Investigations of electron-transfer reactions and the redox mechanism of 2′-deoxyguanosine-5′-monophosphate using electrochemical techniques
作者:Rajendra N. Goyal、Sham M. Sondhi、Anand M. Lahoti
DOI:10.1039/b415452p
日期:——
Electron-transfer reactions of 2â²-deoxyguanosine-5â²-monophosphate (dGMP) have been investigated in phosphate buffers of different pH at a pyrolytic graphite electrode (PGE). In cyclic voltammetry, two well-defined oxidation peaks, Ia (pH 1.9â10.6) and IIa (pH ⥠5.8), were noticed. The peak potentials shifted towards less positive potential when pH was increased. Concentration and sweep rate studies established the adsorption of dGMP on the electrode surface. UV-vis spectral analysis at pH 2.9 and 7.1 indicated formation of a UV-absorbing intermediate, which decayed in a pseudo first-order reaction (k = â¼5.05 à 10â4 sâ1). Coulometric, voltammetric and UV studies revealed the 4H+,4eâ oxidation of dGMP by an EC (electrode reactions followed by chemical reactions) mechanism. The characterization of the oxidation products was achieved by converting them to their trimethylsilyl derivatives. At pH 7.1, 5-hydroxyhydantoin-5-carboxamide (9) and a NâOâC8 linked trimer (18) and, at pH 2.9, monohydrated alloxan (12), deoxyriboside urea (11), two C8OâOC8 and one C8âC8 bridged dimers of dGMP (13, 14 and 15, respectively) were formed as the major oxidation products. A tentative redox mechanism has been suggested for the electrooxidation of dGMP.
已在热解石墨电极 (PGE) 的不同 pH 磷酸盐缓冲液中研究了 2-脱氧鸟苷-5-单磷酸 (dGMP) 的电子转移反应。在循环伏安法中,注意到两个明确的氧化峰,Ia (pH 1.9-10.6) 和 IIa (pH ≤ 5.8)。当 pH 值增加时,峰值电势向较小的正电势移动。浓度和扫描速率研究确定了 dGMP 在电极表面上的吸附。 pH 2.9 和 7.1 下的紫外可见光谱分析表明形成了紫外吸收中间体,该中间体在伪一级反应中衰变 (k = 5.05 10 4 s 1)。库仑分析、伏安分析和紫外研究揭示了 dGMP 的 4H+,4e-氧化是通过 EC(电极反应随后发生化学反应)机制实现的。氧化产物的表征是通过将其转化为三甲基甲硅烷基衍生物来实现的。 pH 7.1 时,5-羟基乙内酰脲-5-甲酰胺 (9) 和 N-O-C8 连接三聚体 (18),pH 2.9 时,一水合四氧嘧啶 (12)、脱氧核苷脲 (11)、两个 C8O- OC8 和 dGMP 的一个 C8→C8 桥接二聚体(分别为 13、14 和 15)作为主要氧化产物形成。已经提出了一种用于 dGMP 电氧化的尝试性氧化还原机制。