Date of Award


Degree Type


Degree Name

Master of Science




Dr. Mahi R. Singh

Second Advisor

Dr. Martin Zinke-Allmang


This thesis is an investigation of the charge conduction mechanism in deoxyribonucleic acid (DNA) molecules. In particular, we study the variable range hopping process and the effects which temperature and external electric field have upon it. The variable range hopping (VRH) conduction is assumed to be mediated by localized small polarons found on the base pairs, which hop in both energy and space coordinates. Phonons are created in the DNA by thermal and helical twisting motions assisting the hopping.

A model of phonon assisted variable range small polaron hopping is developed while considering a constant density of electronic states near the Fermi level. The number of states available in a “hopping space” is calculated and the temperature and electric field dependent nearest neighbour hopping range is found. A T2/3power law is predicted for the conductance of DNA, whereas the behaviour of the electric field dependence is found to be primarily exponential. We apply these results to explain the experimental work and find that our model agrees well with the available data.

To account for higher temperatures, a model of small polaron VRH conduction is developed using an exponential density of states. Through a process similar to that of the constant density of states, we derive a model which is found to agree well with the experimental results of a recent study. Additionally, an electric field dependence of the conductivity is developed to account for high electric fields.



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