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The structure of the O-antigen polysaccharide (PS) from Escherichia coli O173 has been investigated. Sugar and methylation analyses, electrospray ionisation mass spectrometry together with 1H, 31P and 13C NMR spectroscopy were the main methods used. The structure of the pentasaccharide repeating unit of the PS was found to be:
By treatment with 48% HF the phosphoric diester linkage was cleaved together with the glycosidic linkage of the fucosyl group, rendering a tetrasaccharide with the structure: 相似文献
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Evelina L. Zdorovenko Vladimir V. Ovod George V. Zatonsky Aleksander S. Shashkov Nina A. Kocharova Yuriy A. Knirel 《Carbohydrate research》2001,330(4):341
The O-methylation pattern of the O polysaccharide (OPS) of the lipopolysaccharide of Pseudomonas syringae pv. phaseolicola GSPB 1552 was revealed by methylation (CD3I) analysis, Smith degradation, and NMR spectroscopy. Together with the major O repeats consisting of
-rhamnopyranose (
-Rhap) and
-fucofuranose (
-Fucf), there are minor repeats (30%) containing 3-O-methyl-
-rhamnose (
-acofriose), which is 2-substituted in the interior repeats and occupies the terminal non-reducing end of the OPS. It was suggested that the methylated O repeats are linked to each other nearby the non-reducing end of the OPS and that the ‘biological’ O repeat of the OPS has the following structure:
Full-size image (2K) |
Author Keywords: Lipopolysaccharides; O polysaccharides; O-Methylation; Phytopathogens; Pseudomonas syringae 相似文献
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In this report we describe the most suitable protocol for callus formation and plant regeneration for cotton. We screened 15 cotton (Gossypium hirsutum L.) genotypes for metal resistance and two of them, Nazilli M-503 (M503) Nazilli 143 (N-143) selected as Cd, Cu and Ni resistant. The cotyledonary nodes from these genotypes were the best explants for regeneration of shoots (more than 90 %) and roots (50 to 70 %). Shoot apex also gave good shoot regeneration (more than 90 %) but their root regeneration efficiency was low (35 %). These results show that Murashige and Skoog (MS) media containing 0.44 μM naphthaleneacetic acid (NAA) and 0.98 μM indole-3-butyric acid (IBA) was the most suitable recipe for getting high shoot and root regeneration from cotyledonary nodes of N-143 and M503 cotton genotypes.Abbreviations
This work was supported by the Textile Industry grant No. F000301 given to A.R. Memon. 相似文献
2,4 D | 2,4-dichlorophenoxyacetic acid |
BAP | 6-benzylaminopurine |
GA | gibberellic acid |
IBA | indole-3-butyric acid |
MS medium | Murashige and Skoog medium |
NAA | naphthaleneacetic acid |
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The basic idea of the source simulation technique is to replace the scatterer (or radiator by a system of simple sources located within the envelope of the original body. The extent to which the simulated field reproduces the original field depends on the degree of correspondence between the simulated and the given boundary conditions. Numerical simulations have shown that: (1) the shape of the auxiliary surface, (2) the number of sources, and (3) the way the sources are distributed are the most relevant parameters to ensure an accurate solution for the problem. In the case of the single-layer method, sources should not be positioned close to the center of the body, because the problem becomes ill-conditioned. The auxiliary surface and the scatterer should be as similar as possible in order to minimize the boundary error. With respect to the number of sources (N), there are two opposite effects: (1) if (N) is too small, the sound field is not reproduced accurately; (2) if (N) is too large, computing time increases and solution accuracy decreases. The method beaks down when excitation frequency coincides with the eigenfrequencies — a narrow range of frequencies — of the space formed by the auxiliary surface. As the auxiliary surface is frequently represented by simple surfaces (cylinder, sphere), one can easily calculate the eigenfrequencies and therefore avoid them.