore for detecting Na+ that shows in vitro enhancement in the Na+-induced fluorescence intensity and decay time. The Na+-selective molecule 1 was incorporated into a hydrogel as a part of a fiber optical sensor. This sensor allows the direct determination of Na+ in the range of 1–10 mM by measuring reversible fluorescence decay time changes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 182 
KW  - ion optodes
KW  - sensors
KW  - indicators
KW  - chromoionophore
KW  - ionophore
KW  - membrane
KW  - switches
KW  - systems
KW  - samples
KW  - green
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-76785
SP  - 14167
EP  - 14170
PB  - The Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Meyer, Sören
A1  - Schulz, Jacqueline
A1  - Jeibmann, Astrid
A1  - Taleshi, Mojtaba S.
A1  - Ebert, Franziska
A1  - Francesconi, Kevin
A1  - Schwerdtle, Tanja
T1  - Arsenic-containing hydrocarbons are toxic in the in vivo model Drosophila melanogaster
N2  - Arsenic-containing hydrocarbons (AsHC) constitute one group of arsenolipids that have been identified in seafood. In this first in vivo toxicity study for AsHCs, we show that AsHCs exert toxic effects in Drosophila melanogaster in a concentration range similar to that of arsenite. In contrast to arsenite, however, AsHCs cause developmental toxicity in the late developmental stages of Drosophila melanogaster. This work illustrates the need for a full characterisation of the toxicity of AsHCs in experimental animals to finally assess the risk to human health related to the presence of arsenolipids in seafood.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 183 
KW  - cod-liver
KW  - arsenolipids present
KW  - fatty-acids
KW  - rp-hplc
KW  - identification
KW  - fish
KW  - oil
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-76819
VL  - 11
IS  - 6
SP  - 2010
EP  - 2014
ER  -