Electrochemical Determination of Triple Helices: Electrocatalytic Oxidation of Guanine in an Intramolecular Triplex
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- 作者：Rebecca C. Holmberg and H. Holden Thorp
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：August 9, 2004
- 年：2004
- 卷：43
- 期：16
- 页码：5080 - 5085
- 全文大小：129K
- 年卷期：v.43,no.16(August 9, 2004)
- ISSN：1520-510X
文摘
Electrocatalytic oxidation of the oligonucleotide 5'- GAA GAG GTT TTT CCT CTT CTT TTT CTT CTC C (TS) byRu(bpy)32+ was studied by cyclic voltammetry. This oligonucleotide forms either an intramolecular triplex, hairpin,or single strand, depending on the pH (Plum, G. E.; Breslauer, K. J. J. Mol. Biol. 1995, 248, 679-695). In thetriplex form, the guanine doublet in TS is buried inside the folded structure, and as such is less susceptible tooxidation by electrogenerated Ru(bpy)33+. Digital simulations of the catalytic voltammograms gave a rate constantof 3.5 ± 0.2 × 102 M-1 s-1 for oxidation of the triplex form, while oxidation of the duplex and single-stranded formsoccurred with much faster rate constants of (3.5-9.1) × 104 M-1 s-1. Experiments using a truncated form of TSthat lacked the third strand of the triplex were consistent with these measurements. The Ru(bpy)33+ complex wasalso generated by photolyzing Ru(bpy)32+ in the presence of Fe(CN)63-. This reaction produced strand scissionfollowing piperidine treatment, which was visualized using high-resolution gel electrophoresis. These experimentsshowed decreased reactivity for the triplex form, and also gave an unusual reversal of a common selectivity for the5'-G of GG doublets generally seen in B-form DNA. This reversal was ascribed to strain caused by the locationof the GG doublet adjacent to the hairpin loop.