Electron Donor鈥揂cceptor Interactions with Flanking Purines Influence the Efficiency of Thymine Photodimerization

详细信息    查看全文

• 作者：Zhengzheng Pan ; Mahesh Hariharan ; Joshua D. Arkin ; Almaz S. Jalilov ; Martin McCullagh ; George C. Schatz ; Frederick D. Lewis
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：December 28, 2011
• 年：2011
• 卷：133
• 期：51
• 页码：20793-20798
• 全文大小：856K
• 年卷期：v.133,no.51(December 28, 2011)
• ISSN：1520-5126

文摘

Quantum yields for thymine photodimerization (桅<sub>TTsub>) have been determined for a series of short DNA single-strand and base-paired hairpin structures possessing a single thymine鈥搕hymine step with flanking purines. Values of 桅<sub>TTsub> are strongly dependent upon the oxidation potential of the flanking purine, decreasing in the order: inosine > adenine > guanine > deazaguanine. The dependence of 桅<sub>TTsub> on the ionization potential of the flanking purine is more pronounced when the purine of lower oxidation potential is located at the 5鈥? versus 3鈥?position in either a single strand or a hairpin. Molecular dynamics simulations for hairpin structures indicate that the TT step is 蟺-stacked with both the 5鈥?and 3鈥?purine, but that there is little 蟺-stacking with either purine in single-strand structures. The observation of moderately intense long-wavelength UV absorption features for hairpins having 5鈥?Z or G flanking purines suggests that excitation of ground state donor鈥揳cceptor complexes may account for more extensive quenching of dimerization by 5鈥? versus 3鈥?purines. The 鈥減urine effect鈥?on 桅<sub>TTsub> is attributed to a combination of ground state conformation, ground state electron donor鈥揳cceptor interactions, and excited state exciplex formation.