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1.
Enzymatic desulfurization of dibenzothiophene by a cell-free system of Rhodococcus erythropolis D-1 总被引:1,自引:0,他引:1
Abstract Pseudomonas syringae cells were exposed to Cu2+ alone or in the precence of acetate, proline or cysteine, at concentrations that reduced free Cu2+ to 1/10 of the total copper. Ligand concentrations (designated as isoeffective) were determined experimentally using a Cu2+ -selective electrode and confirmed by computer calculations using published stability constants. Exposure of P. syringae cells to Cu2+ alone resulted in rapid and pronounced cell death, and binding of most of the copper in solution. The addition of acetate, proline or cysteine, a few minutes after Cu2+ treatment, resulted in a significant reduction in cell death, and in the amount of copper bound to the cells. For short exposures to Cu2+ , cysteine was more effective than acetate or proline, but after 60 min of treatment, similar results were observed with these ligands. The addition of ligands before Cu2+ resulted in even more reduced copper toxicity. The results showed that, at isoeffective concentrations, weak and moderate copper-ligands can effectively antagonize copper toxicity, and that this protective effect does not require previously equilibrated copper-ligand solutions and is not very dependent of the nature of the ligand. 相似文献
2.
The defatted sclerotia powder was partially hydrolyzed with dilute acid, and the material obtained was fractionated by carbon column chromatography, separated into two disaccharides, three trisaccharides and three tetrasaccharides, respectively. In these hydrolyzates α, α-trehalose, Iaminaribiose, and gentiobiose were identified. 相似文献
3.
Summary (±)-Tricarbonyl 6-3-methylbenzyl alcohol)chromium was resolved to of 100%e.e. and of 92%e.e. by lipase-catalyzed transesterifications arranged in homotopic and heterotopic double resolutions. 相似文献
4.
A high level of arachidonic acid release from [2-14C]arachidonylphosphatidylinositol (PI) was observed at neutral pH (6.0-7.0) in the presence of purified plasma membranes of guinea pig peritoneal macrophages. This activity was at least 10-fold higher than that with arachidonylphosphatidylcholine (PC) or phosphatidylethanolamine (PE) as substrate. The accumulation of [14C]diacylglycerol and [14C]phosphatidic acid was not detected at any time, and arachidonic acid release from [14C]arachidonyldiacylglycerol was not detectable either. The data suggest that arachidonic acid release from PI may not occur via the phospholipase C pathway. In this paper, we demonstrate the possibility that arachidonic acid release from PI at neutral pH in the macrophage plasma membrane is dependent on the action of phospholipase A2 (EC 3.1.1.4) -like activity. The maximum arachidonic acid release was dependent upon both pH and substrate. Particularly, the activity of arachidonic acid release from PI at neutral pH was very high compared with that from PC or PE. We suggest that phosphatidylinositol phospholipase A2 (EC 3.1.1.52) may play an important role in providing arachidonic acid for subsequent metabolic activity in the macrophages. 相似文献
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6.
Jan Oscarsson Yoshimitsu Mizunoe Bernt Eric Uhlin David J. Haydon 《Molecular microbiology》1996,20(1):191-199
The Salmonella typhimurium protein SlyAST, originally described as a cytolysin, shows sequence similarities to several known bacterial regulatory proteins. A homologue to the slyASt gene has been localised to min 37 of the Eschericia coli K-12 chromosome and has been designated slyAEC When introduced in trans on a plasmid, the slyAEC gene conferred a haemolytic phenotype on wild-type but not clyA-knockout strains of E. coli K-12. The clyA gene encodes a novel haemolysin that is not expressed by wild-type E. coli under tested laboratory conditions. Western and Northern blot analyses, and DNA-band-shift assays support a model whereby the SlyAEC protein activates clyA expression by binding to the clyA promoter region, thereby supporting the sequence similarity data in suggesting that SlyAST is a haemolysin activator rather than being a haemolysin per se. 相似文献
7.
Phe(12) of deacetyl-thymosin beta(4) is one of the structural essentials for restorative effect on the impaired blastogenic response of uraemic T-lymphocytes. In order to evaluate the functional roles of this phenyl group in the restorative effect on impaired T-lymphocytes, two analogues, [1- Nal(12)]deacetyl-thymosin beta(4) and [Cha(12)]deacetyl4 thymosin beta(4), were synthesized by a solid-phase method and evaluated for restorative effect on the impaired blastogenic response of uraemic T-lymphocytes. The results indicated that [1-Nal(12)]deacetyl-thymosin beta(4) which had a bulky naphthyl ring showed a stronger restorative effect than that of deacetyl-thymosin beta(4), but it was slightly weaker than that of [Phe(4F)(12)]deacetyl-thymosin beta(4). However, [Cha(12)]deacetyl-thymosin beta(4) showed no restorative effect on the impaired blastogenic response of uraemic T-lymphocytes. 相似文献
8.
9.
Yoshimitsu Ueno Kohsuke Hori Ryo Yamauchi Makoto Kiso Akira Hasegawa Koji Kato 《Carbohydrate research》1981,96(1):65-72
Laminarabiose, cellobiose, and gentiobiose were acetonated with 2,2-dimethoxy-propane under various conditions. Two isopropylidene acetals in which the reducing D-glucose residue had the furanoid form were obtained from laminarabiose, and two, in which the reducing D-glucose residue formed the acyclic dimethyl acetal, from cellobiose. Gentiobiose gave both types of isopropylidene compound. 相似文献
10.
Kenichi Tanaka Masaaki Nakayama Makoto Kanno Hiroshi Kimura Kimio Watanabe Yoshihiro Tani Yuki Kusano Hodaka Suzuki Yoshimitsu Hayashi Koichi Asahi Keiji Sato Toshio Miyata Tsuyoshi Watanabe 《PloS one》2013,8(12)