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101.
The15N resonances in reduced and oxidizedChromatium vinosum high-potential iron protein have been assigned by use of1H-1H COSY spectra and1H-15N HMQC, HMQC-COSY, and HMQC-NOESY spectra. Unambiguous assignment of 70 of 85 backbone15N resonances in the reduced protein and 62 of 85 resonances in the oxidized protein are made, as are 12 of 21 side-chain15N resonances. 相似文献
102.
本文就植物血细胞凝集素(PHA)作用的不同时间对小鼠脾脏淋巴细胞γ-谷氨酰基转肽酶(γ-GT)活性的影响进行了观察。结果表明,脾脏淋巴细胞转化率随给予PHA时间的延长而上升,对照组<24h组<48h组<72h组;淋巴细胞γ-GT活性于24h明显强于对照组(P<0.001),随着PHA作用时间的延长其γ-GT活性逐渐下降,即48h组与对照组已无显著差异,而72h组却低于对照组(P<0.001)。可见PHA在小鼠体内对γ-GT活性有很大影响。 相似文献
103.
利用人粒细胞集落刺激因子(hG-CSF)cDNA3′端非翻译区(3′-UTR)中存在的DraⅠ酶切位点,通过部分酶切与完全酶切,删除3′-UTR不同长度,构建了四种hG-CSFcDNA瞬时重组表达质粒。转染COS-7细胞后,生物活性测定结果提示,hG-CSFcDNA3′-UTR对其表达起负调控作用,其关键性序列位于紧接终止密码子TGA下游的65bp范围内,3′-UTR对hG-CSFcDNA表达的影响与转录水平的差别有一定关系。 相似文献
104.
大瓶螺碱性磷酸酶的分离纯化及部分性质研究李清漪,曾和期(西南师范大学生物系,重庆630715)碱性磷酸酶(EC3.1.3.1,简称AKP)是广泛存在于动物组织中的水解酶。对软体动物中AKP的研究仅有少数报道[1,2],对属于单壳贝类的水生食用螺──大... 相似文献
105.
DNaseⅠ超敏感位点的研究能够发现潜在的调控基因转录活化的位点,比较正常人外周血有核细胞,淋巴瘤细胞株P3HR1和人鼻咽癌低分化磷癌细胞株HOnE1和HNE2中Ha-ras-1瘤基因的DNaseⅠ超敏感位点发现,只有HONE1和HNE2细胞基因组中存在一个DNaseⅠ超敏感位点,位于第一个外显子上游0.37kb处,上述结果提示正常白细胞和P3HR1细胞中Ha-ras-1基因处于失活状态,而在鼻咽癌细胞基因组中则处于活化状态,它的活化可能与0.37kb处的DNA序列有密切的关系。 相似文献
106.
107.
Comparison of models for nucleotide substitution used in maximum- likelihood phylogenetic estimation 总被引:31,自引:15,他引:16
Using real sequence data, we evaluate the adequacy of assumptions made in
evolutionary models of nucleotide substitution and the effects that these
assumptions have on estimation of evolutionary trees. Two aspects of the
assumptions are evaluated. The first concerns the pattern of nucleotide
substitution, including equilibrium base frequencies and the
transition/transversion-rate ratio. The second concerns the variation of
substitution rates over sites. The maximum-likelihood estimate of tree
topology appears quite robust to both these aspects of the assumptions of
the models, but evaluation of the reliability of the estimated tree by
using simpler, less realistic models can be misleading. Branch lengths are
underestimated when simpler models of substitution are used, but the
underestimation caused by ignoring rate variation over nucleotide sites is
much more serious. The goodness of fit of a model is reduced by ignoring
spatial rate variation, but unrealistic assumptions about the pattern of
nucleotide substitution can lead to an extraordinary reduction in the
likelihood. It seems that evolutionary biologists can obtain accurate
estimates of certain evolutionary parameters even with an incorrect
phylogeny, while systematists cannot get the right tree with confidence
even when a realistic, and more complex, model of evolution is assumed.
相似文献
108.
Pot experiments were conducted with a calcareous soil (Inceptisol) to elucidate the effects of bicarbonate (0 and 20 mM) and root zone temperature (15° and 25°C) on the uptake of Zn, Fe, Mn and Cu by "Zn-efficient" and "Zn-inefficient" rice cultivars. Bicarbonate decreased concentrations and total uptake of Zn in shoots of "Zn-inefficient" cultivars, especially of IR 26 at 25°C, but not in Zn-efficient cultivars. Bicarbonate decreased concentrations and uptake of Fe in shoots of Zn inefficient cultivars, particularly in IR 26. Concentrations and total uptake of Mn were lower in bicarbonate treatment in the Zn-inefficient cultivars at 15°C, and in all cultivars at 25°C. However, concentration and uptake of Cu were not affected by bicarbonate in all cultivars. Compared to the 25°C root zone temperature, the concentrations and total uptake of both Zn and Cu in shoots at 15°C were lower in Zn-inefficient than in the Zn-efficient cultivars. The results indicate that Zn-efficiency in rice is causally related to high tolerance of plant to elavated bicarbonate concentrations in soil solution. 相似文献
109.
T. C. Pan T. H. Lin C. L. Tseng M. H. Yang C. W. Huang 《Biological trace element research》1993,39(2-3):117-128
Blackfoot disease is a peripheral vascular disease resulting in gangrene of the lower extremities. Though extensive epidemiological
study has implicated that high arsenic content in artesian well water of the endemic area, bears some important connection
with the disease, the etiology of the disease is still unknown. In this study, attention is paid to multielement determination
in order to find out whether the trace elements in hair of Blackfoot disease patients are different from those of the controls.
Experimental results indicate that the concentrations of As and Se in hair of patients are significantly higher than those
of the controls, but Ca and Zn are significantly lower than those of the controls. The possible connection of these elements
with the etiology of the disease is discussed. 相似文献
110.
Yang S. P.; Bergo G. W.; Krasney E.; Krasney J. A. 《Journal of applied physiology》1994,76(1):303-313