Electronic structure of single stranded DNA base stacks

The electronic density of states (DOS) curves of single stranded periodic and aperiodic DNA base stacks in B-conformation obtained with the help of simple negative factor counting (NFC) method are presented. Band structure results of polyadenine [poly (A)]; polyguanine [poly (G)]; polycytocine [poly (C)] and polythymine [poly (T)] obtained on the basis of ab initio Hartree Fock crystal orbital method using both minimal basis and double zeta basis sets have been used as input to calculate these DOS. In contrast to the periodic systems, the peaks in the DOS curves of the corresponding aperiodic systems are broader with fewer gaps in between for both levels of approximation. The calculated large values of bandgap obtained for these systems rule out the possibility of intrinsic conduction in them.