拉伸干燥DNA中电子行为和局域化的多尺度模型
Multiscale model of electronic behavior and localization in stretched dry DNA
摘要：
当DNA双螺旋受到外力作用时，它可以弹性地伸长，达到其自然长度的100%。这些扭曲，施加在介观或宏观尺度上，在原子尺度上的电子性质和沿DNA的电输运有显着的影响。因此，一个多尺度的方法是必要的，以捕捉拉伸的DNA螺旋的电子行为。为了构建这样一个模型，我们开始与精确的密度泛函理论计算的电子状态在DNA碱基和碱基对中遇到的各种相对配置的平衡和拉伸形式。这些结果是补充了半经验量子力学计算状态的小尺寸[18碱基对聚（CG）-聚（CG）]干燥，中性DNA序列，使用以前公布的模型拉伸DNA。然后使用计算出的电子状态来参数化有效的紧束缚模型，该模型可以描述在存在环境影响的情况下的电子跳跃，例如在衬底的主链或结构特征上存在杂散水分子。这些效应在模型哈密顿量中引入无序，导致电子局域化。相对于未拉伸的结构，拉伸的DNA中的定位长度小几个数量级。
英文摘要：
When the DNA double helix is subjected to external forces it can stretch elastically to elongations reaching 100% of its natural length. These distortions, imposed at the mesoscopic or macroscopic scales, have a dramatic effect on electronic properties at the atomic scale and on electrical transport along DNA. Accordingly, a multiscale approach is necessary to capture the electronic behavior of the stretched DNA helix. To construct such a model, we begin with accurate density-functional-theory calculations for electronic states in DNA bases and base pairs in various relative configurations encountered in the equilibrium and stretched forms. These results are complemented by semi-empirical quantum mechanical calculations for the states of a small size [18 base pair poly(CG)-poly(CG)] dry, neutral DNA sequence, using previously published models for stretched DNA. The calculated electronic states are then used to parametrize an effective tight-binding model that can describe electron hopping in the presence of environmental effects, such as the presence of stray water molecules on the backbone or structural features of the substrate. These effects introduce disorder in the model hamiltonian which leads to electron localization. The localization length is smaller by several orders of magnitude in stretched DNA relative to that in the unstretched structure.
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