Estimates of electronic coupling for excess electron transfer in DNA.
Estimates of electronic coupling for excess electron transfer in DNA.
复制标题
DNA 中过量电子转移的电子耦合估计。
DOI：
10.1063/1.1961400
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发表时间：
2005
影响因子：
4.4
通讯作者：
A. Voityuk
中科院分区：
文献类型：
--
作者：
A. Voityuk
电子耦合V（da）是决定DNA中电荷转移速率的关键参数之一。虽然已经有几个计算研究的V（da）的空穴转移，估计的电子耦合的过量电子转移（ET）在DNA中仍然不可用。本文提出了一种计算π堆栈中碱基对间ET矩阵元素的有效策略。考虑两种方法。首先，我们采用非绝热态（DS）方法，其中供体和受体用典型碱基对腺嘌呤-胸腺嘧啶（AT）和鸟嘌呤-胞嘧啶（GC）的自由基阴离子表示。在这种方法中，使用标准6- 31 G（*）和扩展6-31+ +G（**）基组获得了类似的V（da）值。其次，电子耦合是由中性体系的最低未占分子轨道（LUMO），通过使用广义Mulliken-Hush或碎片电荷方法。由于AT和GC的自由基-阴离子态很好地再现了LUMO的中性碱基对计算没有扩散功能，V（da）的估计值是在良好的协议与自由基-阴离子态使用DS方法得到的耦合。然而，当用扩散函数计算中性堆时，系统的LUMO表现出偶极束缚特性，不能用于估计电子耦合。我们的计算表明，ET矩阵元素V（da）的模型含有intrastrand胸腺嘧啶和胞嘧啶碱基基本上大于耦合在复合物与interstrand嘧啶碱基。过量的电子转移的矩阵元素被发现是相当小的空穴转移的相应值，并在DNA堆栈的结构变化非常敏感。
Electronic coupling V(da) is one of the key parameters that determine the rate of charge transfer through DNA. While there have been several computational studies of V(da) for hole transfer, estimates of electronic couplings for excess electron transfer (ET) in DNA remain unavailable. In the paper, an efficient strategy is established for calculating the ET matrix elements between base pairs in a pi stack. Two approaches are considered. First, we employ the diabatic-state (DS) method in which donor and acceptor are represented with radical anions of the canonical base pairs adenine-thymine (AT) and guanine-cytosine (GC). In this approach, similar values of V(da) are obtained with the standard 6-31G(*) and extended 6-31+ +G(**) basis sets. Second, the electronic couplings are derived from lowest unoccupied molecular orbitals (LUMOs) of neutral systems by using the generalized Mulliken-Hush or fragment charge methods. Because the radical-anion states of AT and GC are well reproduced by LUMOs of the neutral base pairs calculated without diffuse functions, the estimated values of V(da) are in good agreement with the couplings obtained for radical-anion states using the DS method. However, when the calculation of a neutral stack is carried out with diffuse functions, LUMOs of the system exhibit the dipole-bound character and cannot be used for estimating electronic couplings. Our calculations suggest that the ET matrix elements V(da) for models containing intrastrand thymine and cytosine bases are essentially larger than the couplings in complexes with interstrand pyrimidine bases. The matrix elements for excess electron transfer are found to be considerably smaller than the corresponding values for hole transfer and to be very responsive to structural changes in a DNA stack.