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Enzymatic synthesis of
A cell-free particulate enzyme preparation of Mycobacterium smegmatis ATCC 607 catalyzed the transfer of labeled mannose from GDP[14C]mannose to methyl-α-mannopyranoside (an exogenously added acceptor) to form a product that was characterized to be
. This tranmannosylase activity was specific for both the sugar nucleotide donor and methyl monosaccharide acceptor. The reaction was stimulated by the addition of various metal ions and had a pH optimum of 6.0. The apparent Km of this transmannosylase reaction for methyl-α-
-mannopyranoside was 35 mM.The possible relationship between this “artificial” mannosyl-transfer system and the “natural” system which leads to the formation of the oligomannosides and glycoproteins is discussed. 相似文献
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B. Nakajima K. Hirata N. Nishi J. Noguchi 《International journal of biological macromolecules》1981,3(1):46-52
l-Alanylglycyl-l-alanylglycyl-l-alanylglycyl-l-serylglycine and its pentachlorophenyl ester methanesulphonate have been synthesized as monomers for the preparation of silk fibroin model polypeptide. The former octapeptide was polymerized with diphenylphosphorylazide (DPPA) and triethylamine in DMSO or in HMPA—pyridine, and the latter octapeptide pentachlorophenylester was polymerized by adding triethylamine in DMSO to give poly(l-alanylglycyl-l-alanylglycyl-l-alanylglycyl-l-serylglycine). This sequential polypeptide gave a similar i.r. pattern to the crystalline part of Bombyx mori silk fibroin, which indicated antiparallel β-conformation. Dialysis of the solution of this polymer in 60%, aqueous LiBr against water gave mainly the polymer of α-form. O.r.d. measurements suggest that this polypeptide exists as a random structure in dichloroacetic acid on in 60% aqueous LiBr. 相似文献
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Determination of
Ichiro Ono Keizo Matsuda Sachiko Kanno 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,692(2)
A simple, rapid and sensitive two column-switching high-performance liquid chromatographic (HPLC) method with ultraviolet detection at 210 nm has been developed for the determination of
(AY4166, I) and its seven metabolites in human plasma and urine. Measurements of I and its metabolites were carried out by two column-switching HPLC, because metabolites were classified into two groups according to their retention times. After purification of plasma samples using solid-phase extraction and direct dilution of urinary samples, I and each metabolite were injected into HPLC. The calibration graphs for plasma and urinary samples were linear in the ranges 0.1 to 10 μg ml−1 and 0.5 to 50 μg ml−1, respectively. Recoveries of I and its seven metabolites were over 88% by the standard addition method and the relative standard deviations of I and its metabolites were 1–6%. 相似文献
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Synthesis of methyl
-Ribose was converted into methyl
and this, on tin-mediated allylation, gave a mixture of the 2-O-allyl and 3-O-allyl derivatives which were separated by chromatography. The more polar isomer was characterised as the 3-O-allyl derivative after conversion via
(which was also synthesised from
) into the known
. Methyl
was converted into methyl
via methyl
. 相似文献
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Edwin J. Iwanowicz James Lin Daniel G. M. Roberts Inge M. Michel Steven M. Seiler 《Bioorganic & medicinal chemistry letters》1992,2(12):1607-1612
-Hydroxy- and -ketoester functionalized D-Phe-Pro-Lys tripeptides were found to be potent thrombin active site inhibitors. The ketoester derivatives were characterized by slow binding kinetics. The most potent of the series was 9 (BMS 181, 412) with an overall inhibition constant Ki* of 0.0017 μM. 相似文献
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Yoshiko Tajima James M. Anderson P.H. Geil 《International journal of biological macromolecules》1980,2(4):186-192
Observation of random copolypeptides of γ-benzyl-l-glutamate with l-phenylalanine, l-valine and l-alanine was carried out in an electron microscope with samples cast from dilute solution. The relationship between the morphology and the molecular conformation in solution was studied with mixed solvents composed of chloroform and trifluoroacetic acid; these show a preference for α-helix and random coil, respectively. From the solutions in which molecules take α-helical conformation, fibrous films of nematic structure were formed. From random coil solutions discrete precipitates with folded molecules such as lamellar single crystals, piles of lamellae and structureless particles were formed. A copolypeptide containing l-valine in sufficiently large quantity to form β-structure also showed a variation in morphology with solvent, from films to discrete precipitates. It is suggested that the change in stiffness of the molecules contributes to the morphological variation. 相似文献
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Attempted cyclization of 2,3,4-tri-O-methyl-5-seleno-L-arabinose dimethyl acetal in acidic solution gave the corresponding diselenide. Intramolecular attack by the selenobenzyl group at C-5 of 5-O-p-tolylsulfonyl-L-arabinose dibenzyl diseleno-acetal resulted in the formation of benzyl 1,5-diseleno-L-arabinopyranoside. Similarly, 2,3,5-tri-O-methyl-4-O-p-tolylsulfonyl-D-xylose dibenzyl diselenoacetal gave benzyl 2,3,5-tri-O-methyl-1,4-diseleno-L-arabinofuranoside, and 2,3,4-tri-O-acetyl-5-O-p-tolylsulfonyl-D-xylose (or ribose) dibenzyl diselenoacetal gave benzyl 2,3,4-tri-O-acetyl-1,5-diseleno-D-xylo- (or ribo-)pyranoside. The glycosylic benzylseleno group was removed from the pyranoside with mercuric acetate, but attempted deacetylation of the product led to decomposition and not to the expected 5-seleno-D-xylopyranose. 相似文献