TY - GEN
A1 - König, Jana
A1 - Kelling, Alexandra
A1 - Schilde, Uwe
A1 - Strauch, Peter
T1 - [µ2-O,O′,Oʺ,Oʺ′-Bis(1,2-dithiooxalato-S,S′)nickel(II)]bis[-O,O′-bis(1,2-dithiooxalato-S,S′)-nickel(II)pentaquaholmium(III)]hydrate, [Ho2Ni3(dto)6(H2O)10]
N2 - Planar bis(1,2-dithiooxalato)nickelate(II), [Ni(dto)]2− reacts in aqueous solutions with lanthanide ions (Ln3+) to form pentanuclear, hetero-bimetallic complexes of the general composition [{Ln(H2O)n}2{Ni(dto)2}3]·xH2O. (n = 4 or 5; x = 9–12). The complex [{Ho(H2O)5}2{Ni(dto)2}3]·10H2O, Ho2Ni3, was synthesized and characterized by single crystal X-ray structure analysis and powder diffraction. The Ho2Ni3 complex crystallizes as monoclinic crystals in the space group P21/c. The channels and cavities, appearing in the crystal packing of the complex molecules, are occupied by a varying amount of non-coordinated water molecules.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 360
KW - lanthanides
KW - holmium(III)
KW - 1,2-dithiooxalate
KW - crystal structure
KW - nickel(II)
Y1 - 2017
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400598
ER -
TY - GEN
A1 - Ehlert, Christopher
A1 - Holzweber, Markus
A1 - Lippitz, Andreas
A1 - Unger, Wolfgang E. S.
A1 - Saalfrank, Peter
T1 - A detailed assignment of NEXAFS resonances of imidazolium based ionic liquids
N2 - In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([CnC1im]+[NTf2]- and [C4C1im]+[I]-). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 315
KW - ray absorption-spectroscopy
KW - fine-structure
KW - spectra
KW - simulations
KW - molecules
KW - dynamics
KW - graphene
KW - surface
KW - salts
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394417
SP - 8654
EP - 8661
ER -
TY - GEN
A1 - Matis, Jochen René
A1 - Schönborn, Jan Boyke
A1 - Saalfrank, Peter
T1 - A multi-reference study of the byproduct formation for a ring-closed dithienylethene photoswitch
N2 - Photodriven molecular switches are sometimes hindered in their performance by forming byproducts which act as dead ends in sequences of switching cycles, leading to rapid fatigue effects. Understanding the reaction pathways to unwanted byproducts is a prerequisite for preventing them. This article presents a study of the photochemical reaction pathways for byproduct formation in the photochromic switch 1,2-bis-(3-thienyl)-ethene. Specifically, using single- and multi-reference methods the post-deexcitation reaction towards the byproduct in the electronic ground state S0 when starting from the S1–S0 conical intersection (CoIn), is considered in detail. We find an unusual low-energy pathway, which offers the possibility for the formation of a dyotropic byproduct. Several high-energy pathways can be excluded with high probability.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 215
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89594
SP - 14088
EP - 14095
ER -
TY - GEN
A1 - Roder, Phillip
A1 - Hille, Carsten
T1 - A Multifunctional Frontloading Approach for Repeated Recycling of a Pressure-Controlled AFM Micropipette
N2 - Fluid force microscopy combines the positional accuracy and force sensitivity of an atomic
force microscope (AFM) with nanofluidics via a microchanneled cantilever. However, adequate loading and cleaning procedures for such AFM micropipettes are required for various application situations. Here, a new frontloading procedure is described for an AFM micropipette functioning as a force- and pressure-controlled microscale liquid dispenser. This frontloading
procedure seems especially attractive when using target substances featuring high
costs or low available amounts. Here, the AFM micropipette could be filled from the tip side with liquid from a previously applied droplet with a volume of only a few μL using a short low-pressure pulse. The liquid-loaded AFM micropipettes could be then applied for experiments in air or liquid environments. AFM micropipette frontloading was evaluated with the well-known organic fluorescent dye rhodamine 6G and the AlexaFluor647-labeled antibody goat anti-rat IgG as an example of a larger biological compound. After micropipette usage, specific cleaning procedures were tested. Furthermore, a storage method is described, at which the AFM micropipettes could be stored for a few hours up to several days without drying out or clogging of the microchannel. In summary, the rapid, versatile and cost-efficient
frontloading and cleaning procedure for the repeated usage of a single AFM micropipette is beneficial for various application situations from specific surface modifications through to local manipulation of living cells, and provides a simplified and faster handling for already known experiments with fluid force microscopy.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 209
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-86592
ER -
TY - GEN
A1 - Sarauli, David
A1 - Xu, Chenggang
A1 - Dietzel, Birgit
A1 - Schulz, Burkhard
A1 - Lisdat, Fred
T1 - A multilayered sulfonated polyaniline network with entrapped pyrroloquinoline quinone-dependent glucose dehydrogenase
BT - tunable direct bioelectrocatalysis
N2 - A feasible approach to construct multilayer films of sulfonated polyanilines – PMSA1 and PABMSA1 – containing different ratios of aniline, 2-methoxyaniline-5-sulfonic acid (MAS) and 3-aminobenzoic acid (AB), with the entrapped redox enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) on Au and ITO electrode surfaces, is described. The formation of layers has been followed and confirmed by electrochemical impedance spectroscopy (EIS), which demonstrates that the multilayer assembly can be achieved in a progressive and uniform manner. The gold and ITO electrodes subsequently modified with PMSA1:PQQ-GDH and PABMSA1 films are studied by cyclic voltammetry (CV) and UV-Vis spectroscopy which show a significant direct bioelectrocatalytical response to the oxidation of the substrate glucose without any additional mediator. This response correlates linearly with the number of deposited layers. Furthermore, the constructed polymer/enzyme multilayer system exhibits a rather good long-term stability, since the catalytic current response is maintained for more than 60% of the initial value even after two weeks of storage. This verifies that a productive interaction of the enzyme embedded in the film of substituted polyaniline can be used as a basis for the construction of bioelectronic units, which are useful as indicators for processes liberating glucose and allowing optical and electrochemical transduction.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 275
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98744
ER -
TY - GEN
A1 - Pape, Simon
A1 - Wessig, Pablo
A1 - Brunner, Heiko
T1 - A new and environmentally benign synthesis of aroylguanidines using iron trichloride
N2 - A new synthetic approach for the guanylation of aroylthioureas using iron trichloride is presented. Our synthetic method distinguishes itself by benign reaction conditions, low costs and a broad product spectrum. The scope of the reaction and calorimetric studies are described.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 308
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102720
SP - 101408
EP - 101411
ER -
TY - 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 - Liebig, Ferenc
A1 - Henning, Ricky
A1 - Sarhan, Radwan Mohamed
A1 - Prietzel, Claudia Christina
A1 - Schmitt, Clemens Nikolaus Zeno
A1 - Bargheer, Matias
A1 - Koetz, Joachim
T1 - A simple one-step procedure to synthesise gold nanostars in concentrated aqueous surfactant solutions
T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2 - Due to the enhanced electromagnetic field at the tips of metal nanoparticles, the spiked structure of gold nanostars (AuNSs) is promising for surface-enhanced Raman scattering (SERS). Therefore, the challenge is the synthesis of well designed particles with sharp tips. The influence of different surfactants, i.e., dioctyl sodium sulfosuccinate (AOT), sodium dodecyl sulfate (SDS), and benzylhexadecyldimethylammonium chloride (BDAC), as well as the combination of surfactant mixtures on the formation of nanostars in the presence of Ag⁺ ions and ascorbic acid was investigated. By varying the amount of BDAC in mixed micelles the core/spike-shell morphology of the resulting AuNSs can be tuned from small cores to large ones with sharp and large spikes. The concomitant red-shift in the absorption toward the NIR region without losing the SERS enhancement enables their use for biological applications and for time-resolved spectroscopic studies of chemical reactions, which require a permanent supply with a fresh and homogeneous solution. HRTEM micrographs and energy-dispersive X-ray (EDX) experiments allow us to verify the mechanism of nanostar formation according to the silver underpotential deposition on the spike surface in combination with micelle adsorption.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 769
KW - optical-properties
KW - nanoparticles
KW - sers
KW - ultrafast
KW - size
KW - nanotriangles
KW - nanoflowers
KW - wavelength
Y1 - 2019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-438743
SN - 1866-8372
IS - 769
SP - 23633
EP - 23641
ER -
TY - GEN
A1 - Mondal, Suvendu Sekhar
A1 - Bhunia, Asamanjoy
A1 - Kelling, Alexandra
A1 - Schilde, Uwe
A1 - Janiak, Christoph
A1 - Holdt, Hans-Jürgen
T1 - A supramolecular Co(II)₁₄-metal–organic cube in a hydrogen-bonded network and a Co(II)–organic framework with a flexible methoxy substituent
N2 - The reaction of 4,5-dicyano-2-methoxyimidazole (L1) with Co(NO3)2·6H2O under solvothermal conditions in DMF, a MOF, IFP-8 and a hydrogen-bonded network consisting of tetradecanuclear Co(II)14-metal organic cube (1) are achieved. 1 shows the bcu net with 14 cobalt atoms.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 169
KW - zinc
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74098
IS - 169
SP - 5441
EP - 5443
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 - Linker, Torsten
T1 - Addition of Heteroatom Radicals to endo-Glycals
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Radical reactions have found many applications in carbohydrate chemistry, especially in the construction of carbon–carbon bonds. The formation of carbon–heteroatom bonds has been less intensively studied. This mini-review will summarize the efforts to add heteroatom radicals to unsaturated carbohydrates like endo-glycals. Starting from early examples, developed more than 50 years ago, the importance of such reactions for carbohydrate chemistry and recent applications will be discussed. After a short introduction, the mini-review is divided in sub-chapters according to the heteroatoms halogen, nitrogen, phosphorus, and sulfur. The mechanisms of radical generation by chemical or photochemical processes and the subsequent reactions of the radicals at the 1-position will be discussed. This mini-review cannot cover all aspects of heteroatom-centered radicals in carbohydrate chemistry, but should provide an overview of the various strategies and future perspectives
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 873
KW - radicals
KW - carbohydrates
KW - heteroatoms
KW - synthesis
Y1 - 2020
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-459970
SN - 1866-8372
IS - 873
ER -
TY - GEN
A1 - Wirth, Jonas
A1 - Neumann, Rainer
A1 - Antonietti, Markus
A1 - Saalfrank, Peter
T1 - Adsorption and photocatalytic splitting of water on graphitic carbon nitride
BT - a combined first principles and semiempirical study
N2 - Graphitic carbon nitride, g-C₃N₄, is a promising organic photo-catalyst for a variety of redox reactions. In order to improve its efficiency in a systematic manner, however, a fundamental understanding of the microscopic interaction between catalyst, reactants and products is crucial. Here we present a systematic study of water adsorption on g-C₃N₄ by means of density functional theory and the density functional based tight-binding method as a prerequisite for understanding photocatalytic water splitting. We then analyze this prototypical redox reaction on the basis of a thermodynamic model providing an estimate of the overpotential for both water oxidation and H⁺ reduction. While the latter is found to occur readily upon irradiation with visible light, we derive a prohibitive overpotential of 1.56 eV for the water oxidation half reaction, comparing well with the experimental finding that in contrast to H₂ production O₂ evolution is only possible in the presence of oxidation cocatalysts.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 172
KW - augmented-wave method
KW - hydrogen
KW - initio molecular-dynamics
KW - oxidation
KW - photooxidation
KW - reduction
KW - simulations
KW - tight-binding
KW - transition
KW - visible-light
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74391
SP - 15917
EP - 15926
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 - Steeples, Elliot
A1 - Kelling, Alexandra
A1 - Schilde, Uwe
A1 - Esposito, Davide
T1 - Amino acid-derived N-heterocyclic carbene palladium complexes for aqueous phase Suzuki–Miyaura couplings
N2 - In this work, three ligands produced from amino acids were synthesized and used to produce five bis- and PEPPSI-type palladium–NHC complexes using a novel synthesis route from sustainable starting materials. Three of these complexes were used as precatalysts in the aqueous-phase Suzuki–Miyaura coupling of various substrates displaying high activity. TEM and mercury poisoning experiments provide evidence for Pd-nanoparticle formation stabilized in water.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 319
KW - transition-metal-complexes
KW - imidazolium salts
KW - green chemistry
KW - water
KW - catalysts
KW - nhc
KW - hydrogenation
KW - isomerization
KW - nanoparticles
KW - precatalysts
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394488
SP - 4922
EP - 4930
ER -
TY - GEN
A1 - Heck, Christian
A1 - Kanehira, Yuya
A1 - Kneipp, Janina
A1 - Bald, Ilko
T1 - Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures
T2 - Mathematisch-Naturwissenschaftliche Reihe
N2 - Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 732
KW - amorphous carbon
KW - DNA origami
KW - SERS
KW - nanoparticle dimers
KW - nanolenses
Y1 - 2019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-430812
SN - 1866-8372
IS - 732
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 - Tasior, Mariusz
A1 - Bald, Ilko
A1 - Deperasińska, Irena
A1 - Cywiński, Piotr J.
A1 - Gryko, Daniel T.
T1 - An internal charge transfer-dependent solvent effect in V-shaped azacyanines
N2 - New V-shaped non-centrosymmetric dyes, possessing a strongly electron-deficient azacyanine core, have been synthesized based on a straightforward two-step approach. The key step in this synthesis involves palladium-catalysed cross-coupling of dibromo-N,N′-methylene-2,2′-azapyridinocyanines with arylacetylenes. The resulting strongly polarized π-expanded heterocycles exhibit green to orange fluorescence and they strongly respond to changes in solvent polarity. We demonstrate that differently electron-donating peripheral groups have a significant influence on the internal charge transfer, hence on the solvent effect and fluorescence quantum yield. TD-DFT calculations confirm that, in contrast to the previously studied bis(styryl)azacyanines, the proximity of S1 and T2 states calculated for compounds bearing two 4-N,N-dimethylaminophenylethynyl moieties establishes good conditions for efficient intersystem crossing and is responsible for its low fluorescence quantum yield. Non-linear properties have also been determined for new azacyanines and the results show that depending on peripheral groups, the synthesized dyes exhibit small to large two-photon absorption cross sections reaching 4000 GM.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 306
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102704
SP - 11714
EP - 11720
ER -
TY - GEN
A1 - Olejko, Lydia
A1 - Cywiński, P. J.
A1 - Bald, Ilko
T1 - An ion-controlled four-color fluorescent telomeric switch on DNA origami structures
N2 - The folding of single-stranded telomeric DNA into guanine (G) quadruplexes is a conformational change that plays a major role in sensing and drug targeting. The telomeric DNA can be placed on DNA origami nanostructures to make the folding process extremely selective for K+ ions even in the presence of high Na+ concentrations. Here, we demonstrate that the K+-selective G-quadruplex formation is reversible when using a cryptand to remove K+ from the G-quadruplex. We present a full characterization of the reversible switching between single-stranded telomeric DNA and G-quadruplex structures using Förster resonance energy transfer (FRET) between the dyes fluorescein (FAM) and cyanine3 (Cy3). When attached to the DNA origami platform, the G-quadruplex switch can be incorporated into more complex photonic networks, which is demonstrated for a three-color and a four-color FRET cascade from FAM over Cy3 and Cy5 to IRDye700 with G-quadruplex-Cy3 acting as a switchable transmitter.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 254
KW - resonance energy-transfer
KW - g-quadruplex
KW - quantum dots
KW - strand breakage
KW - photonic wires
KW - 3-color fret
KW - nanostructures
KW - recognition
KW - sensitivity
KW - assemblies
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95831
SP - 10339
EP - 10347
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 - Klier, Dennis Tobias
A1 - Kumke, Michael Uwe
T1 - Analysing the effect of the crystal structure on upconversion luminescence in Yb3+,Er3+-co-doped NaYF4 nanomaterials
N2 - NaYF4:Yb:Er nanoparticles (UCNP) were synthesized under mild experimental conditions to obtain a pure cubic lattice. Upon annealing at different temperatures up to Tan = 700 °C phase transitions to the hexagonal phase and back to the cubic phase were induced. The UCNP materials obtained for different Tan were characterized with respect to the lattice phase using standard XRD and Raman spectroscopy as well as steady state and time resolved upconversion luminescence. The standard techniques showed that for the annealing temperature range 300 °C < Tan < 600 °C the hexagonal lattice phase was dominant. For Tan < 300 °C hardly any change in the lattice phase could be deduced, whereas for Tan > 600 °C a back transfer to the α-phase was observed. Complementarily, the luminescence upconversion properties of the annealed UCNP materials were characterized in steady state and time resolved luminescence measurements. Distinct differences in the upconversion luminescence intensity, the spectral intensity distribution and the luminescence decay kinetics were found for the cubic and hexagonal lattice phases, respectively, corroborating the results of the standard analytical techniques used. In laser power dependent measurements of the upconversion luminescence intensity it was found that the green (G1, G2) and red (R) emission of Er3+ showed different effects of Tan on the number of required photons reflecting the differences in the population routes of different energy levels involved. Furthermore, the intensity ratio of Gfull/R is highly effected by the laser power only when the β-phase is present, whereas the G1/G2 intensity ratio is only slightly effected regardless of the crystal phase. Moreover, based on different upconversion luminescence kinetics characteristics of the cubic and hexagonal phase time-resolved area normalized emission spectra (TRANES) proved to be a very sensitive tool to monitor the phase transition between cubic and hexagonal phases. Based on the TRANES analysis it was possible to resolve the lattice phase transition in more detail for 200 °C < Tan < 300 °C, which was not possible with the standard techniques.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 217
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89630
SP - 11228
EP - 11238
ER -
TY - GEN
A1 - Roder, Phillip
A1 - Hille, Carsten
T1 - ANG-2 for quantitative Na+ determination in living cells by time-resolved fluorescence microscopy
N2 - Sodium ions (Na+) play an important role in a plethora of cellular processes, which are complex and partly still unexplored. For the investigation of these processes and quantification of intracellular Na+ concentrations ([Na+]i), two-photon coupled fluorescence lifetime imaging microscopy (2P-FLIM) was performed in the salivary glands of the cockroach Periplaneta americana. For this, the novel Na+-sensitive fluorescent dye Asante NaTRIUM Green-2 (ANG-2) was evaluated, both in vitro and in situ. In this context, absorption coefficients, fluorescence quantum yields and 2P action cross-sections were determined for the first time. ANG-2 was 2P-excitable over a broad spectral range and displayed fluorescence in the visible spectral range. Although the fluorescence decay behaviour of ANG-2 was triexponential in vitro, its analysis indicates a Na+-sensitivity appropriate for recordings in living cells. The Na+-sensitivity was reduced in situ, but the biexponential fluorescence decay behaviour could be successfully analysed in terms of quantitative [Na+]i recordings. Thus, physiological 2P-FLIM measurements revealed a dopamine-induced [Na+]i rise in cockroach salivary gland cells, which was dependent on a Na+-K+-2Cl− cotransporter (NKCC) activity. It was concluded that ANG-2 is a promising new sodium indicator applicable for diverse biological systems.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 184
KW - cockroach salivary-glands
KW - intracellular na+
KW - sodium green
KW - periplaneta-americana
KW - ventricular myocytes
KW - lifetime microscopy
KW - acinar-cells
KW - hela-cells
KW - rat
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-76851
SP - 1699
EP - 1710
PB - The Royal Society of Chemistry
CY - Cambridge
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 - 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 - 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 - 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 -
TY - GEN
A1 - Klaper, M.
A1 - Wessig, Pablo
A1 - Linker, Torsten
T1 - Base catalysed decomposition of anthracene endoperoxide
N2 - Catalytic amounts of a weak base are sufficient to induce the decomposition of anthracene endoperoxides to anthraquinone. The mechanism has been elucidated by isolation of intermediates in combination with DFT calculations. The whole process is suitable for the convenient generation of hydrogen peroxide under very mild conditions.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 219
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89676
SP - 1210
EP - 1213
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 - Hardy, John G.
A1 - Torres-Rendon, Jose Guillermo
A1 - Leal-Egaña, Aldo
A1 - Walther, Andreas
A1 - Schlaad, Helmut
A1 - Cölfen, Helmut
A1 - Scheibel, Thomas R.
T1 - Biomineralization of engineered spider silk protein-based composite materials for bone tissue engineering
N2 - Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 359
KW - spider silk
KW - recombinant protein
KW - biodegradable polymers
KW - biomaterials
KW - biomineralization
KW - bone tissue engineering
Y1 - 2017
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400519
ER -
TY - GEN
A1 - Bartoloni, Marco
A1 - Jin, Xian
A1 - Marcaida, Maria José
A1 - Banha, Joao
A1 - Dibonaventura, Ivan
A1 - Bongoni, Swathi
A1 - Bartho, Kathrin
A1 - Gräbner, Olivia
A1 - Sefkow, Michael
A1 - Darbre, Tamis
A1 - Reymond, Jean-Louis
T1 - Bridged bicyclic peptides as potential drug scaffolds
BT - synthesis, structure, protein binding and stability
N2 - Double cyclization of short linear peptides obtained by solid phase peptide synthesis was used to prepare bridged bicyclic peptides (BBPs) corresponding to the topology of bridged bicyclic alkanes such as norbornane. Diastereomeric norbornapeptides were investigated by 1H-NMR, X-ray crystallography and CD spectroscopy and found to represent rigid globular scaffolds stabilized by intramolecular backbone hydrogen bonds with scaffold geometries determined by the chirality of amino acid residues and sharing structural features of β-turns and α-helices. Proteome profiling by capture compound mass spectrometry (CCMS) led to the discovery of the norbornapeptide 27c binding selectively to calmodulin as an example of a BBP protein binder. This and other BBPs showed high stability towards proteolytic degradation in serum.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 197
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-81239
ER -
TY - GEN
A1 - Ehlert, Christopher
A1 - Unger, Wolfgang E. S.
A1 - Saalfrank, Peter
T1 - C K-edge NEXAFS spectra of graphene with physical and chemical defects
BT - a study based on density functional theory
N2 - Recently, C K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of graphite (HOPG) surfaces have been measured for the pristine material, and for HOPG treated with either bromine or krypton plasmas (Lippitz et al., Surf. Sci., 2013, 611, L1). Changes of the NEXAFS spectra characteristic for physical (krypton) and/or chemical/physical modifications of the surface (bromine) upon plasma treatment were observed. Their molecular origin, however, remained elusive. In this work we study by density functional theory, the effects of selected point and line defects as well as chemical modifications on NEXAFS carbon K-edge spectra of single graphene layers. For Br-treated surfaces, also Br 3d X-ray Photoelectron Spectra (XPS) are simulated by a cluster approach, to identify possible chemical modifications. We observe that some of the defects related to plasma treatment lead to characteristic changes of NEXAFS spectra, similar to those in experiment. Theory provides possible microscopic origins for these changes.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 173
KW - absorbtion fine-structure
KW - graphite
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74429
SP - 14083
EP - 14095
ER -
TY - GEN
A1 - Block, Inga
A1 - Günter, Christina
A1 - Duarte Rodrigues, Alysson
A1 - Paasch, Silvia
A1 - Hesemann, Peter
A1 - Taubert, Andreas
T1 - Carbon Adsorbents from Spent Coffee for Removal of
Methylene Blue and Methyl Orange from Water
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Activated carbons (ACs) were prepared from dried spent coffee (SCD), a biological waste product, to produce adsorbents for methylene blue (MB) and methyl orange (MO) from aqueous solution. Pre-pyrolysis activation of SCD was achieved via treatment of the SCD with aqueous sodium hydroxide solutions at 90 °C. Pyrolysis of the pretreated SCD at 500 °C for 1 h produced powders with typical characteristics of AC suitable and effective for dye adsorption. As an alternative to the rather harsh base treatment, calcium carbonate powder, a very common and abundant resource, was also studied as an activator. Mixtures of SCD and CaCO3 (1:1 w/w) yielded effective ACs for MO and MB removal upon pyrolysis needing only small amounts of AC to clear the solutions. A selectivity of the adsorption process toward anionic (MO) or cationic (MB) dyes was not observed.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1155
KW - water
KW - spent coffee
KW - dye adsorption
KW - methylene blue
KW - methyl orange
KW - calcium carbonate
KW - activated carbon
KW - water treatment
KW - dye removal
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-521653
SN - 1866-8372
IS - 14
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 - 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 - Wirth, Jonas
A1 - Kirsch, Harald
A1 - Wlosczyk, Sebastian
A1 - Tong, Yujin
A1 - Saalfrank, Peter
A1 - Kramer Campen, Richard
T1 - Characterization of water dissociation on α-Al2O3(1102)
BT - theory and experiment
N2 - The interaction of water with α-alumina (i.e. α-Al2O3) surfaces is important in a variety of applications and a useful model for the interaction of water with environmentally abundant aluminosilicate phases. Despite its significance, studies of water interaction with α-Al2O3 surfaces other than the (0001) are extremely limited. Here we characterize the interaction of water (D2O) with a well defined α-Al2O3(1[1 with combining macron]02) surface in UHV both experimentally, using temperature programmed desorption and surface-specific vibrational spectroscopy, and theoretically, using periodic-slab density functional theory calculations. This combined approach makes it possible to demonstrate that water adsorption occurs only at a single well defined surface site (the so-called 1–4 configuration) and that at this site the barrier between the molecularly and dissociatively adsorbed forms is very low: 0.06 eV. A subset of OD stretch vibrations are parallel to this dissociation coordinate, and thus would be expected to be shifted to low frequencies relative to an uncoupled harmonic oscillator. To quantify this effect we solve the vibrational Schrödinger equation along the dissociation coordinate and find fundamental frequencies red-shifted by more than 1500 cm−1. Within the context of this model, at moderate temperatures, we further find that some fraction of surface deuterons are likely delocalized: dissociatively and molecularly absorbed states are no longer distinguishable.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 320
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394497
SP - 14822
EP - 14832
ER -
TY - GEN
A1 - Peter, Martin G.
T1 - Chemische Modifikation von Biopolymeren durch Chinone und Chinonmethide
N2 - Chinone und Vorstufen, die oxidativ in Chinone und/oder Chinonmethide umgewandelt werden können, sind in der Natur weit verbreitet. Als sekundäre Naturstoffe wirken sie häufig antibiotisch, cytotoxisch, aber auch pathogen, und eine Reihe von Pflanzen und Tieren benutzt chinoide Substanzen als Abwehrstoffe, oft mit spektakulärem Erfolg. Auf makromolekularer Ebene spielen Chinonmethide im Pflanzenreich eine Schlüsselrolle bei der Biosynthese von Lignin, während die Bildung von Melanoproteinen ein Beispiel für Reaktionen von o-Chinonen im Tierreich ist. Bei den Insekten dienen Chinone und Chinonmethide zur Bildung des lebensnotwendigen Exoskeletts. Die Reaktivität von Chinonen in biologischen Systemen hat auch für den Menschen unmittelbare Bedeutung in pharmazeutischer, toxikologischer und technologischer Hinsicht. Den Beispielen in diesem Aufsatz liegt ein gemeinsames Prinzip zugrunde, nämlich die chemische Modifikation von Biopolymeren durch Chinone und Chinonmethide. Wie sich besonders bei einer detaillierteren Betrachtung der Reaktionen zeigt, die zur Sklerotisierung der Insektencuticula führen, sind in den letzten Jahren wichtige neue Erkenntnisse hinzugekommen, die vor allem durch die modernen Methoden der Stofftrennung und der Festkörper-NMR-Spektroskopie ermöglicht worden sind.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 043
Y1 - 1989
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16802
ER -
TY - GEN
A1 - Schneider, Matthias
A1 - Günter, Christina
A1 - Taubert, Andreas
T1 - Co-deposition of a hydrogel/calcium phosphate hybrid layer on 3D printed poly(lactic acid) scaffolds via dip coating
BT - Towards automated biomaterials fabrication
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - The article describes the surface modification of 3D printed poly(lactic acid) (PLA) scaffolds with calcium phosphate (CP)/gelatin and CP/chitosan hybrid coating layers. The presence of gelatin or chitosan significantly enhances CP co-deposition and adhesion of the mineral layer on the PLA scaffolds. The hydrogel/CP coating layers are fairly thick and the mineral is a mixture of brushite, octacalcium phosphate, and hydroxyapatite. Mineral formation is uniform throughout the printed architectures and all steps (printing, hydrogel deposition, and mineralization) are in principle amenable to automatization. Overall, the process reported here therefore has a high application potential for the controlled synthesis of biomimetic coatings on polymeric biomaterials.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1057
KW - 3D printing
KW - dip-coating
KW - poly(lactic acid)
KW - PLA
KW - calcium phosphate
KW - gelatin
KW - chitosan
KW - hydrogel
KW - calcium phosphate hybrid material
KW - biomaterials
Y1 - 2020
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-474427
SN - 1866-8372
IS - 1057
ER -
TY - GEN
A1 - Riebe, Daniel
A1 - Erler, Alexander
A1 - Brinkmann, Pia
A1 - Beitz, Toralf
A1 - Löhmannsröben, Hans-Gerd
A1 - Gebbers, Robin
T1 - Comparison of Calibration Approaches in Laser-Induced Breakdown Spectroscopy for Proximal Soil Sensing in Precision Agriculture
T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2 - The lack of soil data, which are relevant, reliable, affordable, immediately available, and sufficiently detailed, is still a significant challenge in precision agriculture. A promising technology for the spatial assessment of the distribution of chemical elements within fields, without sample preparation is laser-induced breakdown spectroscopy (LIBS). Its advantages are contrasted by a strong matrix dependence of the LIBS signal which necessitates careful data evaluation. In this work, different calibration approaches for soil LIBS data are presented. The data were obtained from 139 soil samples collected on two neighboring agricultural fields in a quaternary landscape of northeast Germany with very variable soils. Reference analysis was carried out by inductively coupled plasma optical emission spectroscopy after wet digestion. The major nutrients Ca and Mg and the minor nutrient Fe were investigated. Three calibration strategies were compared. The first method was based on univariate calibration by standard addition using just one soil sample and applying the derived calibration model to the LIBS data of both fields. The second univariate model derived the calibration from the reference analytics of all samples from one field. The prediction is validated by LIBS data of the second field. The third method is a multivariate calibration approach based on partial least squares regression (PLSR). The LIBS spectra of the first field are used for training. Validation was carried out by 20-fold cross-validation using the LIBS data of the first field and independently on the second field data. The second univariate method yielded better calibration and prediction results compared to the first method, since matrix effects were better accounted for. PLSR did not strongly improve the prediction in comparison to the second univariate method.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 786
KW - laser-induced breakdown spectroscopy
KW - LIBS
KW - proximal soil sensing
KW - soil nutrients
KW - elemental composition
Y1 - 2019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-440079
SN - 1866-8372
IS - 786
ER -
TY - GEN
A1 - Brinkmann, Pia
A1 - Köllner, Nicole
A1 - Merk, Sven
A1 - Beitz, Toralf
A1 - Altenberger, Uwe
A1 - Löhmannsröben, Hans-Gerd
T1 - Comparison of handheld and echelle spectrometer to assess copper in ores by means of laser-induced breakdown spectroscopy (LIBS)
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Its properties make copper one of the world’s most important functional metals. Numerous megatrends are increasing the demand for copper. This requires the prospection and exploration of new deposits, as well as the monitoring of copper quality in the various production steps. A promising technique to perform these tasks is Laser Induced Breakdown Spectroscopy (LIBS). Its unique feature, among others, is the ability to measure on site without sample collection and preparation. In this work, copper-bearing minerals from two different deposits are studied. The first set of field samples come from a volcanogenic massive sulfide (VMS) deposit, the second part from a stratiform sedimentary copper (SSC) deposit. Different approaches are used to analyze the data. First, univariate regression (UVR) is used. However, due to the strong influence of matrix effects, this is not suitable for the quantitative analysis of copper grades. Second, the multivariate method of partial least squares regression (PLSR) is used, which is more suitable for quantification. In addition, the effects of the surrounding matrices on the LIBS data are characterized by principal component analysis (PCA), alternative regression methods to PLSR are tested and the PLSR calibration is validated using field samples.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1311
KW - LIBS
KW - copper-bearing minerals
KW - UVR
KW - PCA
KW - PLSR
Y1 - 2023
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-584742
SN - 1866-8372
IS - 1311
ER -
TY - GEN
A1 - Kar, Manaswita
A1 - Körzdörfer, Thomas
T1 - Computational high throughput screening of inorganic cation based halide perovskites for perovskite only tandem solar cells
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - We search for homovalent alternatives for A, B, and X-ions in ABX(3) type inorganic halide perovskites suitable for tandem solar cell applications. We replace the conventional A-site organic cation CH3NH3, by 3 inorganic cations, Cs, K, and Rb, and the B site consists of metals; Cd, Hg, Ge, Pb, and Sn This work is built on our previous high throughput screening of hybrid perovskite materials (Kar et al 2018 J. Chem. Phys. 149, 214701). By performing a systematic screening study using Density Functional Theory (DFT) methods, we found 11 suitable candidates; 2 Cs-based, 3 K-based and 6 Rb-based that are suitable for tandem solar cell applications.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1438
KW - inorganic perovskites
KW - tandem solar cells
KW - density functional theory
Y1 - 2020
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516831
SN - 1866-8372
IS - 5
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 - 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 - 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 - 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 - 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 - Schilde, Uwe
A1 - Paz, Christian
A1 - Ortiz, Leandro
T1 - Crystal structure of erioflorin isolated from Podanthus mitiqui (L.)
N2 - The title compound, erioflorin, C19H24O6 [systematic name: (1aR,3S,4Z,5aR,8aR,9R,10aR)-1a, 2,3,5a, 7,8,8a, 9,10,10a-decahydro-3-hydroxy-4,10a-dimethyl-8-methylidene-7-oxooxireno[5,6] cyclodeca[1,2-b]furan-9-yl methacrylate], is a tricyclic germacrane sesquiterpene lactone, which was isolated from Podanthus mitiqui (L.). The compound crystallizes in the space group P2(1)2(1)2(1), and its molecular structure consists of a methacrylic ester of a ten-membered ring sesquiterpenoid annelated with an epoxide and a butyrolactone. The structure is stabilized by one intramolecular C-H center dot center dot center dot O hydrogen bond. An O-H center dot center dot center dot O hydrogen bond and further C-H center dot center dot center dot O interactions can be observed in the packing.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 379
KW - Podanthus mitiqui
KW - crystal structure
KW - germacrane sesquiterpene lactone
Y1 - 2017
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-401832
ER -
TY - GEN
A1 - Schilde, Uwe
A1 - Kelling, Alexandra
A1 - Umbreen, Sumaira
A1 - Linker, Torsten
T1 - Crystal structures of three bicyclic carbohydrate derivatives
N2 - The title compounds, [(1R,3R,4R,5R,6S)-4,5-bis(acetyloxy)-7-oxo-2-oxabicyclo[4.2.0]octan-3-yl]methyl acetate, C14H18O8, (I), [(1S,4R,5S,6R)-5-acetyloxy-7-hydroxyimino-2-oxobicyclo[4.2.0]octan-4-yl acetate, C11H15NO6, (II), and [(3aR,5R,6R,7R,7aS)-6,7-bis(acetyloxy)-2-oxooctahydropyrano[3,2-b]pyrrol-5-yl]methyl acetate, C14H19NO8, (III), are stable bicyclic carbohydrate derivatives. They can easily be synthesized in a few steps from commercially available glycals. As a result of the ring strain from the four-membered rings in (I) and (II), the conformations of the carbohydrates deviate strongly from the ideal chair form. Compound (II) occurs in the boat form. In the five-membered lactam (III), on the other hand, the carbohydrate adopts an almost ideal chair conformation. As a result of the distortion of the sugar rings, the configurations of the three bicyclic carbohydrate derivatives could not be determined from their NMR coupling constants. From our three crystal structure determinations, we were able to establish for the first time the absolute configurations of all new stereocenters of the carbohydrate rings.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 296
KW - crystal structure
KW - carbohydrate derivatives
KW - conformation
KW - configuration
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-100833
ER -
TY - GEN
A1 - Krueger, Tobias
A1 - Kelling, Alexandra
A1 - Linker, Torsten
A1 - Schilde, Uwe
T1 - Crystal structures of three cyclohexane‑based γ‑spirolactams
BT - determination of configurations and conformations
T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2 - The title compounds, 2-azaspiro[4.5]deca-1-one, C₉H₁₅NO, (1a), cis-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1b), and trans-8-methyl-2-azaspiro[4.5]deca-1-one, C₁₀H₁₇NO, (1c), were synthesized from benzoic acids 2 in only 3 steps in high yields. Crystallization from n-hexane afforded single crystals, suitable for X-ray diffraction. Thus, the configurations, conformations, and interesting crystal packing effects have been determined unequivocally. The bicyclic skeleton consists of a lactam ring, attached by a spiro junction to a cyclohexane ring. The lactam ring adopts an envelope conformation and the cyclohexane ring has a chair conformation. The main difference between compound 1b and compound 1c is the position of the carbonyl group on the 2-pyrrolidine ring with respect to the methyl group on the 8-position of the cyclohexane ring, which is cis (1b) or trans (1c). A remarkable feature of all three compounds is the existence of a mirror plane within the molecule. Given that all compounds crystallize in centrosymmetric space groups, the packing always contains interesting enantiomer-like pairs. Finally, the structures are stabilized by intermolecular N–H···O hydrogen bonds.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 738
KW - 2-Azaspiro[4.5]deca-1-ones
KW - Cis- and trans-form
KW - Configuration
KW - Conformation
KW - Lactams
Y1 - 1019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-434911
IS - 738
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 - 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 - Rethfeldt, Nina
A1 - Brinkmann, Pia
A1 - Riebe, Daniel
A1 - Beitz, Toralf
A1 - Köllner, Nicole
A1 - Altenberger, Uwe
A1 - Löhmannsröben, Hans-Gerd
T1 - Detection of Rare Earth Elements in Minerals and Soils by Laser-Induced Breakdown Spectroscopy (LIBS) Using Interval PLS
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - The numerous applications of rare earth elements (REE) has lead to a growing global demand and to the search for new REE deposits. One promising technique for exploration of these deposits is laser-induced breakdown spectroscopy (LIBS). Among a number of advantages of the technique is the possibility to perform on-site measurements without sample preparation. Since the exploration of a deposit is based on the analysis of various geological compartments of the surrounding area, REE-bearing rock and soil samples were analyzed in this work. The field samples are from three European REE deposits in Sweden and Norway. The focus is on the REE cerium, lanthanum, neodymium and yttrium. Two different approaches of data analysis were used for the evaluation. The first approach is univariate regression (UVR). While this approach was successful for the analysis of synthetic REE samples, the quantitative analysis of field samples from different sites was influenced by matrix effects. Principal component analysis (PCA) can be used to determine the origin of the samples from the three deposits. The second approach is based on multivariate regression methods, in particular interval PLS (iPLS) regression. In comparison to UVR, this method is better suited for the determination of REE contents in heterogeneous field samples. View Full-Text
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1254
KW - LIBS
KW - rare earth elements
KW - minerals
KW - PCA
KW - iPLS regression
Y1 - 2022
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-557469
SN - 1866-8372
SP - 1
EP - 17
PB - Universitätsverlag Potsdam
CY - Potsdam
ER -
TY - GEN
A1 - Dosche, Carsten
A1 - Kumke, Michael Uwe
A1 - Löhmannsröben, Hans-Gerd
A1 - Ariese, F.
A1 - Bader, Arjen N.
A1 - Gooijer, C.
A1 - Miljanic, O. S.
A1 - Iwamoto, M.
A1 - Vollhardt, K. Peter C.
A1 - Puchta, R. ; van Eikema Hommes, N. J. R.
T1 - Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]Phenylene
N2 - Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [4]phenylene (D3h[4]phenylene) were studied using laser-excited Shpolskii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31G*). CH vibrations were identified by their characteristic isotopic shifts in the spectra of deuterated triangular [4]phenylenes. Two CC stretching modes, at 100 cm–1 and 1176 cm–1, suitable as probes for bond strength changes in the excited state, were identified. The isotope effect on the internal conversion rates of triangular [4]phenylene was evaluated from measurements of temperature dependent lifetime. Isotope dependency and the magnitude of the internal conversion rates indicate that internal conversion in triangular [4]phenylene is most likely induced by CH vibrations. The results obtained by LESS and lifetime measurements were compared with PM3 PECI calculations of the excited state structure. The theoretical results and the relation between ground and excited state vibration energies of the 1176 cm–1 probe vibration indicate a reduction of bond alternation of the central cyclohexatriene ring in the excited state.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 002
Y1 - 2004
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11881
ER -
TY - GEN
A1 - Rausch, Ann-Kristin
A1 - Brockmeyer, Robert
A1 - Schwerdtle, Tanja
T1 - Development, validation, and application of a multi-method for the determination of mycotoxins, plant growth regulators, tropane alkaloids, and pesticides in cereals by two-dimensional liquid chromatography tandem mass spectrometry
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Mycotoxins and pesticides regularly co-occur in agricultural products worldwide. Thus, humans can be exposed to both toxic contaminants and pesticides simultaneously, and multi-methods assessing the occurrence of various food contaminants and residues in a single method are necessary. A two-dimensional high performance liquid chromatography tandem mass spectrometry method for the analysis of 40 (modified) mycotoxins, two plant growth regulators, two tropane alkaloids, and 334 pesticides in cereals was developed. After an acetonitrile/water/formic acid (79:20:1, v/v/v) multi-analyte extraction procedure, extracts were injected into the two-dimensional setup, and an online clean-up was performed. The method was validated according to Commission Decision (EC) no. 657/2002 and document N° SANTE/12682/2019. Good linearity (R2 > 0.96), recovery data between 70-120%, repeatability and reproducibility values < 20%, and expanded measurement uncertainties < 50% were obtained for a wide range of analytes, including very polar substances like deoxynivalenol-3-glucoside and methamidophos. However, results for fumonisins, zearalenone-14,16-disulfate, acid-labile pesticides, and carbamates were unsatisfying. Limits of quantification meeting maximum (residue) limits were achieved for most analytes. Matrix effects varied highly (−85 to +1574%) and were mainly observed for analytes eluting in the first dimension and early-eluting analytes in the second dimension. The application of the method demonstrated the co-occurrence of different types of cereals with 28 toxins and pesticides. Overall, 86% of the samples showed positive findings with at least one mycotoxin, plant growth regulator, or pesticide.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1365
KW - 2D-LC-MS/MS
KW - Multi-method
KW - Mycotoxins
KW - Modified mycotoxins
KW - Pesticides
KW - Cereals
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-514795
SN - 1866-8372
IS - 143
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 - Prinz, Julia
A1 - Heck, Christian
A1 - Ellerik, Lisa
A1 - Merk, Virginia
A1 - Bald, Ilko
T1 - DNA origami based Au–Ag-core–shell nanoparticle dimers with single-molecule SERS sensitivity
N2 - DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 1010, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 221
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89714
SP - 5612
EP - 5620
ER -
TY - GEN
A1 - Hildebrand, Viet
A1 - Laschewsky, André
A1 - Päch, Michael
A1 - Müller-Buschbaum, Peter
A1 - Papadakis, Christine M.
T1 - Effect of the zwitterion structure on the thermo-responsive behaviour of poly(sulfobetaine methacrylates)
N2 - A series of new sulfobetaine methacrylates, including nitrogen-containing saturated heterocycles, was synthesised by systematically varying the substituents of the zwitterionic group. Radical polymerisation via the RAFT (reversible addition–fragmentation chain transfer) method in trifluoroethanol proceeded smoothly and was well controlled, yielding polymers with predictable molar masses. Molar mass analysis and control of the end-group fidelity were facilitated by end-group labeling with a fluorescent dye. The polymers showed distinct thermo-responsive behaviour of the UCST (upper critical solution temperature) type in an aqueous solution, which could not be simply correlated to their molecular structure via an incremental analysis of the hydrophilic and hydrophobic elements incorporated within them. Increasing the spacer length separating the ammonium and the sulfonate groups of the zwitterion moiety from three to four carbons increased the phase transition temperatures markedly, whereas increasing the length of the spacer separating the ammonium group and the carboxylate ester group on the backbone from two to three carbons provoked the opposite effect. Moreover, the phase transition temperatures of the analogous polyzwitterions decreased in the order dimethylammonio > morpholinio > piperidinio alkanesulfonates. In addition to the basic effect of the polymers’ precise molecular structure, the concentration and the molar mass dependence of the phase transition temperatures were studied. Furthermore, we investigated the influence of added low molar mass salts on the aqueous-phase behaviour for sodium chloride and sodium bromide as well as sodium and ammonium sulfate. The strong effects evolved in a complex way with the salt concentration. The strength of these effects depended on the nature of the anion added, increasing in the order sulfate < chloride < bromide, thus following the empirical Hofmeister series. In contrast, no significant differences were observed when changing the cation, i.e. when adding sodium or ammonium sulfate.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 298
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102028
ER -
TY - GEN
A1 - Nicolai, Merle Marie
A1 - Weishaupt, Ann-Kathrin
A1 - Baesler, Jessica
A1 - Brinkmann, Vanessa
A1 - Wellenberg, Anna
A1 - Winkelbeiner, Nicola Lisa
A1 - Gremme, Anna
A1 - Aschner, Michael
A1 - Fritz, Gerhard
A1 - Schwerdtle, Tanja
A1 - Bornhorst, Julia
T1 - Effects of manganese on genomic integrity in the multicellular model organism Caenorhabditis elegans
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Although manganese (Mn) is an essential trace element, overexposure is associated with Mn-induced toxicity and neurological dysfunction. Even though Mn-induced oxidative stress is discussed extensively, neither the underlying mechanisms of the potential consequences of Mn-induced oxidative stress on DNA damage and DNA repair, nor the possibly resulting toxicity are characterized yet. In this study, we use the model organism Caenorhabditis elegans to investigate the mode of action of Mn toxicity, focusing on genomic integrity by means of DNA damage and DNA damage response. Experiments were conducted to analyze Mn bioavailability, lethality, and induction of DNA damage. Different deletion mutant strains were then used to investigate the role of base excision repair (BER) and dePARylation (DNA damage response) proteins in Mn-induced toxicity. The results indicate a dose- and time-dependent uptake of Mn, resulting in increased lethality. Excessive exposure to Mn decreases genomic integrity and activates BER. Altogether, this study characterizes the consequences of Mn exposure on genomic integrity and therefore broadens the molecular understanding of pathways underlying Mn-induced toxicity. Additionally, studying the basal poly(ADP-ribosylation) (PARylation) of worms lacking poly(ADP-ribose) glycohydrolase (PARG) parg-1 or parg-2 (two orthologue of PARG), indicates that parg-1 accounts for most of the glycohydrolase activity in worms.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1173
KW - manganese
KW - oxidative stress
KW - DNA repair
KW - DNA damage response
KW - Caenorhabditis elegans
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-523275
SN - 1866-8372
IS - 1173
ER -
TY - GEN
A1 - Farhan, Muhammad
A1 - Chaudhary, Deeptangshu
A1 - Nöchel, Ulrich
A1 - Behl, Marc
A1 - Kratz, Karl
A1 - Lendlein, Andreas
T1 - Electrical actuation of coated and composite fibers based on poly[ethylene-co-(vinyl acetate)]
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Robots are typically controlled by electrical signals. Resistive heating is an option to electrically trigger actuation in thermosensitive polymer systems. In this study electrically triggerable poly[ethylene-co-(vinyl acetate)] (PEVA)-based fiber actuators are realized as composite fibers as well as polymer fibers with conductive coatings. In the coated fibers, the core consists of crosslinked PEVA (cPEVA), while the conductive coating shell is achieved via a dip coating procedure with a coating thickness between 10 and 140 mu m. The conductivity of coated fibers sigma = 300-550 S m(-1) is much higher than that of the composite fibers sigma = 5.5 S m(-1). A voltage (U) of 110 V is required to heat 30 cm of coated fiber to a targeted temperature of approximate to 65 degrees C for switching in less than a minute. Cyclic electrical actuation investigations reveal epsilon '(rev) = 5 +/- 1% reversible change in length for coated fibers. The fabrication of such electro-conductive polymeric actuators is suitable for upscaling so that their application potential as artificial muscles can be explored in future studies.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1375
KW - artificial muscles
KW - fiber actuators
KW - resistive heating
KW - shape‐memory polymer actuators
KW - soft robotics
Y1 - 2020
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-571679
SN - 1866-8372
IS - 2
ER -
TY - GEN
A1 - Crone, Barbara
A1 - Aschner, Michael A.
A1 - Schwerdtle, Tanja
A1 - Karst, Uwe
A1 - Bornhorst, Julia
T1 - Elemental bioimaging of Cisplatin in Caenorhabditis elegans by LA-ICP-MS
N2 - cis-Diamminedichloroplatinum(II) (Cisplatin) is one of the most important and frequently used cytostatic drugs for the treatment of various solid tumors. Herein, a laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) method incorporating a fast and simple sample preparation protocol was developed for the elemental mapping of Cisplatin in the model organism Caenorhabditis elegans (C. elegans). The method allows imaging of the spatially-resolved elemental distribution of platinum in the whole organism with respect to the anatomic structure in L4 stage worms at a lateral resolution of 5 μm. In addition, a dose- and time-dependent Cisplatin uptake was corroborated quantitatively by a total reflection X-ray fluorescence spectroscopy (TXRF) method, and the elemental mapping indicated that Cisplatin is located in the intestine and in the head of the worms. Better understanding of the distribution of Cisplatin in this well-established model organism will be instrumental in deciphering Cisplatin toxicity and pharmacokinetics. Since the cytostatic effect of Cisplatin is based on binding the DNA by forming intra- and interstrand crosslinks, the response of poly(ADP-ribose)metabolism enzyme 1 (pme-1) deletion mutants to Cisplatin was also examined. Loss of pme-1, which is the C. elegans ortholog of human poly(ADP-ribose) polymerase 1 (PARP-1) led to disturbed DNA damage response. With respect to survival and brood size, pme-1 deletion mutants were more sensitive to Cisplatin as compared to wildtype worms, while Cisplatin uptake was indistinguishable.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 192
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-80031
SP - 1189
EP - 1195
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 - Bourgat, Yannick
A1 - Tiersch, Brigitte
A1 - Koetz, Joachim
A1 - Menzel, Henning
T1 - Enzyme degradable polymersomes from chitosan-g-[poly-l-lysine-block-epsilon-caprolactone] copolymer
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - The scope of this study includes the synthesis of chitosan-g-[peptide-poly-epsilon-caprolactone] and its self-assembly into polymeric vesicles employing the solvent shift method. In this way, well-defined core-shell structures suitable for encapsulation of drugs are generated. The hydrophobic polycaprolactone side-chain and the hydrophilic chitosan backbone are linked via an enzyme-cleavable peptide. The synthetic route involves the functionalization of chitosan with maleimide groups and the preparation of polycaprolactone with alkyne end-groups. A peptide functionalized with a thiol group on one side and an azide group on the other side is prepared. Thiol-ene click-chemistry and azide-alkyne Huisgen cycloaddition are then used to link the chitosan and poly-epsilon-caprolactone chains, respectively, with this peptide. For a preliminary study, poly-l-lysin is a readily available and cleavable peptide that is introduced to investigate the feasibility of the system. The size and shape of the polymersomes are studied by dynamic light scattering and cryo-scanning electron microscopy. Furthermore, degradability is studied by incubating the polymersomes with two enzymes, trypsin and chitosanase. A dispersion of polymersomes is used to coat titanium plates and to further test the stability against enzymatic degradation.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1382
KW - chitosan
KW - click chemistry
KW - drug delivery system
KW - enzyme
KW - polymersomes
KW - poly‐ ε ‐ caprolactone
Y1 - 2020
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-566584
SN - 1866-8372
IS - 1
ER -
TY - GEN
A1 - Kopyra, Janina
A1 - Wierzbicka, Paulina
A1 - Tulwin, Adrian
A1 - Thiam, Guillaume
A1 - Bald, Ilko
A1 - Rabilloud, Franck
A1 - Abdoul-Carime, Hassan
T1 - Experimental and theoretical studies of dissociative electron attachment to metabolites oxaloacetic and citric acids
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - In this contribution the dissociative electron attachment to metabolites found in aerobic organisms, namely oxaloacetic and citric acids, was studied both experimentally by means of a crossed-beam setup and theoretically through density functional theory calculations. Prominent negative ion resonances from both compounds are observed peaking below 0.5 eV resulting in intense formation of fragment anions associated with a decomposition of the carboxyl groups. In addition, resonances at higher energies (3–9 eV) are observed exclusively from the decomposition of the oxaloacetic acid. These fragments are generated with considerably smaller intensities. The striking findings of our calculations indicate the different mechanism by which the near 0 eV electron is trapped by the precursor molecule to form the transitory negative ion prior to dissociation. For the oxaloacetic acid, the transitory anion arises from the capture of the electron directly into some valence states, while, for the citric acid, dipole- or multipole-bound states mediate the transition into the valence states. What is also of high importance is that both compounds while undergoing DEA reactions generate highly reactive neutral species that can lead to severe cell damage in a biological environment.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1156
KW - dissociative electron attachment
KW - negative ions
KW - oxaloacetic acid
KW - citric acid
KW - mass spectrometry
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-521829
SN - 1866-8372
IS - 1156
ER -
TY - GEN
A1 - Schönemann, Eric
A1 - Laschewsky, André
A1 - Rosenhahn, Axel
T1 - Exploring the long-term hydrolytic behavior of zwitterionic polymethacrylates and polymethacrylamides
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - The hydrolytic stability of polymers to be used for coatings in aqueous environments, for example, to confer anti-fouling properties, is crucial. However, long-term exposure studies on such polymers are virtually missing. In this context, we synthesized a set of nine polymers that are typically used for low-fouling coatings, comprising the well-established poly(oligoethylene glycol methylether methacrylate), poly(3-(N-2-methacryloylethyl-N,N-dimethyl) ammoniopropanesulfonate) (“sulfobetaine methacrylate”), and poly(3-(N-3-methacryamidopropyl-N,N-dimethyl)ammoniopropanesulfonate) (“sulfobetaine methacrylamide”) as well as a series of hitherto rarely studied polysulfabetaines, which had been suggested to be particularly hydrolysis-stable. Hydrolysis resistance upon extended storage in aqueous solution is followed by ¹H NMR at ambient temperature in various pH regimes. Whereas the monomers suffered slow (in PBS) to very fast hydrolysis (in 1 M NaOH), the polymers, including the polymethacrylates, proved to be highly stable. No degradation of the carboxyl ester or amide was observed after one year in PBS, 1 M HCl, or in sodium carbonate buffer of pH 10. This demonstrates their basic suitability for anti-fouling applications. Poly(sulfobetaine methacrylamide) proved even to be stable for one year in 1 M NaOH without any signs of degradation. The stability is ascribed to a steric shielding effect. The hemisulfate group in the polysulfabetaines, however, was found to be partially labile.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1091
KW - polyzwitterions
KW - stability
KW - polymer degradation
KW - hydrolysis
KW - polysulfobetaine
KW - polysulfabetaine
KW - anti-fouling materials
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-473052
SN - 1866-8372
IS - 1091
ER -
TY - GEN
A1 - Pacholski, Claudia
A1 - Agarwal, Vivechana
A1 - Balderas-Valadez, Ruth Fabiola
T1 - Fabrication of porous silicon-based optical sensors using metal-assisted chemical etching
N2 - Optical biosensors based on porous silicon were fabricated by metal assisted chemical etching. Thereby double layered porous silicon structures were obtained consisting of porous pillars with large pores on top of a porous silicon layer with smaller pores. These structures showed a similar sensing performance in comparison to electrochemically produced porous silicon interferometric sensors.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 316
KW - fourier-transform spectroscopy
KW - nanostructures
KW - nanowires
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394426
SP - 21430
EP - 21434
ER -
TY - GEN
A1 - Engelbrecht, Rainer
A1 - Lau, Steffen
A1 - Salffner, Katharina
A1 - Löhmannsröben, Hans-Gerd
T1 - Fasergekoppelte NIR-Diodenlaser-Spektrometer zur simultanen und isotopen-aufgelösten Messung von CO und CO2 : Anwendungen in Plasma-Diagnostik und Bodengasanalyse
N2 - Die Anwendung zweier ähnlicher fasergekoppelte Diodenlaser-Spektrometer-Systeme werden vorgestellt. Basis sind handelsübliche DFB-Laserdioden der optischen Kommunikationstechnik. Der faseroptische Aufbau, das Detektionsverfahren (2f Wellenlängenmodulations-Spektroskopie mit Balanced Receiver), Rauschverhalten und Detektionslimit werden diskutiert. Zur in-situ Plasma-Diagnostik von CO- und CO2-Konzentrationen in industriellen CO2-Lasern der Materialbearbeitung wurde eine Wellenlänge von 1582 nm verwendet. Bei einem Gasdruck von 100 hPa und einer Absorptionsweglänge von 14,9 cm wurden mit einer Laserdiode simultan CO- und CO2-Konzentrationen von 0% bis 11% im Gasgefäß bei laufender Hochfrequenzgasentladung des CO2-Lasers zeitaufgelöst gemessen. Vorgestellt und diskutiert werden Aufbau und Eigenschaften des Spektrometers sowie die Ergebnisse der dynamischen Gasanalysen, die zu einer Verbesserung der Katalysator-Technik im CO2-Laser beigetragen haben.Mit isotopenaufgelöster CO- und CO2-Spektroskopie können biologische Gasaustauschprozesse, z.B. in Gasen aus dem Erdboden untersucht werden. Hierzu wurde ein fasergekoppeltes feldtaugliches Diodenlaser-Spektrometer bei Wellenlängen um 1605 nm zur Messungder Isotopologe 12C16O, 13C16O, 12C18O und 12C16O2, 13C16O2, 12C18O16O aufgebaut. Die Messung erfolgt extraktiv in Langwegzellen mit unterschiedlichen Absorptionsweglängen von 100.9 m und 29.9 m. Es werden Kalibrationsmessungen zur Linearität und zur Präzision der Bestimmung der Isotopenverhältnisse sowie Wiederholungsmessungen zur Stabilität vorgestellt. Nachweisgrenzen von wenigen ppm konnten für die CO- und CO2-Isotopologen erhalten werden.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 13
Y1 - 2006
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12348
ER -
TY - GEN
A1 - Schulze, Sven
A1 - Wehrhold, Michel
A1 - Hille, Carsten
T1 - Femtosecond-pulsed laser written and etched fiber bragg gratings for fiber-optical biosensing
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - We present the development of a label-free, highly sensitive fiber-optical biosensor for online detection and quantification of biomolecules. Here, the advantages of etched fiber Bragg gratings (eFBG) were used, since they induce a narrowband Bragg wavelength peak in the reflection operation mode. The gratings were fabricated point-by-point via a nonlinear absorption process of a highly focused femtosecond-pulsed laser, without the need of prior coating removal or specific fiber doping. The sensitivity of the Bragg wavelength peak to the surrounding refractive index (SRI), as needed for biochemical sensing, was realized by fiber cladding removal using hydrofluoric acid etching. For evaluation of biosensing capabilities, eFBG fibers were biofunctionalized with a single-stranded DNA aptamer specific for binding the C-reactive protein (CRP). Thus, the CRP-sensitive eFBG fiber-optical biosensor showed a very low limit of detection of 0.82 pg/L, with a dynamic range of CRP detection from approximately 0.8 pg/L to 1.2 µg/L. The biosensor showed a high specificity to CRP even in the presence of interfering substances. These results suggest that the proposed biosensor is capable for quantification of CRP from trace amounts of clinical samples. In addition, the adaption of this eFBG fiber-optical biosensor for detection of other relevant analytes can be easily realized.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1073
KW - fiber Bragg gratings
KW - ultra-fast laser inscription
KW - fiber etching
KW - nanostructure fabrication
KW - fiber-optical sensors
KW - aptamers
KW - C-reactive
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-472692
SN - 1866-8372
IS - 1073
ER -
TY - GEN
A1 - Vacogne, Charlotte D.
A1 - Brosnan, Sarah M.
A1 - Masic, Admir
A1 - Schlaad, Helmut
T1 - Fibrillar gels via the self-assembly of poly(L-glutamate)-based statistical copolymers
N2 - Polypeptides having secondary structures often undergo self-assembly which can extend over multiple length scales. Poly(γ-benzyl-L-glutamate) (PBLG), for example, folds into α-helices and forms physical organogels, whereas poly(L-glutamic acid) (PLGA at acidic pH) or poly(L-glutamate) (PLG at neutral/basic pH) do not form hydrogels. We explored the gelation of modified PBLG and investigated the deprotection of the carboxylic acid moieties in such gels to yield unique hydrogels. This was accomplished through photo-crosslinking gelation of poly(γ-benzyl-L-glutamate-co-allylglycine) statistical copolymers in toluene, tetrahydrofuran, and 1,4-dioxane. Unlike most polymer-based chemical gels, our gels were prepared from dilute solutions (<20 g L−1, i.e., <2% w/v) of low molar mass polymers. Despite such low concentrations and molar masses, our dioxane gels showed high mechanical stability and little shrinkage; remarkably, they also exhibited a porous fibrillar network. Deprotection of the carboxylic acid moieties in dioxane gels yielded pH responsive and highly absorbent PLGA/PLG-based hydrogels (swelling ratio of up to 87), while preserving the network structure, which is an unprecedented feature in the context of crosslinked PLGA gels. These outstanding properties are highly attractive for biomedical materials.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 301
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102289
SP - 5040
EP - 5052
ER -
TY - 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 - 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 - Mayer, Dennis
A1 - Lever, Fabiano
A1 - Picconi, David
A1 - Metje, Jan
A1 - Ališauskas, Skirmantas
A1 - Calegari, Francesca
A1 - Düsterer, Stefan
A1 - Ehlert, Christopher
A1 - Feifel, Raimund
A1 - Niebuhr, Mario
A1 - Manschwetus, Bastian
A1 - Kuhlmann, Marion
A1 - Mazza, Tommaso
A1 - Robinson, Matthew Scott
A1 - Squibb, Richard James
A1 - Trabattoni, Andrea
A1 - Wallner, Måns
A1 - Saalfrank, Peter
A1 - Wolf, Thomas J. A.
A1 - Gühr, Markus
T1 - Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220–250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1301
Y1 - 2022
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-577442
SN - 1866-8372
IS - 1301
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 - Perovic, Milena
A1 - Qin, Qing
A1 - Oschatz, Martin
T1 - From molecular precursors to nanoparticles
BT - tailoring the adsorption properties of porous carbon materials by controlled chemical functionalization
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Nanoporous carbon materials (NCMs) provide the "function" of high specific surface area and thus have large interface area for interactions with surrounding species, which is of particular importance in applications related to adsorption processes. The strength and mechanism of adsorption depend on the pore architecture of the NCMs. In addition, chemical functionalization can be used to induce changes of electron density and/or electron density distribution in the pore walls, thus further modifying the interactions between carbons and guest species. Typical approaches for functionalization of nanoporous materials with regular atomic construction like porous silica, metal-organic frameworks, or zeolites, cannot be applied to NCMs due to their less defined local atomic construction and abundant defects. Therefore, synthetic strategies that offer a higher degree of control over the process of functionalization are needed. Synthetic approaches for covalent functionalization of NCMs, that is, for the incorporation of heteroatoms into the carbon backbone, are critically reviewed with a special focus on strategies following the concept "from molecules to materials." Approaches for coordinative functionalization with metallic species, and the functionalization by nanocomposite formation between pristine carbon materials and heteroatom-containing carbons, are introduced as well. Particular focus is given to the influences of these functionalizations in adsorption-related applications.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1191
KW - composites
KW - heteroatoms
KW - metal species
KW - porous carbon materials
KW - surface functionalization
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516140
SN - 1866-8372
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 - Ermeydan, Mahmut Ali
A1 - Cabane, Etienne
A1 - Hass, Philipp
A1 - Koetz, Joachim
A1 - Burgert, Ingo
T1 - Fully biodegradable modification of wood for improvement of dimensional stability and water absorption properties by poly(ε-caprolactone) grafting into the cell walls
N2 - Materials derived from renewable resources are highly desirable in view of more sustainable manufacturing. Among the available natural materials, wood is one of the key candidates, because of its excellent mechanical properties. However, wood and wood-based materials in engineering applications suffer from various restraints, such as dimensional instability upon humidity changes. Several wood modification treatments increase water repellence, but the insertion of hydrophobic polymers can result in a composite material which cannot be considered as renewable anymore. In this study, we report on the grafting of the fully biodegradable poly(ε-caprolactone) (PCL) inside the wood cell walls by Sn(Oct)2 catalysed ring-opening polymerization (ROP). The presence of polyester chains within the wood cell wall structure is monitored by confocal Raman imaging and spectroscopy as well as scanning electron microscopy. Physical tests reveal that the modified wood is more hydrophobic due to the bulking of the cell wall structure with the polyester chains, which results in a novel fully biodegradable wood material with improved dimensional stability.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 270
KW - ring-opening polymerization
KW - confocal raman microscopy
KW - epsilon-caprolactone
KW - mechanical-properties
KW - structural-characterization
KW - stannous octoate
KW - copolymers
KW - degradation
KW - composites
KW - cellulose
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-97265
SP - 3313
EP - 3321
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 - Mardoukhi, Yousof
A1 - Jeon, Jae-Hyung
A1 - Metzler, Ralf
T1 - Geometry controlled anomalous diffusion in random fractal geometries
BT - looking beyond the infinite cluster
N2 - We investigate the ergodic properties of a random walker performing (anomalous) diffusion on a random fractal geometry. Extensive Monte Carlo simulations of the motion of tracer particles on an ensemble of realisations of percolation clusters are performed for a wide range of percolation densities. Single trajectories of the tracer motion are analysed to quantify the time averaged mean squared displacement (MSD) and to compare this with the ensemble averaged MSD of the particle motion. Other complementary physical observables associated with ergodicity are studied, as well. It turns out that the time averaged MSD of individual realisations exhibits non-vanishing fluctuations even in the limit of very long observation times as the percolation density approaches the critical value. This apparent non-ergodic behaviour concurs with the ergodic behaviour on the ensemble averaged level. We demonstrate how the non-vanishing fluctuations in single particle trajectories are analytically expressed in terms of the fractal dimension and the cluster size distribution of the random geometry, thus being of
purely geometrical origin. Moreover, we reveal that the convergence scaling law to ergodicity, which is known to be inversely proportional to the observation time T for ergodic diffusion processes, follows a power-law BT� h with h o 1 due to the fractal structure of the accessible space. These results provide useful measures for differentiating the subdiffusion on random fractals from an otherwise closely related process, namely, fractional Brownian motion. Implications of our results on the analysis of single particle tracking experiments are provided.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 207
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-85247
ER -
TY - 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 - Niedl, Robert Raimund
A1 - Berenstein, Igal
A1 - Beta, Carsten
T1 - How imperfect mixing and differential diffusion accelerate the rate of nonlinear reactions in microfluidic channels
N2 - In this paper, we show experimentally that inside a microfluidic device, where the reactants are segregated, the reaction rate of an autocatalytic clock reaction is accelerated in comparison to the case where all the reactants are well mixed. We also find that, when mixing is enhanced inside the microfluidic device by introducing obstacles into the flow, the clock reaction becomes slower in comparison to the device where mixing is less efficient. Based on numerical simulations, we show that this effect can be explained by the interplay of nonlinear reaction kinetics (cubic autocatalysis) and differential diffusion, where the autocatalytic species diffuses slower than the substrate.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 253
KW - arsenious acid
KW - fronts
KW - paper
KW - poly(dimethylsiloxane)
KW - scale
KW - systems
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95810
SP - 6451
EP - 6457
ER -
TY - GEN
A1 - Töpfer, Kai
A1 - Tremblay, Jean Christophe
T1 - How surface reparation prevents catalytic oxidation of carbon monoxide on atomic gold at defective magnesium oxide surfaces
N2 - In this contribution, we study using first principles the co-adsorption and catalytic behaviors of CO and O2 on a single gold atom deposited at defective magnesium oxide surfaces. Using cluster models and point charge embedding within a density functional theory framework, we simulate the CO oxidation reaction for Au1 on differently charged oxygen vacancies of MgO(001) to rationalize its experimentally observed lack of catalytic activity. Our results show that: (1) co-adsorption is weakly supported at F0 and F2+ defects but not at F1+ sites, (2) electron redistribution from the F0 vacancy via the Au1 cluster to the adsorbed molecular oxygen weakens the O2 bond, as required for a sustainable catalytic cycle, (3) a metastable carbonate intermediate can form on defects of the F0 type, (4) only a small activation barrier exists for the highly favorable dissociation of CO2 from F0, and (5) the moderate adsorption energy of the gold atom on the F0 defect cannot prevent insertion of molecular oxygen inside the defect. Due to the lack of protection of the color centers, the surface becomes invariably repaired by the surrounding oxygen and the catalytic cycle is irreversibly broken in the first oxidation step.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 325
Y1 - 2016
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394978
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 - Niedl, Robert Raimund
A1 - Beta, Carsten
T1 - Hydrogel-driven paper-based microfluidics
N2 - Paper-based microfluidics provide an inexpensive, easy to use technology for point-of-care diagnostics in developing countries. Here, we combine paper-based microfluidic devices with responsive hydrogels to add an entire new class of functions to these versatile low-cost fluidic systems. The hydrogels serve as fluid reservoirs. In response to an external stimulus, e.g. an increase in temperature, the hydrogels collapse and release fluid into the structured paper substrate. In this way, chemicals that are either stored on the paper substrate or inside the hydrogel pads can be dissolved, premixed, and brought to reaction to fulfill specific analytic tasks. We demonstrate that multi-step sequences of chemical reactions can be implemented in a paper-based system and operated without the need for external precision pumps. We exemplify this technology by integrating an antibody-based E. coli test on a small and easy to use paper device.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 193
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-81083
SP - 2452
EP - 2459
ER -
TY - 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 - Perovic, Milena
A1 - Zeininger, Lukas
A1 - Oschatz, Martin
T1 - Immobilization of gold-on-carbon catalysts onto perfluorocarbon emulsion droplets to promote oxygen delivery in aqueous phase (D)-glucose oxidation
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - The catalytic activity of metal nanoparticles (NPs) supported on porous supports can be controlled by various factors, such as NPs size, shape, or dispersivity, as well as their interaction with the support or the properties of the support material itself. However, these intrinsic properties are not solely responsible for the catalytic behavior of the overall reaction system, as the local environment and surface coverage of the catalyst with reactants, products, intermediates and other invloved species often play a crucial role in catalytic processes as well. Their contribution can be particularly critical in liquid-phase reactions with gaseous reactants that often suffer from low solubiltiy. One example is (D)-glucose oxidation with molecular oxygen over gold nanoparticles supported on porous carbons. The possibility to promote oxygen delivery in such aqueous phase oxidation reactions via the immobilization of heterogenous catalysts onto the interface of perfluorocarbon emulsion droplets is reported here. Gold-on-carbon catalyst particles can stabilize perfluorocarbon droplets in the aqueous phase and the local concentration of the oxidant in the surroundings of the gold nanoparticles accelerates the rate-limiting step of the reaction. Consequently, the reaction rate of a system with the optimal volume fraction of fluorocarbon is higher than a reference emulsion system without fluorocarbon, and the effect is observed even without additional oxygen supply.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1362
KW - perfluorocarbon emulsion
KW - glucose oxidation
KW - porous carbon
KW - gas
KW - solubility
KW - pickering emulsion
KW - liquid-phase catalysis
Y1 - 2020
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-569471
SN - 1867-3880
SN - 1867-3899
SN - 1866-8372
IS - 1
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 Cr4+: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 - Ermeydan, Mahmut Ali
A1 - Cabane, Etienne
A1 - Gierlinger, Notburga
A1 - Koetz, Joachim
A1 - Burgert, Ingo
T1 - Improvement of wood material properties via in situ polymerization of styrene into tosylated cell walls
N2 - As an engineering material derived from renewable resources, wood possesses excellent mechanical properties in view of its light weight but also has some disadvantages such as low dimensional stability upon moisture changes and low durability against biological attack. Polymerization of hydrophobic monomers in the cell wall is one of the potential approaches to improve the dimensional stability of wood. A major challenge is to insert hydrophobic monomers into the hydrophilic environment of the cell walls, without increasing the bulk density of the material due to lumen filling. Here, we report on an innovative and simple method to insert styrene monomers into tosylated cell walls (i.e. –OH groups from natural wood polymers are reacted with tosyl chloride) and carry out free radical polymerization under relatively mild conditions, generating low wood weight gains. In-depth SEM and confocal Raman microscopy analysis are applied to reveal the distribution of the polystyrene in the cell walls and the lumen. The embedding of polystyrene in wood results in reduced water uptake by the wood cell walls, a significant increase in dimensional stability, as well as slightly improved mechanical properties measured by nanoindentation.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 274
Y1 - 2014
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98736
ER -
TY - GEN
A1 - Meyer, S.
A1 - Raber, G.
A1 - Ebert, Franziska
A1 - Leffers, L.
A1 - Müller, Sandra Marie
A1 - Taleshi, M. S.
A1 - Francesconi, Kevin A.
A1 - Schwerdtle, Tanja
T1 - In vitro toxicological characterisation of arsenic-containing fatty acids and three of their metabolites
N2 - Arsenic-containing fatty acids are a group of fat-soluble arsenic species (arsenolipids) which are present in marine fish and other seafood. Recently, it has been shown that arsenic-containing hydrocarbons, another group of arsenolipids, exert toxicity in similar concentrations comparable to arsenite although the toxic modes of action differ. Hence, a risk assessment of arsenolipids is urgently needed. In this study the cellular toxicity of a saturated (AsFA 362) and an unsaturated (AsFA 388) arsenic-containing fatty acid and three of their proposed metabolites (DMAV, DMAPr and thio-DMAPr) were investigated in human liver cells (HepG2). Even though both arsenic-containing fatty acids were less toxic as compared to arsenic-containing hydrocarbons and arsenite, significant effects were observable at μM concentrations. DMAV causes effects in a similar concentration range and it could be seen that it is metabolised to its highly toxic thio analogue thio-DMAV in HepG2 cells. Nevertheless, DMAPr and thio-DMAPr did not exert any cytotoxicity. In summary, our data indicate that risks to human health related to the presence of arsenic-containing fatty acids in marine food cannot be excluded. This stresses the need for a full in vitro and in vivo toxicological characterisation of these arsenolipids.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 199
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-82008
ER -
TY - 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 - 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 - Dettmann, Sophie
A1 - Huittinen, Nina Maria
A1 - Jahn, Nicolas
A1 - Kretzschmar, Jerome
A1 - Kumke, Michael Uwe
A1 - Kutyma, Tamara
A1 - Lohmann, Janik
A1 - Reich, Tobias
A1 - Schmeide, Katja
A1 - Azzam, Salim Shams Aldin
A1 - Spittler, Leon
A1 - Stietz, Janina
T1 - Influence of gluconate on the retention of Eu(III), Am(III), Th(IV), Pu(IV), and U(VI) by C-S-H (C/S = 0.8)
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - The retention of actinides in different oxidation states (An(X), X = III, IV, VI) by a calcium-silicate-hydrate (C-S-H) phase with a Ca/Si (C/S) ratio of 0.8 was investigated in the presence of gluconate (GLU). The actinides considered were Am(III), Th(IV), Pu(IV), and U(VI). Eu(III) was investigated as chemical analogue for Am(III) and Cm(III). In addition to the ternary systems An(X)/GLU/C-S-H, also binary systems An(X)/C-S-H, GLU/C-S-H, and An(X)/GLU were studied. Complementary analytical techniques were applied to address the different specific aspects of the binary and ternary systems. Time-resolved laser-induced luminescence spectroscopy (TRLFS) was applied in combination with parallel factor analysis (PARAFAC) to identify retained species and to monitor species-selective sorption kinetics. ¹³C and ²⁹Si magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to determine the bulk structure and the composition of the C-S-H surface, respectively, in the absence and presence of GLU. The interaction of Th(IV) with GLU in different electrolytes was studied by capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS). The influence of GLU on An(X) retention was investigated for a large concentration range up to 10⁻² M. The results showed that GLU had little to no effect on the overall An(X) retention by C-S-H with C/S of 0.8, regardless of the oxidation state of the actinides. For Eu(III), the TRLFS investigations additionally implied the formation of a Eu(III)-bearing precipitate with dissolved constituents of the C-S-H phase, which becomes structurally altered by the presence of GLU. For U(VI) sorption on the C-S-H phase, only a small influence of GLU could be established in the luminescence spectroscopic investigations, and no precipitation of U(VI)-containing secondary phases could be identified.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1318
KW - actinide, organic ligand, sorption, cementitious material, concrete, luminescence
KW - organic ligand
KW - sorption
KW - cementitious material
KW - concrete
KW - luminescence
Y1 - 2023
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-588455
SN - 1866-8372
IS - 1318
ER -
TY - GEN
A1 - Enzenberg, Anne
A1 - Laschewsky, André
A1 - Boeffel, Christine
A1 - Wischerhoff, Erik
T1 - Influence of the near molecular vicinity on the temperature regulated fluorescence response of poly(N-vinylcaprolactam)
N2 - A series of new fluorescent dye bearing monomers, including glycomonomers, based on maleamide and maleic esteramide was synthesized. The dye monomers were incorporated by radical copolymerization into thermo-responsive poly(N-vinyl-caprolactam) that displays a lower critical solution temperature (LCST) in aqueous solution. The effects of the local molecular environment on the polymers' luminescence, in particular on the fluorescence intensity and the extent of solvatochromism, were investigated below as well as above the phase transition. By attaching substituents of varying size and polarity in the close vicinity of the fluorophore, and by varying the spacer groups connecting the dyes to the polymer backbone, we explored the underlying structure-property relationships, in order to establish rules for successful sensor designs, e.g., for molecular thermometers. Most importantly, spacer groups of sufficient length separating the fluorophore from the polymer backbone proved to be crucial for obtaining pronounced temperature regulated fluorescence responses.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 363
KW - thermo-responsive polymers
KW - poly(N-vinylcaprolactam)
KW - lower critical solution temperature
KW - fluorescent dyemonomers
KW - naphthalimide
KW - solvatochromism
KW - polymeric sensors
KW - molecular thermometers
Y1 - 2017
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400634
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 - Raju, Rajarshi Roy
A1 - Koetz, Joachim
T1 - Inner Rotation of Pickering Janus Emulsions
T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Janus droplets were prepared by vortex mixing of three non-mixable liquids, i.e., olive oil, silicone oil and water, in the presence of gold nanoparticles (AuNPs) in the aqueous phase and magnetite nanoparticles (MNPs) in the olive oil. The resulting Pickering emulsions were stabilized by a red-colored AuNP layer at the olive oil/water interface and MNPs at the oil/oil interface. The core–shell droplets can be stimulated by an external magnetic field. Surprisingly, an inner rotation of the silicon droplet is observed when MNPs are fixed at the inner silicon droplet interface. This is the first example of a controlled movement of the inner parts of complex double emulsions by magnetic manipulation via interfacially confined magnetic nanoparticles.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1249
KW - Janus droplets
KW - Pickering emulsions
KW - magnetic manipulation
KW - gold nanoparticles
KW - magnetite nanoparticles
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-553628
SN - 1866-8372
IS - 1249
ER -
TY - GEN
A1 - Hentrich, Doreen
A1 - Junginger, Mathias
A1 - Bruns, Michael
A1 - Börner, Hans Gerhard
A1 - Brandt, Jessica
A1 - Brezesinski, Gerald
A1 - Taubert, Andreas
T1 - Interface-controlled calcium phosphate mineralization
BT - effect of oligo(aspartic acid)-rich interfaces
N2 - The phase behavior of an amphiphilic block copolymer based on a poly(aspartic acid) hydrophilic block and a poly(n-butyl acrylate) hydrophobic block was investigated at the air–water and air–buffer interface. The polymer forms stable monomolecular films on both subphases. At low pH, the isotherms exhibit a plateau. Compression–expansion experiments and infrared reflection absorption spectroscopy suggest that the plateau is likely due to the formation of polymer bi- or multilayers. At high pH the films remain intact upon compression and no multilayer formation is observed. Furthermore, the mineralization of calcium phosphate beneath the monolayer was studied at different pH. The pH of the subphase and thus the polymer charge strongly affects the phase behavior of the film and the mineral formation. After 4 h of mineralization at low pH, atomic force microscopy shows smooth mineral films with a low roughness. With increasing pH the mineral films become inhomogeneous and the roughness increases. Transmission electron microscopy confirms this: at low pH a few small but uniform particles form whereas particles grown at higher pH are larger and highly agglomerated. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirm the formation of calcium phosphate. The levels of mineralization are higher in samples grown at high pH.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 213
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89540
SP - 6901
EP - 6913
ER -
TY - GEN
A1 - Machatschek, Rainhard Gabriel
A1 - Schöne, Anne-Christin
A1 - Raschdorf, Elisa
A1 - Ihlenburg, Ramona
A1 - Schulz, Burkhard
A1 - Lendlein, Andreas
T1 - Interfacial properties of morpholine-2,5-dione-based oligodepsipeptides and multiblock copolymers
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Oligodepsipeptides (ODPs) with alternating amide and ester bonds prepared by ring-opening polymerization of morpholine-2,5-dione derivatives are promising matrices for drug delivery systems and building blocks for multifunctional biomaterials. Here, we elucidate the behavior of three telechelic ODPs and one multiblock copolymer containing ODP blocks at the air-water interface. Surprisingly, whereas the oligomers and multiblock copolymers crystallize in bulk, no crystallization is observed at the air-water interface. Furthermore, polarization modulation infrared reflection absorption spectroscopy is used to elucidate hydrogen bonding and secondary structures in ODP monolayers. The results will direct the development of the next ODP-based biomaterial generation with tailored properties for highly sophisticated applications.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1106
KW - block-copolymer
KW - enzymatic degradation
KW - poly(ester amide)s
KW - controlled-release
KW - films
KW - nanocarriers
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-469755
SN - 1866-8372
IS - 1106
SP - 170
EP - 180
ER -
TY - GEN
A1 - de Carvalho, Sidney J.
A1 - Metzler, Ralf
A1 - Cherstvy, Andrey G.
T1 - Inverted critical adsorption of polyelectrolytes in confinement
N2 - What are the fundamental laws for the adsorption of charged polymers onto oppositely charged surfaces, for convex, planar, and concave geometries? This question is at the heart of surface coating applications, various complex formation phenomena, as well as in the context of cellular and viral biophysics. It has been a long-standing challenge in theoretical polymer physics; for realistic systems the quantitative understanding is however often achievable only by computer simulations. In this study, we present the findings of such extensive Monte-Carlo in silico experiments for polymer–surface adsorption in confined domains. We study the inverted critical adsorption of finite-length polyelectrolytes in three fundamental geometries: planar slit, cylindrical pore, and spherical cavity. The scaling relations extracted from simulations for the critical surface charge density sc—defining the adsorption–desorption transition—are in excellent agreement with our analytical calculations based on the ground-state analysis of the Edwards equation. In particular, we confirm the magnitude and scaling of sc for the concave interfaces versus the Debye screening length 1/k and the extent of confinement a for these three interfaces for small ka values. For large ka the critical adsorption condition approaches the known planar limit. The transition between the two regimes takes place when the radius of surface curvature or half of the slit thickness a is of the order of 1/k. We also rationalize how sc(k) dependence gets modified for semi-flexible versus flexible chains under external confinement. We examine the implications of the chain length for critical adsorption—the effect often hard to tackle theoretically—putting an emphasis on polymers inside attractive spherical cavities. The applications of our findings to some biological systems are discussed, for instance the adsorption of nucleic acids onto the inner surfaces of cylindrical and spherical viral capsids.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 214
Y1 - 2015
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-89562
SP - 4430
EP - 4443
ER -
TY - GEN
A1 - Abbas, Ioana M.
A1 - Vranic, Marija
A1 - Hoffmann, Holger
A1 - El-Khatib, Ahmed H.
A1 - Montes-Bayón, María
A1 - Möller, Heiko Michael
A1 - Weller, Michael G.
T1 - Investigations of the Copper Peptide Hepcidin-25 by
LC-MS/MS and NMR⁺
T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2 - Hepcidin-25 was identified as themain iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II) binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandemmass spectrometry (MS/MS), high-resolutionmass spectrometry (HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or referencematerial comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 701
KW - hepcidin-25
KW - copper
KW - nickel
KW - copper complex
KW - ATCUN motif
KW - metal complex
KW - MS
KW - NMR structure
KW - metal peptide
KW - metalloprotein
KW - metallopeptide
KW - isomerization
KW - racemization
KW - purity
KW - reference material
Y1 - 2019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-427926
SN - 1866-8372
IS - 701
ER -
TY - 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 - Vioux, André
A1 - Taubert, Andreas
T1 - Ionic liquids 2014 and selected papers from ILMAT 2013
BT - Highlighting the ever-growing potential of Ionic Liquids
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1055
KW - electrolytes
KW - extraction
KW - system
Y1 - 2020
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-475062
SN - 1866-8372
IS - 1055
ER -
TY - GEN
A1 - Zehbe, Kerstin
A1 - Kollosche, Matthias
A1 - Lardong, Sebastian
A1 - Kelling, Alexandra
A1 - Schilde, Uwe
A1 - Taubert, Andreas
T1 - Ionogels based on poly(methyl methacrylate) and metal-containing ionic liquids
BT - correlation between structure and mechanical and electrical properties
N2 - Ionogels (IGs) based on poly(methyl methacrylate) (PMMA) and the metal-containing ionic liquids (ILs) bis-1-butyl-3-methlimidazolium tetrachloridocuprate(II), tetrachloride cobaltate(II), and tetrachlorido manganate(II) have been synthesized and their mechanical and electrical properties have been correlated with their microstructure. Unlike many previous examples, the current IGs show a decreasing stability in stress-strain experiments on increasing IL fractions. The conductivities of the current IGs are lower than those observed in similar examples in the literature. Both effects are caused by a two-phase structure with micrometer-sized IL-rich domains homogeneously dispersed an IL-deficient continuous PMMA phase. This study demonstrates that the IL-polymer miscibility and the morphology of the IGs are key parameters to control the (macroscopic) properties of IGs.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 361
KW - microstructure
KW - ionogels
KW - ionic liquids
KW - phase separation
KW - mechanical properties
KW - ionic conductivity
Y1 - 2017
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400607
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 (3001)III / (000) band of 12CO2 around 1.6 μm, the dominating isotope species 12CO2, 13CO2, and 12C18O16O 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 CO2, respectively— renders this experimental approach a promising analytical concept for isotope-ratio determination of carbon dioxide in soil and breath gas. For a moderate 12CO2 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 -