Gnedenko B B, Ryabov A D
Department of Chemistry, Moscow State University, Russia.
Anal Chem. 1994 Jul 15;66(14):2240-4. doi: 10.1021/ac00086a007.
The reaction of amylose with NaH and FcCH2NMe3+I- in dimethyl sulfoxide brought about a redox-labeled polymer with a low degree of modification, viz. 1 ferrocene residue per 60 glucose units. The preparation, (0.017ferrocene)amylose, displays one-electron irreversible behavior at a pyrographite electrode in terms of the Delahay formalism, the formal redox potential E degree' being equal to 0.38 V at pH 6 and 40 degrees C versus SCE. Specific to amylose enzymes endo-depolymerases, which carry out random hydrolysis, accept the labeled amylose providing a significant increase in the peak current on cyclic voltammograms. The absence of potential drifts suggests that the effect is due an increase in the diffusion coefficients of the amylose fragments in the course of enzymatic digestion of (0.017ferrocene)amylose. This proposal was confirmed by the simulation of experimental cyclic voltammograms. Several practical applications of the results of this study for electrochemical assaying the amylolytic activity and evaluation of the mechanisms of the enzymatic catalysis by amylases have been demonstrated.
直链淀粉与氢化钠以及二茂铁基甲基三甲基碘化铵在二甲基亚砜中发生反应，生成了一种修饰度较低的氧化还原标记聚合物，即每60个葡萄糖单元含有1个二茂铁残基。该制剂（0.017二茂铁）直链淀粉，根据德拉海形式理论，在热解石墨电极上表现出单电子不可逆行为，在pH值为6、温度为40摄氏度时相对于饱和甘汞电极的形式氧化还原电位E°等于0.38 V。对直链淀粉具有特异性的内切淀粉酶，即进行随机水解的酶，能够接受标记的直链淀粉，这使得循环伏安图上的峰值电流显著增加。电位无漂移表明，这种效应是由于在（0.017二茂铁）直链淀粉的酶促消化过程中直链淀粉片段的扩散系数增加所致。这一推测通过对实验循环伏安图的模拟得到了证实。本研究结果在电化学测定淀粉分解活性以及评估淀粉酶酶促催化机制方面的几个实际应用已经得到了证明。
