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41.
Patricia E. Gallagher Thomas P. Brent 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1984,782(4):394-401
Further purification of a human placental 3-methyladenine-DNA glycosylase by phosphocellulose column chromatography yielded a 6000-fold increase in specific activity with greater than 5% recovery. Although 3-methyladenine was the predominant base released from double-stranded methylated DNA by this enzyme, minor releasing activities for 7-methylguanine and 3-methylguanine were also observed. During purification, the three DNA glycosylase activities consistently copurified with constant ratios of specific activity. Moreover, all the activities were heat-inactivated at 50°C at the same rate, required double-stranded methylated DNA as substrate, were inhibited by spermine and spermidine, and were not subject to product inhibition. These data strengthen the likelihood that the three activities are associated with a single DNA glycosylase. 相似文献
42.
Brent R. Larson 《Life sciences》1982,30(12):1003-1012
Presented is a pilot project describing a new strategy for mass spectrometric peptide sequencing. Using orthophthalaldehyde (OPA), two peptides were derivatized and their fluorescent adducts isolated using reversed phase high performance liquid chromatography. The OPA-peptides were permethylated and the derivatized molecules subjected to direct probe mass spectral analysis. The spectra obtained from the OPA-peptides was analogous to those observed for standard -acyl permethyl derivatives enabling the complete sequence of the peptides to be determined. 相似文献
43.
A quartz-flow-cell system for irradiation of large volumes of Escherichia coli cultures with ultraviolet light is described. With this system kilogram quantities of irradiated cells can be obtained for biochemical studies. Changes in respiration and in specific activities of superoxide dismutase and catalase, after an ultraviolet treatment that reduced viability of culture samples to 0.2%, were in good agreement with those for cultures irradiated (52J/m2) by a conventional small-scale method to produce the same reduction in viability. 相似文献
44.
Shoot tip, bud, leaf, stem and root explants from bearing trees, offshoots, seedlings, and asexual plantlets ofPhoenix dactylifera L. were cultured on modified Murashige and Skoog nutrient media containing 3 g/l activated charcoal, 100 mg/l 2,4-dichlorophenoxyacetic acid, 3 mg/l
N
6-(Δ2-isopentyl)adenine to obtain callus. Differential morphogenetic responses were obtained from calli dependent on the explant
type and parent source. Subcultured shoot tips and leafy lateral buds callus on nutrient media devoid of charcoal and supplemented
with 0.1 mg/l α-naphthaleneacetic acid (NAA) produced adventitious plantlets. Subcultured leaf calli produced roots only. Root callus failed
to exhibit any morphogenetic response upon subculturing. Undifferentiated non-leafy buds and stem tissues did not give rise
to callus, regardless of the parent source. Generally, the best callus and embryogenetic responses from explants were obtained
from seedling and plantlet parent sources. Similarly, organogenetic responses such as root formation and shoot development
from shoot tips cultured on media containing 10 mg/l NAA were also related to the parent explant source.
Mention of a trademark or proprietary product in the paper does not constitute a guarantee or warranty of the product by the
U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be available. 相似文献
45.
F. Brent Johnson 《Chemico-biological interactions》1982,40(1):97-112
Quantitative assays for the morphological transformation of 3T3 Swiss mouse cells by herpes simplex type 2 virus (HSV-2) were employed to examine the effect on cell transformation of chemical carcinogens and suspected carcinogens. Exposure of the cells to the chemical compound, followed by virus infection, resulted in enhancement of transformation when compared to that observed with chemical or virus alone. Enhancement occurred in tests utilizing either UV light-inactivated HSV-2 (strain 333) or a temperature-sensitive (ts) mutant of HSV-2 [A8(293)]. A series of seven ts-mutants were tested and exhibited varying degrees of transformation. Enhancement of transformation occurred in cells treated with hydrazine (HZ) and 1,2-dimethylhydrazine (SDMH). No enhancement occurred when cells were treated with monomethylhydrazine, 1,1-dimethylhydrazine and the jet fuels JP-5, JP-10, RJ-4 and RJ-5. A strong time dependence after treatment was demonstrated with some enhancement seen at 6 h after chemical treatment but the greatest enhancement appeared when virus infection began after 24 h of chemical exposure. 相似文献
46.
47.
G R Williams J W Harney B M Forman H H Samuels G A Brent 《The Journal of biological chemistry》1991,266(29):19636-19644
48.
49.
Smith Roy H.; Gottesman Suzy; Hobbs Brent; Lear Eliot; Kristofferson David; Benton David; Smith P.R. 《Bioinformatics (Oxford, England)》1991,7(1):111-112
In this paper, we describe an automated system for distributingupdates to the GenBank nucleic acid sequence database, usingthe Usenet news system as the underlying transport mechanism.Our system allows new loci to be distributed as soon as thesequences are available, over existing networks, using existingUsenet software and infrastructure currently available on awide range of computer systems. 相似文献
50.
Identification of ancillary fim genes affecting fimA expression in Salmonella typhimurium.
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Regulation of the gene, fimA, encoding the major fimbrial subunit of S. typhimurium S6704 was examined by using a lambda fimA-lacZ lysogen. Transformation of the lambda fimA-lacZ lysogen with various derivatives of the recombinant plasmid that encodes type 1 fimbrial expression, pISF101, indicated that two regions of this plasmid alter beta-galactosidase production. One plasmid is a deletion resulting in the loss of a 28-kDa polypeptide downstream of fimA, while the other plasmid encodes a 24- and a 27-kDa polypeptide. Northern (RNA) blot analyses indicated that the steady-state fimA mRNA levels of these transformants were high. In addition, phenotypic expression of type 1 fimbriae by agar-grown cultures is observed only in those transformants bearing plasmids which show increased beta-galactosidase and fimA mRNA levels. 相似文献