Abstract:

We discuss a small polaron hopping model, in order to explain the intense temperature (T) dependence of the electrical conductivity (σ) observed at high temperatures along the DNA molecules. The model takes into account the one-dimensional character of the system as well as the presence of disorder in the DNA double helix. Theoretical considerations based on percolation lead to analytical expressions for the high temperature multiphonon-assisted small polaron hopping conductivity, the maximum hopping distance and their temperature dependence. For example, experimental data for the lambda-phage DNA, the poly(dA)-poly(dT) DNA, and the native wet-spun calf thymus Li-DNA, follow nicely the theoretically predicted behavior, EQUATION, over wide high-T ranges. In contrast to some previously presented theoretical suggestions, our model leads to realistic values for the maximum hopping distances, supporting the idea of multiphonon-assisted hopping of small polarons between next nearest neighbors of the DNA molecular “wire”. We also examine the low temperature case.

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