Abstract
Delocalization of charges thorough DNA occurs due to the natural and continuous movements of molecule which stimulates the charge transfer through the molecule. A model is presented showing that the mechanism of electrical conduction occurs mainly by thermally-activated drift motion of holes under control of the localized carriers: where electrons are localized in the conduction band. These localized (stationary-trapped) electrons control the movements of the positive charges and do not play an effective role in the electrical conduction itself. It is found that the localized charge-carriers in the bands have characteristic relaxation times at 5 x 10 boolean AND(-2) s, 1.94 x 10 boolean AND(-4) s, 5x 10 boolean AND(-7) s, and 2 x 10 boolean AND(-11) s respectively which are corresponding to four intrinsic thermal activation energies 0.56 eV, 0.33 eV, 0.24 eV, and 0.05 eV respectively. The ac-conductivity of some published data are well fitted with the presented model and the total charge density in DNA molecule is calculated to be n = 1.88 x 10 boolean AND(19) cm boolean AND(-3) at 300 K which is corresponding to a linear electron density n = 8.66 x 10 boolean AND(3) cm boolean AND(-1) at 300 K. The model shed light on the role of transfer and/or localization of charges through DNA which has multiple applications in medical, nano-technical, bio-sensing and different domains. So, repair DNA by adjusting the charge transport through the molecule is future challenges to new medical applications. (C) 2012 Elsevier B.V. All rights reserved.