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21.
Shin DH 《Protein and peptide letters》2008,15(6):630-632
The phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS) catalyzes the phosphorylation and transportation of its sugar substrates. A sugar-specific enzyme II complex involved in the PTS finally functions to translocate substrates across the membrane. A PTS EIIB(fruc) protein, a fructose specific EIIB subunit, from Escherichia coli has been cloned, expressed, refolded, purified, and crystallized. The synchrotron data were collected to 2.6 A from the crystal of a selenomethionine substitute PTS EIIB(fruc) protein. The crystal belongs to the primitive trigonal space group P3(1)21, with unit-cell parameters of a = 33.4 A, b = 33.4 A, c = 154.0 A, and beta = 120.0 degrees . A full structure determination is under way to provide insights into the structure-function relationships of this protein. 相似文献
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记山西榆社晚新生代鹿科化石两新种 总被引:2,自引:0,他引:2
本文记述了山西榆社盆地晚新生代鹿科化石中的两个新种:Eucladoceros proboulei sp.nov.和Procapreolus jinensis sp.nov.,并列出了已鉴定完毕的所有产于榆社盆地晚新生代地层的鹿类动物化石单. 相似文献
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Jian Liu Shi-Chu Liang Feng-Hong Liu Ren-Qing Wang Ming Dong 《Diversity & distributions》2005,11(4):341-347
Plant invasions have been attracting increasing attention from ecologists because of their worldwide environmental impacts and huge economic costs. Research on the characteristics of the recipient regions is essential for understanding the process of plant invasion. However, few previous studies on invasibility of habitats include social factors, although human activities are critical in the process of plant invasion. China is a vast country with high plant species diversity and a long history of introduction of exotic plant species and is particularly vulnerable to invasive plant species. Alien plant species are widespread in the country. Therefore, the study of invasive plants in China is urgent in practice and theoretically important for developing invasion ecology. For the present study, 126 species were selected to represent the major invasive plant species in China. We then collected data on their species richness in 31 provincial administrative units of China and performed Spearman rank correlations between species richness and possible natural and socio‐economic factors. We found that socio‐economic factors, such as human density and GDP, correlated positively with the species richness of invasive plants in China. In conjunction with the natural and socio‐economic correlations in the study of regional distribution pattern of the major invasive plants, we discussed the factors influencing the regional distribution pattern of the major invasive plants in China. We suggest that native plant species richness was mainly determined by the natural conditions of the regions, while invasive species richness was influenced by natural conditions and human disturbance together. 相似文献
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【目的】考察固态和液态两种培养方式对丝状真菌华根霉(Rhizopus chinensis)CCTCC M201021产胞外蛋白的影响,以加深对微生物固、液态培养特异性产酶的认识。【方法】利用成分相同的培养基对华根霉分别进行平板固态培养和液态培养,提取华根霉所产胞外蛋白,采用二维凝胶电泳(2-DE)结合质谱分析,分离鉴定差异蛋白。【结果】固态培养下华根霉所产胞外蛋白的蛋白酶活性是液态培养的9.2倍。胞外蛋白质组数据分析表明,华根霉固态和液态培养所产胞外蛋白存在显著差异,其中约70%是固态和液态培养下各自产生的特有蛋白。质谱鉴定进一步表明,固、液态培养对华根霉产胞外蛋白的种类和表达量都有显著影响,其中水解酶类所占比例较大,主要是与蛋白质降解相关的蛋白。【结论】固态和液态不同培养方式影响了华根霉产胞外蛋白的组成,有些基因只在特定培养方式下表达。固态培养下华根霉产胞外蛋白酶种类相对更多以及大部分蛋白酶的上调表达,可能是固态培养下胞外蛋白酶活性很高的原因。研究结果提示需要注意固液态不同培养方式下丝状真菌胞外酶的筛选和生产可能存在的不一致性。 相似文献
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The redox-induced conformational equilibrium of cytochrome c (cyt c) adsorbed on DNA-modified metal electrode and the interaction mechanism of DNA with cyt c have been studied by electrochemical, spectroscopic and spectroelectrochemical techniques. The results indicate that the external electric field induces potential-dependent coordination equilibrium of the adsorbed cyt c between its oxidized state (with native six-coordinate low-spin and non-native five-coordinate high-spin heme configuration) and its reduced state (with native six-coordinate low-spin heme configuration) on DNA-modified metal electrode. The strong interactions between DNA and cyt c induce the self-aggregation of cyt c adsorbed on DNA. The orientational distribution of cyt c adsorbed on DNA-modified metal electrode is potential-dependent, which results in the deviation from an ideal Nernstian behavior of the adsorbed cyt c at high electrode potentials. The electric-field-induced increase in the activation barrier of proton-transfer steps attributed to the rearrangement of the hydrogen bond network and the self-aggregation of cyt c upon adsorption on DNA-modified electrode strongly decrease the interfacial electron transfer rate. In addition, the strongly Coulombic interactions between DNA and cyt c only disturb the microenvironment of the heme, and do not affect the states of heme ligation and spin. The secondary structure of the adsorbed cyt c is retained, while the conformation of DNA is changed from the B form DNA to A form DNA. 相似文献
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天名精倍半萜内酯化合物 总被引:2,自引:0,他引:2
从菊科天名精全草中分得天名精内酯酮,特勒内酯,11(13)-二氢特勒内酯和异埃瓦内酯。其中11(13)-二氢特勒内酯和异埃瓦内酯为新的天然产物。 相似文献