TY - JOUR A1 - Jancke, Harald A1 - Beetz, Silke A1 - Bechmann, Wolfgang T1 - Non-selective signal loss in the 13C CPMAS NMR spectra of soil organic matter : investigations of particle size fractions N2 - In the CPMAS spectra of soil samples, the paramagnetic soil constituents partially discriminate against the Signal intensity of the 13C atoms.The aim of the study was to check to what extend the signal depression is selective to a certain kind of carbon species. A strong linear correlation between the detectability of carbon and the cube root of wt.% Fe was observed for both, the total signal and the signal of the carbon species as well. For a C:Fe ratio of 1,5 - 20 non selective signal loss caused by the iron particles dominates. Despite the high percentage of non-detectable carbon the 13C CPMAS spectra correctly reflect the relative composition of soil organic matter Y1 - 2002 ER - TY - JOUR A1 - Virtanen, Janne A1 - Arotcarena, Michel A1 - Heise, Bettina A1 - Ishaya, Sultana A1 - Laschewsky, André A1 - Tenhu, Heikki T1 - Dissolution and aggregation of a poly (NIPA-block-sulfobetaine) copolymer in pure and saline aqueous solutions N2 - Thermal properties of block copolymer, poly(N-isopropyl acrylamide)-block-poly(3-[N-(3-methacrylamido-propyl)- N,N-dimethyl]-ammonio propane sulfonate), PNIPA-b-PSPP have been studied in pure and saline (NaCl) aqueous solutions by dynamic laser light scattering (DLS). The copolymer [Mw(PNIPA) 10800 g/mol and Mw(PSPP) 9700 g/mol] exhibits both an upper (UCST 9 oC) and lower (LCST 32 oC) critical solution temperatures in pure water. The addition of NaCl enhances the solubility of the zwitterionic polymer, PSPP, leading to the disappearance of the UCST. On the other hand, the solubility of PNIPA in water decreases as NaCl is added. At 20 oC the copolymer shows a bimodal size distribution through the NaCl concentration range of 0-0.93 M above a certain limiting polymer concentration. The slow and fast components of the diffusion coefficients of the polymer have been calculated. A gradual addition of salt turns the mutual interactions from zwitterionic attractions between PSPP blocks to hydrophobic attractions between PNIPA blocks. The formation of the aggregates and the aggregate sizes at T < UCST and T > LCST are influenced by polymer and salt concentrations. Below UCST the aggregates in saline polymer solutions are larger than those in pure polymer solutions. Above LCST the aggregate size is determined by the salt concentration. Y1 - 2002 ER - TY - JOUR A1 - Hellweg, Thomas A1 - Brulet, Anni A1 - Lapp, A. A1 - Robertson, Daniela A1 - Koetz, Joachim T1 - Temperature and polymer induced structural changes in SDS/decanol based multilamellar vesicles Y1 - 2002 ER - TY - JOUR A1 - Kamlage, Stefan A1 - Sefkow, Michael A1 - Zimmermann, Nicole A1 - Peter, Martin G. T1 - Concise synthesis of (+)-beta-benzyl gamma-butyrolactones from butynediol Y1 - 2002 ER - TY - JOUR A1 - Arotcarena, Michel A1 - Heise, Bettina A1 - Ishaya, Sultana A1 - Laschewsky, André T1 - Switching the inside and the outside of aggregates of water-soluble block copolymers with double thermoresponsivity N2 - Water-soluble block copolymers were prepared from the non-ionic monomer N-isopropylacrylamide (NIPA) and the zwitterionic monomer 3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]-ammonio propane sulfonate (SPP) by sequential free radical polymerization via the RAFT process. Such block copolymers with two hydrophilic blocks exhibit double thermo- responsive behavior in water: the poly-NIPA block shows a lower critical solution temperature, whereas the poly-SPP block exhibits an upper critical solution temperature. Appropriate design of the block lengths leads to block copolymers which stay in solution in the full temperature range between 0°C and 100°C. Both blocks of these polymers dissolve in water at intermediate temperatures, whereas at high temperatures, the poly-NIPA block forms colloidal hydrophobic associates that are kept in solution by the poly-SPP block, and at low temperatures, the poly-SPP block forms colloidal polar aggregates that are kept in solution by the poly-NIPA block. In this way, colloidal aggregates can be prepared in water which switch reversibly, and without any additive, their "inside" to the "outside", and vice versa. The aggregates provide microdomains and surfaces of different character, which can be controlled by a simple thermal stimulus. Y1 - 2002 ER - TY - JOUR A1 - Peter, Martin G. T1 - Chitin and Chitosan from Animal Sources N2 - A review on the chem. and biochem. of chitin and the chem. and application of chitosan. The following topics were discussed: structure of chitin and chitosan; occurrence and physiol. functions of chitin; detection of chitin in animals and anal. of chitin and chitosan; biosynthesis and biodegrdn. of chitin in animals; prodn. of chitin and chitosan; properties of chitin and chitosan; and applications of chitin and chitosan. Y1 - 2002 SN - 3-527-30227-1 ER - TY - JOUR A1 - Lunkenheimer, K. A1 - Laschewsky, André A1 - Warszynski, P. A1 - Hirte, R. T1 - On the adsorption behaviour of soluble, surface-chemically pure hemicyanine dyes at the air/water interface N2 - Equilibrium surface tension (se) versus concentration isotherms of surface-chemically pure aqueous solutions of the homologous series of N-n-alkyl-4'-(dimethylamino)-stilbaziumbromides ('hemicyanines') were measured at 295 K. The adsorption parameters of saturation adsorption and standard free energy of adsorption of the hemicyanines were determined from the evaluation of the se vs. c isotherms by using a two state approach to surface equation of state. The adsorption parameters reveal a very pronounced phenomenon of alternation (even/ odd- effect) which has so far not been met to a large extent like this. Thus, the cross-sectional areas of the odd members are almost twice those of the related even members. Surface activity of the odd is stronger than that of the even members. UV-Vis investigations showed that there is no indication of aggregate formation in the adsorption layer. The thermodynamic results give evidence for distinct differences between the surface conformations of the even- and the odd-chain hemicyanine dyes although the reasons for it are not known. Y1 - 2002 ER - TY - JOUR A1 - Koetz, Joachim A1 - Kosmella, Sabine T1 - Interactions of Polyelectrolytes with Clay Surfaces Y1 - 2002 SN - 0-8247-0633-1 ER - TY - JOUR A1 - Peter, Martin G. T1 - Chitin and Chitosan from Fungi Y1 - 2002 SN - 3-527-30227-1 ER - TY - JOUR A1 - Yenesew, Abiy A1 - Midiwo, Jacob O. A1 - Guchu, S. M. A1 - Heydenreich, Matthias A1 - Peter, Martin G. T1 - Three iosoflav-3-enes and a 2-arylbenzofuran from the root bark of Erythrina burttii N2 - From the root bark of Erythrina burttii three new isoflav-3-enes, 7,4'-dihydroxy-2'-methoxy-6- (1'',1''-dimethylallyl)isoflav-3-ene (trivial name, burttinol-A), 4'-hydroxy-2'- methoxy-(2'',2''-dimethylpyrano[5'',6'':8,7]isoflav-3-ene (trivial name, burttinol-B), 7,4'-dihydroxy-2'-methoxy-8-(3'',3''-dimethylallyl)isoflav-3-ene (trivial name, burttinol-C), and a new 2-arylbenzofuran, 6,4'-dihydroxy-2'-methoxy-5- (1'',1''-dimethylallyl)-2-arylbenzofuran (trivial name, burttinol-D) were isolated. In addition, the known compounds, abyssinone V-4'-methyl ether, bidwillol A, calopocarpin, erybraedin A, erythrabyssin II, isobavachalcone, phaseollidin and phaseollin were identified. The structures were determined on the basis of spectroscopic evidence. Y1 - 2002 ER - TY - JOUR A1 - Mickler, Wulfhard A1 - Bukowsky, Heinz A1 - Holdt, Hans-Jürgen T1 - Separation of Palladium(II) with immobilized Maleonitrile-Dithiocrown ethers N2 - Especially sulphur containing compounds are suitable for the separation of noble metals. 1,2-Dithioethenes are weak chelate-forming ligands and in the case of bis(methylthio)maleo-nitrile the donor power of both of the sulphur atoms is further decreased by the electron withdrawing effect of the cyanogroups. Crowned dithiomaleonitrile are macrocyclic chelate ligands which extract Pd(II) at sufficient rate in a very good yields. The synthesis of the immobilised ligands proceeds from the 2-allyloxy-1,2-propanediol forming the dicar-bon acid which is reduced to the diole. With the help of thionylchloride the dichloro compound is synthe-sized forming the macrocycle together with a dithiolate (1,2-disodium-1,2-dicyanethene-1,2-dithiolate, 1,2-disodium-4-methylbenzene-1,2-dithiolate) at high dilution conditions. The allylsubstituted crown ether is sillylated and the resulting alkoxysilane is immobilised onto activated silica gel. The extraction results with crown ethers are compared with that achieved with the help of substituted ß- diketones and 4-acyl-5-pyrazolones. By modification of the cavity of the macrocyclus the extraction rate increases from the acyclic compound through maleonitrile-dithio-21-crown-7, maleonitrile-dithio-15-crown-5 and maleonitrile-18-crown-6. The best results can be observed at the maleonitrile-dithio-12-crown-4. The rise of the function log D= f(log L) gives the composition of the extracted compounds as 1:1. The separa-tion is unsatisfactory in the case of Ag(I), Hg(II), Pt(II), Tl (I) and the most 3d-elements. Summarizing, a very good separation of palladium from the examined elements can be specified. Additional to the extraction experiments, as well as the crystal structures and by UV spectroscopy the for- mation constants of selected chelates were determined. Y1 - 2002 ER - TY - JOUR A1 - Dosche, Carsten A1 - Löhmannsröben, Hans-Gerd A1 - Bieser, A. A1 - Dosa, P. I. A1 - Han, S. A1 - Iwamoto, M. A1 - Schleifenbaum, A. A1 - Vollhardt, K. Peter C. T1 - Photophysical properties of [N]phenylenes Y1 - 2002 ER - TY - JOUR A1 - Bahrke, Sven A1 - Einarsson, Jon M. A1 - Gislason, Johannes A1 - Haebel, Sophie A1 - Letzel, Matthias C. A1 - Peter-Katalinic, Jasna A1 - Peter, Martin G. T1 - Sequence analysis of chitooligosaccharides by matrix-assisted laser desorption ionization postsource decay mass spectrometry N2 - Oligosaccharides composed of 2-acetamido-2-deoxy-D-glucopyranose (GlcNAc) and/or 2-amino-2-deoxy-D- glucopyranose (GlcN) were prepd. by chem. degrdn. of chitin or chitosan and sepd. by gel permeation chromatog. Oligosaccharides obtained after enzymic hydrolysis of chitosan [FA 0.19] with a fungal chitinase were derivatized by reductive amination with 2-aminoacridone and sequenced by matrix-assisted laser desorption ionization time-of-flight postsource decay (PSD) mass spectrometry (MS). The sequence of a trimer, D1A2, was established as D-A-A. The compn. of a hexamer D3A3 was .apprx.65% D-A-D-D-A-A and 35% D-D-A-D-A-A. The PSD MS of a nonamer D5A4-amac revealed four isobaric species D-X-Y-D-X-Y-D-A-A, where A is GlcNAc, D is GlcN, and X and Y (X ¹ Y) are mutually either D or A. This structure motif was also obsd. in a dodecamer D7A5 which was composed of eight isobaric sequences of the general formula (D-X-Y)3- D-A-A. Y1 - 2002 ER - TY - JOUR A1 - Vuillaume, Pascal Y. A1 - Jonas, Alain M. A1 - Laschewsky, André T1 - Ordered polyelectrolyte "multilayers" : 5. photo-cross-linking of hybrid films containing a new unsaturated and hydrophobized poly(diallylammonium) salt and exfoliated clay N2 - A simple synthetic route to a new poly(diallylammonium) salt functionalized by a styrene group is presented. This reactive polymer was employed for polyelectrolyte multilayer films using electrostatical layer-by-layer self- assembly, together with an inorganic polyanion, namely an exfoliated hectorite clay. To enhance their stability, the final hybrid multilayers were cross-linked by exposure to UV light, leading only to a minor shrinkage. Alternatively, the reactive polycation was cross-linked after each adsorption step. X-ray reflectometry revealed that the two types of films dispose of an internal order with a short length scale, that seems insensitive to the photo-cross-linking. Cross- linking after each adsorption step, however, results in more regular film growth, and reduces the films? roughness and the amount of polyanion deposited. Under these conditions, the films seem to grow by deposition of submonolayers with a combined vertical and lateral expansion, resulting in the self-healing of previously deposited, incomplete layers. Y1 - 2002 ER - TY - JOUR A1 - Glinel, Karine A1 - Laschewsky, André A1 - Jonas, Alain M. T1 - Ordered polyelectrolyte "multilayers" : 4. internal structure of clay-based multilayers N2 - We report on the growth and structure of hybrid clay-based multilayers obtained by electrostatic self-assembly (also known as layer-by-layer assembly) of poly(diallylpyrrolidinium bromide) and a synthetic hectorite (Laponite). By combining ellipsometry, atomic force microscopy, and specular and off-specular grazing angle X-ray scattering measurements, we show that platelets pack in the vertical direction according to a distribution of distances between nearest neighbors of about 3 Å standard deviation. The accumulation of such random fluctuations in the vertical direction results in the loss of layering of the platelets farther than about 75 Å from the substrate. In this respect, most of the film should be considered as a nanocomposite with preferential orientation of the platelets, rather than as a real multilayer. The model is quantitatively supported by simulations of the specular and off-specular scattering of such multilayers. Y1 - 2002 ER - TY - JOUR A1 - Kotzev, Anton A1 - Laschewsky, André A1 - Adriaensens, Pieter A1 - Gelan, Jan T1 - Micellar Polymers with Hydrocarbon and Fluorocarbon Hydrophobic Chains : a Strategy to Multicompartment Micelles N2 - Cationic ionenes bearing hydrophobic side chains were synthesized, which behave as micellar polymers of the polysoap type. The hydrophobic chains were either hydrocarbons or fluorocarbons, or a mixture of both, in the form of statistical as well as block copolymers. These amphiphilic polymers were studied and compared with each other and with low molar mass analogous surfactants, especially with respect to their hydrophobic association in aqueous solution. The particular molecular structure of the ionenes synthesized results in polymeric surfactants with high mobility of the fluorocarbon chains. Most noteworthy, the behavior of the hydrocarbon-fluorocarbon block copolymer soaps in aqueous solution indicates microphase separation into hydrocarbon-rich and fluorocarbon-rich hydrophobic domains, thus yielding multicompartment micelles. Y1 - 2002 ER - TY - JOUR A1 - Glinel, Karine A1 - Moussa, Alain A1 - Jonas, Alain M. A1 - Laschewsky, André T1 - The influence of polyelectrolyte charge density on the formation of multilayers of strong polyelectrolytes at low ionic strength N2 - The influence of the charge density of polyelectrolytes on the growth of polyelectrolyte multilayers via layer- by-layer self-assembly from pure aqueous solutions was studied. Multilayers were built from strong polyanions, namely poly(styrenesulfonate) and an exfoliated synthetic hectorite, and cationic copolymers of diallyldimethylammonium chloride (DADMAC) with N-methyl-N-vinylformamide (NMVF) for which the composition and thus the charge density was varied systematically. The analysis of the system {cationic copolymer/poly(styrenesulfonate)} reveals that a critical linear charge density Ïc of 0.036 elementary charge/Å of contour length is necessary to obtain stable multilayer growth in pure water. Above Ïc, the increment of thickness/deposition cycle varies with the linear charge density of the cationic copolymers, in good agreement with current theories of polyelectrolyte solutions. As linear charge density increases, the system passes successively through a charge-dependent ?Debye-Hu ckel? regime and then through a chargeindependent ?strong-screening? regime where counterion condensation dominates the behavior. Analogous results were obtained for the variation of the basal spacing of internally structured hybrid multilayers {cationic copolymer/hectorite}. However, by contrast with the first system, no critical linear charge density was found for the hybrid system. This is explained by additional, nonelectrostatic interactions between the clay platelets and the formamide fragment. Y1 - 2002 ER - TY - JOUR A1 - Mangeney, Claire A1 - Ferrage, Fabien A1 - Jullien, Ludovic A1 - Ouari, Olivier A1 - Rékaï, El-Djouhar A1 - Laschewsky, André A1 - Vikholm, Inger A1 - Sadowski, Janusz W. T1 - Synthesis and properties of water-soluble gold colloids covalently derivatized with neutral polymer monolayers N2 - Citrate-capped gold nanoparticles as well as planar gold surfaces can be efficiently grafted with a covalently attached polymer monolayer a few nanometers thick, by simple contact of the metal surface with dilute aqueous solutions of hydrophilic polymers that are end-capped with disulfide moieties, as shown by UV/vis absorption, dynamic light scattering, and surface plasmon resonance studies. The hydrophilic polymer-coated gold colloids can be freeze-dried and stored as powders that can be subsequently dissolved to yield stable aqueous dispersions, even at very large concentrations. They allow for applying filtrations, gel permeation chromatography, or centrifugation. They do not suffer from undesirable nonspecific adsorption of proteins while allowing the diffusion of small species within the hydrogel surface coating. In addition, specific properties of the original hydrophilic polymers are retained such as a lower critical solution temperature. The latter feature could be useful to enhance optical responses of functionalized gold surfaces toward interaction with various substrates. Y1 - 2002 ER - TY - JOUR A1 - Houston, Douglas R. A1 - Shiomi, Kazuro A1 - Arai, Noriko A1 - Omura, Satoshi A1 - Peter, Martin G. A1 - Turberg, Andreas A1 - Synstad, Bjoenar A1 - Eijsink, Vincent G. H. A1 - Van Aalten, Daan M. F. T1 - High-resolution structures of a chitinase complexed with natural product cyclopentapeptide inhibitors : mimicry of carbohydrate substrate N2 - Over the past years, family 18 chitinases have been validated as potential targets for the design of drugs against human pathogens that contain or interact with chitin during their normal life cycles. Thus far, only one potent chitinase inhibitor has been described in detail, the pseudotrisaccharide allosamidin. Recently, however, two potent natural-product cyclopentapeptide chitinase inhibitors, argifin and argadin, were reported. Here, we describe high- resoln. crystal structures that reveal the details of the interactions of these cyclopeptides with a family 18 chitinase. The structures are examples of complexes of a carbohydrate-processing enzyme with high-affinity peptide-based inhibitors and show in detail how the peptide backbone and side chains mimic the interactions of the enzyme with chitooligosaccharides. Together with enzymol. characterization, the structures explain why argadin shows an order of magnitude stronger inhibition than allosamidin, whereas argifin shows weaker inhibition. The peptides bind to the chitinase in remarkably different ways, which may explain the differences in inhibition consts. The two complexes provide a basis for structure-based design of potent chitinase inhibitors, accessible by std. peptide chem. Y1 - 2002 ER - TY - JOUR A1 - Koetse, Marc M. A1 - Laschewsky, André A1 - Jonas, Alain M. A1 - Wagenknecht, W. T1 - The influence of charge density and distribution on the internal structure of electrostatically self-assembled polyelectrolyte films N2 - Electrostatically self-assembled (ESA) polyelectrolyte films show in general no internal structure. The use of special polycations, however, namely of lyotropic ionenes, may give rise to highly ordered coatings. In this article, the influence of the charge density of the polyanion, as well as the distribution of the charged groups within this polymer, is examined, using a series of anionic cellulose derivatives. Various techniques were used to study the films? growth and internal structure. Both showed to be affected in particular by the charge density but also by the substitution pattern. Y1 - 2002 ER -