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51.
52.
The composition and distribution of metal clusters in the MoFe protein from a nifZ deletion strain (DJ 194) of Azotobacter vinelandii 总被引:1,自引:0,他引:1
ZHOUHuina ZHANGChunxi ZHAOYing BIANShaomin WANGHuangping HUANGJufu 《科学通报(英文版)》2005,50(13):1342-1347
Through the anaerobic chromatography on the columns of DEAE 52, Q-Sepharose and Sephacryl S-200, a nitrogenase MoFe protein (△nifZ Av1) was obtained from a nifZ deleted mutant of Azotobacter vinelandii (stain DJ194).The results of Western blotting after anoxic native electrophoresis and SDS-PAGE showed that △nifZ Av1 was similar to wild type MoFe protein (OP Av1) at the electrophoretic mobility, molecular weight and subunit composition. Furthermore, △nifZ Avl was also similar to OP Av1 at the molybdenum content, EPR signal (g≈4.3, 3.65 and 2.01), and the molar extinction coefficient (△ε) of circular dichroism (CD)at 660 nm region. All of these indicated that, besides having the same α2β2 composition as OP Av1, the △nifZ Av1 also contained equal amount of reductive FeMoco in the spin state of S=3/2 to OP Av1. However, the iron content and substrate (C2H2, H^ and N2)-reduction activity of △nifZ Av1 were 74% and 46%-50% of those of OP Av1, respectively. Furthermore, the △ε at around 450 nm, which reflects P-cluster in Av1, was obviously lower than that of OP Av1. It suggested that the difference between △nifZ Avl and OP Av1 resulted from P-cluster rather than FeMoco, and from the half number of P-cluster in △nifZ Av1, but the composition or redoxstate of P-cluster in △nifZ Av1 were not changed. Thus it could propose that △nifZ Av1 is composed of two different αβsubunit pairs. One is a FeMoco-and P-cluster-containing pair, and the other is a P-cluster-deficient but FeMoco-containing pair. Since the deletion of nifZ gene leads to the deficiency of only one of two P-clusters in a α2β2 tetramer, the assembly of P-cluster may not simply depend on one gene product, and so a possible mechanism of NifZ is supposed here. 相似文献
53.
Symons MC 《Cellular and molecular life sciences : CMLS》2000,57(7):999-1007
This review emphasises the need to use spectroscopy in order to understand the behaviour of water, and summarises the background
of the subject. The various forms of spectroscopy that are especially informative are described, with particular reference
to near-infrared (NIR) spectrophotometry. The key results are outlined, first those obtained with small molecules and ions,
and second those involving proteins, DNA and cell membranes. Finally, some interpretations are offered which include the novel
but possibly controversial concept of free OH and free lone-pair groups. 相似文献
54.
生态产业共生网络运营成本及其优化模型开发研究 总被引:2,自引:0,他引:2
从构成生态产业共生网络的微观要素———企业环境责任入手,开发了基于企业环境责任市场化机制的生态产业共生网络运营成本模型,并对模型假设做了改进研究.模型研究结果表明,环境责任代理企业的环境责任履行成本是影响生态产业共生网络运营总成本大小的关键要素,而环境责任委托企业和中间物流企业的各种参数对生态产业共生网络运行总费用的影响相对较小.基于这种认识,最后又探讨了影响代理企业运营成本的主要因子,并对费用优化模型做了应用研究. 相似文献
55.
提出了一种以EPR纠缠为基础的新的量子密钥分配方案.不需要密钥双方Alice,Bob进行测量基的选择,提高了传输产生的密钥效率.同时,检测偷听者需要对比更少的量子位. 相似文献
56.
Molybdenum nitride powder with Sg of 115 m2 · g1 (passivated) has been prepared by a temperature programmed reaction of MoO3in H2/N2 mixture. It exhibited high catalytic activity in CO oxidation at low temperature. XPS, EPR and LRS studies have shown the
existence of mixed valence states of Mo ions, especially Mo5+ ion (g(tT=1.932,g||=1.892) observed for the first time, in the passivation layer of molybdenum nitride. A surface Superoxide species, O2 (g = 2.001, Raman band 1 124 cm1), was found to be produced accompanying the transformation of Mo5+/Mo4+ redox pair. Evidence has been given to suggest that this surface superoxide might be responsible for CO oxidation over Mo2N catalyst. 相似文献
57.
用双自旋 轨道耦合模型和半经验的分子轨道法研究了Cr3 在Cs2 CdX4 (X =F ,Cl)四角晶位中的EPR零场分裂和 g 因子 .结果表明 ,不应忽略配体Cl对Cr3 的零场分裂和 g因子的贡献 . 相似文献
58.
介绍了一种自检式微波边缘振荡EPR谱仪,利用它既可作微波源又可作检波器(自检),用于电子顺磁共振(EPR)具有很高的灵敏度(≤10~(13)自旋/DPPH)。 相似文献
59.
量子纠缠的理论与实践 总被引:3,自引:1,他引:2
耿天明 《中国传媒大学学报》2004,(Z1)
量子纠缠是量子体系的一种奇妙特性。本文对量子纠缠的历史渊源和基本概念、近年来在理论和实践研究方面的重要进展以及在量子信息科学领域的应用前景,做了介绍与讨论,并对原子气池内的超光速传播的物理机制作了探讨。 相似文献
60.