Hatcher Elizabeth, Balaeff Alexander, Keinan Shahar, Venkatramani Ravindra, Beratan David N
Department of Chemistry, Duke University, French Family Science Center, Durham, North Carolina 27708, USA.
J Am Chem Soc. 2008 Sep 3;130(35):11752-61. doi: 10.1021/ja802541e. Epub 2008 Aug 12.
The effects of structural fluctuations on charge transfer in double-stranded DNA and peptide nucleic acid (PNA) are investigated. A palindromic sequence with two guanine bases that play the roles of hole donor and acceptor, separated by a bridge of two adenine bases, was analyzed using combined molecular dynamics (MD) and quantum-chemical methods. Surprisingly, electronic structure calculations on individual MD snapshots show significant frontier orbital electronic population on the bridge in approximately 10% of the structures. Electron-density delocalization to the bridge is found to be gated by fluctuations of the covalent conjugated bond structure of the aromatic rings of the nucleic bases. It is concluded, therefore, that both thermal hopping and superexchange should contribute significantly to charge transfer even in short DNA/PNA fragments. PNA is found to be more flexible than DNA, and this flexibility is predicted to produce larger rates of charge transfer.
研究了结构波动对双链DNA和肽核酸（PNA）中电荷转移的影响。使用分子动力学（MD）和量子化学相结合的方法，分析了一个回文序列，该序列有两个鸟嘌呤碱基分别作为空穴供体和受体，由两个腺嘌呤碱基构成的桥隔开。令人惊讶的是，对单个MD快照进行的电子结构计算表明，在大约10%的结构中，桥上存在显著的前沿轨道电子布居。发现电子密度向桥的离域受核酸碱基芳香环共价共轭键结构波动的控制。因此得出结论，即使在短的DNA/PNA片段中，热跳跃和超交换对电荷转移也应起显著作用。发现PNA比DNA更具柔性，预计这种柔性会产生更大的电荷转移速率。
