抗坏血酸诱导的2，6-二甲氧基-1，4-苯醌的完全可逆氧化还原循环。,Biochemistry. Biokhimiia

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抗坏血酸诱导的2，6-二甲氧基-1，4-苯醌的完全可逆氧化还原循环。
Biochemistry. Biokhimiia Pub Date : 1998-06-02
V A Roginsky ₁ , G Bruchelt , H B Stegmann

Affiliation

在pH值为7.40的磷酸盐缓冲液中，研究了抗坏血酸（AscH-）诱导的2,6-二甲氧基-1，4-苯醌（DMOBQ）（众所周知的有效抗癌剂）的循环氧化还原转化的动力学。摄氏度使用Clark电极和ESR技术。该过程是由于电子从AscH-转移到醌（Q）：Q + AscH--> Q *-+ Asc.- + H +（1），然后是半醌（Q.-）氧化：Q.- + O2-> Q + O2.-（2）。甚至在亚微摩尔浓度下使用的DMOBQ也能有效地催化AscH氧化，这通过大量消耗氧气和增加抗坏血酸基团（Asc.-）的稳态浓度来体现。氧气消耗率ROX长时间保持几乎恒定。发现ROX与[Q] [AscH-]产物成正比，而与各个试剂的浓度无关。由ROX和[Asc.-]确定的反应（1）的速率常数分别高达380 +/- 40和280 +/- 30 M-1.sec-1。在无氧缓冲液中将DMOBQ与相应的氢醌QH2混合时，观察到由于平衡Q + QH2左右箭头2Q.- + 2H +而形成的Q.-的ESR信号（3）。计算出（2.6 +/- 0.4）.10-5的平衡常数K3和-280 mV的还原电势变化DeltaE3 = E（Q / Q.-）-E（Q .- / QH2）从pH 7.4和37摄氏度下Q.-的稳态浓度得出。从本研究中确定的DeltaE3与文献中报道的E7（Q / Q.-）结合得出，对于标准第二单电子还原电位E（Q *-/ QH2），计算出+ 190mV的值。后者比所有研究的1，4-对苯二酚低270-230 mV。E（Q / Q.-）和E（Q .- / QH2）的非常有益的组合被认为是DMOBQ作为氧化还原循环剂的完美工作及其显着的抗癌活性的基本原因。

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Fully reversible redox cycling of 2,6-dimethoxy-1,4-benzoquinone induced by ascorbate.

The kinetics of cyclic redox transformation of 2,6-dimethoxy-1, 4-benzoquinone (DMOBQ)--the well-known effective anticancer agent--induced by ascorbate (AscH-) were studied in phosphate buffer, pH 7.40, at 37 degreesC using the Clark electrode and ESR techniques. The process is due to the electron transfer from AscH- to quinone (Q): Q + AscH- --> Q*- + Asc.- + H+ (1), followed by semiquinone (Q.-) oxidation: Q.- + O2 --> Q + O2.- (2). DMOBQ, taken even at submicromolar concentrations, effectively catalyzed AscH- oxidation that manifested itself by intensive oxygen consumption and an increase in the steady-state concentration of the ascorbyl radical (Asc.-). The rate of oxygen consumption, ROX, was kept almost constant for a long time. ROX was found to be proportional to the [Q][AscH-] product and not dependent on the concentrations of the individual reagents. The rate constant for reaction (1) determined from ROX and [Asc.-] was as much as 380 +/- 40 and 280 +/- 30 M-1.sec-1, respectively. When DMOBQ was mixed with the corresponding hydroquinone, QH2, in oxygen-free buffer, the ESR signal of Q.- which formed due to the equilibrium Q + QH2 left and right arrow 2Q.- + 2H+ (3) was observed. The equilibrium constant K3 of (2.6 +/- 0.4).10-5 and the change in the reduction potential, DeltaE3 = E(Q/Q.-) - E(Q.-/QH2), of -280 mV were calculated from the steady-state concentration of Q.- at pH 7.4 and 37 degrees C. From combination of DeltaE3 determined in this study with E7(Q/Q.-) reported in the literature, a value of +190 mV was calculated for the standard second one-electron reduction potential E(Q*-/QH2). The latter is lower by 270-230 mV than that for all the studied 1, 4-hydroquinones. The very beneficial combination of E(Q/Q.-) and E(Q.-/QH2) was suggested to be the basic reason for the perfect work of DMOBQ as a redox cycling agent and its pronounced anticancer activity.

更新日期：2019-11-01

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