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排序方式: 共有570条查询结果,搜索用时 15 毫秒
111.
Yamei Liu Victor G Stepanov Ulrich Strych Richard C Willson George W Jackson George E Fox 《BMC biotechnology》2010,10(1):85
Background
Manufacturing large quantities of recombinant RNAs by overexpression in a bacterial host is hampered by their instability in intracellular environment. To overcome this problem, an RNA of interest can be fused into a stable bacterial RNA for the resulting chimeric construct to accumulate in the cytoplasm to a sufficiently high level. Being supplemented with cost-effective procedures for isolation of the chimera from cells and recovery of the recombinant RNA from stabilizing scaffold, this strategy might become a viable alternative to the existing methods of chemical or enzymatic RNA synthesis. 相似文献112.
In experiments on mollusks (Planorbis corneus) the topical organization of outputs of neurons RPal and RPa2 of the right parietal ganglion was investigated. Outputs were identified by coherence analysis of accumulated electrical activity in dissected nerves during activation of the above neurons. The analysis was based on a number of features described in this paper. Axons of the test neurons were found to be present in the left and right pallial nerves; polysynaptic pathways activated by these neurons also were discovered. The topical organization of outputs of the test neurons was shown to be invariant for different preparations.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 458–463, July–August, 1984. 相似文献
113.
M Iu Gololobov I P Morozova T L Voiushina E A Timokhina V M Stepanov 《Biokhimii?a (Moscow, Russia)》1991,56(2):230-240
A comparative study of the hydrolysis of various p-nitroanilide substrates (Z-A2-A1-pNA, Z-A3-A2-A1-pNA, and Z-A4-A3-A2-A1-pNA, where A1-An are various amino acid residues, Z is the benzoyloxycarbonylic group and pNA is the p-nitroanilide group), catalyzed by serine proteinase from Bacillus subtilis strain 72, was carried out. It was found that depending on the substrate structure, the hydrolysis may involve both the peptide-p-nitroaniline and the amino acid-amino acid bonds. A kinetic analysis of substrate hydrolysis occurring simultaneously at these two bonds was carried out. The physico-chemical meaning of the kinetic parameters of the given scheme was determined. The quantitative estimation of the enzyme specificity with respect to both hydrolyzing bonds can be found by using the parameters calculated during the analysis of the kinetic curve of p-nitroaniline production. It was found that according to their specificity the amino acid residues at position A1 can be arranged in the following order: L-Leu greater than P-Phe greater than L-Ile greater than L-Ala. The beta-branched amino acid residues, L-Val and L-Ile, do not bind to subsite S1. If these residues occupy position A1, the substrate splitting occurs exclusively between residues A1 and A2. The tetrapeptide N-protected p-nitroanilide substrates are also hydrolyzed at this bond. Partial hydrolysis of the amino acid-amino acid bond between residues A1 and A2 occurs in two cases: i) when residue A1 is loosely bound to subsite S1 and/or, ii) when residue A2 is firmly bound to subsite S1. 相似文献
114.
O B Puzanova A S Stepanov N I Beliakova O G Loginova B N Il'iashenko S Ia Ditatkin 《Molekuliarnaia genetika, mikrobiologiia i virusologiia》1989,(12):26-30
Possibility of cryotransformation of Bacillus anthracis cells by the DNA of pUB110 plasmid has been established. The parameters of cryotransformation process have been optimized permitting one to increase the efficiency of transformation up to 3.1 . 10(2) transformants per 1 mkg of transforming DNA. The factors affecting the efficiency of cryotransformation and its reproducibility have been studied including the treatment of recipient cells by glycine, the procedure of freeze-thawing, the composition of freezing medium. The recipient activity of Bacillus anthracis cells has been shown to depend on the set of their own plasmids. 相似文献
115.
116.
E N Filippova IYuLysogorskaya E S Oksenoit G N Rudenskaya V M Stepanov 《Analytical biochemistry》1984,143(2):293-297
L-Pyroglutamyl-L-phenylalanyl-L-leucine-p-nitroanilide (PFLNA)--a convenient chromogenic substrate for assay of thiol proteinases papain, ficin, and bromelain--was prepared by enzymatic synthesis with chymotrypsin as a catalyst. The thiol proteinases hydrolyze PFLNA with the liberation of p-nitroaniline, estimated spectrophotometrically by its absorbance at 410 nm. The phenylalanine residue in the P2 position of PFLNA meets the specificity demands of thiol proteinases. The following values of Km were found for PFLNA hydrolysis: by papain, 0.34 mM; by ficin, 0.43 mM; by bromelain, 0.30 mM. This substrate was successfully applied to monitor thiol proteinase affinity chromatography on bacitracin-Sepharose, which resulted in a 2- to 4-fold purification from commercial preparations. 相似文献
117.
G P Stepanov M P Bondarenko P I Larovo? 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1977,(4):133-139
The authors conducted a prospective controlled epidemiological observation in two towns of the Moldavian SSR. There were 50 000 persons under observation. Over 300 000 parenteral manipulations carried out in them were recorded. Analysis of the materials obtained on the Minsk-22 computer demonstrated the same incidence of viral hepatitis in the groups given parenteral manipulations and without them. Consequently, the instrumental transmission factor had no essential significance in the epidemiology of viral hepatitis, this corresponding to the results of the authors' preceding theoretical study. 相似文献
118.
The numeral density of the revealed with the help of PTA-plane and twisted asymmetric and symmetric interneuronal contacts of the sensomotor brain cortex of rats after 6 minutes mechanical asphyxia has been studied. It was revealed that in 90 minutes and 6 hours the relative contacts of the concave synapses will be increased progressively. This reaction has the compensatory-adaptive character and ensures the restoration of the integrative activity of the brain during the early postresuscitation period. 相似文献
119.
120.
Using ion-exchange chromatography on QAE-Sephadex A-50, affinity chromatography on DNP-hexamethylenediamine-Sepharose and gramicidin S-Sepharose and gel filtration, a metalloproteinase was isolated from the cultural fluid of L. pneumophila (strain Philadelphia-1) grown for 20 hours. The enzyme was purified 1606-fold with a 31% yield. The enzyme has a Mr of 38,000, pI approximately 4.0 and optimum of proteolytic activity at pH 6.0-7.0, 55 degrees C. The proteinase is the most stable within the pH range of 6.0-9.0. The enzyme contains one atom of zinc per molecule. The amino acid composition of metalloproteinase is close to that of thermolysin and is characterized by a high methionine content--17 residues out of 348. In the B-chain of oxidized bovine insulin the enzyme hydrolyzes the bonds precedent to the amino groups of leucine, phenylalanine and tyrosine. The enzyme is inhibited by chelating agents--Na2-EDTA and o-phenanthroline as well as by diethylpyrocarbonate. The serine and thiol proteinase inhibitors do not influence the enzyme activity. Under the given conditions of cultivation metalloproteinase is the major endopeptidase produced by L. pneumophila. Thus, the proteolytic system of Legionelles is characterized by the combination of metalloproteinase and the earlier described phenylalanine aminopeptidase. 相似文献