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During the incorporation of 8-amino-dG into oligomeric DNA, the deprotection conditions previously recommended (28% ammonia at room temperature) do not effect complete removal of the dimethylaminomethylene protecting groups. At elevated temperatures oxidative degradation of the oligomer and exchange of ammonia with dimethylamine in the protecting group at C8 occurred. The resolution of these problems and a method to obtain a series of homogeneous oligomers in reasonable yield containing 8-amino-dG located site-specifically are described. 相似文献
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This study was aimed at the development of a method for detection of colonies of nuclease-secreting marine bacteria. The BAL nuclease-producing marine bacterium Pseudoalteromonas espejiana BAL-31 was used as the test object. A new method was developed involving the congo red (CR) anionic dye. The P. espejiana culture was plated on nutrient agar with CR and denatured DNA. In such media, CR was found to form complexes with DNA. After two days of incubation at 30°C, halos were found around the P. espejiana colonies. No halos appeared when DNA was not introduced, when BAL nuclease was inactivated, or when the plates were inoculated with Escherichia coli. It was concluded that the halos around the colonies indicated nuclease secretion. The halos were shown to result from the coagulation of CR released after digestion of the CR-DNA complex by the nuclease. This method for detection of nuclease-producing colonies can probably be used for all marine bacteria and possibly for halophilic bacteria as well. 相似文献
57.
Phylogenetic analysis of the outer-membrane-protein genes of Chlamydiae, and its implication for vaccine development 总被引:9,自引:0,他引:9
Examination of 18 complete and 6 partial sequences of the major outer-
membrane protein from 24 chlamydiae isolates was used to reconstruct their
evolutionary relationships. From this analysis, assuming that the clades
with 100% bootstrap support are correct, come the following conclusions:
(1) The tree of these sequences is not congruent with the phylogeny of the
hosts, and thus host switching would seem to have occurred, thereby
limiting the extent to which there has been coevolution of parasite and
host. (2) The tree is also noncongruent with clustering by type of cell
infected, thereby limiting the extent to which there has been coevolution
of parasite and the cell type that it infects. (3) The tree is also
noncongruent with clustering by the organ infected (eyes or genitalia),
thereby limiting the extent to which there has been coevolution of parasite
and the organ that it infects. (4) The tree is also noncongruent with
genital strains arising from lymphogranuloma venereum strains. (5) The tree
is also noncongruent with the geographic site at which the isolates were
obtained, thereby limiting the extent of divergence explained by geographic
separation. (6) There are estimated to be 185 amino acid positions that are
invariable (as opposed to unvaried) in the major outer-membrane protein.
There are 10 unvaried positions in the variable domains, of which 9 appear
to be invariable, giving some reason to hope that development of a vaccine
might be possible. (7) The rate of change of this protein is too small to
see increased divergence over the time span of isolation of these genes,
giving hope to any vaccine having longevity. Bootstrapping supports those
portions of the tree on which the first five conclusions above depend. The
picture that these results provide is more one of pathogen versatility than
one of coevolutionary constraints. In addition, we examined 10 60-KDa,
outer-membrane protein- 2 genes, all but one of which were from these same
strains. The tree was not, among the trachomatis strains, congruent with
the major-outer- membrane protein tree, suggesting that gene exchange could
be occurring among strains. Moreover, there is an apparent slowdown in
divergence in this gene, among the trachomatis strains.
相似文献
58.
E M Gonikberg 《Molekuliarnaia biologiia》1979,13(5):1064-1069
Major kinetic parameters of endonuclease S1 were determined on superhelical bacteriophage PM2 DNA and on relaxed nicked circular PM2 DNA. At 37 degrees and 0,25 M NaCl, the Michaelis constants were respectively 1.7 . 10(-8) M and 1 . 10(-9) M, and catalytic constants were respectively 0.36 sec-1 and 1.2 . 10(-2) sec-1. The inhibition of the enzyme reaction by its product was detected. 相似文献
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TL Kieft EM Murphy DL Haldeman PS Amy BN Bjornstad EV McDonald DB Ringelberg DC White J Stair RP Griffiths TC Gsell WE Holben DR Boone 《Microbial ecology》1998,36(3):336-348
Abstract Two chronosequences of unsaturated, buried loess sediments, ranging in age from <10,000 years to >1 million years, were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession was inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Core samples were collected at two sites 40 km apart in the Palouse region of eastern Washington State, near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the Winona site elevation is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was approximately 250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: approximately 1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Same-age sediments had equal quantities of microorganisms, but different community types. Differences in community makeup between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the microbial community age can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be considerably older than the porewater ages, since microbial transport is severely restricted in unsaturated sediments. This is particularly true at the Winona site, which was never flooded. 相似文献