TY  - JOUR
A1  - Garnier, Sebastien
A1  - Laschewsky, Andre
T1  - Non-ionic amphiphilic block copolymers by RAFT-polymerization and their self-organization
JF  - Colloid and polymer science : official journal of the Kolloid-Gesellschaft
N2  - Water-soluble, amphiphilic diblock copolymers were synthesized by reversible addition fragmentation chain transfer polymerization. They consist of poly(butyl acrylate) as hydrophobic block with a low glass transition temperature and three different nonionic water-soluble blocks, namely, the classical hydrophilic block poly(dimethylacrylamide), the strongly hydrophilic poly(acryloyloxyethyl methylsulfoxide), and the thermally sensitive poly(N-acryloylpyrrolidine). Aqueous micellar solutions of the block copolymers were prepared and characterized by static and dynamic light scattering analysis (DLS and SLS). No critical micelle concentration could be detected. The micellization was thermodynamically favored, although kinetically slow, exhibiting a marked dependence on the preparation conditions. The polymers formed micelles with a hydrodynamic diameter from 20 to 100 nm, which were stable upon dilution. The micellar size was correlated with the composition of the block copolymers and their overall molar mass. The micelles formed with the two most hydrophilic blocks were particularly stable upon temperature cycles, whereas the thermally sensitive poly(N-acryloylpyrrolidine) block showed a temperature-induced precipitation. According to combined SLS and DLS analysis, the micelles exhibited an elongated shape such as rods or worms. It should be noted that the block copolymers with the most hydrophilic poly(sulfoxide) block formed inverse micelles in certain organic solvents.
KW  - macrosurfactants
KW  - block copolymers
KW  - micelles
KW  - inverse micelles
KW  - sulfoxide
Y1  - 2006
U6  - https://doi.org/10.1007/s00396-006-1484-9
SN  - 0303-402X
VL  - 284
SP  - 1243
EP  - 1254
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Füchsel, Gernot
A1  - Klamroth, Tillmann
A1  - Dokic, Jadranka
A1  - Saalfrank, Peter
T1  - On the electronic structure of neutral and ionic azobenzenes and their possible role as surface mounted molecular switches
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - We report quantum chemical calculations, mostly based on density functional theory, on azobenzene and substituted azobenzenes as neutral molecules or ions, in ground and excited states. Both the cis and trans configurations are computed as well as the activation energies to transform one isomer into the other and the possible reaction paths and reaction surfaces along the torsion and inversion modes. All calculations are done for the isolated species, but results are discussed in light of recent experiments aiming at the switching of surface mounted azobenzenes by scanning tunneling microscopes.
Y1  - 2006
U6  - https://doi.org/10.1021/jp060969v
SN  - 1520-6106
VL  - 110
IS  - 33
SP  - 16337
EP  - 16345
PB  - Soc.
CY  - Washington
ER  - 
TY  - GEN
A1  - Lutz, Jean-Francois
A1  - Kristen, Juliane
A1  - Skrabania, Katja
A1  - Laschewsky, Andre
T1  - POLY 14-Synthetic strategies for preparing multicompartment micelles
T2  - Abstracts of papers / American Chemical Society
N2  - The fabrication of compartmented micellar systems is an exciting new area of research in the field of polymer self-assembly. Multicompartment micelles composed of a water-soluble shell and a segregated hydrophobic core can be obtained via direct aqueous self-assembly of preformed polymeric amphiphiles possessing one hydrophilic segment and two incompatible hydrophobic segments (e.g. hydrocarbon and fluorocarbon blocks). Such macromolecular building-blocks were prepared in the present work principally via reversible addition-fragmentation transfer polymerization (RAFT). Polysoaps or triblock macrosurfactants can be synthesized in high yields by RAFT under relatively straightforward experimental conditions.
Y1  - 2006
SN  - 0-8412-7426-6
SN  - 0065-7727
VL  - 232
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Nave, Stefan
T1  - Stereoselective syntheses of enantiomerically pure 2,5-disubstituted dihydropyrans based on olefin metathesis
JF  - The journal of organic chemistry
N2  - A short synthesis of 2,5-disubstituted dihydropyrans starting from D-mannitol as a chiral building block is described. Our synthetic approach combines ruthenium-catalyzed ring closing olefin metathesis and palladium-catalyzed nucleophilic substitution.
Y1  - 2006
U6  - https://doi.org/10.1021/jo061190k
SN  - 0022-3263
VL  - 71
IS  - 19
SP  - 7364
EP  - 7369
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kapp, A.
A1  - Beissenhirtz, Moritz Karl
A1  - Geyer, F.
A1  - Scheller, F.
A1  - Viezzoli, Maria Silvia
A1  - Lisdat, Fred
T1  - Electrochemical and sensorial behavior of SOD mutants immobilized on gold electrodes in aqueous/organic solvent mixtures
JF  - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis
N2  - A cysteine mutant of a monomeric human Cu, Zn-SOD (Glycine 61, Serine 142) has been immobilized directly on gold electrodes using the thiol groups introduced. The electrochemical behavior of the surface confined protein was studied in mixtures of aqueous buffer and DMSO up to an organic solvent content of 60%. The formal potential was found to be rather independent of the DMSO content. However, half peak width increased and the redoxactive amount clearly decreased with raising DMSO content. In addition, the kinetics of the heterogeneous electron transfer became slower; but still a quasireversible electrochemical conversion of the mutant SOD was feasible. Thus, the electrodes were applied for sensorial superoxide detection. At a potential of +220 mV vs. Ag/AgCl advantage was taken of the partial oxidation reaction of the enzyme. A defined superoxide signal was obtained in solutions up to 40% DMSO. The sensitivity of the mutant electrodes decreased linearly with the organic solvent content in solution but was still higher compared to conventional cyt.c based sensors. At DMSO concentrations higher than 40% no sensor response was detected.
KW  - SOD
KW  - mutants
KW  - gold electrodes
KW  - DMSO
KW  - electrochemistry
Y1  - 2006
U6  - https://doi.org/10.1002/elan.200603620
SN  - 1040-0397
VL  - 18
SP  - 1909
EP  - 1915
PB  - Wiley
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Saalfrank, Peter
T1  - Quantum dynamical approach to ultrafast molecular desorption from surfaces
JF  - Chemical reviews
Y1  - 2006
U6  - https://doi.org/10.1021/cr0501691
SN  - 0009-2665
SN  - 1520-6890
VL  - 106
IS  - 10
SP  - 4116
EP  - 4159
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Note, Carine
A1  - Koetz, Joachim
A1  - Kosmella, Sabine
T1  - Structural changes in poly(ethyleneimine) modified microemulsion
JF  - Journal of colloid and interface science
N2  - The influence of branched poly(ethyleneimine) on the phase behavior of the system sodium dodecylsulfate/toluene-pentanol (1:1)/water has been studied. The isotropic microemulsions still exist when water is replaced with aqueous solutions of PEI (up to 30% in weight), but their stability is significantly influenced. From a polymer concentration of 20 wt%, the polymer enhances the solubilization of water in oil, changes the sign of the spontaneous curvature of the surfactant film, and induces an inversion of the microemulsion type from water-in-oil (L-2) to oil-in-water (L-1), by the formation of a bicontinuous channel. Further investigations show that the addition of polymer in the L-2 phase changes the droplet-droplet interactions as the conductivity drops and the percolation disappears. In the bicontinuous channel, higher viscosities can be detected, as well as a weak percolation followed by a steep increase of the conductivity, which can be related to evident structural changes in the system. DSC measurements allow then to follow the changes of the water properties in the system, from interfacial-water in the L-2 phase to free-water in the sponge-like phase. Finally, all the measurements performed permit to characterize the structural transitions in the system and to understand the role of the added polymer.
KW  - polyelectrolyte
KW  - microemulsion
KW  - bicontinuous phase
Y1  - 2006
U6  - https://doi.org/10.1016/j.jcis.2006.06.071
SN  - 0021-9797
VL  - 302
SP  - 662
EP  - 668
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Lange, Birger
A1  - Wagner, Jürgen
A1  - Zentel, Rudolf
T1  - Fabrication of robust high-quality ORMOCER (R) inverse opals
JF  - Macromolecular rapid communications
N2  - The nanostructuring of ORMOCER (R) to form inverse opals is described. For this purpose a polymer opal is used as a template and infiltrated with liquid ORMOCER (R). After photopolymerization of the resin the host opal is dissolved in tetrahydrofuran and an ORMOCER (R) inverse opal is obtained. It shows excellent periodicity (by SEM) and optical properties to reveal a high degree of face centered cubic order. This replication process leads to a nanostructured photonic crystal with the outstanding mechanical properties of ORMOCER (R) and high temperature stability up to 350 degrees C.
KW  - colloids
KW  - inverse opals
KW  - ORMOCER (R)
KW  - photonic crystal
KW  - self-assembly
Y1  - 2006
U6  - https://doi.org/10.1002/marc.200600429
SN  - 1022-1336
VL  - 27
SP  - 1746
EP  - 1751
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Teixeira, C. V.
A1  - Blanzat, Muriel
A1  - Koetz, Joachim
A1  - Rico-Lattes, I.
A1  - Brezesinski, Gerald
T1  - In-plane miscibility and mixed bilayer microstructure in mixtures of catanionic glycolipids and zwitterionic phospholipids
JF  - Biochimica et biophysica acta : Biomembranes
N2  - SAXS/WAXS studies were performed in combination with freeze fracture electron microscopy using mixtures of a new Gemini catanionic surfactant (Gem 16-12, formed by two sugar groups bound by a hydrocarbon spacer with 12 carbons and two 16-carbon chains) and the zwitterionic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine(DPPC) to establish the phase diagram. Gem 16-12 in water forms bilayers with the same amount of hydration water as DPPC. A frozen interdigitated phase with a low hydration number is observed below room temperature. The kinetics of the formation of this crystalline phase is very slow. Above the chain melting temperature, multilayered vesicles are formed. Mixing with DPPC produces mixed bilayers above the corresponding chain melting temperature. At room temperature, partially lamellar aggregates with local nematic order are observed. Splitting of infinite lamellae into discs is linked to immiscibility in frozen state. The ordering process is always accompanied by dehydration of the system. As a consequence, an unusual order-disorder phase transition upon cooling is observed.
KW  - SAXS
KW  - bilayer
KW  - gemini surfactant
KW  - ordering process
KW  - Anti-HIV
KW  - miscibility
Y1  - 2006
U6  - https://doi.org/10.1016/j.bbamem.2006.05.025
SN  - 0005-2736
VL  - 1758
SP  - 1797
EP  - 1808
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kozlevcar, Bojan
A1  - Golobic, Amalija
A1  - Strauch, Peter
T1  - Dynamic pseudo Jahn-Teller distortion in a compressed octahedral CuO6 complex
JF  - Polyhedron : the international journal of inorganic and organometallic chemistry
N2  - The crystal structure of cis-[Cu(C8H7O3)(2)(H2O)(2)] (115 K data) reveals bidentate vanillinate ions coordinated via methoxy and deprotonated hydroxy oxygen atoms and water molecules in a distorted octahedral CuO6 chromophore. A cis orientation of the ligands enables two non-identical O(methoxy)-Cu-O(water) coordination axes (2.354(l) + 2.163(1); 2.151(1) + 2.020(1) angstrom), and the third shortest O(hydroxy)-Cu-O(hydroxy) axis (1.919(1) + 1.914(1) angstrom). This 115 K coordination sphere differs importantly to the one obtained from the 293 K data of the same compound, where two long 0(methoxy)-Cu-O(water) axes are of the same length, and only minor changes at the short 0(hydroxy)-Cu-O(hydroxy) axis are noticed. An axial symmetry of the complex with an inverse g(1.2)(g(perpendicular to)) > g(3)(g(parallel to)) pattern is observed in the temperature range from 298 to 180 K. A further decrease of temperature reveals gradual changes from axial to rhombic symmetry (g(1) > g(2) > g(3)) that is reversible. A mean-square displacement amplitude (MDSA) analysis reveals a disorder in the Cu-O(methoxy) bonds, but not in the other metal-ligand Cu-O(hydroxy) and Cu-O(water) bonds at 293 and 115 K. The disorder is significantly weaker in the 115 K structure. The MSDA analysis and the structural-EPR agreement show vibrational disorder in two coordination axes, due to the cis conformation of the complex with two 0(methoxy)-Cu-O(water) axes.
KW  - copper
KW  - vanillin
KW  - Jahn-Teller distortion
KW  - MSDA
KW  - cis
KW  - EPR
Y1  - 2006
U6  - https://doi.org/10.1016/j.poly.2006.04.009
SN  - 0277-5387
VL  - 25
IS  - 15
SP  - 2824
EP  - 2828
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Vomdran, Katja
A1  - Linker, Torsten
T1  - Auxiliary controlled singlet-oxygen ene reactions of cyclohexenes
JF  - Tetrahedron
N2  - The photooxygenation of homochiral cyclohexene ketals, which are easily available from 2-cyclohexenone and L-tartrates, affords hydroperoxides and after reduction the corresponding allylic alcohols in good yields and high regioselectivities. This can be rationalized by electronic repulsions in a perepoxide intermediate and provides evidence for unfavorable 1,3 diaxial interactions with a dioxolane oxygen atom. Only low stereoselectivities were observed, due to the flexibility of the cyclohexene ring. However, the diastereomers could be separated and after cleavage of the auxiliary, 4-hydroxy-2-cyclohexen-1-one was isolated in enantiomerically pure form, which can serve as a building block for natural product synthesis.
KW  - singlet oxygen
KW  - auxiliary control
KW  - regioselectivity
KW  - stereoselectivity
Y1  - 2006
U6  - https://doi.org/10.1016/j.tet.2006.07.104
SN  - 0040-4020
VL  - 62
IS  - 46
SP  - 10639
EP  - 10646
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Note, Carine
A1  - Kosmella, Sabine
A1  - Koetz, Joachim
T1  - Poly(ethyleneimine) as reducing and stabilizing agent for the formation of gold nanoparticles in w/o microemulsions
JF  - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects
N2  - This paper is focused on the use of branched poly(ethyleneimine) (PEI) as reducing as well as stabilizing agent for the formation of gold nanoparticles in different media. The process of nanoparticle formation was investigated, in the absence of any other reducing agents, in microemulsion template phase in comparison to the nucleation process in aqueous polymer solution. On the one hand, it was shown that the polyelectrolyte can be used for the controlled single-step synthesis and stabilization of gold nanoparticles via a nucleation reaction and particles with an average diameter of 7.1 nm can be produced. On the other hand, it was demonstrated that the polymer can also act as reducing and stabilizing agent in much more complex systems, i.e. in water-in-oil (w/o) microemulsion droplets. The reverse microemulsion droplets of the quaternary system sodium dodecylsulfate (SDS)/toluene-pentanol (1:1)/water were successfully used for the synthesis of gold nanoparticles. The polymer, incorporated in the droplets, exhibits reducing properties, adsorbs on the surface of the nanoparticles and prevents their aggregation. Consequently, nanoparticles of 8.6 nm can be redispersed after solvent evaporation without a change of their size. Nevertheless, the polymer acts already as a "template" during the formation of the nanoparticles in water and in microemulsion, so that an additional template effect of the microemulsion is not observed. The particle formation for both methods is checked by means of UV-vis spectroscopy and the particle size and size distribution are investigated via dynamic light scattering and transmission electron microscopy (TEM). (c) 2006 Elsevier B.V. All rights reserved.
KW  - polyelectrolyte
KW  - microemulsion
KW  - gold nanoparticles
Y1  - 2006
U6  - https://doi.org/10.1016/j.colsurfa.2006.05.018
SN  - 0927-7757
VL  - 290
IS  - 1-3
SP  - 150
EP  - 156
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Martinazzo, Rocco
A1  - Nest, Mathias
A1  - Saalfrank, Peter
A1  - Tantardini, Gian Franco
T1  - A local coherent-state approximation to system-bath quantum dynamics
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - A novel quantum method to deal with typical system-bath dynamical problems is introduced. Subsystem discrete variable representation and bath coherent-state sets are used to write down a multiconfigurational expansion of the wave function of the whole system. With the help of the Dirac-Frenkel variational principle, simple equations of motion-a kind of Schrodinger-Langevin equation for the subsystem coupled to (pseudo) classical equations for the bath-are derived. True dissipative dynamics at all times is obtained by coupling the bath to a secondary, classical Ohmic bath, which is modeled by adding a friction coefficient in the derived pseudoclassical bath equations. The resulting equations are then solved for a number of model problems, ranging from tunneling to vibrational relaxation dynamics. Comparison of the results with those of exact, multiconfiguration time-dependent Hartree calculations in systems with up to 80 bath oscillators shows that the proposed method can be very accurate and might be of help in studying realistic problems with very large baths. To this end, its linear scaling behavior with respect to the number of bath degrees of freedom is shown in practice with model calculations using tens of thousands of bath oscillators.
Y1  - 2006
U6  - https://doi.org/10.1063/1.2362821
SN  - 0021-9606
SN  - 1089-7690
VL  - 125
IS  - 19
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Staude, Lucia
T1  - Unexpected transfer hydrogenation of C-C-double bonds during Tandem-RCM-isomerization reactions
JF  - Journal of organometallic chemistry
N2  - Unexpected hydrogen transfer from 2-propanol to C-C-double bonds has been observed in the course of a Tandem RCM-isomerization reaction leading to sterically congested spirocycles.
KW  - ruthenium
KW  - metathesis
KW  - isomerization
KW  - hydrogenation
KW  - transferhydrogenation
KW  - tandem sequence
Y1  - 2006
U6  - https://doi.org/10.1016/j.jorganchem.2006.07.011
SN  - 0022-328X
VL  - 691
IS  - 24-25
SP  - 5218
EP  - 5221
PB  - Elsevier
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Fudickar, Werner
A1  - Linker, Torsten
T1  - Imaging by sensitized oxygenations of photochromic anthracene films
BT  - Examination of effects that improve performance and reversibility
JF  - Chemistry - a European journal
N2  - The aliphatic anthracene compound 1 and the oligomeric anthracene 2 were synthesized. Thin films of 1 and 2 mixed with the sensitizers tetraphenylporphyrin (TPP) and methylene blue (MB) were irradiated with visible light in air. Upon formation of singlet oxygen, the anthracene units were converted quantitatively to the corresponding endoperoxides. Heating of the irradiated samples afforded the parent anthracenes with high yields. Here, we demonstrate that the kinetics and reversibility of this reaction strongly depend on the microenvironment of the anthracene groups in the two compounds. The photooxidation of thin films of I is accompanied by interesting changes in the morphology of the film and allows the first application of 1 as a nondestructive negative-tone photo-resist for lithography and as an oxidizing ink. The morphology of 2 remained unchanged after photooxidation as a result of the stabilizing oligomer backbone. This stabilizing effect significantly improves the photochromic performance of 2. The reversibility of the photooxidation is very high (> 90%) for oligomeric films of 2 after several cycles of irradiation and beating. Decomposition of the anthracene and a loss of the activity of the sensitizer diminish slightly the performance of the monomeric species.
KW  - anthracenes
KW  - lithography
KW  - photochromism
KW  - singlet oxygen
KW  - thin films
Y1  - 2006
U6  - https://doi.org/10.1002/chem.200600387
SN  - 0947-6539
VL  - 12
SP  - 9276
EP  - 9283
PB  - WILEY‐VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Andrianov, Ivan
A1  - Saalfrank, Peter
T1  - Free vibrational relaxation of H adsorbed on a Si(100) surface investigated with the multi-configurational time-dependent Hartree method
JF  - Chemical physics letters
N2  - The results of a quantum-mechanical study of vibrational relaxation of hydrogen adsorbed on a Si(100) surface with the multi-configurational time-dependent Hartree (MCTDH) method are presented. A two-dimensional subsystem is coupled non-linearly to a bath of harmonic oscillators (phonons of the Si bulk), and the relaxation of subsystem vibrations proceeds primarily via a two-phonon process. Characteristic times of the system evolution agree well with our previous perturbation theory study. The vibrational population decay is non-exponential, exhibiting pronounced recurrences due to finite bath size. The dependence of the lifetimes of the vibrational levels on the bath size and on the coupling details is investigated.
Y1  - 2006
U6  - https://doi.org/10.1016/j.cplett.2006.11.067
SN  - 0009-2614
VL  - 433
SP  - 91
EP  - 96
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Zen, Achmad
A1  - Saphiannikova, Marina
A1  - Neher, Dieter
A1  - Grenzer, Jörg
A1  - Grigorian, Souren A.
A1  - Pietsch, Ullrich
A1  - Asawapirom, Udom
A1  - Janietz, Silvia
A1  - Scherf, Ullrich
A1  - Lieberwirth, Ingo
A1  - Wegner, Gerhard
T1  - Effect of molecular weight on the structure and crystallinity of poly(3-hexylthiophene)
N2  - Recently, two different groups have reported independently that the mobility of field-effect transistors made from regioregular poly(3-hexylthiophene) (P3HT) increases strongly with molecular weight. Two different models were presented: one proposing carrier trapping at grain boundaries and the second putting emphasis on the conformation and packing of the polymer chains in the thin layers for different molecular weights. Here, we present the results of detailed investigations of powders and thin films of deuterated P3HT fractions with different molecular weight. For powder samples, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to investigate the structure and crystallization behavior of the polymers. The GPC investigations show that all weight fractions possess a rather broad molecular weight distribution. DSC measurements reveal a strong decrease of the crystallization temperature and, most important, a significant decrease of the degree of crystallinity with decreasing molecular weight. To study the structure of thin layers in lateral and vertical directions, both transmission electron microscopy (TEM) and X-ray grazing incidence diffraction (GID) were utilized. These methods show that thin layers of the low molecular weight fraction consist of well-defined crystalline domains embedded in a disordered matrix. We propose that the transport properties of layers prepared from fractions of poly(3-hexylthiophene) with different molecular weight are largely determined by the crystallinity of the samples and not by the perfection of the packing of the chains in the individual crystallites
Y1  - 2006
UR  - http://pubs.acs.org/doi/full/10.1021/ma0521349
U6  - https://doi.org/10.1021/Ma0521349
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Laschewsky, André
A1  - Stoesser, Reinhard
A1  - Zehl, Andrea
A1  - Herrmann, Werner
T1  - Mobility of spin probes in ionic liquids
N2  - The spin probes TEMPO, TEMPOL, and CAT-1 were used to investigate microviscosity and micropolarity of imidazolium based ionic liquids bearing either tetrafluoroborate or hexafluorophosphate as anions and a variation of the substitution at the imidazolium ion. The average rotational correlation times (r) obtained by complete simulation of the X-band ESR spectra of TEMPO, TEMPOL, and CAT-1 increase with increasing viscosity of the ionic liquid although no Stokes Einstein behavior is observed. This is caused by microviscosity effects of the ionic liquids shown by application of the Gierer-Wirtz theory. Interestingly, the jump of the probe molecule into the free volume of the ionic liquids is a nonactivated process. The hyperfine coupling constants (A(iso) (N-14)) of TEMPO and TEMPOL dissolved in the ionic liquids do not depend on the structure of the ionic liquids. The A(iso) (N-14) values show a micropolarity of the ionic liquids that is comparable with methylenchloride in case of TEMPO and with dimethylsulfoxide in case of TEMPOL. Micropolarity monitored by CAT-1 strongly depends on structural variation of the ionic liquid. CAT-1 dissolved in imidazolium salts substituted with shorter alkyl chains at the nitrogen atom exhibits a micropolarity comparable with dimethylsulfoxide. A significant lower micropolarity is found for imidazolium. salts bearing a longer alkyl substituent at the nitrogen atom or a methyl substituent at C-2. Copyright (c) 2006 John Wiley & Sons, Ltd
Y1  - 2006
UR  - http://onlinelibrary.wiley.com/doi/10.1002/poc.1072/pdf
U6  - https://doi.org/10.1002/poc.1072
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Nave, Stefan
T1  - Control of ring size selectivity by substrate directable RCM
N2  - Hydroxy groups may exert strong catalyst-directing effects in olefin metathesis reactions, which are exploited for a ring size-selective RCM reaction
Y1  - 2006
UR  - http://pubs.rsc.org/en/content/articlehtml/2006/cc/b604359c
U6  - https://doi.org/10.1039/B604359c
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
T1  - Olefin metathesis and isomerization : from undesired side reactions to useful synthetic methodology
N2  - Conversion of ruthenium carbene complexes to ruthenium hydride complexes by organometallic transformations in situ opens up interesting synthetic perspectives. In this account the use of Grubbs' catalyst to synthesize pent-4- enals selectively from diallyl- and allyl homoallyl ethers and scope and limitations of a Tandem RCM-isomerization sequence for the synthesis of cyclic enol ethers are discussed. (c) 2006 Elsevier B.V. All rights reserved
Y1  - 2006
UR  - http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGM-4JT9C6D- 2&_user=1584062&_coverDate=07%2F19%2F2006&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_sea rchStr
U6  - https://doi.org/10.1016/j.molcata.2006.03.026
ER  - 
TY  - JOUR
A1  - Rullens, F
A1  - Vuillaume, Pascal Y.
A1  - Moussa, Alain
A1  - Habib-Jiwan, Jean-Louis
A1  - Laschewsky, André
T1  - Ordered polyelectrolyte "Multilayers". 7. Hybrid films self-assembled from fluorescent and smectogenic poly(diallylammonium) salts and delaminated clay
N2  - Homopolymers were prepared from diallylammonium monomers bearing 4-methylcoumarin and 4-cyanobiphenyl as fluorescent and mesogenic side groups, as well as their copolymers with diallyldimethylammonium chloride (DADMAC). Organic-inorganic hybrid films were electrostatically self-assembled via the layer-by-layer technique on silicon wafers and quartz plates from the chromophore-bearing polymers and an exfoliated synthetic hectorite. Photophysical studies performed in solution as well as in the self-assembled films demonstrated only a weak tendency for aggregation of the chromophores in the macromolecules. Moreover, assemblies made from the polymers carrying the cyanobiphenyl mesogen were found to exhibit a pronounced internal order
Y1  - 2006
UR  - http://pubs.acs.org/doi/full/10.1021/cm060209x
U6  - https://doi.org/10.1021/Cm060209x
ER  - 
TY  - JOUR
A1  - Rullens, F
A1  - Laschewsky, André
A1  - Devillers, M
T1  - Bulk and thin films of bismuth vanadates prepared from hybrid materials made from an organic polymer and inorganic salts
N2  - A new precursor route for the preparation of bulk oxides and thin films of bismuth vanadates is proposed. The method involves the thermal treatment under air and mild conditions of hybrid organic-inorganic precursors, made from a zwitterionic salt-free polymer matrix and selected inorganic species. Monoclinic BiVO4 was obtained in the form of bulk oxide by calcination of the powdered homogeneous hybrid materials at 600 degrees C, from precursors containing Bi and V in stoichiometric amounts. In the same way, thermodiffractometry studies performed on a hybrid material exhibiting a Bi/ V molar ratio of 2 revealed that the ionic conductor gamma-Bi4V2O11 phase can be stabilized under very soft thermal conditions (300 degrees C). Additionally, thin films of yellow monoclinic BiVO4 were for the first time fabricated, by thermal treatment of the same hybrid polymeric precursors deposited on quartz substrates by spin coating, using a layer- by-layer technique. The presence of the target phase at the surface of the plates was confirmed by X-ray diffraction as well as UV-vis measurements
Y1  - 2006
UR  - http://pubs.acs.org/doi/full/10.1021/cm051516q
U6  - https://doi.org/10.1021/Cm051516q
ER  - 
TY  - JOUR
A1  - Kozlevcar, Bojan
A1  - Odlazek, Darja
A1  - Golobic, Amalija
A1  - Pevec, Andrej
A1  - Strauch, Peter
A1  - Segedin, Primoz
T1  - Complexes with lignin model compound vanillic acid : two different carboxylate ligands in the same dinuclear tetracarboxylate complex [Cu-2(C8H7O4)(2)(O2CCH3)(2)(CH3OH)(2)]
N2  - Two copper(II) coordination compounds with vanillic acid C8H8O4 (1), namely [Cu- 2(C8H7O4)(2)(O2CCH3)(2)(CH3OH)(2)] (2) and [Cu-2(C8H7O4)(4)(H2O2)(2)] (3), were synthesized and characterized. Single crystals of 1-3 were obtained and their crystal structures determined. The structure of 2 shows dinuclear cage structure of copper acetate hydrate type, however with two different carboxylates, acetates and vanillic acid anions,. respectively. Both bridging anions are in pairs in trans orientation. Methanol molecules are apically coordinated (Cu-O7 2.160(2) angstrom), fulfilling square-pyramidal coordination sphere around both copper ions. The compound 2 decomposes outside mother-liquid (yielding [Cu-2(C8H7O4)(2)(O2CCH3)(2)(H2O)(2)] (2a)) with the removal of methanol, but without significant change of the dicopper tetracarboxylate cage structure, as noticed by mu(eff) 1.48 BM for 2a. Similar was found also in the X-band EPR spectra with three signals H-z1, H-perpendicular to 2 and H-z2 in the region from 0 to 600 mT. The structure of free vanillic acid 1 is composed of dimeric units of two molecules, connected by two parallel hydrogen bonds between carboxylate group of each other (O1-H(...)O2 2.642(3) angstrom), while the structure of 3 is of [Cu-2(O2CCH3)(4)(H2O)(2)] type. Interestingly, an additional signal in the EPR spectra of 3 is found at 80 mT (H- perpendicular to 1) at 298 and at 116 K, next to three signals H-z1, H-perpendicular to 2 and H-z2.
Y1  - 2006
UR  - http://www.sciencedirect.com/science/journal/02775387
U6  - https://doi.org/10.1016/j.poly.2005.08.031
SN  - 0277-5387
ER  - 
TY  - JOUR
A1  - Koetz, Joachim
A1  - Jagielski, Nicole
A1  - Kosmella, Sabine
A1  - Friedrich, Alwin
A1  - Kleinpeter, Erich
T1  - CdS nanocubes formed in phosphatidylcholin-based template phases
N2  - The paper is focused on the characterization and use of phosphatidylcholine (PC)-based inverse microemulsions as a template phase for the CdS nanoparticle formation. The optically clear, isotropic phase in the oil corner was identified as a "classicalö water-in-oil microemulsion by means of NMR-diffusion measurements. Because of the very small dimensions of the water droplets, the isotropic phase shows a Newtonian-like flow behavior, and adequate amounts of bulk water cannot be detected by DSC. It is demonstrated that this w/o microemulsion can be used successfully as a nanoreactor for the formation of CdS nanoparticles with diameters of 4-5 nm. During the following process of solvent evaporation the individual small CdS nanoparticles aggregate to significant larger cubic nanoparticles, with an edge length of 2-40 nm, arranged in well-defined mosaic-like superstructures. In presence of SDS the nanocubes were stable up to 800 °C. It has to be stated here that polyelectrolytes prevent the formation of such well-ordered superstructures.
Y1  - 2006
UR  - http://www.sciencedirect.com/science/journal/09277757
U6  - https://doi.org/10.1016/j.colsurfa.2006.01.013
SN  - 0927-7757
VL  - 288
SP  - 43
EP  - 1-3
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Holzberger, Anja
T1  - Structure, intramolecular flexibility, and complexation of aza crown ethers to anions H2PO4- and HSO4- in nonprotic solvents
JF  - Tetrahedron
N2  - Both the structure and intramolecular flexibility of a series of aza crown ethers were studied by experimental NMR and theoretical molecular modeling. The stoichiometries of complexation to the anions H2PO4- and resulting complex stabilities were determined by experimental NMR (1H, 31P) titration and, in addition, the structure and mobility changes of the aza crown ethers upon complexation were also examined.
Y1  - 2006
UR  - https://www.sciencedirect.com/science/article/abs/pii/S0040402006012130
U6  - https://doi.org/10.1016/j.tet.2006.07.074
SN  - 0040-4020
VL  - 62
IS  - 43
SP  - 10237
EP  - 10247
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Engelhard, Sonja
A1  - Kumke, Michael Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - Examples of the application of optical process and quality sensing (OPQS) to beer brewing and polyurethane foaming processes
N2  - Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near- infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O-2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant
Y1  - 2006
UR  - http://www.springerlink.com/content/100417
U6  - https://doi.org/10.1007/s00216-005-3364-4
SN  - 1618-2642
ER  - 
TY  - JOUR
A1  - Dambacher, Michael
A1  - Kliegl, Reinhold
A1  - Hofmann, Markus
A1  - Jacobs, Arthur M.
T1  - Frequency and predictability effects on event-related potentials during reading
N2  - Effects of frequency, predictability, and position of words on event-related potentials were assessed during word-by-word sentence reading in 48 subjects in an early and in a late time window corresponding to P200 and N400. Repeated measures multiple regression analyses revealed a P200 effect in the high-frequency range also the P200 was larger on words at the beginning and end of sentences than on words in the middle of sentences (i.e., a quadratic effect of word position). Predictability strongly affected the N400 component; the effect was stronger for low than for high- frequency words. The P200 frequency effect indicates that high-frequency words are lexically accessed very fast, independent of context information. Effects on the N400 suggest that predictability strongly moderates the late access especially of low-frequency words. Thus, contextual facilitation on the N400 appears to reflect both lexical and post- lexical stages of word recognition, questioning a strict classification into lexical and post-lexical processes.
Y1  - 2006
UR  - http://www.sciencedirect.com/science/journal/00068993
U6  - https://doi.org/10.1016/j.brainres.2006.02.010
SN  - 0006-8993
ER  - 
TY  - JOUR
A1  - Balci, Kubilay
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - A comparative vibrational spectroscopic investigation of free mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers based on DFT calculations
N2  - A successful assignment for the fundamental bands observed in the experimental IR spectra of mn-12S(2)O(2) and fn-12S(2)O(2) dithiacrown ethers was achieved by the aid of the density functional theory (DFT) based quantum mechanical calculations carried out at the 133LYP/6-31G(d) and B3LYP/6-31 + G(d) level of theory. Two different scaling approaches, '(i) scaled quantum mechanics force field (SQM FF) methodology', and (ii) the 'scaling frequencies with dual empirical scale factors', were used in order to fit the calculated harmonic frequencies to the experimental ones. Potential energy distribution (PED) calculations were carried out to define the internal coordinate contributions to each normal mode and to define the corresponding normal modes of the molecules. The effects of the conformational differences onto the IR active normal modes of the two isomeric molecules and their corresponding experimental frequencies were discussed in the light of the calculated spectral data.
Y1  - 2006
UR  - http://www.sciencedirect.com/science/journal/00222860
U6  - https://doi.org/10.1016/j.molstruc.2005.10.048
SN  - 0022-2860
ER  - 
TY  - JOUR
A1  - Andayi, Andrew W.
A1  - Yenesew, Abiy
A1  - Derese, Solomon
A1  - Midiwo, Jacob O.
A1  - Gitu, Peter M.
A1  - Jondiko, Ogoche J. I.
A1  - Akala, Hoseah M.
A1  - Liyala, Pamela
A1  - Wangui, Julia
A1  - Waters, Norman C.
A1  - Heydenreich, Matthias
A1  - Peter, Martin G.
T1  - Antiplasmodial flavonoids from Erythrina sacleuxii
N2  - The acetone extracts of the root bark and stem bark of Erythrina sacleuxii showed antiplasmodial activities against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the acetone extract of the root bark afforded a new isoflavone, 7-hydroxy-4 -methoxy-3'- prenylisoflavone (trivial name 5-deoxy-3' - prenylbiochanin A) along with known isoflavonoids as the antiplasmodial principles. Flavonoids and isoflavonoids isolated from the stem bark of E. sucleuxii were also tested and showed antiplasmodial activities. The structures were determined on the basis of spectroscopic evidence
Y1  - 2006
UR  - http://www.thieme-connect.com/ejournals/toc/plantamedica
U6  - https://doi.org/10.1055/s-2005-873200
SN  - 0032-0943
ER  - 
TY  - JOUR
A1  - Wattebled, Laurent
A1  - Laschewsky, André
A1  - Moussa, Alain
A1  - Habib-Jiwan, Jean-Louis
T1  - Aggregation numbers of cationic oligomeric surfactants : A time-resolved fluorescence quenching study
N2  - The micelle aggregation numbers (N-agg) of several series of cationic oligomeric surfactants were determined by time-resolved fluorescence quenching (TRFQ) experiments, using advantageously 9,10-dimethylanthracene as fluorophore. The study comprises six dimeric ("gemini"), three trimeric, and two tetrameric surfactants, which are quaternary ammonium chlorides, with medium length spacer groups (C-3-C-6) separating the individual surfactant fragments. Two standard cationic surfactants served as references. The number of hydrophobic chains making up a micellar core is relatively low for the oligomeric surfactants, the spacer length playing an important role. For the dimers, the number decreases from 32 to 21 with increasing spacer length. These numbers decrease further with increasing degree of oligomerization down to values of about 15. As for many conventional ionic surfactants, the micelles of all oligomers studied grow only slightly with the concentration, and they remain in the regime of small micelles up to concentrations of at least 3 wt %.
Y1  - 2006
UR  - http://pubs.acs.org/doi/full/10.1021/la052414h
U6  - https://doi.org/10.1021/La052414h
ER  - 
TY  - JOUR
A1  - Shainyan, Bagrat A.
A1  - Ushakov, Igor A.
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
T1  - Stereodynamics of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane: Experimental and theoretical analysis
N2  - Dynamic NMR of 1-(methylsulfonyl)-3,5-bis(trifluoromethylsulfonyl)-1,3,5-triazinane reveals the existence of three conformers and two dynamic processes: ring inversion and rotation about the N-S bond, both processes having Delta G(double dagger) = 13.5 kcal/mol. An unprecedented large reverse Perlin effect (J(CHax) > J(CHeq)) was found experimentally and calculated theoretically.
Y1  - 2006
UR  - http://pubs.acs.org/doi/full/10.1021/jo061112x
U6  - https://doi.org/10.1021/Jo061112x
ER  - 
TY  - JOUR
A1  - Laschewsky, André
A1  - Kirsten, Juliane
A1  - Skrabania, Katja
A1  - Storsberg, Joachim
T1  - Designing functional macrosurfactants via triblock tercopolymers
Y1  - 2006
SN  - 0065-7727
ER  - 
TY  - JOUR
A1  - Sonnenburg, Kirstin
A1  - Adelhelm, Philipp
A1  - Antonietti, Markus
A1  - Smarsly, Bernd
A1  - Nöske, Robert
A1  - Strauch, Peter
T1  - Synthesis and characterization of SiC materials with hierarchical porosity obtained by replication techniques
N2  - Porous silicon carbide monoliths were obtained using the infiltration of preformed SiO2 frameworks with appropriate carbon precursors such as mesophase pitch. The initial SiO2 monoliths possessed a hierarchical pore system, composed of an interpenetrating bicontinuous macropore structure and 13 nm mesopores confined in the macropore walls. After carbonization, further heat treatment at ca. 1400 degrees C resulted in the formation of a SiC-SiO2 composite, which was converted into a porous SiC monolith by post-treatment with ammonium fluoride solution. The resulting porous SiC featured high crystallinity, high chemical purity and showed a surface area of 280 m(2) g(-1) and a pore volume of 0.8 ml g(-1)
Y1  - 2006
UR  - http://pubs.rsc.org/en/Content/ArticleLanding/2006/CP/b604819f
U6  - https://doi.org/10.1039/B604819F
ER  - 
TY  - JOUR
A1  - Kumke, Michael Uwe
A1  - Dosche, Carsten
A1  - Flehr, Roman
A1  - Trowitzsch-Kienast, Wolfram
A1  - Löhmannsröben, Hans-Gerd
T1  - Spectroscopic characterization of the artificial siderophore pyridinochelin
Y1  - 2006
UR  - http://www.znaturforsch.com/c.htm
SN  - 0939-5075
ER  - 
TY  - JOUR
A1  - Grobosch, Thomas
A1  - Schilde, Uwe
A1  - Tiersch, Brigitte
T1  - Abtrennung von Arsen und anderer Schwermetalle mit imprägnierten Adsorberpolymeren - teil 2: Abtrennung von Blei, Kupfer, Nickel und Zink
Y1  - 2006
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/60500203/
U6  - https://doi.org/10.1002/cite.200500171
SN  - 0009-286X
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Nave, Stefan
T1  - Palladium-catalyzed O-allylation of alpha-hydroxy carbonyl compounds
N2  - alpha-Hydroxy carbonyl compounds undergo smooth O-allylation using allylic carbonates and Pd(0) catalysts. This method has significant advantages over other O-allylation methods as it provides a solution to several problems previously observed for this synthetic transformation
Y1  - 2006
UR  - http://onlinelibrary.wiley.com/doi/10.1002/adsc.200505361/pdf
U6  - https://doi.org/10.1002/adsc.200505361
ER  - 
TY  - JOUR
A1  - Szatmari, Istvan
A1  - Toth, Diana
A1  - Koch, Andreas
A1  - Heydenreich, Matthias
A1  - Kleinpeter, Erich
A1  - Fulop, Ferenc
T1  - Study of the substituent-influenced anomeric effect in the ring-chain tautomerism of 1-alkyl-3-aryl-naphth[1,2- e][1,3]oxazines
N2  - The stabilities of the trans (B) and cis (C) tautomeric ring forms that are experimentally observed in the ring- chain tautomeric interconversion of 1-alkyl-3-aryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines has been investigated. Stability differences are explained by the analysis of the natural bond orbital results for the lone pairs of electrons that are on the heteroatoms in the oxazine ring system and by regression analysis of the calculated 13C NMR chemical shift values.
Y1  - 2006
UR  - http://onlinelibrary.wiley.com/doi/10.1002/ejoc.200600563/pdf
U6  - https://doi.org/10.1002/ejoc.200600563
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Laschewsky, André
A1  - Wetzel, Hendrik
A1  - Gornitz, Eckhard
T1  - Free radical polymerization of n-butyl methacrylate in ionic liquids
N2  - Ionic liquids based on imidazolium, pyridinium, and alkylammonium salts were investigated as solvents in free radical polymerization of the model monomer n-butyl methacrylate. The properties of the ionic liquids were systematically varied by changing the length of the alkyl substituents on the cations, and by employing different anions such as tetrafluoroborate, hexafluorophosphate, tosylate, triflate, alkyl sulfates and dimethyl phosphate. Results were compared to analogous polymerizations in toluene and in bulk. The solvents have no detectable influence on polymer tacticity. However, the molar masses obtained and the degree of polymerization, respectively, are very sensitive to the choice of the solvent. The degrees of polymerization are significantly higher when polymerizations were carried out in ionic liquids compared to polymerization in toluene, and can even exceed the values obtained by bulk polymerization. Imidazolium salts unsubstituted at C-2 result in an increase in the degree of polymerization of the poly(butyl methacrylate) with increasing viscosity of these ionic liquids. Methyl substitution at C-2 of the imidazolium ion results in an increase in the viscosity of the ionic liquid and in a viscosity independent degree of polymerization of the poly(butyl methacrylate). Ionic liquids based on imidazolium salts seem preferable over pyridinium and alkylammonium salts because of the higher degree of polymerization of the poly(butyl methacrylate)s obtained in the imidazolium salts. The glass transition temperatures and thermal stabilities are higher for poly(butyl methacrylate)s synthesized in the ionic liquids compared to the polymer made in toluene
Y1  - 2006
UR  - http://pubs.acs.org/doi/full/10.1021/ma0516945
U6  - https://doi.org/10.1021/Ma0516945
ER  - 
TY  - JOUR
A1  - Klinka, Karel D.
A1  - Balentova, Eva
A1  - Bernát, Juraj
A1  - Imrich, Ján
A1  - Vavrusová, Martina
A1  - Pihlaja, Kalevi
A1  - Koch, Andreas
A1  - Kleinpeter, Erich
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
T1  - Structural revision of products resulting from the reaction of methylhydrazine with acridin-9-yl isothiocyanate due to unexpected acridinyl migration And further reactions
N2  - The reaction of methyl acridin-9-ylthiosemicarbazide under basic conditions with methyl bromoacetate resulted in a 1,3-thiazolin-4-one structure as provided by X-ray crystallography. The structure forced a re-evaluation of the reactant methyl acridin-9-ylthiosemicarbazide, originally thought to be 2-methyl 4-acridin-9-ylthiosemicarbazide based on synthetic expectations, but which when examined by X-ray crystallography was found to be in fact the isomeric 2- methyl 1-acridin-9-ylthiosemicarbazide resulting from rearrangement via a spiro form which it is in equilibrium with in solution. The product resulting from reaction with methyl iodide was also studied and the previously reported semicarbazide produced by reaction with MNO was re-examined. In both cases, the 1,2 isomer rather than the 2,4 isomer was found to be present based on the sign of the 3JCH3,N11 coupling. Full characterization of the compounds was rendered by 1H, 13C, and 15N solution-state NMR, and in the solid state, by both 13C and 15N NMR.
Y1  - 2006
UR  - http://arkat-usa.org/home.aspx?VIEW=BROWSE&MENU=ARKIVOC
SN  - 1551-7004
ER  - 
TY  - JOUR
A1  - Grobosch, Thomas
A1  - Mickler, Wulfhard
A1  - Feistel, Lothar
A1  - Schilde, Uwe
T1  - Separation of arsenic and other heavy metals with impregnated adsorber polymers : chapter 1: synthesis of the impregnation medium and separation of arsenic
Y1  - 2006
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/60500203/
U6  - https://doi.org/10.1002/cite.200500170
SN  - 0009-286X
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
T1  - Push-pull alkenes : structure and pi-electron distribution
N2  - Push-pull alkenes are substituted alkenes with one or two electron-donating substituents on one end of C=C double bond and with one or two electron-accepting substituents at the other end. Allowance for pi-electron delocalization leads to the central C=C double bond becoming ever more polarized and with rising push-pull character, the pi-bond order of this double bond is reduced and, conversely, the corresponding pi-bond orders of the C-Don and C- Ace bonds are accordingly increased. This push-pull effect is of decisive influence on both the dynamic behavior and the chemical reactivity of this class of compounds and thus it is Of Considerable interest to both determine and to quantify the inherent push-pull effect. previously, the barriers to rotation about the C=C, C-Don and/or C-Acc partial double bonds (Delta G(not equal), as determined by dynamic NMR spectroscopy) or the C-13 chemical shift difference of the polarized C=C partial double bond (Delta delta(C=C)) were employed for this purpose, However, these parameters can have serious limitations, viz. the barriers can be immeasurable on the NMR timescale (either by being too high or too low-, heavily-biased conformers are present, etc.) or Delta delta(C=C) behaves in a non-additive manner with respect to the combination of the four substituents. Hence, a general parameter to quantify the push-pull effect is not yet available. Ab initio MO calculations on a collection of compounds, together with NBO analysis, provided valuable information on the structure, bond energies, electron occupancies and bonding/antibonding interactions. In addition to Delta G(C=C)(not equal) (either experimentally determined or theoretically calculated) and Delta delta(C=C), the bond length of the C=C partial double bond was also examined and it proved to be a reliable parameter to quantify the push-pull effect. Equally so, the quotient of the occupation numbers of the antibonding and bonding pi orbitals of the central C=C partial double bond ( pi*(C=C)/pi(C=C) ) could also be employed for this purpose
Y1  - 2006
UR  - http://www.shd.org.rs/JSCS/
U6  - https://doi.org/10.2298/Jsc0601001k
ER  - 
TY  - THES
A1  - Köhler, Karen
T1  - Temperature-induced rearrangements of polyelectrolyte multilayer capsules : mechanisms and applications
Y1  - 2006
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Gorfman, Semen
A1  - Tsirelson, Vladimir
A1  - Pucher, Andreas
A1  - Morgenroth, Wolfgang
A1  - Pietsch, Ullrich
T1  - X-ray diffraction by a crystal in a permanent external electric field : electric-field-induced structural response in alpha-GaPO4
N2  - For the first time, site-selective distortion has been investigated for two different structural units in the ternary compound alpha-GaPO4 under the influence of a permanent external electric field. Based on 54 measured reflection intensities, the electric-field-induced distortion of PO4 and GaO4 tetrahedra in alpha-GaPO4 crystals is evaluated using a model of pseudoatomic displacements introduced recently [Gorfman, Tsirelson & Pietsch (2005). Acta Cryst. A61, 387- 396]. A stronger variation of the P-O bond lengths in the PO4 tetrahedron was found compared to the bonds in the GaO4 tetrahedron. The different distortions of the tetrahedra owing to the electric field were analysed in terms of the valence charge density of alpha-GaPO4 and its topological characteristics. The larger charge of the P pseudoatom compared to the Ga atom was recognized as the main reason for the higher sensitivity of the PO4 tetrahedron to a permanent external electric field
Y1  - 2006
UR  - http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1600-5724
U6  - https://doi.org/10.1107/S0108767305036111
SN  - 0108-7673
ER  - 
TY  - JOUR
A1  - Kietzke, Thomas
A1  - Egbe, Daniel A. M.
A1  - Hörhold, Hans-Heinrich
A1  - Neher, Dieter
T1  - Comparative study of M3EH-PPV-based bilayer photovoltaic devices
N2  - We have recently shown that efficient polymer solar cells can be fabricated by using a weakly soluble derivative of poly-p-vinylene (M3EH-PPV) as the electron donor. Here we present studies on bilayer devices using organic electron acceptors with varying LUMO levels and M3EH-PPV. It is found that the open-circuit voltage scales linearly with the LUMO level of the acceptor, reaching values as high as 1.5 V when cyano-substituted poly(p-phenyleneethynylene)-alt- poly(p-phenylenevinylene) copolymers are used. Further, we discovered that for an increasing number of triple bonds in the repeat unit of the acceptor polymer the device performance decreases with increasing thickness of the acceptor layer. Also, the quantum efficiency was smaller when using polymers with higher LUMO levels. Thus, further effort is needed to design optimum acceptor polymers for devices exhibiting large open-circuit voltage and high quantum efficiency
Y1  - 2006
UR  - http://pubs.acs.org/journal/mamobx
U6  - https://doi.org/10.1021/Ma0601991
SN  - 4018-4022
ER  - 
TY  - JOUR
A1  - Schmidt, Bernd
A1  - Hermanns, Jolanda
T1  - Ring closing metathesis of substrates containing more than two C-C-double bonds : rapid access to functionalized heterocycles
N2  - In most cases where ring closing metathesis is applied to the synthesis of heterocycles, alpha,omega-dienes are used as precursors. If substrates containing more than two double bonds are subjected to a metathesis reaction, carba- or heterocycles bearing additional exocyclic alkene functionality result, or multiple ring closing processes occur. This offers interesting and potentially very useful synthetic perspectives. On the other hand, selectivity problems need to be addressed as the cyclization of substrates with more than two double bonds available for olefin metathesis may result in constitutional isomers or stereoisomers. This review highlights problems and opportunities evolving from ring closing metathesis of tri-, tetra-, and polyenes as a strategy for the selective synthesis of functionalized heterocycles. The chapter on RCM of trienes is subdivided according to the symmetry of the metathesis precursor. The following two chapters deal with the double or multiple RCM of tetra- or polyenes. These processes are further classified according to the preferred cyclization mode. Finally, the application of cascade or domino metathesis reactions to the synthesis of heterocycles will be discussed. These processes can be classified into those where exclusively C-C-double bonds take part in the metathesis reaction, and those where one or more C-C-triple bonds are involved
Y1  - 2006
ER  - 
TY  - THES
A1  - Kim, Boo Geun
T1  - Radikalische Additionen an ungesättigte Kohlenhydrate als Schlüsselschritt in der Synthese von Kohlenhydrat-C-Analoga
Y1  - 2006
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Stöcklein, Walter F. M.
T1  - Molecule-detective
BT  - Molekül-Detektive : Biosensoren
N2  - Biosensors are analytical devices incorporating biological material (receptor) intimately associated with or integrated within a physicochernical transducer. Advantages are the high selectivity for analyte detection. Examples given comprise the very successful commercial blood glucose biosensors made for the self-control by the diabetic patients. Other biosensors are part of an analytic system, including the sensor chips Of surface plasmon resonance or interferometry based devices, piezoelectric or reflectometric sensors capable of direct measurement of mass changes, and thermometric and other reagentless sensors. The development of nanotubes-based devices allows for significant enhancment of the signal-to-noise ratio of the biosensors. A milestone on the way towards miniaturization and parallelization of biosensors is the recently developed and prize-winning electronic DNA chip
Y1  - 2006
ER  - 
TY  - JOUR
A1  - Yenesew, Abiy
A1  - Kiplagat, John T.
A1  - Derese, Solomon
A1  - Midiwo, Jacob O.
A1  - Kabaru, Jacques M.
A1  - Heydenreich, Matthias
A1  - Peter, Martin G.
T1  - Two unusual rotenoid derivatives, 7a-O-methyl-12a-hydroxydeguelol and spiro-13-homo-13-oxaelliptone, from the seeds of Derris trifoliata
N2  - The crude methanol extract of the seeds of Derris trifoliata showed potent and dose dependent larvicidal activity against the 2nd instar larvae of Aedes aegypti. From this extract two unusual rotenoid derivatives, a rotenoloid (named 7a-O-methyl-12a-hydroxydeguelol) and a spirohomooxarotenoid (named spiro-13-homo-13-oxaelliptone), were isolated and characterised. In addition a rare natural chromanone (6,7-dimethoxy-4-chromanone) and the known rotenoids rotenone, tephrosin and dehydrodeguelin were identified. The structures were assigned on the basis of spectroscopic evidence. The larvicidal activity of the crude extract is mainly due to rotenone. (c) 2006 Elsevier Ltd. All rights reserved
Y1  - 2006
UR  - http://www.sciencedirect.com/science/article/pii/S0031942206000045
U6  - https://doi.org/10.1016/j.phytochem.2006.01.002
ER  - 
TY  - JOUR
A1  - Holdt, Hans-Jürgen
A1  - Müller, Holger
A1  - Kelling, Alexandra
A1  - Drexler, Hans-Joachim
A1  - Müller, Thomas
A1  - Schwarze, Thomas
A1  - Schilde, Uwe
A1  - Starke, Ines
T1  - Mercury(II) chloride and iodide complexes of dithia- and tetrathiacrown ethers
N2  - The complexes [(HgCl2)(2)((ch)(2)30S(4)O(6))] (1), [HgCl,(mn21S(2)O(5))] (2), [HgCl2(ch18S(2)O(4))] (3) and [HgI(meb12S(2)O(2))](2)[Hg2I6] (4) have been synthesized, characterized and their crystal structures were determined. In [(HgCl2)(2)((ch)(2)3OS(4)O(6))] two HgCl2 units are discretely bonded within the ligand cavity of the 30-membered dichinoxaline-tetrathia-30-crown-10 ((ch)(2)30S(4)O(6)) forming a binuclear complex. HgCl2 forms I : I "in-cavity" complexes with the 21-membered maleonitrile-dithia-21-crown-7(mn21S(2)O(5)) ligand and the 18-membered chinoxaline- dithia-18-crown-6 (ch18S(2)O(4)) ligand, respectively. The 12-membered 4-methyl-benzo-dithia-12-crown-4 (meb12S(2)O(2)) ligand gave with two equivalents HgI2 the compound [HgI(meb12S(2)O(2))](2)[Hg2I6]. In the cation [HgI(meb12S(2)O(2))](+) meb12S(2)O(2) forms with the cation HgI+ a half-sandwich complex
Y1  - 2006
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/10005159
U6  - https://doi.org/10.1002/zaac.200500281
SN  - 0044-2313
ER  - 
TY  - THES
A1  - Klamroth, Tillmann
T1  - Quantum mechanical simulations for correlated many-electron dynamics and electron induced processes at surfaces
Y1  - 2006
CY  - Potsdam
ER  - 
TY  - THES
A1  - Kohlmeier, Alexandra
T1  - Synthese und Eigenschaften supramolekularer polyphiler Blockmesogene
Y1  - 2006
CY  - Potsdam
ER  - 
TY  - THES
A1  - Bellin, Ingo
T1  - Thermosensitive Polymer Networks with Two Different Shapes in Memory
Y1  - 2006
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Kammer, Stefan
A1  - Müller, Holger
A1  - Grunwald, Nicolas
A1  - Bellin, Anja
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Mickler, Wulfhard
A1  - Dosche, Carsten
A1  - Holdt, Hans-Jürgen
T1  - Supramolecular assemblies with honeycomb structures by pi-pi stacking of octahedral metal complexes of 1,12- diazaperylene
N2  - Homoleptic Ni-II and Fe-II complexes of the "large-surface" phenanthroline-type ligand 1,12-diazaperylene (dap), [Ni(dap)(3)](BF4)(2) (1) and [Fe(dap)(3)](PF6)(2) (2), respectively, were synthesized. In the crystal structure the complex cation [M(dap)(3)](2+) (M = Ni, Fe) exhibits C-3 symmetry and interacts with three other cations by pi-pi stacking. It forms a new metalla-supramolecular assembly with a honeycomb structure containing nanochannels running parallel to the crystallographic c axis. Aggregation by pi-pi stacking between metal complexes of "large-surface" ligands should give new perspectives for inorganic supramolecular chemistry.
Y1  - 2006
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/27721/
U6  - https://doi.org/10.1002/ejic.200600092
SN  - 1343-1948
ER  - 
TY  - JOUR
A1  - Katterle, Martin
A1  - Holzwarth, Alfred R.
A1  - Jesorka, Aldo
T1  - A Heck-type coupling for the synthesis of novel bridged metallochlorin-fullerene C-60 dyads
N2  - A short and convenient synthesis of metallochlorin-C-60 dyads based on a Heck-type hetero coupling at the 3(2) position of a chlorin is described. p-Bromobenzaldehyde was treated with Zn-metalated 13(2)- demethoxycarbonylmethylpheophorbide a, using a palladium acetate/LiCl catalyst mixture under phase-transfer conditions in DMF at 70 degrees C. The resulting asymmetric olefin was obtained in a high trans/cis ratio. The desired trans isomer was separated and subsequently transformed into a donor-acceptor dyad by a 1,3-dipolar cycloaddition to C-60 in the presence of sarcosine in refluxing toluene. The resulting dyads are expected to undergo efficient photoinduced electron transfer and can potentially be utilized in solar energy conversion devices.
Y1  - 2006
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/27380/
U6  - https://doi.org/10.1002/ejoc.200500494
SN  - 1434-193X
ER  - 
TY  - JOUR
A1  - Holdt, Hans-Jürgen
A1  - Müller, Holger
A1  - Potter, Matthias
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Starke, Ines
A1  - Heydenreich, Matthias
A1  - Kleinpeter, Erich
T1  - The first sandwich complex with an octa(thioether) coordination sphere : Bis(maleonitrile-tetrathia-12-crown- 4)silver(I)
N2  - The new tetrathiacrown ethers maleonitrile-tetrathia-12-crown-4 (mn12S(4)) and maleonitrile-tetrathia-13-crown- 4 (mn13S(4)) have been prepared and characterised by X-ray crystallographic analysis. These crown ethers form 2:1, 3:2 and 1: 1 complexes with AgY (Y = BF4, PF6). The crystal structures of [Ag(mn12S(4))(2)]BF4 (3a), [Ag(mn13S(4))(2)]BF4 (4a) and [Ag-2(mn13S(4))(3)](PF6)(2) (6b) have been determined. Compound 3a contains the centrosymmetric sandwich complex cation [Ag(mn12S(4))(2)](+) where each mn12S(4) ligand is coordinated to the Ag centre in an endo manner through all four S atoms. The 2:1 complex [Ag(mn12S(4))(2)](+) is the first sandwich complex with a tetrathiacrown ether and the first complex with an octa(thioether) coordination sphere. The crystal structure of compound 4a also reveals a 2:1 complex. This complex, [Ag(mnl3S(4))(2)](+), exhibits a half-sandwich structure. One mn13S(4) ligand coordinates to Ag+ by all four S donor atoms and the other 13S(4) crown by only one S atom. Compound 6b contains a dinuclear Ag complex. The Ag complexes 3a,b-8a,b were also studied by electrospray ionisation mass spectrometry. Collision-induced dissociation (CID) was used to compare the relative stability of 2:1 complexes [AgL2]+ and 1:1 complexes [AgL](+) (L = mn12S(4), mn13S(4)). The C-13 NMR chemical shifts of 2:1 and 1:1 Ag complexes and their corresponding free ligands were also estimated and compared. The free energy of the barrier of ring inversion (Delta G(double dagger)) for [Ag(mn12S(4))(2)](+) was determined to be 64 kJmol(-1).
Y1  - 2006
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/27721/
U6  - https://doi.org/10.1002/ejic.200501109
SN  - 1434-1948
ER  - 
TY  - JOUR
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Klod, Sabrina
A1  - Szatmari, Istvan
A1  - Fulop, Ferenc
A1  - Kleinpeter, Erich
T1  - Synthesis and conformational analysis of naphth[1', 2':5,6][1,3]oxazino[3,2-c][1,3]benzoxazine and naphth[1', 2':5,6][1,3]oxazino[3,4-c][1,3]benzoxazine derivatives
JF  - Tetrahedron
N2  - A new functional group, the hydroxy group, was inserted into a Betti base by reaction with salicylaldehyde, and the naphthoxazine derivatives thus obtained were converted by ring-closure reactions with formaldehyde, acetaldehyde, propionaldehyde or phosgene to the corresponding naphth[1',2':5,6][1,3]oxazino[3,2-c][1,3]benzoxazine derivatives. Further, the conformational analysis of these polycyclic compounds by NMR spectroscopy and an accompanying molecular modelling are reported; especially, both quantitative anisotropic ring current effects of the aromatic moieties in these compounds and steric substituent effects were employed to determine the stereochemistry of the naphthoxazinobenzoxazine derivatives.
Y1  - 2006
UR  - http://www.sciencedirect.com/science/journal/00404020
U6  - https://doi.org/10.1016/j.tet.2006.09.037
SN  - 0040-4020
VL  - 62
IS  - 48
SP  - 11081
EP  - 11089
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Laschewsky, André
A1  - Wetzel, Hendrik
T1  - Homopolymerization of a highly polar zwitterionic methacrylate in ionic liquids and its copolymerization with a non-polar methacrylate
N2  - Free radical homo- and copolymerization of the highly polar 3-(N-[2-methacryloyloxyethyl]-N,N-dimethylammonio) propane sulfonate with the nonpolar n-butylmethacrylate was investigated in the ionic liquids 1-butyl-3-methyl imidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluoro phosphate, and compared to analogous polymerizations in standard solvents. Higher molar masses are obtained for the zwitterionic homopolymer when the polymerization is carried out in an ionic liquid compared to the classical reaction in water. Although homopolymerization of the sulfobetain monomer as well as of n-butylmethacrylate results in phase separation during the polymerization process, copolymerization of a stoichiometric ratio of the two monomers in the ionic liquids produced transparent gels indicating that no macrophase separation occurs. The use of ionic liquids as reaction medium improved the copolymerization behavior of the two methacrylates significantly. Whereas only minor amounts of n-butyl methacrylate were incorporated in the copolymer when synthesized in acetonitrile, the content of the non-polar monomer units in the zwitterionic copolymer approached increasingly its content in the polymerization mixture when ionic liquids were employed as solvents
Y1  - 2006
ER  - 
TY  - JOUR
A1  - Hayer, Anna
A1  - de Halleux, Veronique
A1  - Köhler, Anna
A1  - El-Garoughy, Abdel
A1  - Meijer, E. W.
A1  - Barbera, Joaquin
A1  - Tant, Julien
A1  - Levin, Jeremy
A1  - Lehmann, Matthias
A1  - Gierschner, Johannes
A1  - Cornil, Jerome
A1  - Geerts, Yves Henri
T1  - Highly fluorescent crystalline and liquid crystalline columnar phases of pyrene-based structures
N2  - A concept for highly ordered solid-state structures with bright fluorescence is proposed: liquid crystals based on tetraethynylpyrene chromophores, where the rigid core is functionalized with flexible, promesogenic alkoxy chains. The synthesis of this novel material is presented. The therniotropic properties are studied by means of differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM), and X-ray diffraction. The mesogen possesses an enantiotropic Col(h) phase over a large temperature range before clearing. The material is highly fluorescent in solution and, most remarkably, in the condensed state, with a broad, strongly red shifted emission. Fluorescence quantum yields (Phi(F)) have been determined to be 70% in dichloromethane solution and 62% in the solid state. Concentration- and temperature-dependent absorption and emission studies as well as quantum-chemical calculations on isolated molecules and dimers are used to clarify the type of intermolecular interactions present as well as their influence on the fluorescence quantum yield and spectral properties of the material. The high luminescence efficiency in the solid state is ascribed to rotated chromophores, leading to an optically allowed lowest optical transition
Y1  - 2006
UR  - http://pubs.acs.org/journal/jpcbfk
U6  - https://doi.org/10.1021/Jp0573689
SN  - 1520-6106
ER  - 
TY  - JOUR
A1  - Koetz, Joachim
A1  - Andres, S.
A1  - Kosmella, Sabine
A1  - Tiersch, Brigitte
T1  - BaSO4 nanorods produced in polymer-modified bicontinuous microemulsions
N2  - The influence of the water soluble polymer poly(ethylene glycol) (PEG) on structure formation in the quasiternary system sodium dodecylsulfate (SDS)/pentanol-xylene/water was checked by means of conductometry, rheology, and micro differential calorimetry. The polymer induces the formation of an isotropic phase channel between the o/w and w/o microemulsion. The transition from the normal as well as from the inverse micellar to the bicontinuous phase range can be detected by conductometry, rheology as well as micro-DSC. As a result of polymer-surfactant interactions, the spontaneous curvature of the surfactant film is changed and a sponge phase is formed. The bicontinuous phase is characterized by a moderate shear viscosity, a Newtonian flow behaviour, and the disappearence of interphasal water in the heating curve of the micro-DSC. When the polymer-modified bicontinuous phase is used as a template phase for the nanoparticle formation, spherical BaSO4 nanoparticles were formed. During the following solvent evaporation process the primarily formed spherical nanoparticles aggregate to nanorods and triangular structures due to the non-restriction of the bicontinuous template phase in longitudinal direction
Y1  - 2006
UR  - http://www.ingentaconnect.com/content/vsp/ci
U6  - https://doi.org/10.1163/156855406777408629
SN  - 0927-6440
ER  - 
TY  - JOUR
A1  - Starke, Ines
A1  - Fürstenberg, Sylvia
A1  - Müller, Holger
A1  - Holdt, Hans-Jürgen
A1  - Kleinpeter, Erich
T1  - Electrospray mass spectrometric studies of the complexational behavior of maleonitrile thiacrown ethers with various metals
N2  - Electrospray ionization was employed to study the mass spectrometric behavior of the maleonitrile tetrathiacrown ethers mn12S(4) (1) and mn13S(4) (2) and maleonitrile pentathiacrown ether mn15S(5) (3) and of their complexes with various metal salts (MX2, M=Pd, Pt, Ni, Co, Fe; X=Cl, CrCl3, Ni(BF4)(2), TIPF6 or Cd(NO3)(2)) and Cu(SO3CF3)(2). Both singly charged, [MXL](+) and [MXL2]+, and doubly charged complexes, [MLn](2+) (n = 2-5), were observed. The formation of the different complexes consisting of the transition metal ion, the counterion and the various crown ethers and their subsequent dissociation was also studied by collision-induced dissociation measurements which were also used to evaluate the relative stabilities of the complexes. It was found that the collisional voltages for the dissociation of the complexes were generally greater in the [MXL](+) complexes than in the corresponding [MXL2]+ complexes. Copyright (c) 2006 John Wiley & Sons, Ltd
Y1  - 2006
UR  - http://onlinelibrary.wiley.com/doi/10.1002/rcm.2384/full
U6  - https://doi.org/10.1002/Rcm.2384
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Schulenburg, Anja
T1  - Quantification of the push-pull effect in tolanes and a revaluation of the factors affecting the C-13 chemical shifts of the carbon atoms of the C=C triple bond
N2  - Variously substituted tolanes were employed to show that the push-pull effect is also active in C equivalent to C triple bonds by the successful correlation of the occupation quotient pi*/pi of the pi orbital in resonance with the substituted phenyl moieties of tolanes versus the bond length of the C equivalent to C triple bond. In addition, the influences of the ortho phenyl ring substituents on the C-13 chemical shifts of the triple bond carbon atoms, which were estimated by Rubin et al.(4) to be "inapplicable for describing triple bond polarization", were re-evaluated, leading to the conclusion that, while anisotropic effects of ortho substituents are negligible, the steric ortho-substituent effects do in fact dominate the deviations obtained. A detailed theoretical NBO/NCS study has been employed to illuminate the facts of this case
Y1  - 2006
UR  - http://pubs.acs.org/journal/joceah
U6  - https://doi.org/10.1021/Jo060199j
SN  - 0022-3263
ER  - 
TY  - JOUR
A1  - Garnier, Sebastien
A1  - Laschewsky, André
T1  - New amphiphilic diblock copolymers : surfactant properties and solubilization in their micelles
N2  - Several series of amphiphilic diblock copolymers are investigated as macrosurfactants in comparison to reference low-molar-mass and polymeric surfactants. The various copolymers share poly(butyl acrylate) as a common hydrophobic block but are distinguished by six different hydrophilic blocks (one anionic, one cationic, and four nonionic hydrophilic blocks) with various compositions. Dynamic light scattering experiments indicate the presence of micelles over the whole concentration range from 10(-4) to 10 g(.)L(-1). Accordingly, the critical micellization concentrations are very low. Still, the surface tension of aqueous solutions of block copolymers decreases slowly but continuously with increasing concentration, without exhibiting a plateau. The longer the hydrophobic block, the shorter the hydrophilic block, and the less hydrophilic the monomer of the hydrophilic block is, the lower the surface tension is. However, the effects are small, and the copolymers reduce the surface tension much less than standard low-molar-mass surfactants. Also, the copolymers foam much less and even act as anti-foaming agents in classical foaming systems composed of standard surfactants. The copolymers stabilize O/W emulsions made of methyl palmitate as equally well as standard surfactants but are less efficient for O/W emulsions made of tributyrine. However, the copolymer micelles exhibit a high solubilization power for hydrophobic dyes, probably at their core-corona interface, in dependence on the initial geometry of the micelles and the composition of the block copolymers. Whereas micelles of copolymers with strongly hydrophilic blocks are stable upon solubilization, solubilization-induced micellar growth is observed for copolymers with moderately hydrophilic blocks
Y1  - 2006
UR  - http://pubs.acs.org/journal/langd5
U6  - https://doi.org/10.1021/La0600595
SN  - 0743-7463
ER  - 
TY  - JOUR
A1  - Klinka, Karel D.
A1  - Balentova, Eva
A1  - Bernát, Juraj
A1  - Imrich, Jan
A1  - Vavrusova, Martina
A1  - Kleinpeter, Erich
A1  - Pihlaja, Kalevi
A1  - Koch, Andreas
T1  - Tautomerism, regioisomerism, and cyclization reactions of acridinyl thiosemicarbazides
N2  - The regioselectivities of methyl- and phenylhydrazine with acridin-9-yl isothiocyanate (thus yielding thiosemicarbazides with acridine substituted on the urea-type side) were examined. Methythydrazine regioselectivity was high with the alpha-nitrogen atom overwhelmingly more nucleophilic than the beta-nitrogen atom; phenylhydrazine regioselectivity was poor but varied with the solvent and only in the case of ethanol was nucleophilic predominance of the alpha-nitrogen atom pronounced. Of note, whilst both phenyl thiosemicarbazides were present in solution only as spiro forms, the methyl product was present as an equilibrium mixture of open-chain and spiro thiosemicarbazides. Reactions on the NH2 blocked analogue of methyl acridin-9-ylthiosemicarbazide (1-isopropylidene-2- methylthiosemicarbazide) were also examined. Interestingly, present in the starting material itself was a structural motif of novelty wherein a triazolethione represented the major species of an equilibrium between cyclic and open-chain forms
Y1  - 2006
UR  - http://www3.interscience.wiley.com/journal/121521817/toc
U6  - https://doi.org/10.1002/jhet.5570430317
SN  - 0022-152X
ER  - 
TY  - JOUR
A1  - Schilde, Uwe
A1  - Erk, Çakil
A1  - Kleinpeter, Erich
T1  - The crystal and molecular structures of sodium and barium complexes of dibenzo-24-crown-8 ether
N2  - The sodium and barium isothiocyanate complexes of 6,7,9,10,12,13,20,21,23,24,26,27-dodecahydrodibenzo[b,n]- 1,4,7,10,13,16,19,22-octaoxacyclotetracosin (dibenzo-24-crown-8 ether = DB24C8) were synthesized and analyzed by X-ray diffraction. The sodium complex, [Na(DB24C8)(NCS)(H2O)] 1, crystallizes in the orthorhombic space group Fdd2 with 16 molecules in the unit cell. The coordination number of Na is 6 and the central ion is located in a distorted octahedric environment. Only four of the crown ether oxygen atoms are involved. The coordination polyhedron is completed by the isothiocanate anion and by a water molecule, which is stabilized by hydrogen bonds. The barium complex, [Ba(DB24C8)(NCS)(2)] 2, crystallizes in the trigonale space group P3(1)21 with 3 molecules in the unit cell. Crystallographic C-2 symmetry is observed for the complex. The coordination number of Ba is 10. Barium is coordinated with the eight oxygen atoms of the macrocyclic ligand and with two isothiocyanate anions. The absolute structure was estimated using the FLACK parameter
Y1  - 2006
U6  - https://doi.org/10.1524/zkri.2006.221.3.231
ER  - 
TY  - JOUR
A1  - Walz, Bernd
A1  - Baumann, Otto
A1  - Krach, Christian
A1  - Baumann, Arnd
A1  - Blenau, Wolfgang
T1  - The aminergic control of cockroach salivary glands
N2  - The acinar salivary glands of cockroaches receive a dual innervation from the subesophageal ganglion and the stomatogastric nervous system. Acinar cells are surrounded by a plexus of dopaminergic and serotonergic varicose fibers. In addition, seroton-ergic terminals lie deep in the extracellulor spaces between acinar cells. Excitation-secretion coupling in cockroach salivary glands is stimulated by both dopamine and serotonin. These monoamines cause increases in the intracellular concentrations of cAMP and Ca2+. Stimulation of the glands by serotonin results in the production of a protein-rich saliva, whereas stimulation by dopamine results in saliva that is protein-free. Thus, two elementary secretary processes, namely electrolyte/water secretion and protein secretion, are triggered by different aminergic transmitters. Because of its simplicity and experimental accessibility, cockroach salivary glands have been used extensively as a model system to study the cellular actions of biogenic amines and to examine the pharmacological properties of biogenic amine receptors. In this review, we summarize current knowledge concerning the aminergic control of cockroach salivary glands and discuss our efforts to characterize Periplaneta biogenic amine receptors molecularly
Y1  - 2006
UR  - 1960 = Doi 10.1002/Arch.20128
ER  - 
TY  - JOUR
A1  - Kamm, Birgit
A1  - Kamm, Michael
A1  - Schmidt, Matthias
A1  - Starke, Ines
A1  - Kleinpeter, Erich
T1  - Chemical and biochemical generation of carbohydrates from lignocellulose-feedstock (Lupinus nootkatensis) : quantification of glucose
N2  - Different chemical and enzymatic methods were applied for the hydrolysis of main stems from Lupinus nootkatensis (harvest November 2002). The whole process (all steps) is based on the lignocellulose-feedstock biorefinery regime. The acid hydrolysis of L. was performed with concentrated hydrochloric acid; advantages in this process are exothermic hydrolysis and the possibility of acid recovery. Enzymatic hydrolysis achieved high yields of fermentable carbohydrates (regarding to input cellulose) with high selectivity. However, this way requires the generation of cellulose from L. by chemical pulping. Monosaccharide derivatives thus obtained were identified by their GC retention times and the corresponding MS fragmentation. Hexamethyldisilazane was used as derivatization reagent to prepare the trimethylsilyl derivatives of the carbohydrates and of the degradations products of cellulose from the different fractions. The glucose content was quantified by GC peak integration with respect to an internal standard.
Y1  - 2006
UR  - http://www.sciencedirect.com/science/journal/00456535
U6  - https://doi.org/10.1016/j.chemosphere.2005.03.073
SN  - 0045-6535
ER  - 
TY  - JOUR
A1  - Delorme, Nicolas
A1  - Dubois, Monique
A1  - Garnier, Sebastien
A1  - Laschewsky, André
A1  - Weinkamer, Richard
A1  - Zemb, Thomas
A1  - Fery, Andreas
T1  - Surface immobilization and mechanical properties of catanionic hollow faceted polyhedrons
N2  - We report here for the first time on surface immobilization of hollow faceted polyhedrons formed from catanionic surfactant mixtures. We find that electrostatic interaction with the substrate dominates their adhesion behavior. Using polyelectrolyte coated surfaces with tailored charge densities, polyhedrons can thus be immobilized without complete spreading, which allows for further study of their mechanical properties using AFM force measurements. The elastic response of individual polyhedrons can be locally resolved, showing pronounced differences in stiffness between faces and vertexes of the structure, which makes these systems interesting as models for structurally similar colloidal scale objects such as viruses, where such effects are predicted but cannot be directly observed due to the smaller dimensions. Elastic constants of the wall material are estimated using shell and plate deformation models and are found to be a factor of 5 larger than those for neutral lipidic bilayers in the gel state. We discuss the molecular origins of this high stiffness
Y1  - 2006
UR  - http://pubs.acs.org/journal/jpcbfk
U6  - https://doi.org/10.1021/Jp054473+
SN  - 1520-1758
ER  - 
TY  - JOUR
A1  - Beitz, Toralf
A1  - Laudien, Robert
A1  - Löhmannsröben, Hans-Gerd
A1  - Kallies, Bernd
T1  - Ion mobility spectrometric investigation of aromatic cations in the gas phase
N2  - In this work, ion mobility (IM) spectra of more than 50 aromatic compounds were recorded with a laser-based IM spectrometer at atmospheric pressure. IM spectra of PAH in the laser desorption experiment show a high complexity resulting from the occurrence of monomeric, dimeric, and oligomeric cluster ions. The mobilities of all compounds were determined in helium as drift gas. This allows the calculation of the diffusion cross sections (Omega(calc)) on the basis of the exact hard sphere scattering model and their comparison with the experimentally determined diffusion cross sections (Omega(exp)). Extended Omega(exp)/Omega(calc) and Omega(exp/)mass correlations were performed in order to gain insight into conformational properties of cationic alkyl benzenes and internal rotation of phenyl rings in aromatic ions. This is demonstrated with some examples, such as the evaluation of the dihedral angle of the ions of 9,10- diphenylanthracene, o- and m-terphenyl, and 1,2,3- and 1,3,5-triphenylbenzene. Furthermore, sandwich and T-structures of dimeric PAH cations are discussed. The analysis was extended to oligomeric ions with up to nine monomer units. Experimental evidence is presented suggesting the formation of pi-stacks with a transition toward modified pi-stacks with increasing cluster size. The distance between monomeric units in dimeric and oligomeric ions was obtained
Y1  - 2006
UR  - http://pubs.acs.org/journal/jpcafh
U6  - https://doi.org/10.1021/Jp055335n
SN  - 1089-5639
ER  - 
TY  - JOUR
A1  - Kleinpeter, Erich
A1  - Rolla, Nadja
A1  - Koch, Andreas
A1  - Taddei, Fernando
T1  - Hyperconjugation and the increasing bulk of OCOCX3 substituents in trans-1,4-disubstituted cyclohexanes destabilize the diequatorial conformer
N2  - The trans diesters of 1,4-cyclohexanediol with a number of acetic acid analogues, CX3COOH, of varying steric hindrance and polarity (CX3 = Me, Et, iso-Pr, tert-Bu, CF3, CH2Cl, CHCl2, CCl3, CH2Br, CHBr2, CBr3) were synthesized, and the axial, axial/equatorial, equatorial conformational equilibria were studied by low-temperature H-1 NMR spectroscopy in CD2Cl2. The structures and relative energies of the axial, axial and equatorial, equatorial conformers were calculated at both the MP2/6-311G* and the MP2/6-311+G* levels of theory, and it was only by including diffuse functions that a good correlation of Delta G degrees(calcd) vs Delta G(exptl) could be obtained. Both the structures and the energy differences of the axial, axial and equatorial, equatorial conformers are discussed with respect to the established models of conformational analysis, viz., steric 1,3-diaxial and hyperconjugative interactions. Interestingly, the hyperconjugative interactions sigma(C-C)/sigma(C-H)->sigma*(C-O), together with a steric effect which also destabilizes the equatorial, equatorial conformers on increasing bulk of the substituents, proved to dominate the position of the conformational equilibria. In addition, the preference of the axial, axial conformers with respect to their equatorial, equatorial analogues was greater than expected from the conformational energies of the corresponding substituents in the monosubstituted cyclohexyl esters. The reason for this very interesting and unexpected result is also discussed
Y1  - 2006
UR  - http://pubs.acs.org/journal/joceah
U6  - https://doi.org/10.1021/Jo0600858
SN  - 4393-4399
ER  - 
TY  - THES
A1  - Robertson, Daniela
T1  - Polymermodifizierte Phospholipid : Vesikel als neuartige Templat-Phase
Y1  - 2006
CY  - Potsdam
ER  - 
TY  - THES
A1  - Holzberger, Anja
T1  - Bestimmung der Konformationen und der Komplexbildungstendenzen von Kronenverbindungen in Lösung unter kombiniertem Einsatz von Kernmagnetischer Resonanzspektriskopie und Molecular Modelling
Y1  - 2006
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Laschewsky, André
A1  - Garnier, Sebastien
A1  - Kirsten, Juliane
A1  - Mertoglu, Murat
A1  - Skrabania, Katja
A1  - Lutz, Jean-Francois
T1  - Comb-like polymeric surfactants by combining block and graft copolymer architectures
Y1  - 2006
SN  - 0065-7727
ER  - 
TY  - THES
A1  - Wattebled, Laurent
T1  - Oligomeric surfactants as novel type of amphiphiles : structure - property relationships and behaviour with additives
T1  - Oligomere Tenside als neuer Typ von Amphiphilen : Struktur-Eigenschaft-Beziehungen und Verhalten mit Additiven.
N2  - The properties of a series of well-defined new surfactant oligomers (dimers to tetramers)were examined. From a molecular point of view, these oligomeric surfactants consist of simple monomeric cationic surfactant fragments coupled via the hydrophilic ammonium chloride head groups by spacer groups (different in nature and length). Properties of these cationic surfactant oligomers in aqueous solution such as solubility, micellization and surface activity, micellar size and aggregation number were discussed with respect to the two new molecular variables introduced, i.e. degree of oligomerization and spacer group, in order to establish structure – property relationships. Thus, increasing the degree of oligomerization results in a pronounced decrease of the critical micellization concentration (CMC). Both reduced spacer length and increased spacer hydrophobicity lead to a decrease of the CMC, but to a lesser extent. For these particular compounds, the formed micelles are relatively small and their aggregation number decreases with increasing the degree of oligomerization, increasing spacer length and sterical hindrance. In addition, pseudo-phase diagrams were established for the dimeric surfactants in more complex systems, namely inverse microemulsions, demonstrating again the important influence of the spacer group on the surfactant behaviour. Furthermore, the influence of additives on the property profile of the dimeric compounds was examined, in order to see if the solution properties can be improved while using less material. Strong synergistic effects were observed by adding special organic salts (e.g. sodium salicylate, sodium vinyl benzoate, etc.) to the surfactant dimers in stoichiometric amounts. For such mixtures, the critical aggregation concentration is strongly shifted to lower concentration, the effect being more pronounced for dimers than for analogous monomers. A sharp decrease of the surface tension can also be attained. Many of the organic anions produce viscoelastic solutions when added to the relatively short-chain dimers in aqueous solution, as evidenced by rheological measurements. This behaviour reflects the formation of entangled wormlike micelles due to strong interactions of the anions with the cationic surfactants, decreasing the curvature of the micellar aggregates. It is found that the associative behaviour is enhanced by dimerization. For a given counterion, the spacer group may also induce a stronger viscosifying effect depending on its length and hydrophobicity. Oppositely charged surfactants were combined with the cationic dimers, too. First, some mixtures with the conventional anionic surfactant SDS revealed vesicular aggregates in solution. Also, in view of these catanionic mixtures, a novel anionic dimeric surfactant based on EDTA was synthesized and studied. The synthesis route is relatively simple and the compound exhibits particularly appealing properties such as low CMC and σCMC values, good solubilization capacity of hydrophobic probes and high tolerance to hard water. Noteworthy, mixtures with particular cationic dimers gave rise to viscous solutions, reflecting the micelle growth.
N2  - Die Eigenschaften einer Reihe gut definierter neuer oligomerer Tenside (von Dimeren bis zu Tetrameren) wurden untersucht. Strukturell bestehen diese oligomeren Tenside aus einfachen monomeren kationischen Tensidfragmenten, die über die hydrophile Kopfgruppe (Tetraalkyl-Ammoniumchlorid) durch „Spacer“-Gruppen unterschiedlicher Natur und Länge miteinander verbunden/gekoppelt sind. Die Eigenschaften dieser kationischen oligomeren Tenside in wässriger Lösung wie Löslichkeit, kritische Mizellbildungskonzentration und Oberflächenaktivität, Mizellgröße und Aggregationszahl werden in Bezug auf die zwei neuen molekularen Variabeln (d.h. dem Oligomerisationsgrad und der Spacer-Gruppe) untersucht, um Struktur-Eigenschafts-Beziehungen abzuleiten. Die Erhöhung des Oligomerizationsgrads verringert stark die kritische Mizellbildungskonzentration (CMC). Eine kurze Spacer-Länge oder ein erhöhte Hydrophobie des Spacers erniedrigt die CMC ebenfalls, aber in einem geringeren Umfang. Die gebildeten Mizellen sind relativ klein und ihre Aggregationszahl nimmt mit zunehmendem Oligomerisationsgrad ab, genau wie mit zunehmender Spacerlänge oder sterischer Behinderung. Außerdem wurden Pseudo-Phasendiagramme für die Gemini-Tenside in komplexen Systemen, nämlich in inversen Mikroemulsionen untersucht. Auch hier zeigt die Spacer-Gruppe einen großen Einfluß auf das Tensidverhalten. Weiterhin wurde der Einfluss von Zusätzen auf das Eigenschaftsprofil der dimeren Tenside untersucht. Starke Synergien wurden beobachtet, wenn man spezielle organische Anionen (z.B. Natriumsalicylat, Natriumvinylbenzoat, etc.) zu den dimeren Tensiden in stöchiometrischen Mengen hinzugibt. Für solche Mischungen wird die Mizellbildungskonzentration stark zu niedrigen Konzentrationen verschoben, wobei der Effekt für die Dimere ausgeprägter als für die analogen Monomere ist. Eine Verringerung der Oberflächenspannung wird ebenfalls erreicht. Gemini-Tenside mit geeigneten Spacer-Gruppen bilden nach Zugabe ausgewählter organischer Anionen viskoelastische Lösungen, selbst wenn die dimeren Tenside nur über relativ kurz Alkylketten verfügen. Dies wurde mittels rheologischer Messungen gezeigt. Dieses Verhalten resultiert aus der Bildung langer Zylinder-Mizellen aufgrund der starken Wechselwirkung der Anionen mit den kationischen Tensiden, die die Krümmung der mizellaren Strukturen verringern. Es wurde auch festgestellt, dass das assoziative Verhalten durch die Dimerisation erhöht wird. Für ein gegebenes Gegenion kann die Spacer-Gruppe den verdickenden Effekt verstärken, in Abhängichkeit von seiner Länge und Hydrophobie. Als weitere Zusätze wurden entgegengesetzt geladene Tenside wurden mit den kationischen Dimeren kombiniert. Einige Mischungen mit dem käuflichen anionischen Tensid SDS bilden Vesikel in Lösung. Mit Blick auf diese katanionischen Mischungen wurde ein neues anionisches Gemini-Tensid, das auf EDTA basiert ist, synthetisiert und charakterisiert. Der Syntheseweg ist relativ einfach und das Tensid zeigt interessante Eigenschaften wie niedrige CMC- und scmc-Werte, gute Solubilisierungskapazität von hydrophoben Substanzen und hohe Toleranz gegen hartes Wasser. Mischungen dieses anionischen Tensids mit bestimmten kationischen Dimeren bilden visköse Lösungen, was ein starkes Mizell-Wachstum widerspiegelt.
KW  - Tenside
KW  - Oligomere
KW  - "Spacer"-Gruppe
KW  - Mizellbildung
KW  - Hydrotrope
KW  - surfactants
KW  - oligomers
KW  - spacer group
KW  - micellization
KW  - hydrotropes
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12855
ER  - 
TY  - THES
A1  - Hildebrandt, Niko
T1  - Lanthanides and quantum dots : time-resolved laser spectroscopy of biochemical Förster Resonance Energy Transfer (FRET) systems
T1  - Lanthanide und Quantenpunkte : zeitaufgelöste Laserspektroskopie an biochemischen Förster-Resonanzenergietransfer (FRET) Systemen
N2  - Förster Resonance Energy Transfer (FRET) plays an important role for biochemical applications such as DNA sequencing, intracellular protein-protein interactions, molecular binding studies, in vitro diagnostics and many others. For qualitative and quantitative analysis, FRET systems are usually assembled through molecular recognition of biomolecules conjugated with donor and acceptor luminophores. Lanthanide (Ln) complexes, as well as semiconductor quantum dot nanocrystals (QD), possess unique photophysical properties that make them especially suitable for applied FRET. In this work the possibility of using QD as very efficient FRET acceptors in combination with Ln complexes as donors in biochemical systems is demonstrated. The necessary theoretical and practical background of FRET, Ln complexes, QD and the applied biochemical models is outlined. In addition, scientific as well as commercial applications are presented. FRET can be used to measure structural changes or dynamics at distances ranging from approximately 1 to 10 nm. The very strong and well characterized binding process between streptavidin (Strep) and biotin (Biot) is used as a biomolecular model system. A FRET system is established by Strep conjugation with the Ln complexes and QD biotinylation. Three Ln complexes (one with Tb3+ and two with Eu3+ as central ion) are used as FRET donors. Besides the QD two further acceptors, the luminescent crosslinked protein allophycocyanin (APC) and a commercial fluorescence dye (DY633), are investigated for direct comparison. FRET is demonstrated for all donor-acceptor pairs by acceptor emission sensitization and a more than 1000-fold increase of the luminescence decay time in the case of QD reaching the hundred microsecond regime. Detailed photophysical characterization of donors and acceptors permits analysis of the bioconjugates and calculation of the FRET parameters. Extremely large Förster radii of more than 100 Å are achieved for QD as acceptors, considerably larger than for APC and DY633 (ca. 80 and 60 Å). Special attention is paid to interactions with different additives in aqueous solutions, namely borate buffer, bovine serum albumin (BSA), sodium azide and potassium fluoride (KF). A more than 10-fold limit of detection (LOD) decrease compared to the extensively characterized and frequently used donor-acceptor pair of Europium tris(bipyridine) (Eu-TBP) and APC is demonstrated for the FRET system, consisting of the Tb complex and QD. A sub-picomolar LOD for QD is achieved with this system in azide free borate buffer (pH 8.3) containing 2 % BSA and 0.5 M KF. In order to transfer the Strep-Biot model system to a real-life in vitro diagnostic application, two kinds of imunnoassays are investigated using human chorionic gonadotropin (HCG) as analyte. HCG itself, as well as two monoclonal anti-HCG mouse-IgG (immunoglobulin G) antibodies are labeled with the Tb complex and QD, respectively. Although no sufficient evidence for FRET can be found for a sandwich assay, FRET becomes obvious in a direct HCG-IgG assay showing the feasibility of using the Ln-QD donor-acceptor pair as highly sensitive analytical tool for in vitro diagnostics.
N2  - Förster Resonanzenergietransfer (FRET) spielt eine wichtige Rolle in biochemischen Anwendungen, wie z.B. DNA-Sequenzierung, intrazellulären Protein-Protein-Wechselwirkungen, molekularen Bindungsstudien, in-vitro-Diagnostik und vielen anderen. Zur quantitativen und qualitativen Analyse werden FRET Systeme normalerweise durch molekulare Erkennung von Biomolekülen, die mit Donator- und Acceptorluminophoren markiert sind, ermöglicht. Durch die besonderen photophysikalischen Eigenschaften sowohl von Lanthanidkomplexen (Ln-Komplexen), als auch Halbleiternanokristallen (sog. Quantenpunkten oder Quantumdots - QD), sind diese besonders für FRET Anwendungen geeignet. In der vorliegenden Arbeit wird effizienter FRET zwischen Ln-Komplexen und QD in biochemischen Systemen demonstriert. Die notwendigen theoretischen und praktischen Grundlagen über FRET, Ln-Komplexe, QD und die verwendeten biochemischen Modelle werden dargestellt, und wissenschaftliche als auch kommerzielle Anwendungen werden präsentiert. FRET kann zur Messung von strukturellen Veränderungen und Dynamiken im Bereich von ca. 1 bis 10 nm verwendet werden. Der sehr starke und gut charakterisierte Bindungsprozess zwischen Streptavidin (Strep) und Biotin (Biot) wird als biomolekulares Modellsystem eingesetzt. Ein FRET System wird durch Streptavidinkonjugation mit Ln-Komplexen und QD-Biotinylierung etabliert. Drei Ln-Komplexe (einer mit Tb3+ und zwei mit Eu3+ als Zentralion) werden als Donatoren verwendet, und neben QD werden zwei weitere Acceptoren, das lumineszierende, quervernetzte Protein Allophycocyanin (APC) und ein kommerzieller Fluoreszenzfarbstoff (DY633), untersucht. FRET kann für alle Donator-Acceptor Paare nachgewiesen werden, zum einen durch sensibilisierte Acceptorlumineszenz und zum anderen durch eine über 1000-fach erhöhte Lumineszenzabklingzeit der QD mit über 100 Mikrosekunden. Mittels detailierter photophysikalischer Charakterisierung der Donatoren und Acceptoren können die Biokonjugate analysiert und die FRET Parameter berechnet werden. Für die QD FRET Systeme ergeben sich extrem große Försterradien von über 100 Å, die wesentlich größer sind als für APC und DY633 (ca. 80 bzw. 60 Å). Besondere Aufmerksamkeit gilt der Wechselwirkung mit den Zusatzreagenzien Boratpuffer, Bovines Serumalbumin (BSA), Natriumazid und Kaliumfluorid (KF) in den wässrigen Lösungen. Im Vergleich zum ausgiebig charakterisierten und vielfach verwendeten Donator-Acceptor Paar aus Europium-tris(Bipyridin) (Eu-TBP) und APC wird eine mehr als 10-fache Senkung der Nachweisgrenze für das FRET-System, bestehend aus Tb-Komplex und QD, erreicht. In azidfreiem Boratpuffer (pH 8,3) mit 2 % BSA und 0,5 M KF wird eine subpicomolare QD-Nachweisgrenze für dieses System aufgezeigt. Um den Transfer des Strep-Biot Modellsystems in eine echte in-vitro-diagnostische Anwendung zu demonstrieren, werden zwei Immuntests zum HCG-(Humanes Choriongonadotropin)-Nachweis untersucht. Sowohl HCG als auch monoklonale anti-HCG Maus-IgG-(Immunoglobulin G)-Antikörper werden mit dem Tb-Komplex bzw. mit QD markiert. Obwohl kein ausreichender Nachweis für FRET in einem immunometrischen Assay (oder Sandwichassay) erbracht werden kann, wird FRET in einem direkten HCG-IgG Assay erzielt, wodurch die Realisierbarkeit von Ln-QD Donator-Acceptor Paaren zur hochsensitiven Anwendung in der in-vitro-Diagnostik gezeigt werden kann.
KW  - FRET
KW  - Lanthanide
KW  - Quantenpunkte
KW  - Zeitaufgelöster Immunoassay
KW  - Spektroskopie
KW  - FRET
KW  - Lanthanides
KW  - Quantum Dots
KW  - Time-resolved Immunoassay
KW  - Spectroscopy
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12686
ER  - 
TY  - THES
A1  - Mauser, Tatjana
T1  - Multilayer capsules with stimuli-sensitive properties : pH-response and carbohydrate-sensing
T1  - Multischicht-Hohlkugeln mit stimulisensitiven Eigenschaften : Auswirkungen von pH-Wert- und Zuckerkonzentrationsänderungen
N2  - Polyelectrolyte microcapsules containing stimuli-responsive polymers have potential applications in the fields of sensors or actuators, stimulable microcontainers and controlled drug delivery. Such capsules were prepared, with the focus on pH-sensitivity and carbohydrate-sensing. First, pH-responsive polyelectrolyte capsules were produced by means of electrostatic layer-by-layer assembly of oppositely charged weak polyelectrolytes onto colloidal templates that were subsequently removed. The capsules were composed of poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) or poly(4-vinylpyridine) (P4VP) and PMA and varied considerably in their hydrophobicity and the influence of secondary interactions. These polymers were assembled onto CaCO3 and SiO2 particles with diameters of ~ 5 µm, and a new method for the removal of the silica template under mild conditions was proposed. The pH-dependent stability of PAH/PMA and P4VP/PMA capsules was studied by confocal laser scanning microscopy (CLSM). They were stable over a wide pH-range and exhibited a pronounced swelling at the edges of stability, which was attributed to uncompensated positive or negative charges within the multilayers. The swollen state could be stabilized when the electrostatic repulsion was counteracted by hydrogen-bonding, hydrophobic interactions or polymeric entanglement. This stabilization made it possible to reversibly swell and shrink the capsules by tuning the pH of the solution. The pH-dependent ionization degree of PMA was used to modulate the binding of calcium ions. In addition to the pH-sensitivity, the stability and the swelling degree of these capsules at a given pH could be modified, when the ionic strength of the medium was altered. The reversible swelling was accompanied by reversible permeability changes for low and high molecular weight substances. The permeability for glucose was evaluated by studying the time-dependence of the buckling of the capsule walls in glucose solutions and the reversible permeability modulation was used for the encapsulation of polymeric material. A theoretical model was proposed to explain the pH-dependent size variations that took into account an osmotic expanding force and an elastic restoring force to evaluate the pH-dependent size changes of weak polyelectrolyte capsules. Second, sugar-sensitive multilayers were assembled using the reversible covalent ester formation between the polysaccharide mannan and phenylboronic acid moieties that were grafted onto poly(acrylic acid) (PAA). The resulting multilayer films were sensitive to several carbohydrates, showing the highest sensitivity to fructose. The response to carbohydrates resulted from the competitive binding of small molecular weight sugars and mannan to the boronic acid groups within the film, and was observed as a fast dissolution of the multilayers, when they were brought into contact with the sugar-containing solution above a critical concentration. It was also possible to prepare carbohydrate-sensitive multilayer capsules, and their sugar-dependent stability was investigated by following the release of encapsulated rhodamine-labeled bovine serum albumin (TRITC-BSA).
N2  - Die Entwicklung von stimulisensitiven Systemen hat in den vergangenen Jahren großes Interesse hervorgerufen. Diese Systeme verändern ihre Eigenschaften in Abhängigkeit von äußeren Einflüssen und haben potenzielle Anwendungsgebiete im Bereich von Sensoren und der kontrollierten Wirkstofffreisetzung. Beispiele für äußere Einflüsse sind die Temperatur, die Salzkonzentration der Lösung, der pH-Wert oder die Gegenwart bestimmter chemischer Substanzen. Polyelektrolyt-Multischicht-Hohlkugeln stellen viel versprechende stimulisensitive Systeme dar, da sie aus dünnen Membranen mit veränderbaren Eigenschaften aufgebaut sind, und eingekapselte Substanzen definiert freigesetzt werden können. Im Rahmen dieser Arbeit wurden zum einen Polyelektrolytkapseln untersucht, deren Stabilität, Größe und Durchlässigkeit abhängig ist vom pH-Wert und der Salzkonzentration der Lösung. Zum anderen wurden Hohlkugeln entwickelt, deren Stabilität durch die Gegenwart verschiedener Zucker in der umgebenden Lösung beeinflusst wurde. Hierbei war es möglich, eine eingekapselte Substanz in Abhängigkeit der Zuckerkonzentration der Lösung freizusetzen. pH-sensitive Polyelektrolyt-Hohlkugeln wurden mit Hilfe der elektrostatischen Layer-by-Layer Methode aufgebaut. Hierbei wurden abwechselnd schwache Polysäuren und Polybasen auf kolloidalen Partikeln adsorbiert und in einem weiteren Schritt wurde das Templat entfernt. Als Polyelektrolyte fanden Poly(allylaminhydrochlorid) (PAH) und Poly(methacrylsäure) (PMA) bzw. Poly(4-vinylpyridin) (P4VP) und PMA Verwendung. Diese zwei Systeme unterscheiden sich in ihren hydrophoben Eigenschaften und dem Einfluss von Sekundärwechselwirkungen. Die Polymere wurden auf CaCO3 und SiO2 Partikeln mit Durchmessern von ~ 5 µm aufgebracht, und eine neue Methode zum Entfernen des Silica-Templats wurde vorgestellt. Die pH-abhängige Stabilität von PAH/PMA und P4VP/PMA Hohlkugeln wurde mit der konfokalen Fluoreszenzmikroskopie untersucht. Beide Systeme waren über einen breiten pH-Bereich stabil und zeigten an der Grenze der Stabilität ein ausgeprägtes Schwellen, das den unkompensierten positiven oder negativen Ladungen der Mulitschichten zugeordnet werden konnte. Gab es innerhalb der Multischichten stabilisierende Wechselwirkungen, z.B. Wasserstoffbrückenbindungen oder hydrophobe Anziehungskräfte, welche der elektrostatischen Destabilisierung entgegenwirkten, so ließ sich der geschwollene Zustand stabilisieren. Diese Stabilisierung ermöglichte das reversible Schwellen der Hohlkugeln durch Veränderung des pH-Wertes der Lösung. Der pH-abhängige Ionisationsgrad von PMA wurde zur Bindung von Calcium-Ionen verwendet. Die Stabilität und das Schwellen der Hohlkugeln konnten durch Variation der Ionenstärke der Lösung modifiziert werden. Das reversible Schwellen wurde von reversiblen Permeabilitätsänderungen für nieder- und hochmolekulare Substanzen begleitet. Die Permeabilität für Glucose wurde mit Hilfe der Zeitabhängigkeit der Verformung der Kapselmembranen in Glucoselösungen untersucht, und die reversible Veränderung der Permeabilität wurde zur Einkapselung von Polymeren verwendet. Die pH-abhängigen Größenänderungen ließen sich mit einem theoretischen Modell beschreiben, das von einem Kräftegleichgewicht zwischen einer osmotischen expansiven Kraft und einer elastischen kontraktiven Kraft ausging. Als zweites stimulisensitives System wurden zuckersensitive Multischichten untersucht. Diese wurden über reversible kovalente Esterbindungen stabilisiert. Als Polymere für den Schichtaufbau fanden das Polysaccharid Mannan und Polyacrylsäure, die mit Aminophenylboronsäure modifiziert war, Verwendung. Die daraus entstehenden Multischichten waren sensitiv gegenüber verschiedenen Kohlenhydraten, mit der größten Selektivität für Fructose. Diese Affinitäten ergaben sich aus der kompetitiven Bindung zwischen niedermolekularen Zuckern und Mannan an die Boronsäuregruppen. Oberhalb einer kritischen Zuckerkonzentration kam es zur schnellen Auflösung der Multischichten. Darüber hinaus war es möglich zuckersensitive Polymerkapseln herzustellen, deren zuckerabhängige Stabilität durch die Freisetzung von eingekapseltem Rinderserumalbumin verfolgt wurde.
KW  - layer-by-layer
KW  - stimuli-response
KW  - polyelectrolyte
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12529
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  - Engelhard, Sonja
A1  - Kumke, Michael Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - OPQS – optical process and quality sensing : exemplary applications in the beerbrewing and polyurethane foaming processes
N2  - Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near-infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 004 
KW  - process analytical technology
KW  - beer
KW  - biomass
KW  - foam analysis
KW  - NIR spectroscopy
KW  - fluorescence quenching
KW  - photon density wave spectroscopy
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12191
ER  - 
TY  - GEN
A1  - Schmälzlin, Elmar
A1  - Walz, Bernd
A1  - Klimant, Ingo
A1  - Schewe, Bettina
A1  - Löhmannsröben, Hans-Gerd
T1  - Monitoring hormone-induced oxygen consumption in the salivary glands of the blowfly, Calliphora vicina, by use of luminescent microbeads
N2  - The salivary glands of the blowfly were injected with luminescent oxygen-sensitive microbeads. The changes in oxygen content within individual gland tubules during hormone-induced secretory activity were quantified. The measurements are based on an upgraded phase-modulation technique, where the phase shift of the sensor phosphorescence is determined independently from concentration and background signals. We show that the combination of a lock-in amplifier with a fluorescence microscope results in a convenient setup to measure oxygen concentrations within living animal tissues at the cellular level.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 006 
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12206
ER  - 
TY  - GEN
A1  - Hildebrandt, Nico
A1  - Charbonnière, Loïc J.
A1  - Ziessel, Raymond F.
A1  - Löhmannsröben, Hans-Gerd
T1  - Quantum dots as resonance energy transfer acceptors for monitoring biological interactions
N2  - Quantum dots (QDs) are common as luminescing markers for imaging in biological applications because their optical properties seem to be inert against their surrounding solvent. This, together with broad and strong absorption bands and intense, sharp tuneable luminescence bands, makes them interesting candidates for methods utilizing Forster Resonance Energy Transfer (FRET), e. g. for sensitive homogeneous fluoroimmunoassays (FIA). In this work we demonstrate energy transfer from Eu3+-trisbipyridin (Eu-TBP) donors to CdSe-ZnS-QD acceptors in solutions with and without serum. The QDs are commercially available CdSe-ZnS core-shell particles emitting at 655 nm (QD655). The FRET system was achieved by the binding of the streptavidin conjugated donors with the biotin conjugated acceptors. After excitation of Eu-TBP and as result of the energy transfer, the luminescence of the QD655 acceptors also showed lengthened decay times like the donors. The energy transfer efficiency, as calculated from the decay times of the bound and the unbound components, amounted to 37%. The Forster-radius, estimated from the absorption and emission bands, was ca. 77Å. The effective binding ratio, which not only depends on the ratio of binding pairs but also on unspecific binding, was obtained from the donor emission dependent on the concentration. As serum promotes unspecific binding, the overall FRET efficiency of the assay was reduced. We conclude that QDs are good substitutes for acceptors in FRET if combined with slow decay donors like Europium. The investigation of the influence of the serum provides guidance towards improving binding properties of QD assays.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 012 
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12213
ER  - 
TY  - THES
A1  - Note, Carine
T1  - Influence of hydrophobically modified polyelectrolytes on nanoparticle synthesis in self-organized systems and in water
T1  - Einfluss von hydrophob modifizierten Polyelektrolyten auf die Nanopartikelsynthese in selbst-organisierten Systemen und in Wasser
N2  - The formation of colloids by the controlled reduction, nucleation, and growth of inorganic precursor salts in different media has been investigated for more than a century. Recently, the preparation of ultrafine particles has received much attention since they can offer highly promising and novel options for a wide range of technical applications (nanotechnology, electrooptical devices, pharmaceutics, etc). The interest derives from the well-known fact that properties of advanced materials are critically dependent on the microstructure of the sample. Control of size, size distribution and morphology of the individual grains or crystallites is of the utmost importance in order to obtain the material characteristics desired. Several methods can be employed for the synthesis of nanoparticles. On the one hand, the reduction can occur in diluted aqueous or alcoholic solutions. On the other hand, the reduction process can be realized in a template phase, e.g. in well-defined microemulsion droplets. However, the stability of the nanoparticles formed mainly depends on their surface charge and it can be influenced with some added protective components. Quite different types of polymers, including polyelectrolytes and amphiphilic block copolymers, can for instance be used as protecting agents. The reduction and stabilization of metal colloids in aqueous solution by adding self-synthesized hydrophobically modified polyelectrolytes were studied in much more details. The polymers used are hydrophobically modified derivatives of poly(sodium acrylate) and of maleamic acid copolymers as well as the commercially available branched poly(ethyleneimine). The first notable result is that the polyelectrolytes used can act alone as both reducing and stabilizing agent for the preparation of gold nanoparticles. The investigation was then focused on the influence of the hydrophobic substitution of the polymer backbone on the reduction and stabilization processes. First of all, the polymers were added at room temperature and the reduction process was investigated over a longer time period (up to 8 days). In comparison, the reduction process was realized faster at higher temperature, i.e. 100°C. In both cases metal nanoparticles of colloidal dimensions can be produced. However, the size and shape of the individual nanoparticles mainly depends on the polymer added and the temperature procedure used. In a second part, the influence of the prior mentioned polyelectrolytes was investigated on the phase behaviour as well as on the properties of the inverse micellar region (L2 phase) of quaternary systems consisting of a surfactant, toluene-pentanol (1:1) and water. The majority of the present work has been made with the anionic surfactant sodium dodecylsulfate (SDS) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) since they can interact with the oppositely charged polyelectrolytes and the microemulsions formed using these surfactants present a large water-in-oil region. Subsequently, the polymer-modified microemulsions were used as new templates for the synthesis of inorganic particles, ranging from metals to complex crystallites, of very small size. The water droplets can indeed act as nanoreactors for the nucleation and growth of the particles, and the added polymer can influence the droplet size, the droplet-droplet interactions, as well as the stability of the surfactant film by the formation of polymer-surfactant complexes. One further advantage of the polymer-modified microemulsions is the possibility to stabilize the primary formed nanoparticles via a polymer adsorption (steric and/or electrostatic stabilization). Thus, the polyelectrolyte-modified nanoparticles formed can be redispersed without flocculation after solvent evaporation.
N2  - Die Bildung von Kolloiden durch kontrollierte Reduktion, durch Keimbildung und durch Wachstum anorganischer Precurser in unterschiedlichen Medien wird seit mehr als einem Jahrhundert intensiv beforscht. Vor kurzem hat die Herstellung ultrafeiner Partikel viel Aufmerksamkeit errungen, da sich hieraus vielversprechende neue Möglichkeiten für ein breites Spektrum an technischen Anwendungen (Nanotechnologie, elektrooptische Materialen, Pharmazeutik, usw.) ergeben. Das Interesse leitet sich von der weithin bekannten Tatsache ab, dass die Eigenschaften der „advanced materials“ von der Mikrostruktur der Probe deutlich abhängig sind. Die gezielte Steuerung der Größe, der Größenverteilung und der Morphologie der einzelnen Keime oder Kristallite ist von größter Wichtigkeit, um die gewünschten Eigenschaften zu erreichen. Verschiedene Methoden können für die Synthese von Nanopartikel verwendet werden. Einerseits kann eine Reduktion in verdünnten wässrigen oder alkoholischen Lösungen stattfinden, andererseits kann der Reduktionsprozess in einer Templatphase, z.B. in definierten Mikroemulsionströpfchen stattfinden. Die Stabilität der produzierten Nanopartikel hängt hauptsächlich von ihrer Oberflächenladung ab, welche durch schützende Komponenten zusätzlich beeinflusst werden kann. Verschiedene Arten von Polymeren, einschließlich Polyelektrolyte und amphiphile Blockcopolymere, können als solche Komponenten benutzt werden. Die Reduktion und Stabilisierung von Metallkolloiden in der wässrigen Lösung durch Addition von hydrophob modifizierten Polyelektrolyten werden bereits ausführlich studiert. Die verwendeten Polymere sind hydrophob modifizierte Derivate des Natrium-Polyacrylat, der Maleinsäure Copolymere sowie das verzweigte Poly(ethylenimin). Erstaunlicherweise genügt bereits die Anwesenheit die verwendeten Polyelektrolyte zu Reduzierung und Stabilisierung der Goldnanopartikel. Darüber hinaus wurde der Einfluss der hydrophoben Seitenkette des Polymer auf den Reduktions- und Stabilisierungsprozess bei unterschiedliche Reaktionstemperatur untersucht. In beiden Fällen können Metallnanopartikel kolloidaler Größe hergestellt werden, jedoch hängt die Größe und die Form der einzelnen Nanopartikel hauptsächlich vom dem zugefügten Polymer und vom verwendeten Temperaturverfahren ab. Im zweiten Teil wurde der Einfluss der vorher erwähnten Polyelektrolyte auf das Phaseverhalten sowie auf die Eigenschaften der inversen mizellaren Region (L2 Phase) der quaternären Systeme untersucht, die aus einem Tensid, Toluol-Pentanol – Gemisch (1:1) sowie Wasser bestehen. Dabei wurden hauptsächlich ionische Tenside, wie z.B. das anionische Natriumdodecylsulfate (SDS) und das kationische Cetyltrimethylammonium-bromid (CTAB) verwendet, da sie mit den geladenen Polyelektrolyten wechselwirken können. Darüber hinaus wurden die polymer-modifizierten Mikroemulsionen als neue Template für die Synthese von anorganischen Nanopartikeln verwendet. Die Wassertröpfchen können in der Tat als Nanoreaktoren für die Keimbildung und das Wachstum der Partikel dienen, und das zugefügte Polymer kann die Tröpfchengröße, die Tröpfchen-Tröpfchen Wechselwirkungen, sowie die Stabilität des Tensidfilms durch Polyelektrolyt-Tensid Komplexbildung beeinflussen. Ein weiterer Vorteil der polymer-modifizierten Mikroemulsionen ist die Stabilizierung der produzierten Primärteilchen über eine Polymeradsorption (durch sterische bzw. elektrostatische Stabilisierung), welche eine Redispergierung der Polyelektrolyte-modifiziert Nanopartikel, nach Lösungsmittel-verdampfung, ohne Aggregation der Partikel erlaubt.
KW  - Mikroemulsion
KW  - Nanopartikel
KW  - Polyelektrolyte
KW  - microemulsion
KW  - polyelectrolyte
KW  - nanoparticle
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11670
ER  - 
TY  - THES
A1  - Peikow, Dirk
T1  - Synthese und Glycosidasehemmung von Thio-analogen Kohlenhydraten
T1  - Synthesis and glycosidase inhibition of thio-analogues carbohydrates
N2  - Chitin ist ein Polysaccharid, welches aus N-Acetylglucosamin (GlcNAc) aufgebaut ist. Das Biopolymer kommt in der Natur in Invertebraten, Algen, Pilzen und Einzellern vor. Chitinasen hydrolysieren Chitin. Diese Enzyme sind essentiell für die Regulierung und Entwicklung von Arthropoden und Mikroorganismen. Sie fungieren in Pflanzen als Phytoalexine.  Das verstärkt das Interesse am Design neuer natürlicher und synthetischer Chitinase-inhibitoren, die als potentielle Insektizide, Fungizide, Antimalaria bzw. Antiasthmatika eingesetzt werden können.  Ziel dieser Arbeit war die Synthese von neuen Thioglycosidanaloga von N-Acetyl-chitooligosacchariden und deren Untersuchung als Enzyminhibitoren.  Die geschützten 4-O-Tf-galactopyranosylthioglycoside wurden aus den korrespondierenden p-Methoxyphenylglycosiden von GlcNAc nach einer neuen Methode in einer Stufe hergestellt. Die Reaktion der galacto-Triflate mit 2-Acetamido-3,4,6-tri-O-acetyl-2-desoxy-1-thio-ß-D-glucopyranose in Gegenwart von Natriumhydrid und 15-Krone-5 in THF lieferte die Pseudo-Trisaccharide. Die Herstellung der Glycosyl-Thiazoline aus den entsprechenden p-Methoxyphenyl-glycosiden mit Lawesson's Reagenz ist nach einem neuen Reaktionsweg beschrieben wie auch die Synthese der Thioacetamide von GlcNAc-Oligomeren. Die Pseudo-Oligosaccharide wurden als Inhibitoren der Chitinasen von Serratia marcescens, Chironomus tentans, Acanthocheilonema viteae und Hevaea brasiliensis sowie der N-Acetyl-glucosaminidase von Chironomus tentans getestet. In einigen Fällen ergab sich eine Hemmung (IC50) im µM-Bereich.
N2  - Chitin is a polysaccharide composed of N-acetylglucosamine (GlcNAc). The biopolymer is distributed in Invertebrates, algae, fungi and Protozoa. Chitinases hydrolyse chitin. These enzymes are essential for the regulation and development of Arthropoda and micro organisms. In bacteria chitinase degrade chitin as source of carbon and act in plants as phytoalexins. Currently, there is a great interest in the design of novel natural and synthetic chitinase inhibitors, which may act as potential insecticides, fungicides, antimalaria or antiasthmatics. Thio-oligosaccharides and related thio-glycosides are rarely described in the literature. Thio-analogues of oligosaccharides derived from N-acetylglucosamine are of interest as potential enzyme inhibitors. The synthesis and enzymatic investigations of thio-glycoside analogues of N-acetyl-chitooligosaccharides are described in this thesis. The protected 4-O-Tf-galactopyranosyl thioglycosides were prepared by a new method in one step from the corresponding p-methoxyphenyl glycosides of N-acetylglucosamine. Coupling of galacto-triflates with 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-1-thio-ß-D-glucopyranose in the presence of sodium hydride and 15-crown-5 in THF, followed by deprotection, afforded the pseudo-trisaccharides.  The preparation of glycosyl thiazolines by a new manner from the analogues p-methoxyphenyl glycosides with Lawesson's reagent is also described however the synthesis of thioacetamides of N-acetylglucosamine. The pseudo-oligosaccharides were tested for inhibition of chitinases from Serratia marcescens, Chironomus tentans, Acanthocheilonema viteae, and Hevaea brasiliensis, and also with N-acetyl-glucosaminidase from Chironomus tentans. Inhibition with IC50 values in the µM range was found in a few cases.
KW  - Chitin
KW  - Chitinasen
KW  - N-Acetyl-chitooligosaccharide
KW  - Thioglycoside
KW  - potentielle Chitinaseinhibitoren
KW  - chitin
KW  - chitinase
KW  - N-acetyl-chitooligosaccharides
KW  - thio-glycosides
KW  - potential chitinase inhibitors
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-11192
ER  - 
TY  - THES
A1  - Meyer, Matthias
T1  - PIPOX-PEP : kontrollierte Synthese und Aggregationsverhalten von Blockcopolymeren mit schaltbarer Hydrophilie
T1  - PIPOX-PEP : controlled synthesis and aggregation behaviour of blockcopolymers with switchable hydrophilicity
N2  - Es wurden Poly(2-isopropyl-2-oxazolin)-Makroinitiatoren mit terminaler Ammoniumtrifluoracetat-Endgruppe synthetisiert, die anschließend für die Ammonium vermittelte NCA Polymerisation in NMP eingesetzt wurden. Die hierbei synthetisierten Poly(2-isopropyl-2-oxazolin)-block-poly(L-glutamat) (PIPOX-PEP) Blockcopolymere hatten eine Molekulargewichtsverteilung von 1,2 (UZ). Es wurde beobachtet, dass Poly(2-isopropyl-2-oxazolin) bei langen Zeiten oberhalb der LCST irreversibel sphärische Strukturen bildet, die eine hierarchische Struktur besitzen und bei denen es sich möglicherweise um "large compound micelles" handelt. PIPOX-PEP kann in wässeriger Lösung bei langen Zeiten oberhalb der LCST "cottonball" Strukturen bilden. Die Aggregate wurden mittels Lichtstreuung, NMR und TEM charakterisiert. Im Rahmen der Arbeit wurden Strukturbildungsmodelle entwickelt.
N2  - A convenient procedure for the synthesis of well-defined poly(2-isopropyl-2-oxazoline)-block-poly(L-glutamate) (PIPOX-PEP) through combined cationic/anionic ring-opening polymerization is described. The key step is the preparation of an ω-(ammonium trifluoroacetate)-poly(2-isopropyl-2-oxazoline), which is used as a macroinitiator for the “ammonium-mediated” polymerization of γ-benzyl L-glutamate N-carboxyanhydride (NCA). PIPOX is a thermoresponsive polymer exhibiting a lower critical solution temperature (LCST) near human body temperature, while PEP responds to changes in pH (helix-to-coil transition). The phase behavior of aqueous PIPOX and PIPOX-PEP solutions has been characterized by means of light scattering, NMR spectroscopy, and transmission electron microscopy (TEM). Phase transition is usually reversible, but renders irreversible when solution are annealed for longer times at 65 °C, far above the LCST. Coagulate particles with hierarchical ordering in the range of nanometers to micrometers, considered as “large compound micelles” or “cottonballs”, are then produced. A tentative mechanism for the formation of such particles is described.
KW  - Polymer
KW  - Polyoxazolin
KW  - Polypeptid
KW  - Aggregate
KW  - polyoxazoline
KW  - polypeptide
KW  - aggregate
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10832
ER  - 
TY  - THES
A1  - Rettig, Hartmut Arnim
T1  - Methoden zur Synthese von definierten bioorganisch-synthetischen Blockcopolymeren
T1  - Pathways to defined bioorganic-synthetic conjugates
N2  - Bioorganisch-synthetische Blockcopolymere sind sowohl für die Materialwissenschaft als auch für die Medizin hochinteressant. Diese Arbeit beschäftigte sich mit neuen Synthesewegen für die Herstellung dieser Blockcopolymere. Zunächst wurde der klassische Ansatz zur Herstellung eines Blockcopolymers über die Kupplung der beiden Segmente aufgegriffen. Hierzu wurde eine Methode zur Synthese von selektiv säureendfunktionalisierten Polyacrylaten mittels einer terminalen Benzylesterschutzgruppe vorgestellt. Für die Herstellung von bioorganisch-synthetischen Blockcopolymeren mit einem größeren Polymersegment wurde daher ein anderer Syntheseansatz entwickelt. Dieser geht von einem funktionalisierten Oligopeptid aus, an dem durch Polymerisation das synthetische Segment aufgebaut wird. Der Aufbau erfolgte durch kontrolliert radikalische Polymerisation, um ein möglichst definiertes Segment zu erhalten. Zunächst wurde eine Synthese von Oligopeptid-Makroinitiatoren für die ATRP-Polymerisation durchgeführt. Es konnte gezeigt werden, dass in geeigneten polaren Lösungsmitteln (DMSO, DMF) eine Polymerisation mit dem ATRP-Oligopeptid-Makroinitiator erfolgreich ist. Allerdings treten während der Polymerisation Wechselwirkungen zwischen dem Katalysator und dem Oligopeptid auf. Eine Alternative bietet die RAFT-Polymerisation, da sie ohne einen Katalysator durchgeführt wird. Es gelang ausgehend von dem Oligopeptid-ATRP-Makroinitiator den Überträger herzustellen. Die RAFT-Polymerisation mit einem Oligopeptidüberträger stellt eine wichtige Methode für die Herstellung von bioorganisch-synthetischen Blockcopolymeren dar. Sie besitzt eine hohe Toleranz gegenüber funktionellen Gruppen. Die so hergestellten Blockcopolymere sind frei von Verunreinigungen, wie z.B. Übergangsmetallen. Dabei läßt sich das Molekulargewicht des synthetischen Blocks bei einer Polydispersität um 1,2 gut kontrollieren.
N2  - Bioorganic – synthetic conjugates have received a lot of attention concerning their potentials in the fields of material science, pharmaceutics and medicine. This work presents new synthetic routes to these conjugates. For conjugates consisting of small blocks an approach via coupling is possible. For larger blocks it was necessary to develop a different approach via controlled radical polymerisation methods. To begin with oligopeptide macroinitiators for Atom Transfer Radical Polymerisation were synthesized and successful applied in polymerization. The reaction conditions were optimized by studying the polymerisation kinetics. Although the polymerization results in well-defined products, interactions between the copper catalyst and the peptide are evident and cannot be suppressed. To overcome this problem the polymerization method had to be changed. Therefore oligopeptide-based reversible addition fragmentation transfer (RAFT) agents were developed. Well-defined conjugates comprising sequenz-defined peptides and synthetic polymers could be accessed by applying RAFT polymerization techniques in combination with the peptide macrotransfer agents. Polymerization reactions of n-butyl acrylate were performed in solution, yielding peptide-polymer conjugates with controllable molecular weight and low polydispersities.
KW  - ATRP
KW  - ATRP
KW  - RAFT
KW  - Blockcopolymer
KW  - Peptid
KW  - Makroinitiator
KW  - ATRP
KW  - RAFT
KW  - conjugates
KW  - peptide
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10293
ER  - 
TY  - GEN
A1  - Niederkrüger, Matthias
A1  - Salb, Christian
A1  - Beck, Michael
A1  - Hildebrandt, Niko
A1  - Löhmannsröben, Hans-Gerd
A1  - Marowsky, Gerd
T1  - Improvement of a fluorescence immunoassay with a compact diode-pumped solid state laser at 315 nm
N2  - We demonstrate the improvement of fluorescence immunoassay (FIA) diagnostics in deploying a newly developed compact diode-pumped solid state (DPSS) laser with emission at 315 nm. The laser is based on the quasi-three-level transition in Nd:YAG at 946 nm. The pulsed operation is either realized by an active Q-switch using an electro-optical device or by introduction of a Cr<SUP>4+</SUP>:YAG saturable absorber as passive Q-switch element. By extra-cavity second harmonic generation in different nonlinear crystal media we obtained blue light at 473 nm. Subsequent mixing of the fundamental and the second harmonic in a β-barium-borate crystal provided pulsed emission at 315 nm with up to 20 μJ maximum pulse energy and 17 ns pulse duration. Substitution of a nitrogen laser in a FIA diagnostics system by the DPSS laser succeeded in considerable improvement of the detection limit. Despite significantly lower pulse energies (7 μJ DPSS laser versus 150 μJ nitrogen laser), in preliminary investigations the limit of detection was reduced by a factor of three for a typical FIA.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 016 
KW  - Immunoassay
KW  - Fluoreszenz-Resonanz-Energie-Transfer
KW  - Neodym-YAG-Laser
KW  - 946 nm
KW  - 473 nm
KW  - 315 nm
KW  - gepulster DPSS Laser
KW  - sättigbarer Absorber
KW  - fluorescence immunoassay
KW  - 946 nm
KW  - 473 nm
KW  - 315 nm
KW  - pulsed DPSS laser
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10150
ER  - 
TY  - GEN
A1  - Lau, Steffen
A1  - Salffner, Katharina
A1  - Löhmannsröben, Hans-Gerd
T1  - Isotopic resolution of carbon monoxide and carbon dioxide by NIR diode laser spectroscopy
N2  - Near-infrared (NIR) absorption spectroscopy with tunable diode lasers allows the simultaneous detection of the three most important isotopologues of carbon dioxide (<SUP>12</SUP>CO<SUB>2</SUB>, <SUP>13</SUP>CO<SUB>2</SUB>, <SUP>12</SUP>C<SUP>18</SUP>O<SUP>16</SUP>O) and carbon monoxide (<SUP>12</SUP>CO, <SUP>13</SUP>CO, <SUP>12</SUP>C<SUP>18</SUP>O). The flexible and compact fiber-optic tunable diode laser absorption spectrometer (TDLAS) allows selective measurements of CO<SUB>2</SUB> and CO with high isotopic resolution without sample preparation since there is no interference with water vapour. For each species, linear calibration plots with a dynamic range of four orders of magnitude and detection limits (LOD) in the range of a few ppm were obtained utilizing wavelength modulation spectroscopy (WMS) with balanced detection in a Herriott-type multipass cell. The high performance of the apparatus is illustrated by fill-evacuation-refill cycles.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 017 
KW  - Isotop
KW  - Kohlenmonoxid
KW  - Kohlendioxid
KW  - Diodenlaserspektroskopie
KW  - isotope
KW  - carbon monoxide
KW  - carbon dioxide
KW  - diode laser spectroscopy
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10135
ER  - 
TY  - GEN
A1  - Löhmannsröben, Hans-Gerd
A1  - Beck, Michael
A1  - Hildebrandt, Niko
A1  - Schmälzlin, Elmar
A1  - van Dongen, Joost T.
T1  - New challenges in biophotonics : laser-based fluoroimmuno analysis and in-vivo optical oxygen monitoring
N2  - Two examples of our biophotonic research utilizing nanoparticles are presented, namely laser-based fluoroimmuno analysis and in-vivo optical oxygen monitoring. Results of the work include significantly enhanced sensitivity of a homogeneous fluorescence immunoassay and markedly improved spatial resolution of oxygen gradients in root nodules of a legume species.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 018 
KW  - Sauerstoff
KW  - Quantenpunkt
KW  - Lumineszenz
KW  - Immunoassay
KW  - Energietransfer
KW  - Fluoreszenz-Resonanz-Energie-Transfer
KW  - Nanopartikel
KW  - Lanthanoide
KW  - Optode
KW  - Förster Resonanz Energie Transfer
KW  - Biophotonik
KW  - biophotonics
KW  - nanoparticles
KW  - immunoassay
KW  - oxygen
KW  - optode
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10120
ER  - 
TY  - THES
A1  - Ba, Jianhua
T1  - Nonaqueous synthesis of metal oxide nanoparticles and their assembly into mesoporous materials
T1  - Nichtwässrige Synthese von Metalloxid-Nanopartikeln und deren Anordnung zu mesoporösen Materialien
N2  - This thesis mainly consist of two parts, the synthesis of several kinds of technologically interesting crystalline metal oxide nanoparticles via nonaqueous sol-gel process and the formation of mesoporous metal oxides using some of these nanoparticles as building blocks via evaporation induced self-assembly (EISA) technique.  In the first part, the experimental procedures and characterization results of successful syntheses of crystalline tin oxide and tin doped indium oxide (ITO) nanoparticles are reported. SnO2 nanoparticles exhibit monodisperse particle size (3.5 nm in average), high crystallinity and particularly high dispersibility in THF, which enable them to become the ideal particulate precursor for the formation of mesoporous SnO2. ITO nanoparticles possess uniform particle morphology, narrow particle size distribution (5-10 nm), high crystallinity as well as high electrical conductivity.  The synthesis approaches and characterization of various mesoporous metal oxides, including TiO2, SnO2, mixture of CeO2 and TiO2, mixture of BaTiO3 and SnO2, are reported in the second part of this thesis. Mesoporous TiO2 and SnO2 are presented as highlights of this part. Mesoporous TiO2 was produced in the forms of both films and bulk material. In the case of mesoporous SnO2, the study was focused on the high order of the porous structure. All these mesoporous metal oxides show high crystallinity, high surface area and rather monodisperse pore sizes, which demonstrate the validity of EISA process and the usage of preformed crystalline nanoparticles as nanobuilding blocks (NBBs) to produce mesoporous metal oxides.
N2  - Diese Arbeit besteht hauptsächlich aus zwei Teilen. Der erste Teil befasst sich mit der Synthese von mehreren technologisch wichtigen, kristallinen Metalloxid-Nanopartikeln mittels nichtwässriger Sol-Gel Chemie. Der zweite Teil beinhaltet die Herstellung von mesoporösen Metalloxiden. Dabei wurden ausgewählte Nanopartikel als Bausteine verwendet und durch langsames Verdampfen des Lösungsmittels in die entsprechenden porösen Strukturen überführt.  Das experimentelle Vorgehen wie auch die Charakterisierung der erfolgreich hergestellten Zinnoxid- und Indiumzinnoxid-Nanopartikel sind im ersten Teil beschrieben. Die Zinnoxid-Nanpartikel zeichnen sich durch einheitliche Partikelgrösse (im Durchschnitt ca. 3.5 nm), hoher Kristallinität, und guter Dispergierbarkeit in Tetrahydrofuran aus. Diese Eigenschaften machen aus den Zinnoxid-Nanopartikeln die perfekten Bausteine für den Aufbau von mesoporösem Zinnoxid. Die Indiumzinnoxid-Nanopartikel haben eine einheitliche Partikelform, eine schmale Grösseverteilung (5-10 nm), hohe Kristallinität wie auch gute elektrische Leitfähigkeit.  Die Synthese und Charakterisierung von verschiedenen mesoporösen Metalloxiden wie TiO2, SnO2, Mischungen von CeO2 und TiO2, wie auch Mischungen von BaTiO3 und SnO2 werden im zweiten Teil der Arbeit diskutiert. Mesoporöses TiO2 und SnO2 werden als besonders gelungene Beispiele herausgehoben. Mesoporöses TiO2 wurde in Form von Dünnfilmen wie auch als Bulkmaterial hergestellt. Im Falle von SnO2 galt das Augenmerk vor allem der hohen Ordnung der Mesoporen. Alle diese mesoporösen Materialien zeigen eine hohe Kristallinität, grosse Oberfläche und relativ einheitliche Porengrössen. Diese Eigenschaften unterstreichen, wie wertvoll der Ansatz ist, vorgeformte Nanopartikel als Bausteine für die Synthese von porösen Materialien zu verwenden.
KW  - Nanopartikel
KW  - transparent-leitendes Oxid
KW  - Selbstorganisation
KW  - nanoparticles
KW  - oxides
KW  - assembly
KW  - mesostructure
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-10173
ER  - 
TY  - GEN
A1  - Beck, Michael
A1  - Hildebrandt, Niko
A1  - Löhmannsröben, Hans-Gerd
T1  - Quantum dots as acceptors in FRET-assays containing serum
N2  - Quantum dots (QDs) are common as luminescing markers for imaging in biological applications because their optical properties seem to be inert against their surrounding solvent. This, together with broad and strong absorption bands and intense, sharp tuneable luminescence bands, makes them interesting candidates for methods utilizing Förster Resonance Energy Transfer (FRET), e. g. for sensitive homogeneous fluoroimmunoassays (FIA). In this work we demonstrate energy transfer from Eu<SUP>3+</SUP>-trisbipyridin (Eu-TBP) donors to CdSe-ZnS-QD acceptors in solutions with and without serum. The QDs are commercially available CdSe-ZnS core-shell particles emitting at 655 nm (QD655). The FRET system was achieved by the binding of the streptavidin conjugated donors with the biotin conjugated acceptors. After excitation of Eu-TBP and as result of the energy transfer, the luminescence of the QD655 acceptors also showed lengthened decay times like the donors. The energy transfer efficiency, as calculated from the decay times of the bound and the unbound components, amounted to 37%. The Förster-radius, estimated from the absorption and emission bands, was ca. 77 Å. The effective binding ratio, which not only depends on the ratio of binding pairs but also on unspecific binding, was obtained from the donor emission dependent on the concentration. As serum promotes unspecific binding, the overall FRET efficiency of the assay was reduced. We conclude that QDs are good substitutes for acceptors in FRET if combined with slow decay donors like Europium. The investigation of the influence of the serum provides guidance towards improving binding properties of QD assays.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 019 
KW  - Quantenpunkt
KW  - Lumineszenz
KW  - Serum
KW  - Europium
KW  - Immunoassay
KW  - Energietransfer
KW  - Fluoreszenz-Resonanz-Energie-Transfer
KW  - Förster-Resonanz-Energie-Transfer
KW  - Quantum Dot
KW  - Luminescence
KW  - Serum
KW  - Europium
KW  - Immunoassay
KW  - Energy Transfer
KW  - FRET
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-9504
ER  - 
TY  - THES
A1  - Bhattacharryya, Saroj Kumar
T1  - Development of detector for analytical ultracentrifuge. - [korr. Fassung]
T1  - Detektor-Entwicklung für die analytische Ultrazentrifuge. - [korr. Fassung]
N2  - In this work approaches for new detection system development for an Analytical Ultracentrifuge (AUC) were explored. Unlike its counterpart in chromatography fractionation techniques, the use of a Multidetection system for AUC has not yet been implemented to full extent despite its potential benefit. In this study we tried to couple existing fundamental spectroscopic and scattering techniques that are used in day to day science as tool for extracting analyte information. Trials were performed for adapting Raman, Light scattering and UV/Vis (with possibility to work with the whole range of wavelengths) to AUC. Conclusions were drawn for Raman and Light scattering to be a possible detection system for AUC, while the development for a fast fiber optics based multiwavelength detector was completed. The multiwavelength detector demonstrated the capability of data generation matching the literature and reference measurement data and faster data collection than that of the commercial instrument. It became obvious that with the generation of data in 3-D space in the UV/Vis detection system, the user can select the wavelength for the evaluation of experimental results as the data set contains the whole range of information from UV/Vis wavelength. The detector showed the data generation with much faster speed unlike the commercial instruments. The advantage of fast data generation was exemplified with the evaluation of data for a mixture of three colloids. These data were in conformity with measurement results from normal radial experiments and without significant diffusion broadening. Thus conclusions were drawn that with our designed Multiwavelength detector, meaningful data in 3-D space can be collected with much faster speed of data generation.
N2  - In der vorliegenden Arbeit wurde die Entwicklung neuer Detektoren für die Analytische Ultrazentrifugation (AUZ) untersucht und vorangetrieben. Im Gegensatz zu chromatgraphischen. Fraktionierungsmethoden werden Multidetektionssysteme bis heute nicht in der AUZ eingesetzt. Hier wird die Möglichkeit geprüft, bekannte spektroskopische sowie Streumethoden simultan zur Probenanalyse in der AUZ einzusetzen mit dem Ziel, simultan komplimentäre Informationen über die Probe zu erhalten. So wurde versucht, Raman- und UV/VIS-Spektroskopie (letztere mit der Möglichkeit, das gesamte Wellenlängenspektrum auszunutzen) und statische Lichtstreuung zu kombinieren, um das Analytverhalten während des Ultrazentrifugationsexperimentes zu untersuchen. Es wurden zum einen die Ramanspektroskopie als Detektionssystem für chemische Funktionalität in der AUZ geprüft und zum anderen gezeigt, daß die statische Kleinwinkel Lichtstreuung als direkter Molmassendetektor für den Einsatz in der AUZ geeignet erscheint. Zum anderen wurde die Entwicklung eines Multi-Wellenlängen-UV/VIS-Detektors abgeschlossen, um seine Eignung für den Einsatz in der AUZ und die damit verbundene Möglichkeiten der schnelleren und umfassenderen Datenerzeugung gegenüber kommerziellen Geräten zu zeigen. Dieser Multiwellendetektor liefert anstelle eines Absorptionswertes für jede radiale Position in der Messzelle direkt ein ganzes UV-Vis Spektrum und erzeugt eine zusaetzliche Dimension der Messdaten, was die Möglichkeiten der Analyse von komplexen Systemen mit multiplen Chromophoren, Teilchengrößenbestimmung über Wellenlängenabhängigkeit der Trübung oder auch der Datenmittelung enorm vergrößert. Desweiteren erlaubt der Detektor die Anwendung von Geschwindigkeitsprofilen zur Analyse extrem polydisperser Systeme. Die Entwicklung des Detektors beruht auf einem auf Linsen basierenden System mit modularem Aufbau. Dabei war die sorgfältige Ausrichtung des optischen Systems ein essentieller Punkt, um seine Eignung zu überprüfen zu können. An einer Mischung von drei Kolloiden, Halbleiternanopartikeln sowie Proteinen und deren Mischungen ist es hier gelungen, die erfolgreiche Entwicklung des UV/VIS-Detektors zu demonstrieren: Die Daten konnten schneller und mit wesentlich mehr Informationsgehalt, als auf allen kommerziellen Geräten generiert werden. Die Sedimentationskoeffizientenverteilungen stimmen dabei mit denen aus herkömmlichen Sedimentationsgeschwindigkeitsexperimenten überein, unterliegen jedoch nicht einer signifikanten diffusionsbedingten Verbreiterung. Es ist in dieser Arbeit somit gelungen, zum einen die Lichtstreuung als aussichtsreiche Methode für ein Detektorsystem in der AUZ aufzuzeigen, und zum anderen einen Multi-Wellenlängen-UV/VIS-Detektor zu entwickeln, der eine Datenerzeugung von bislang noch nicht erreichter Schnelligkeit im dreidimensionalen Raum ermöglicht.
KW  - Ultrazentrifuge
KW  - Detektor
KW  - Detektor-Entwicklung
KW  - SLS
KW  - UV/VIS
KW  - Raman
KW  - detector development
KW  - SLS
KW  - UV/VIS
KW  - Raman
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-8215
ER  - 
TY  - THES
A1  - Gehrke, Nicole
T1  - Retrosynthese von Perlmutt
T1  - Retrosynthesis of nacre
N2  - In dieser Arbeit ist es gelungen, die Bedeutung physikalisch-chemischer Mechanismen in der Biomineralisation gegenüber der bisher angenommenen Dominanz spezifischer biomolekularer Erkennungsmechanismen aufzuzeigen. Dazu wurden drei Ansätze verfolgt: Zum einen wurden Studien zur Calciumcarbonatkristallisation durchgeführt. Zum anderen wurde das Biomineral Perlmutt intensiv untersucht. Als drittes wurde ein Modellsystem entwickelt, mit dem künstliches Perlmutt synthetisiert und ein Mechanismus für die Perlmuttmineralisation vorgeschlagen werden konnte.  Im ersten Schritt wurden in einem simplen Kristallisationsansatz komplexe Calciumcarbonatüberstrukturen ohne die Verwendung von Additiven synthetisiert. Es wurde gezeigt, daß diese durch orientierte Anlagerung von Nanopartikeln gebildet werden, bei der dipolare Felder eine wichtige Rolle zu spielen scheinen. Dieser Mechansimus war bislang für Calciumcarbonat unbekannt und ermöglicht die Synthese komplexer Kristallmorphologien, wodurch die Frage aufgeworfen wird, ob er bei der Biomineralbildung von Bedeutung sein kann. Durch Einsatz minimaler Mengen eines einfachen, synthetischen Additivs bei der Kristallisation wurden zu Überstrukturen angeordnete Aragonitplättchen synthetisiert, die von einer wenige nm dicken Schicht aus amorphen Calciumcarbonat umgeben sind. Eine solche Schicht wurde auch bei den Aragonitplättchen Perlmutts entdeckt (s.u.) und bietet möglicherweise in verschiedenen Systemen eine Erklärung für die Stabilisierung der sonst metastabilen Aragonitphase.  Im zweiten Schritt wurden bei der Untersuchung von natürlichem Perlmutt zwei bislang unbekannte Strukturmerkmale entdeckt: Es gibt Bereiche, die nicht aus den charakteristischen Plättchen bestehen, sondern wesentlich weniger stark mineralisert sind. Die Mineralphase besteht in diesen Bereichen aus Nanopartikeln. Es wurde weiterhin gezeigt, daß die Aragonitplättchen von einer wenige nm dicken Schicht aus amorphem Calciumcarbonat umgeben ist. Die gängigen Modelle der Perlmuttbildung sind mit diesen Beobachtungen nicht zu vereinbaren und somit zu hinterfragen. Dagegen deuten diese Ergebnisse ein Wachstum von Perlmutt über ACC-Nanopartikel an.  Unter der Annahme der Bedeutung physikalisch-chemischer Mechanismen in der Biomineralisation wurde schließlich als dritter Schritt ein Ansatz zur in vitro-Retrosynthese von Biomineralien ausgehend von ihrer unlöslichen Matrix entwickelt.  Mit diesem Ansatz ist es erstmals gelungen, künstliches Perlmutt auf synthetischem Wege herzustellen, das morphologisch nicht vom Original zu unterscheiden ist. Die existierenden Unterschiede konnten zeigen, daß der Mineralisationsprozeß nicht auf ein spezifisches Mikroumgebungssystem beschränkt, sondern "allgemeiner gültig"' sein muß.  Bei der Retrosynthese gibt es zwei Schlüsselfaktoren: Zum einen die demineralisierte unlösliche Perlmuttmatrix als dreidimensionales Gerüst für das künstliche Perlmutt, zum anderen amorphe Precursorpartikel, die die Mineralphase bilden. Es werden keinerlei Proteine oder andere Biomoleküle verwendet. Dieser Ansatz bietet die Möglichkeit, den Mineralisationsprozeß an einem in vitro-Modellsystem zu verfolgen, was für das in vivo-System, wenn überhaupt, nur unter starken Einschränkungen möglich ist. Es wurde gezeigt, daß das künstliche Perlmutt über die Mesoskalentransformation von ACC-Precursorn innerhalb der Matrix gebildet wird und als möglicher Mechanismus bei der Biomineralisation von natürlichem Perlmutt diskutiert. Es konnte in der vorliegenden Arbeit konsequent gezeigt werden, daß die Imitation von Biomineralisationsprozessen in in vitro-Ansätzen möglich ist, wobei chemisch-physikalische Parameter dominieren.  In zukünftigen Studien sollten einerseits die mechanischen Eigenschaften des künstlichen Perlmutts untersucht werden, wofür sich in Vorversuchen im Rahmen dieser Arbeit die Nanoindentierung als geeignet herausgestellt hat. Es sollte geprüft werden, ob das hier ermittelte Prinzip zur Mineralisierung in der Materialentwicklung angewendet werden kann. Andererseits sollte die Retrosynthese auf andere Systeme ausgeweitet und in vivo-Studien durchgeführt werden, um die Gültigkeit der vorgeschlagenen Mechanismen zu überprüfen.
N2  - This thesis highlights the importance of physical-chemical mechanisms in biomineralisation and, thus, challenges the widely accepted dominance of specific biomolecular recognition mechanisms.  The work is divided into three parts: the first part addresses the crystallisation of calcium carbonate; the second part focuses on an intensive study of the biomineral, nacre, and, lastly, a retrosynthesis model system is designed and applied to synthesize artificial nacre. A mechanism for nacre mineralisation in nature is proposed.  Initially, complex calcium carbonate superstructures were synthesized in the absence of any additive. These were shown to grow by an oriented attachment mechanism of nanoparticles, presumably under the influence of dipolar fields. This growth mechanism has, to date, not been described for calcium carbonate. This mechanism opens the possibility to synthesize complex crystal morphologies of calcium carbonate and arises the question as to whether it plays a role in the growth of biominerals.  With the presence of small amounts of additives in calcium carbonate crystallisation it was possible to synthesize superstructures of aragonite platelets, each of which surrounded by a layer of amorphous calcium carbonate (ACC). Such ACC layers were also found in natural nacre (see below) and may explain the stabilisation of the metastable calcium carbonate polymorph aragonite.  In the second part of this thesis two unknown features of nacre structures were distinguished: Some areas within the nacre do not consist of the characteristic aragonite platelets but are mineralized only to a low degree. In these areas the mineral phase is clearly composed of nanoparticles. Furthermore, the aragonite platelets of nacre are shown to be surrounded by an ACC layer. Both observations contradict the classical models of nacre growth mechanisms but hint towards a growth via ACC nanoparticles.  Assuming the importance of physical-chemical mechanisms in biomineralisation, an approach for the in vitro retrosynthesis of biominerals was designed. Through this, it was possible, for the first time, to synthesize artificial nacre, which was indistinguishable in morphology from the original. The non-morphological differences between original and synthesized nacre showed that the biological process of mineralization is not limited to one specific microenvironment, but must be more general.  Two key factors are of importance for the retrosynthesis approach: 1) The demineralised nacre matrix, which forms a scaffold for the artificial mineral phase and; 2) amorphous nanoparticles as precursors, which transform into the mineral phase. No proteins or other biomolecules were utilized. In this way, the biomineralisation process could be followed in an in vitro model, a process, which is hardly possible in such detail under in vivo conditions. This work proves that the artificial nacre grows by a mesoscale transformation of ACC nanoparticles, and discusses this mechanism as a possible growth mechanism of natural nacre. This work consequently shows that it is possible to imitate biomineralisation processes in vitro and that, in–vitro, these processes are driven by physico-chemical parameters.  Future studies will involve investigation of the mechanical properties of the artificial nacre. First experiments indicate, that nanoindentation is hereby suitable. The potential application of the in vitro mineralization mechanism for new material development will be investigated. Furthermore, the retrosynthesis will be applied to other biomineral systems and, subsequently, in vivo studies will be performed so as to investigate the role of the proposed mechanisms for the natural biomineralisation process.
KW  - Biomineralisation
KW  - Perlmutt
KW  - Retrosynthese
KW  - Präkursor
KW  - Calciumcarbonat
KW  - physikalisch-chemisch
KW  - amorph
KW  - Mesoskalentransformation
KW  - biomineralization
KW  - nacre
KW  - retrosynthesis
KW  - mesoscale transormation
KW  - calcium carbonate
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7971
ER  - 
TY  - THES
A1  - Nolte, Marc
T1  - Integration of freestanding polyelectrolyte multilayer membranes in larger scale structures
T1  - Integratrion freistehender Polyelektrolytmembranden in makroskopische Strukturen
N2  - Ultrathin, semi-permeable membranes are not only essential in natural systems (membranes of cells or organelles) but they are also important for applications (separation, filtering) in miniaturized devices.  Membranes, integrated as diffusion barriers or filters in micron scale devices need to fulfill equivalent requirements as the natural systems, in particular mechanical stability and functionality (e.g. permeability), while being only tens of nm in thickness to allow fast diffusion times. Promising candidates for such membranes are polyelectrolyte multilayers, which were found to be mechanically stable, and variable in functionality. In this thesis two concepts to integrate such membranes in larger scale structures were developed. The first is based on the directed adhesion of polyelectrolyte hollow microcapsules. As a result, arrays of capsules were created. These can be useful for combinatorial chemistry or sensing. This concept was expanded to couple encapsulated living cells to the surface. The second concept is the transfer of flat freestanding multilayer membranes to structured surfaces. We have developed a method that allows us to couple mm2 areas of defect free film with thicknesses down to 50 nm to structured surfaces and to avoid crumpling of the membrane. We could again use this technique to produce arrays of micron size. The freestanding membrane is a diffusion barrier for high molecular weight molecules, while small molecules can pass through the membrane and thus allows us to sense solution properties. We have shown also that osmotic pressures lead to membrane deflection. That could be described quantitatively.
N2  - Die Entwicklung von “Labors auf einem Chip” hat in den vergangenen Jahren großes Interesse hervorgerufen. Diese Chips ermöglichen schnelle vor Ort Analytik, wie sie beispielsweise in Arztpraxen oder bei der Schadstoff Überwachung wünschenswert wäre. Die Entwicklung solcher Systeme stellt große Herausforderungen an Forscher verschiedenster Disziplinen.  Ein großer Vorteil solcher Systeme sind die verkürzten Reaktionszeiten durch die Verkleinerung der Dimensionen. Membranen, die als Diffusionsbarrieren oder Filter in solche Systeme integriert werden sollen, müssen den Ansprüchen an mechanische Stabilität, Funktionalität (z.B. Permeabilität) bei einer Dicke von einigen 10 nm genügen. Die Reduktion der Membrandicke ist erforderlich um die Diffusionszeiten durch die Membran zu minimieren. Polyelektrolyte sind vielversprechende Kandidaten für solche Membranen, da sie sowohl mechanisch stabil sind, als auch variabel in ihrer Funktionalität In dieser Arbeit werden zwei Konzepte zur Integration solcher Membranen vorgestellt. Das erste Konzept basiert auf der selektiven Adhäsion von Polyelektrolytkapseln auf strukturierten Oberflächen. Für das gewählte Kapselsystem konnte bereits eine große Stabilität und eine breite Funktionalität gezeigt werden. Die Strukturierung wird durch Mikrokontaktdrucken erzielt und führt. zu attraktiven und repulsiven Bereichen auf der Oberfläche. Die Kapesladhäsion findet auf den attraktiven Bereichen statt. Auf diese Weise werden die Kapseln 2-dimensional auf der Oberfläche angeordnet. Die definierte laterale Position der Kapseln ermöglicht Anwendungen in der kombinatorischen Chemie oder der Sensorik. Der makroskopische Transfer von bis zu 50 nm dünnen Polyelektrolytmembranen auf microstrukturierte Substrate ist das zweite präsentierte Konzept zur Integration freistehender Membranen. Dabei entsteht ein großflächiger Bereich (mm2) von Millionen von Hohlräumen mit einem Volumen in der Größe von pL (10-12l). Diese Holräume können mit Reagenzien gefüllt werden. Diese reagieren durch die Membran auf Änderungen in der umgebenden Flüssigkeit. Von besonderem Interesse ist der Aspekt, daß nicht nur eingekapselte Reagenzien als Sensormaterial fungieren können, sondern auch durch die Deformation der Membran Änderungen im osmotischen Druck der Umgebung quantitativ erfaßt werden können.
KW  - Polyelektrolyt
KW  - Diffusionsbarriere
KW  - Freistehende Membranen
KW  - Kraftsensoren
KW  - polyelectrolyte membranes
KW  - force sensors
KW  - diffusion barrier
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7355
ER  -