Calculation of the band structure of polyguanilic acid in the presence of water and Na+ ions

Abstract

Using the Hartree-Fock crystal orbital method with a combined symmetry (helix) operation, the band structure of polyguanilic acid was calculated in the presence of water and Na+ ions. The water structure was optimized with the help of molecular mechanics.The obtained band structure shows that both the valence and conduction bands are purely guanine type. The three impurity bands in the 10.66 eV large gap are close to the conduction band and therefore cannot play any role in the assumed hole conduction of the system. Namely, according to detailed x-ray diffraction investigations of the nucleosomes in chromatin, there are possibilities of charge transfer from the negative sites of DNA to the positive ones in histones. Therefore most probably there is a hole conduction in DNA and an electronic one in the histone proteins. © 2007 American Institute of Physics.