Photooxidation of guanine by a ruthenium dipyridophenazine complex intercalated in a double-stranded polynucleotide monitored directly by picosecond visible and infrared transient absorption spectroscopy
Photooxidation of guanine by a ruthenium dipyridophenazine complex intercalated in a double-stranded polynucleotide monitored directly by picosecond visible and infrared transient absorption spectroscopy
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DOI：
10.1002/chem.200700564
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发表时间：
2008-01-01
影响因子：
4.3
通讯作者：
Kelly, John M.
中科院分区：
文献类型：
--
作者：
Elias, Benjamin;Creely, Caitriona;Kelly, John M.
通过[Ru（dppz）（tap）（2）]（2+）（1）的光激发（400 nm）形成的瞬态物质（dppz =联吡啶并[3，2-a：2 '，3'-c]吩嗪; tap = 1，4，5，8-四氮杂菲），当插入双链合成多核苷酸[poly（dG-dC）]（2）时，在皮秒时间尺度上，通过可见瞬态吸收和（允许监测金属络合物中间体）和瞬态红外（IR）吸收光谱（允许直接研究DNA核碱基）。与其在水溶液中游离时的行为相反，当1与[poly（dGdC）]结合时，由于形成还原的络合物[Ru（dppz）（tap）（2）]（+）（速率常数=（2.0 +/- 0.2）x 10（9）s（-1）），1的激发导致515 nm处吸光度的强烈增加。1的后续重整以（1.1 +/-0.2）X 10（8）s（-1）的速率常数进行。当在D_2O中进行该过程时，[Ru（dppz）（tap）（2）]（+）的形成和去除速率降低（速率常数分别为（1.5 +/-0.3）× 10 ~（9）和（0.7 +/-0.2）× 10 ~（8）s ~（-1）），与质子耦合电子转移过程一致。在D_2O溶液中1540-1720 cm（-1）区域的皮秒瞬态红外测量证实，1嵌入[poly（dG-dC）]（2）的还原伴随着鸟嘌呤（1690 cm（-1））和胞嘧啶（1656 cm（-1））的红外基态带的漂白，它们各自具有相似的速率常数。
Transient species formed by photoexcitation (400 nm) of [Ru(dppz)(tap)(2)](2+) (1) (dppz = dipyrido[3,2-a:2',3'-c]phenazine; tap = 1,4,5,8-tetraazaphenanthrene) in aqueous solution and when intercalated into a double-stranded synthetic polynucleotide, [poly(dG-dC)](2), have been observed on a picosecond timescale by both visible transient absorption (allowing monitoring of the metal complex intermediates) and transient infrared (IR) absorption spectroscopy (allowing direct study of the DNA nucleobases). By contrast with its behavior when free in aqueous solution, excitation of 1 when bound to [poly(dGdC), causes a strong increase in absorbance at 515 nm due to formation of the reduced complex [Ru(dppz)(tap)(2)](+) (rate constant = (2.0 +/- 0.2) x 10(9) s(-1)). The subsequent reformation of 1 proceeds with a rate constant of (1.1 +/- 0.2) x 10(8) s(-1). When the process is carried out in D2O, the rates of forma-tion and removal of [Ru(dppz)(tap)(2)](+) are reduced (rate constants (1.5 +/- 0.3) x 10(9) and (0.7 +/- 0.2) x 10(8) s(-1) respectively) consistent with proton-coupled electron transfer processes. Picosecond transient IR measurements in the 1540-1720 cm(-1) region in D2O solution confirm that the reduction of 1 intercalated into [poly(dG-dC)](2) is accompanied by bleaching of IR ground-state bands of guanine (1690 cm(-1)) and cytosine (1656 cm(-1)), each with similar rate constants.