Oxidation of 7-Deazaguanine by One-Electron and Oxo-Transfer Oxidants: Mismatch-Dependent Electrochemistry and Selective Strand Scission

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• 作者：Ivana V. Yang and H. Holden Thorp
• 刊名：Inorganic Chemistry
• 出版年：2001
• 出版时间：March 26, 2001
• 年：2001
• 卷：40
• 期：7
• 页码：1690 - 1697
• 全文大小：170K
• 年卷期：v.40,no.7(March 26, 2001)
• ISSN：1520-510X

文摘

Addition of oligonucleotides containing 7-deazaguanine (Z) to solutions containing Ru(dmb)₃²⁺ (dmb = 4,4'-dimethyl-2,2'-bipyridine) produces an enhancement in the oxidative current in the cyclic voltammogram of themetal complex that can be used, through digital simulation, to determine the rate of oxidation of 7-deazaguanineby Ru(dmb)₃³⁺. The measured rate constants are about 10 times higher than those for oxidation of guanine byRu(bpy)₃³⁺, even though the redox potential of Ru(dmb)₃^3+/2+ is 200 mV lower. A potential of 0.75 V (vs Ag/AgCl) can therefore be estimated for the oxidation of 7-deazaguanine, which can be selectively oxidized overguanine when Ru(dmb)₃³⁺ is the oxidant. The rate of oxidation was much faster in single-stranded DNA, and thedifference between rates of single-stranded and duplex DNA was higher than for guanine. The oxidation rate wasalso sensitive to the presence of a single-base mismatch at the 7-deazaguanine in the order Z·C < Z·T < Z·G ~Z·A < single-stranded. The Z·T mismatch was much more readily distinguished than the G·T mismatch, consistentwith the overall greater sensitivity to secondary structure for Z. The oxidation reaction was also probed bymonitoring piperidine-labile cleavage at the Z nucleotide, which could be generated by treatment with eitherphotogenerated Ru(bpy)₃³⁺ or the thermal oxidant Ru(tpy)(bpy)O²⁺ (tpy = 2,2',2' '-terpyridine). These oxidantsgave qualitatively similar selectivities to the electron-transfer rates from cyclic voltammetry, although the magnitudesof the selectivities were considerably lower on the sequencing gels.