Conformational Control of TT Dimerization in DNA Conjugates. A Molecular Dynamics Study
Conformational Control of TT Dimerization in DNA Conjugates. A Molecular Dynamics Study
复制标题
DOI：
10.1021/jp100983t
复制
发表时间：
2010-04-22
影响因子：
3.3
通讯作者：
Schatz, George C.
中科院分区：
文献类型：
--
作者：
McCullagh, Martin;Hariharan, Mahesh;Schatz, George C.
本文给出了几种DNA结构中TT步骤的[2+2]和6-4光二聚反应的量子产率结果，其中发夹决定了光二聚反应产率的上下文依赖关系，并发展了一个理论模型，正确地描述了二聚反应产率随DNA结构的变化趋势。所考虑的DNA偶联物包括dt(20)、da(20)dt(20)和三个含有单一TT步骤的烷基连接发夹。[2+2]过程的理论模型建立在乙烯+乙烯的CASSCF电子结构计算的基础上，计算结果表明，低激发态的光激发导致在接近二聚体结构的几何位置与基态表面锥形相交的势表面没有明显的势垒。对二聚化的主要约束是两个双键之间的距离d，并且发现d<；3.52埃导致的量子产率趋势在3倍内与观察到的趋势相匹配。对两个双键之间的二面角的约束不是那么重要，尽管通过包括这些约束可以对某些结构产生更好的二聚化产率预测，但没有约束地获得了最佳的总体情况。对于6-4二聚化，距离g<；2.87埃和对二面角的限制提供了对产率的准确描述。
The paper presents quantum yield results for the [2+2] and 6-4 photodimerization of TT steps in several DNA structures, including hairpins where the context dependence of the photodimerization yield is determined, and it develops a theoretical model that correctly describes the trends in dimerization yield with DNA structure. The DNA conjugates considered include dT(20), dA(20)dT(20), and three alkane-linked hairpins that contain a single TT step. The theoretical modeling of the [2+2] process is based on CASSCF electronic structure calculations for ethylene + ethylene, which show that photoexcitation of low-lying excited states leads to potential surfaces that correlate without significant barriers to a conical intersection with the ground state surface at geometries close to the dimer structure. The primary constraint on dimerization is the distance d between the two double bonds, and it is found that d < 3.52 angstrom leads to quantum yield trends that match the observed trends within a factor of 3. Constraints on the dihedral angle between the two double bonds are not as important, and although it is possible to generate better dimerization yield predictions for some structures by including these constraints, the best overall picture is obtained with no constraint. For 6-4 dimerization, a distance g < 2.87 angstrom and no constraint on dihedral angle provide an accurate description of the yield.