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61.
Ron Janzon Jürgen Puls Andreas Bohn Antje Potthast Bodo Saake 《Cellulose (London, England)》2008,15(5):739-750
Different paper grade pulps were extracted with nitren in order to produce dissolving pulps and polymeric xylan. The yield
and molecular structure of the extracted pulps were investigated by carbohydrate analysis and HPSEC combined with fluorescence
labelling in order to additionally monitor the carbonyl and carboxyl group profiles of the pulps. The supramolecular structure
of selected pulps were further studied by solid state 13C-CP/MAS-NMR and wide-angle X-ray scattering (WAXS). These supramolecular data of nitren extracted pulps were compared to
samples extracted with NaOH and a conventional dissolving pulp in order to classify the properties of nitren extracted pulps.
Nitren extraction results in selective xylan removal without noticeable degradation or oxidation of the cellulose fraction.
The resulting dissolving pulps have high molar masses, a narrow molar mass distribution and the typical contents of carbonyl
and carboxyl groups. The supramolecular structure of cellulose is less affected by nitren compared to strong NaOH, and the
resultant dissolving pulps still have the cellulose I structure.
All laboratories are members of the European polysaccharide network of excellence EPNOE. 相似文献
62.
63.
Fast‐Track,One‐Step E. coli Detection: A Miniaturized Hydrogel Array Permits Specific Direct PCR and DNA Hybridization while Amplification 下载免费PDF全文
Antje Beyer Sibyll Pollok Anne Rudloff Dana Cialla‐May Karina Weber Jürgen Popp 《Macromolecular bioscience》2016,16(9):1325-1333
A timesaving and convenient method for bacterial detection based on one‐step, one‐tube deoxyribonucleic acid (DNA) hybridization on hydrogel array while target gene amplification is described. The hydrogel array is generated by a fast one‐pot synthesis, where N,N′‐dimethylacrylamide/polyethyleneglycol(PEG1900)‐bisacrylamide mixture polymerizes via radical photoinitiation by visible light within 20 min concomitant with in situ capture probe immobilization. These DNA‐functionalized hydrogel droplets arrayed on a planar glass surface are placed in the polymerase chain reaction (PCR) mixture during the thermal amplification cycles. The bacterial cells can be implemented in a direct PCR reaction, omitting the need for prior template DNA extraction. The resulting fluorescence signal is immediately detectable after the end of the PCR (1 h) following one short washing step by microscopy. Therefore a valid signal can be reached within 1.5 h including 10 min for pipetting and placement of the tubes and chips. The performance of this novel hydrogel DNA array was successfully proven with varying cell numbers down to a limit of 101Escherichia coli cells.
64.
Wolf A Zimmermann M Hofmann-Apitius M 《Journal of chemical information and modeling》2007,47(3):1036-1044
Since the development of the first docking algorithm in the early 1980s a variety of different docking approaches and tools has been created in order to solve the docking problem. Subsequent studies have shown that the docking performance of most tools strongly depends on the considered target. Thus it is hard to choose the best algorithm in the situation at hand. The docking tools FlexX and AutoDock are among the most popular programs for docking flexible ligands into target proteins. Their analysis, comparison, and combination are the topics of this study. In contrast to standard consensus scoring techniques which integrate different scoring algorithms usually only by their rank, we focus on a more general approach. Our new combined docking workflow-AutoxX-unifies the interaction models of AutoDock and FlexX rather than combining the scores afterward which allows interpretability of the results. The performance of FlexX, AutoDock, and the combined algorithm AutoxX was evaluated on the basis of a test set of 204 structures from the Protein Data Bank (PDB). AutoDock and FlexX show a highly diverse redocking accuracy at the different complexes which assures again the usefulness of taking several docking algorithms into account. With the combined docking the number of complexes reproduced below an rmsd of 2.5 A could be raised by 10. AutoxX had a strong positive effect on several targets. The highest performance increase could be found when redocking 20 protein-ligand complexes of alpha-thrombin, plasmepsin, neuraminidase, and d-xylose isomerase. A decrease was found for gamma-chymotrypsin. The results show that--applied to the right target-AutoxX can improve the docking performance compared to AutoDock and FlexX alone. 相似文献
65.
Ute Henniges Elisabeth Kloser Anjan Patel Antje Potthast Paul Kosma Martin Fischer Klaus Fischer Thomas Rosenau 《Cellulose (London, England)》2007,14(5):497-511
The oxidative effect of carbanilation mixtures containing dimethylsulfoxide (DMSO) was demonstrated by means of alcohol model
substances in which competitive carbanilation was prevented due to steric hindrance of the hydroxyl function, rendering those
compounds specific probes for oxidation effects. Dimethylsulfonium ions and derived ylide species were shown to be the actually
oxidizing species according to trapping methodology using lipophilic olefins which were converted into the corresponding cyclopropane
and epoxide derivatives. The experimental data were in good agreement with DFT computations carried out on the B3LYP/6-311+G(d,p)
level of theory. The direct interaction of cellulose and sulfoxide solvent was proven by means of methyl-(2-naphthyl)sulfoxide
(MNSO) as a model for DMSO, which caused introduction of UV-detectable methylthionaphthyl ether moieties into the cellulose,
formed in Pummerer-type side reaction paralleling the chemical behavior of DMSO. A facile color test—responding to sulfoxide-derived
oxidizing species—was developed to assess the suitability of carbanilation conditions with regard to cellulose oxidation and
degradation. DMSO-based carbanilation systems have to be used with great caution for determination of molecular weight parameters
and for similar purposes which require complete maintenance of the cellulose integrity. Cellulose oxidation/degradation by
DMSO-derived intermediates upon carbanilation can be minimized but cannot be avoided completely. Thus, if cellulose integrity
is an issue as it is in cellulose analytics, it is recommended to replace DMSO by solvent components of similar solution behavior
but without the inherent danger of generating oxidants, such as pyridine or DMAc, whenever possible.
相似文献
Thomas RosenauEmail: |
66.
Vagin SI Frickenschmidt A Kammerer B Hanack M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(3):985-991
The zinc dehydrophthalocyanine 2 and zinc dehydrobenzoporhyrazine 8 a were generated from the 1N-aminobenzotriazole-annulated zinc phtalocyanine 1 and zinc benzoporhyrazine 8, respectively, by oxidation with Pb(OAc)(4) in different solvents, for example, diethyl ether, tetrahydrofuran, acetic acid, and benzene. The reactivity of 2 and 8 a was studied in detail. These species not only easily undergo Diels-Alder additions with dienes, but also the used solvents can be added. Among the addition products with solvents ethoxy-, acetoxy-, acetoxybutyloxy-substituted and barrelen-fused phthalocyanines and benzoporpyrazines were isolated. No products resulting from the dimerization of two dehydro species were observed either for 2 or 8 a. Analysis of the reaction products in comparison with those obtained by oxidation of 1-aminobenzotriazole 15 under similar conditions proves a higher reactivity (electrophilicity) of the dehydro-PcZn 2 and dehydro-PzZn 8 a in comparison with unsubstituted benzyne towards the solvents used, such as diethyl ether and benzene. 相似文献
67.
Axel Rußler Thomas Lange Antje Potthast Thomas Rosenau Elena Berger-Nicoletti Herbert Sixta Paul Kosma 《Macromolecular Symposia》2005,223(1):189-200
Analytical monitoring of xanthation in the viscose process along with xanthate group analysis in the viscose material is a long-debated problem in cellulose chemistry. The task is rendered extremely intricate by the lability of the starting material and the harshness of the reaction medium, which adds to a lack of suitable analytical approaches. In a four-years' endeavor in our lab, a method is being developed which allows to analyze the distribution of xanthate groups in viscoses relative to the anhydroglucose units and along the cellulose chain. In a first step the xanthate groups are stabilized by alkylation, which was optimized towards quantitative conversion. In a second step, the remaining free hydroxyl groups are protected by carbanilation, followed by selective removal of the stabilized xanthate groups. Steps two and three thus generate an inverse image of the initial xanthate pattern. In the forth and fifth step, the liberated hydroxyl groups are methylated, and the carbanilates are removed, so that in the overall process the xanthates were replaced by methyl groups. All reaction steps have been comprehensively tested with regard to completeness of conversion and orthogonality of the protecting groups. 相似文献
68.
69.
Doris Pospiech Hartmut Komber Dieter Voigt Dieter Jehnichen Liane Häußler Antje Gottwald Wolfram Kollig Kathrin Eckstein Angela Baier Karina Grundke 《Macromolecular Symposia》2003,199(1):173-186
The goal of the investigation presented here was to evaluate the influence of semifluorinated side chains on the bulk structure and the surface properties of polysulfones with different chain structure. Thus, segmented block copolymers consisting of polysulfone and semifluorinated aromatic polyester segments as well as polysulfones having semifluorinated side chains randomly distributed over the polymer backbone were synthesized and characterized. Oxydecylperfluorodecyl side chains were used because of their strong tendency for self-organization. The influence of the chain architecture on the self-organization as well as on the surface properties, particularly the wetting behavior, was examined. It could be shown that despite of the higher self-organizing tendency of block copolymers the surface properties of both polymer types are comparable and depend only on the concentration of side chains. 相似文献
70.
Gerhart Braunegg Anna de Raadt Sabine Feichtenhofer Herfried Griengl Irene Kopper Antje Lehmann Hans-Jorg Weber 《Angewandte Chemie (International ed. in English)》1999,38(18):2763-2766
A general principle for biohydroxylation , in which time-consuming screening and enrichment techniques are avoided, is demonstrated by the introduction of a docking/protecting group into the substrate. This facilitates acceptance by the microorganism and allows the use of a narrow range of microorganisms, for example Beauveria bassiana ATTC 7159 (B. b.), for the hydroxylation of compounds with diverse structures. After the biohydroxylation, the docking/protecting group is removed (see scheme). 相似文献