ELECTROCHEMICAL OXIDATION OF GUANINE AT PYROLYTIC GRAPHITE ELECTRODE
ELECTROCHEMICAL OXIDATION OF GUANINE AT PYROLYTIC GRAPHITE ELECTRODE
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DOI：
10.1149/1.2407283
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发表时间：
1970-01-01
影响因子：
3.9
通讯作者：
PACE, GF
中科院分区：
文献类型：
--
作者：
DRYHURST, G;PACE, GF
在1M醋酸水溶液中，用线性和循环扫描伏安法和控制电极电位电解法研究了鸟嘌呤在热解石墨电极上的电化学氧化。鸟嘌呤通过在-N(7)~C(8)-双键上的初始2E/2H+电势决定攻击被氧化，然后-C(4)~C(5)-双键进一步的2E/2H+氧化得到2-氨基-6，8-二氧基吡啶-4，5-二醇，它是不稳定的，通过两条路线进一步反应：(A)进一步的电化学氧化成对羟基苯甲酸、胍和二氧化碳；和(B)水解成草酰基胍和二氧化碳。通过广泛使用快速扫描循环伏安法，更彻底地确定了鸟嘌呤和尿酸电氧化过程中中间物种的确切性质。特别是，在中等pH的氨缓冲液中，中间体是4，5-二胺而不是4，5-二醇。鸟嘌呤(2-氨基-6-氧嘌呤)是存在于核酸中的两种主要嘌呤之一，因此参与了许多生物过程。以前的工作已经表明，腺嘌呤或尿酸(1，2)等自然产生的嘌呤的多相电化学氧化和酶催化氧化之间存在相似之处，尽管这种平行关系似乎并不延伸到具有外环硫原子(3，4)的嘌呤。然而，观察到的这些后一种化合物的电化学可能有助于解释非常不完全了解的生物氧化。几种非含硫嘌呤的快速扫描循环伏安法表明，一般的机理可能包括形成一个共同的最终初级电化学产物，该产物被认为是二碳离子或4，5-二醇(5)。然而，不久将发表的一些甲基化黄嘌呤(6)的最新结果表明，如果N-7位甲基化，那么
The electrochemical oxidation of guanine at the pyrolytic graphite electrode was investigated by linear and cyclic scan voltammetry between pH 0-12.5 and by controlled electrode potential electrolysis in aqueous 1M acetic acid solution. Guanine is oxidized by an initial 2e/2H+ potential determining attack at the--N (7)~ C (8)--double bond followed by a further 2e/2H+ oxidation of the--C (4)~ C (5)--double bond to give 2-amino-6, 8-dioxypurine-4, 5-diol which, being unstable, undergoes further reaction by two routes:(a) further electrochemical oxidation to parabanic acid, guanidine, and carbon dioxide; and (b) hydrolysis to oxalyl guanidine and carbon dioxide. The exact nature of intermediate species in the electro-oxidation of guanine and uric acid were more thoroughly established by extensive use of fast sweep cyclic voltammetry. In particular it appears that in ammonia buffers at moderately high pH, the intermediate is a 4, 5-diamine rather than a 4, 5-diol.Guanine (2-amino-6-oxypurine) is one of the two principal purines found in nucleic acids and as such is involved in many biological processes. Previous work has indicated a similarity between the heterogeneous electrochemical and enzymatic oxidation of naturally occurring purines such as adenine or uric acid (1, 2), although this parallelism does not appear to extend to purines with exocyclic sulfur atoms (3, 4). Nevertheless, the observed electrochemistry of these latter compounds might aid in interpreting the very incompletely understood biological oxidation. Fast scan cyclic voltammetry of several nonsulfurcontaining purines has indicated that a general mechanism might be operative involving formation of a common ultimate primary electrochemical product which has been postulated to be a dicarbonium ion or a 4, 5-diol (5). However, recent results on some methylated xanthines (6) which will be published shortly indicates that if the N-7 position is methylated, then