Veerman E C, Van Leeuwen J W, Van Buuren K J, Van Gelder B F
Biochim Biophys Acta. 1982 May 19;680(2):134-41. doi: 10.1016/0005-2728(82)90004-4.
(1) Using the pulse-radiolysis and stopped-flow techniques, the reactions of iron-free (porphyrin) cytochrome c and native cytochrome c with cytochrome aa3 were investigated. The porphyrin cytochrome c anion radical (generated by reduction of porphyrin cytochrome c by the hydrated electron) can transfer its electron to cytochrome aa3. The bimolecular rate constant for this reaction is 2 x 10(7) M-1 . s-1 (5 mM potassium phosphate, 0.5% Tween 20, pH 7.0, 20 degrees C). (2) The ionic strength dependence of the cytochrome c-cytochrome aa3 interaction was measured in the ionic strength range between 40 and 120 mM. At ionic strengths below 30 mM, a cytochrome c-cytochrome aa3 complex is formed in which cytochrome c is no longer reducible by the hydrated electron. A method is described by which the contributions of electrostatic forces to the reaction rate can be determined. (3) Using the stopped-flow technique, the effect of the dielectric constant (epsilon) of the reaction medium on the reaction of cytochrome C with cytochrome aa3 was investigated. With increasing epsilon the second-order rate constant decreased.
(1) 运用脉冲辐解和停流技术，研究了无铁（卟啉）细胞色素c和天然细胞色素c与细胞色素aa3的反应。卟啉细胞色素c阴离子自由基（由水合电子还原卟啉细胞色素c产生）能将其电子转移给细胞色素aa3。该反应的双分子速率常数为2×10⁷ M⁻¹·s⁻¹（5 mM磷酸钾，0.5%吐温20，pH 7.0，20℃）。(2) 在40至120 mM的离子强度范围内测量了细胞色素c - 细胞色素aa3相互作用对离子强度的依赖性。在离子强度低于30 mM时，形成了一种细胞色素c - 细胞色素aa3复合物，其中细胞色素c不再能被水合电子还原。描述了一种可确定静电力对反应速率贡献的方法。(3) 运用停流技术，研究了反应介质的介电常数（ε）对细胞色素C与细胞色素aa3反应的影响。随着ε增大，二级速率常数降低。
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