Levine Ariel D, Iv Michael, Peskin Uri
Schulich Faculty of Chemistry , Technion - Israel Institute of Technology , Haifa 32000 , Israel . Email:
Chem Sci. 2016 Feb 1;7(2):1535-1542. doi: 10.1039/c5sc03495g. Epub 2015 Nov 20.
Experiments on hole transfer in DNA between donor and acceptor moieties revealed transfer rates which are independent of the molecular bridge length (within experimental error). However, the physical origin of this intriguing observation is still unclear. The hopping model implies that the hole propagates in multiple steps along the bridge from one localized state to another, and therefore the longer the bridge, the slower the transfer. This can explain weak length-dependence but not a length-independent transfer rate. We show that the rigid molecular structure of a poly-A bridge supports single step transitions from a localized hole state to delocalized states, spread over the entire bridge. Since propagation to the bridge end is a single step process (termed quantum unfurling) the transfer rate becomes independent of the bridge length. This explanation is consistent with experimental results, and emphasizes the importance of structural order in charge transfer through bio-molecular systems.
关于供体和受体部分之间DNA中空穴转移的实验揭示了转移速率与分子桥长度无关（在实验误差范围内）。然而，这一有趣观察结果的物理起源仍不清楚。跳跃模型表明，空穴沿着桥以多步从一个局域态传播到另一个局域态，因此桥越长，转移越慢。这可以解释较弱的长度依赖性，但无法解释与长度无关的转移速率。我们表明，聚腺苷酸桥的刚性分子结构支持从局域空穴态到扩展在整个桥上的离域态的单步跃迁。由于传播到桥端是一个单步过程（称为量子展开），转移速率变得与桥长度无关。这一解释与实验结果一致，并强调了结构有序性在通过生物分子系统进行电荷转移中的重要性。
