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1.
2.
The defatted starch was dispersed in NaOH (1 M) and neutralized with HCl (1 M). The amylose 1-butanol complex is adsorbed on defatted cellulose powder in the solvent system containing acetate buffer (pH 4.8,0.1 M) + urea (2 M) + 1-butanol (8.5%, v/v). The complex adsorbed on cellulose powder is separated by centrifugation (2418 g). The sediment is washed with the solvent system-I to obtain the intermediate fraction. The adsorbed amylose is eluted with urea (2 M) in acetate buffer (pH 4.8, 0.1 M). The amylose, intermediate fraction and amylopectin were precipitated with ethanol, washed free of urea and air dried. They were characterized by determining their blue value and beta -amylolysis limit. 相似文献
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Nielsen J; Peixoto AA; Piccin A; Costa R; Kyriacou CP; Chalmers D 《Molecular biology and evolution》1994,11(6):839-853
The region of the clock gene period (per) that encodes a repetitive tract
of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran
species both within and outside the Drosophilidae. All the non-
Drosophilidae sequences in this region are short and present a remarkably
stable picture compared to the Drosophilidae, in which the region is much
larger and extremely variable, both in size and composition. The
accelerated evolution in the repetitive region of the Drosophilidae appears
to be mainly due to an expansion of two ancestral repeats, one encoding a
Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and
asparagine or threonine. In some drosophilids the expansion involves a
duplication of the pentapeptide sequence, but in Drosophila pseudoobscura
both the dipeptide and the pentapeptide repeats are present in larger
numbers. In the nondrosophilids, however, the pentapeptide sequence is
represented by one copy and the dipeptide by two copies. These observations
fulfill some of the predictions of recent theoretical models that have
simulated the evolution of repetitive sequences.
相似文献
5.
Evolutionary origin of human and primate malarias: evidence from the circumsporozoite protein gene 总被引:8,自引:1,他引:7
We have analyzed the conserved regions of the gene coding for the
circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria
parasite. The closest evolutionary relative of P. falciparum, the agent of
malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is
consistent with the hypothesis that P. falciparum is an ancient human
parasite, associated with humans since the divergence of the hominids from
their closest hominoid relatives. Three other human Plasmodium species are
each genetically indistinguishable from species parasitic to nonhuman
primates; that is, for the DNA sequences included in our analysis, the
differences between species are not greater than the differences between
strains of the human species. The human P. malariae is indistinguishable
from P. brasilianum, and P. vivax is indistinguishable from P. simium; P.
brasilianum and P. simium are parasitic to New World monkeys. The human P.
vivax-like is indistinguishable from P. simiovale, a parasite of Old World
macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are
evolutionarily recent human parasites, the first two at least acquired only
within the last several thousand years, and perhaps within the last few
hundred years, after the expansion of human populations in South America
following the European colonizations. We estimate the rate of evolution of
the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year.
The divergence between the P. falciparum and P. reichenowi lineages is
accordingly dated 8.9 Myr ago. The divergence between the three lineages
leading to the human parasites is very ancient, about 100 Myr old between
P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between
P. falciparum and the other two.
相似文献
6.
Photosynthetic enhancement studies performed at 619 nm (excitation of Systems I and II) and at 446 nm (mainly excitation of System I) revealed an 18% photosynthetic enhancement simultaneously with a 31% reduction in glycolate excretion. This observation supports the hypothesis that some glycolate may be consumed in an oxidation process associated with System I when System II is poorly excited and the supply of electrons from the water splitting process of photosynthesis is low. 相似文献
7.
On exposure to visible light, riboflavin and lumiflavin produced reactive oxygen species such as singlet oxygen and superoxide radicals. The reaction was found to be time- and concentration-dependent. Both riboflavin and lumiflavin, upon illumination, showed mutagenic response in the umu test as well as in the Ames/Salmonella assay with Salmonella typhimurium TA102. The mutagenic response was partially abolished by superoxide dismutase while sodium azide did not have any effect. No mutagenicity was observed if the compounds were not illuminated. The results suggested the involvement of superoxide radicals in light-induced mutagenicity of riboflavin as well as lumiflavin. 相似文献
8.
P.G. Kale 《Mutation research》1980,72(2):177-186
Relative biological effectiveness of neutrons vs. X-rays in inducing crossing-over in males of D. melanogaster was investigated using 812 and 834 rad of neutrons and the same dose of X-rays. Crossing-over was induced in spermatocytes and spermatogonia of adults and pupae. Neutrons were 4 times more effective in spermatocytes of adults and their effectiveness in pupal spermatocytes was even more. Neutrons also induced more exchanges in spermatogonial cells including predefinitive spermatogonia. Higher effectiveness of neutrons can be attributed to their high linear energy transfer. 相似文献
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