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首页> 外文期刊>Biochemistry >Roles of dipolar effects and local charge in the ionic strength dependence of redox reactions between c-type cytochromes.
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Roles of dipolar effects and local charge in the ionic strength dependence of redox reactions between c-type cytochromes.

机译:偶极效应和局部电荷在c型细胞色素之间氧化还原反应的离子强度依赖性中的作用。

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摘要

Redox reactions between different c-type cytochromes were monitored by stopped-flow spectroscopy. Second-order rate constants were determined at different ionic strengths for the reactions of Paracoccus denitrificans cytochrome c-551i with its physiologic redox partner cytochrome c-550, and with the nonphysiologic partner horse heart cytochrome c. The latter two cytochromes are structurally quite similar and exhibit identical redox potentials but bear net charges of -7 and +7, respectively. Despite these opposite overall charges, the ionic strength dependencies for the reaction of each with the acidic cytochrome c-551i were very similar. The observed decrease in reaction rate with increasing ionic strength that was observed with cytochromes c-550 and c-551i, the latter of which bears a net charge of -20, cannot be explained simply on the basis of monopole-monopole interactions. These data were analyzed by two different methods: one which treats proteins as both monopoles and dipoles and considers the net charge; and another which neglects dipolar effects and considers only the local charge of the reactive site of the protein rather than net charge. The applicability of each method to the analysis of these data and to protein electrostatic interactions in general is discussed.
机译:通过停止流光谱法监测不同c型细胞色素之间的氧化还原反应。在不同的离子强度下,对于反硝化副球菌细胞色素c-551i与其生理氧化还原伴侣细胞色素c-550和与非生理伴侣马心脏细胞色素c的反应,确定了二级速率常数。后两种细胞色素在结构上非常相似,并显示相同的氧化还原电位,但净电荷分别为-7和+7。尽管有这些相反的总电荷,但每种离子与酸性细胞色素c-551i反应的离子强度依赖性非常相似。不能简单地根据单极-单极相互作用来解释用细胞色素c-550和c-551i观察到的反应速率随离子强度增加而降低的情况,后者的净电荷为-20。这些数据通过两种不同的方法进行了分析:一种将蛋白质同时视为单极子和偶极子并考虑净电荷。另一个忽略了偶极效应,只考虑了蛋白质反应位点的局部电荷而不是净电荷。讨论了每种方法对这些数据的分析以及蛋白质静电相互作用的适用性。

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