Solvent isotope effects on the structure and function of mitochondrial membranes in aqueous media.
Solvent isotope effects on the structure and function of mitochondrial membranes in aqueous media.
复制标题
溶剂同位素对水介质中线粒体膜的结构和功能的影响。
DOI：
10.1016/0003-9861(74)90505-0
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发表时间：
1974
影响因子：
3.9
通讯作者：
Y. Hatefi
中科院分区：
文献类型：
--
作者：
W. Hanstein;K. A. Davis;Y. Hatefi
线粒体膜和酶复合物的电子传递系统的结构稳定性，和小分子量的非电解质（2-甲基萘醌）的溶解度，已被研究作为水结构的函数。D 2 O被认为比普通水更具有结构性，而H 2 O被用作溶剂，与已被证明能破坏水结构的离液离子一起使用。膜稳定性的测定是（a）关于至少一种组分酶的溶解的分辨率，和（B）离液剂诱导的脂质自氧化，其是结构不稳定的量度。溶剂同位素效应表示为引起相同效应所需的离液剂（NaClO 4）浓度的商（CD CH），发现（a）在很宽的NaClO 4浓度范围内，每个系统基本上是恒定的，（B）在所有试验中仅限于1.2-1.8的窄范围，尽管所研究的系统和所使用的测量方法存在显著差异。的同位素效应的幅度和恒定性表明，增加膜的稳定性（即，增加膜中的疏水相互作用的强度），并减少水溶性的非电解质在D2 O主要是由于更高程度的顺序的氘代溶剂。因此，在线粒体电子传递链和许多其他酶系统中，溶剂同位素效应已被观察到，同位素效应似乎是更多的构象变化的结果施加在酶的D2 O，因为它是一个更结构化的溶剂，而不是在反应机制中的质子或水分子的直接参与的指示。
The structural stability of mitochondrial membranes and the enzyme complexes of the electron transport system, and the solubility of a small molecular-weight nonelectrolyte (2-methylnaphthoquinone), have been studied as a function of water structure. D 2 O, which is considered to be more structured than ordinary water, and H 2 O were used as solvents in conjunction with chaotropic ions which have been shown to break down water structure. Assays for membrane stability were (a) resolution with respect to solubilization of at least one constituent enzyme, and (b) chaotrope-induced lipid autoxidation, which is a measure of structural destabilization. Solvent isotope effects expressed as the quotient of chaotrope (NaClO 4) concentration (C D C H) necessary to elicit the same effect were found to be (a) essentially constant for each system over a wide range of NaClO 4 concentration, and (b) limited to the narrow range of 1.2–1.8 in all tests despite significant differences in the systems studied and the measurements used. The magnitude and the constancy of the isotope effects indicate that increased membrane stability (ie, the increased strength of hydrophobic interactions in membranes), and decreased water-solubility of nonelectrolytes in D 2 O are mainly due to the higher degree of order of the deuterated solvent. Thus, in the mitochondrial electron transport chain and many other enzyme systems where solvent isotope effects have been observed, the isotope effect appears to be more a consequence of conformational changes imposed on the enzymes by D 2 O, because it is a more structured solvent, rather than an indication of direct involvement of protons or the water molecule in the reaction mechanisms.