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排序方式: 共有214条查询结果,搜索用时 15 毫秒
1.
2.
Stereospecific binding of diastereomeric peptides to salmon sperm deoxyribonucleic acid. Further evidence for partial intercalation 总被引:1,自引:0,他引:1
A series of diastereomeric dipeptide amides, containing an N-terminal L-lysyl residue and a C-terminal L- or D-amino acid with a derivatized aromatic ring on the side chain, was synthesized to determine the dependence of (1) the chirality of the N-terminal amino acid alpha-carbon and (2) the length of the N-terminal amino acid side chain for intercalation of the aromatic ring. The nature of the complex between the peptide and DNA (i.e., electrostatic, intercalative, or a combination of these) was determined by UV and CD studies, viscometric titrations, and 1H NMR studies. The results of these studies reveal distinct differences in the binding site of the aromatic rings of the various peptides. In particular, the results suggest that the alpha- and epsilon-amino groups of the lysyl residue bind electrostatically to adjacent phosphates on the DNA backbone in a stereospecific manner. As a result of this stereospecificity, the aromatic rings of the peptides with the L-L designation point toward the DNA helix, while those of the peptides of the L-D designation point away from the helix. This is completely consistent with previously reported work [Gabbay, E.J., Adawadkar, P. D., & Wilson, W. D. (1976) Biochemistry 15, 146; Gabbay, E. J., Adawadkar, P. D., Kapicak, L., Pearce, S., & Wilson, W. D. (1976) Biochemistry 15, 152]. The results also indicate a great dependence on the length of the side chain for intercalation of the aromatic ring. Specifically, if the side chain is long enough, and flexible enough, the aromatic ring can fully or partially intercalate, regardless of the chirality of the N-terminal amino acid alpha-carbon. However, if the side chain is too short, only partial intercalation is observed for peptides of the L-D designation, and no intercalation is observed for peptides of the L-D designation. 相似文献
3.
We have isolated the delta-globin gene of the New-World spider monkey,
Ateles geoffroyi, and compared its nucleotide sequence with those of other
primate delta- and beta-globin genes. Among primate delta-globin genes, the
rate of nonsynonymous substitutions is much less than the rate of
synonymous substitutions. This suggests that primate delta- globin genes
may remain under evolutionary conservation, perhaps because hemoglobin A2
has an as yet unknown physiological importance.
相似文献
4.
Growth hormone regulates the abundance of insulin-like growth factor I RNA in adult rat liver 总被引:2,自引:0,他引:2
C T Roberts A L Brown D E Graham S Seelig S Berry K H Gabbay M M Rechler 《The Journal of biological chemistry》1986,261(22):10025-10028
Insulin-like growth factor I (IGF-I) is a mitogenic polypeptide present in the plasma of man and rat that is thought to mediate the actions of pituitary growth hormone on cartilage to promote skeletal elongation. In the rat, plasma levels of IGF-I show both developmental and hormonal regulation: levels are low at birth, increase with age, and are decreased in growth hormone-deficient adult animals. The present study demonstrates that these changes in plasma IGF-I reflect the abundance of IGF-I RNA in rat liver. A human IGF-I cDNA probe hybridized to multiple RNA species in adult rat liver with sizes 8.6, 4.6, 3.2, 2.1, and 1.0-1.4 kilobases. These RNA species were decreased by greater than 80% in neonatal (2- and 12-day-old) rat liver and by greater than 90% in liver from adult rats made growth hormone-deficient by hypophysectomy. Treatment of hypophysectomized rats with growth hormone increased the abundance of all species of IGF-I RNA. These results suggest that growth hormone regulates the expression of its physiological mediator by altering the synthesis, stability, or both of IGF-I RNA in rat liver. 相似文献
5.
Biochemical pathways in prokaryotes can be traced backward through evolutionary time 总被引:10,自引:0,他引:10
For the first time, a credible prokaryotic phylogenetic tree is being
assembled by Woese and others using quantitative sequence analysis of
oligonucleotides in the highly conservative rRNA. This provides an
evolutionary scale against which the evolutionary steps that led to the
arrangement and regulation of contemporary biochemical pathways can be
measured. This paper presents an emerging evolutionary picture of aromatic
amino acid biosynthesis within a large superfamily assemblage of
prokaryotes that is sufficiently developed to illustrate a new perspective
that will be applicable to many other biochemical pathways.
相似文献
6.
7.
In Drosophila pseudoobscura, the amylase (Amy) multigene family is
contained within a series of inversions, or gene arrangements, on the third
chromosome. The Standard (ST), Santa Cruz (SC), and Tree Line (TL)
inversions are central to the phylogeny of arrangements, and have clusters
of other arrangements derived from them. The gene arrangements belonging to
each of these three clusters have a characteristic number of Amy genes,
ranging from three in ST to two in SC to one in TL. This distribution
pattern can reflect a history of either duplications or deletions, although
the data available in the past did not permit a decision between these
alternatives. We provide unambiguous evidence that three Amy genes were
present before the divergence of the ST, SC, and TL arrangements. Thus, the
current status of the Amy multigene family is the result of deletions in
the TL and SC arrangements, which created three new pseudogenes: TL
Amy2-psi, TL Amy3-psi, and SC Amy3- psi. Analysis of pseudogene sequences
revealed that, in the SC and ST arrangements, pseudogene evolution has been
retarded, most likely due to the homogenization effect of gene conversion.
Finally, by determining the original copy number, we have reconstructed the
evolutionary history of the Amy multigene family and linked it with the
evolution of the central gene arrangements.
相似文献
8.
Linkage of the VNTR/insulin-gene and type I diabetes mellitus: increased gene sharing in affected sibling pairs. 总被引:3,自引:2,他引:1
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Ninety-six multiplex type I diabetic families were typed at the 5' flanking region of the insulin gene by using a PCR assay that better resolves the VNTR into multiple alleles. Affected sibling pairs shared 2, 1, and 0 VNTR alleles--identical by descent--at a frequency of .47, .45, and .08, respectively, a ratio that deviated from the expected 1:2:1 ratio (P < .001). These results confirm linkage of the chromosome 11p15.5 region with type I diabetes mellitus susceptibility. 相似文献
9.
The application of sensory methodology for measuring deodorizing effect of an air conditioner equipped with electric plasma was introduced. Deodorizing effect was measured using chemical and sensory methods at different time (0, 30 and 60 min) and mode (control, blowing and cooling) of an air conditioner. Smoke from a roll of cigarette in a closed room was used as a source of odor and the concentrations of acetic acid and ammonia were measured as odorous chemical components. As one of the sensory methods triangle test was used and as a first step to obtain deodorizing effects by triangle test, the threshold of each panelist was obtained as the log dilution ratio of odor concentration at which the difference from odorless air was detected. The odor concentration at each time and mode was calculated using the threshold of the panel and the deodorizing effect was obtained on the basis of the odor concentration. In addition to a triangle test, scaling methods such as category scaling or magnitude estimation were used to measure deodorizing effect of an air conditioner. Deodorizing effects by scaling methods were calculated based on odor intensity with time at each mode. The regression analysis was done between the efficacy of deodorizing effect by sensory test and those by acetic acid and ammonia, the R2 values of the regression equations for triangle test, category scale, and magnitude estimation were 0.84, 0.72 and 0.69, respectively. Deodorizing effect by triangle test explained the decrease of acetic acid and ammonia better than those by category scaling or magnitude estimation while high cost and time consuming labor involved in triangle tests reduced the merit. The results of this study demonstrated that various sensory methods could be used to measure deodorizing effect of air conditioners and further researches on fast and reliable methods are needed to establish the official procedures. 相似文献
10.
Elijahu G. Stoupel Eugene Abramson Uri Gabbay Albert I. Pick 《International journal of biometeorology》1995,38(2):89-91
The possible relationship between epidemics and extremes of solar activity has been discussed previously. The purpose of the present study was to verify whether differences in the levels of immunoglobulins (IgA, IgG, IgM) could be noted at the highest (July 1989) and lowest (September 1986) points of the last (21st) and present (22nd) 11-year solar cycle. The work was divided into a 1-month study (covering the month of minimal or maximal solar activity), a 3-month study (1 month before and after the month of minimal or maximal solar activity) and a 5-month study (2 months before and after the month of minimal or maximal solar activity). A trend of a drop-off for all three immunoglobulins was seen on the far side of the maximal point of the solar cycle. Statistical significance was achieved in the 5-month study for IgM (P=0.04), and a strong trend was shown for IgG (P=0.07). Differences between the sexes were also noted. 相似文献