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首页> 外文期刊>Electroanalysis >Estimation of coupling rate constant of L-cysteine radical studied by concentration-step coulometry using porous carbon felt electrode impregnated with an electrolyte
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Estimation of coupling rate constant of L-cysteine radical studied by concentration-step coulometry using porous carbon felt electrode impregnated with an electrolyte

机译：通过使用电解质浸渍的多孔碳毡电极，通过浓度-步骤库仑法研究的L-半胱氨酸自由基的耦合速率常数的估计

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Controlled potential coulometry using carbon felt electrode impregnated with electrolytic solution realizes very rapid complete electrolysis and can be used to measure the faster reaction rate constant than that using conventional electrolytic cell. In this research, concentration step method was adopted to investigate coupling reaction rate of L-cysteine radical. The coupling reaction rate of L-cysteine radical becomes much larger than further electrode reaction rate of L-cysteine radical at high L-cysteine concentration, because the coupling reaction rate is proportional to the second order of L-cysteine radical concentration although the further electrode reaction rate is proportional to the first order of L-cysteine radical concentration. At a low constant potential value, apparent number of electrons (n(app)) increased from 1 (L-cystine is produced) to 2 (L-cysteine sulfenic acid, RSOH, may be produced) according to decrease in concentration of L-cysteine to be electrolyzed. The second order rate constant of coupling reaction was estimated to be about 1200 dm(3) mol(-1) s(-1) at 20 degrees C by curve fitting method for n(app) vs. logarithm of L-cysteine concentration. Apparent number of electrons (n(app)) consumed in the electrode oxidation of L-cysteine gradually increased as an applied potential increases, because the consecutive electrode reaction steps with different electrode reaction rates were involved in the electrode oxidation of L-cysteine. In the present method, the constant limited electrolytic current was observed at high electrode potential range, which suggests that electrode oxidation rate of L-cysteine is kinetically controlled.
机译：使用浸渍有电解液的碳毡电极的可控电库仑法可以实现非常快速的完全电解，并且可以用来测量比使用常规电解池更快的反应速率常数。本研究采用浓度阶梯法研究L-半胱氨酸自由基的偶联反应速率。在高L-半胱氨酸浓度下，L-半胱氨酸自由基的偶联反应速率变得比L-半胱氨酸自由基的进一步电极反应速率大得多，因为尽管另外的电极，偶联反应速率与L-半胱氨酸自由基浓度的二阶成比例。反应速率与L-半胱氨酸自由基浓度的第一级成正比。在低恒定电势值下，随着L-浓度的降低，表观电子数（n（app））从1（产生L-胱氨酸）增加到2（可能产生L-半胱氨酸亚磺酸，RSOH）。半胱氨酸被电解。对于n（app）对L-半胱氨酸浓度的对数，通过曲线拟合方法，在20摄氏度下偶联反应的二级速率常数估计约为1200 dm（3）mol（-1）s（-1）。 L-半胱氨酸的电极氧化过程中消耗的表观电子数（n（app））随施加电势的增加而逐渐增加，因为L-半胱氨酸的电极氧化过程涉及具有不同电极反应速率的连续电极反应步骤。在本方法中，在高电极电位范围内观察到恒定的有限电解电流，这表明L-半胱氨酸的电极氧化速率是动力学控制的。

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