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991.
The results of the phage typing of 5, 168 Staph. aureus strains isolated in a surgical hospital between 1959 and 1977 are analyzed for each year of this period. The wave of increase in the number of staphylococci belonging to phage group II which began, as discovered in this study, in 1965 and still showed no tendency towards decrease in 1977, as well as the periodicity of rises and falls in the number of staphylococci belonging to phage groups I and III are discussed and compared with the data contained in the literature. The authors come to the conclusion that Staph. aureus is subject to wave-like rises and falls in the number of strains belonging to the main phage groups of the species, and among them the strains belonging to phage groups I and III seem to be inversely related in respect of rises and falls in number, such changes occurring periodically at an interval of 10-12 years, while in the strains belonging to phage group II changes in number occur at a slower rate. The constant account of the percentage of phage groups I, II and III is recommended to ensure rational antibiotic therapy.  相似文献   
992.
Crystals of the self-complementary decadeoxyoligonucleotide d(CpGpTpApCpGpTpApCpG) have been grown from a solution containing [Co(NH3)6]Cl3 and spermine. The amber-colored crystals are hexagonal and belong to the space group P6(5) (or P6(1] with unit cell parameters a = 17.93 A, c = 43.41 A. Precession photography and molecular packing considerations indicate that the unit cell consists of a 12 nucleotide duplex. The asymmetric unit, therefore, is a disordered duplex dimer in which each pyrimidine-purine base-pair is occupied 60% of the time by a C . G pair and 40% of the time by a T . A pair. The above considerations and preliminary structure analysis reveal that this alternating pyrimidine-purine oligomer assumes a Z-DNA conformation.  相似文献   
993.
A simple, 3-step method was described for purification of murine C4 binding protein (C4-bp), a recently recognized serum protein that functions as one of the regulatory proteins of the complement system. The method consists of 1) affinity chromatography using TNBS-BGG-conjugated Sepharose beads, 2) gel filtration on a Sepharose 6B column, and 3) heparin-Sepharose chromatography. By this method, milligram quantities of C4-bp can be easily purified by more than 500-fold from EDTA-serum of various mouse strains, and the whole purification process can be completed within 1 wk. The overall yield of C4-bp is about 15%. The C4-bp thus prepared is homogeneous as judged by SDS-polyacrylamide gel electrophoresis and immunelectrophoresis. The purified mouse C4-bp showed physicochemical properties very similar to those described for human C4-bp. Like human C4-bp, mouse C4-bp is composed of several apparently identical subunits of the m.w. of 80,000. However unlike the human counterpart, the subunits of mouse C4-bp are not linked by disulfide bonds but are connected by non-covalent forces that can be disrupted by SDS. The purified mouse C4-bp retained binding affinity for C4 and showed unaltered antigenicity. Immunization of rabbits with the purified mouse C4-bp resulted in the production of potent and monospecific antisera.  相似文献   
994.
995.
A genomic library of Erwinia chrysanthemi DNA was constructed in bacteriophage lambda 1059 and recombinants expressing Er. chrysanthemi asparaginase detected using purified anti-asparaginase IgG. The gene was subcloned on a 4.7 kb EcoRI DNA restriction fragment into pUC9 to generate the recombinant plasmid pASN30. The position and orientation of the asparaginase structural gene was determined by subcloning. The enzyme was produced at high levels in Escherichia coli (5% of soluble protein) and was shown to be exported to the periplasmic space. Purified asparaginase from E. coli cells carrying pASN30 was indistinguishable from the Erwinia enzyme on the basis of specific activity [660-700 units (mg protein)-1], pI value (8.5), and subunit molecular weight (32 X 10(3]. Expression of the cloned gene was subject to glucose repression in E. coli but was not significantly repressed by glycerol. Recombinant plasmids, containing the asparaginase gene, when introduced into Erwinia carotovora, caused increased synthesis of the enzyme (2-4 fold higher than the current production strain).  相似文献   
996.
Whole rat liver nuclei were reacted with UDP-[14C]galactose in the presence of bovine beta(1----4) galactosyltransferase. The reaction mixture was electrophoresed on a reducing sodium dodecyl sulfate-polyacrylamide gel. Autoradiograms of the gel demonstrated a major labeled broad band migrating with an apparent molecular weight of 65,000-66,000. A number of other less prominently labeled bands were also present. The labeled 65,000-66,000 band when cut from the gel and subjected to alkaline reduction while in the gel matrix exclusively yielded a 14C-labeled disaccharide that co-migrated with a [14C]Gal-GlcNAcol standard in descending paper chromatography. Treatment of this disaccharide with beta-galactosidase (beta-D-galactoside galactohydrolase; EC 3.2.1.23) from Aspergillus niger removed all the [14C]galactose label. Treatment of the labeled 65,000-66,000 polypeptide with Endoglycosidase F, however, did not remove the [14C]galactose label. Western transfer blots of sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels performed with horseradish peroxidase-labeled succinyl wheat germ agglutinin, a lectin specific for GlcNAc, on unlabeled nuclei revealed a dominant band at 63,000-64,000. Subjecting 14C-labeled nuclei to this procedure resulted in a shift of the major horseradish peroxidase-labeled succinyl wheat germ agglutinin band to 65,000-66,000. The shifted band was coincident with the [14C]galactose band as visualized on an autoradiogram. A survey of other rat tissue nuclei revealed the same spectrum of [14C]galactose acceptor proteins with a dominant 65,000-66,000 galactose-labeled band.  相似文献   
997.
A strain of Methylomonas albus BG8WM, a type 1 obligate methanotroph, which had been maintained for 2 ycars by serial passage on solid medium containing methanol as a carbon source was found to mutate at a frequency of 10-5-10-6 to resistance to dichloromethane (DCMR), the parental strain BG8 did not give rise to DCMR colonies. DCMR strains were no longer capable of growth on methane as a carbon cource and exhibited greatly reduced or undetectable methane mono-oxygenase activity. The mutants fell into three groups on the basis of SDS-PAGE analysis of the polypeptide profiles of the particulate fraction of cell extracts. One or more of four polypeptides of Mr 70,000, 50,000, 25,000 and 23,000 were implicated as being components of the methane mono-oxygenase. Spontaneous reversion to growth on methane and sensitivity to dichloromethane occurred at a frequency of about 10-8. The loss of methane mono-oxygenase activity was not associated with loss of the resident 55 kb plasmid.Abbreviations DCMR dichloromethane-resistant - SDS-PAGE sodium dodecyl sulphate polyacrylamide gel electrophoresis - NMS nitrate minimal salts medium  相似文献   
998.
999.
1000.
Immediate fragmentation of parental DNA by near-ultraviolet irradiation at 313 nm was measured in cultured skin fibroblasts from normal individuals, patients with Xeroderma pigmentosum of complementation group A (XPA) and Xeroderma pigmentosum variants (XPV) by the alkaline elution procedure. For a dose of 2.25 KJm?2 given at Oo fragmentation was comparable in all cell strains. However, fragmentation was strongly increased relative to Oo in XPV but not in normal fibroblasts and the XPA strains when irradiation was carried out at 37o. From our results it appears that a step in the repair of parental DNA is abnormal in XPV.  相似文献   
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