Summary:
We employ two Tight Binding approaches in order to describe single carrier
(hole or lectron) transfer in some periodic B-DNA segments made up of N base
pairs: (I) at the base-pair level, using the on-site energies of the base
pairsand the hopping integrals between successive ase pairs and (II) at the
single-base level, using the on-site energies of the bases and the hopping
parameters between neighboring bases, specifically between (a) two successive
bases in the same strand, (b) complementary bases that define a base pair, and
(c) diagonally located bases of successive base pairs. These Tight Binding
parameters are taken from the literature and are used to solve a system of MD
coupled equations [MD =N (Ι), MD = 2N (ΙΙ)] for the time-independent problem
and a system of MD coupled differential equations of first order for the
time-dependent problem. We solve those systems for three categories of periodic
B-DNA segments, defined by the way the base-pair sequence is constructed. For
each of these categories, we study the HOMO/LUMO eigenspectra, as well as the
HOMO/LUMO densities of states (DOS). Then, we calculate the mean (over time)
probabilities to find the extra carrier at each site [base pair (I) or base
(II)] of a given segment, the Fourier spectra, which reflect the frequency
content of charge transfer, and the pure mean transfer rates ki,i’ from a
certain site to another. We discuss the results and conclusions of both our
approaches for the three categories of segments. The comparison of the two
approaches leads to the understanding of complementary aspects of charge
transfer through DNA.
Keywords:
DNA, Charge transfer, Biological systems, One-dimensional systems, Tight binding model
