DEPENDENCE OF HOMO–LUMO GAP OF DNA BASE PAIR STEPS ON TWIST ANGLE: A DENSITY FUNCTIONAL APPROACH

Abstract

Electronic structure calculations of all 10 unique base pair (bp) steps have been calculated to study the interaction energies of the bp steps, density of states (DOS), projected density of states (pDOS) using the density functional theory (DFT). Plane wave basis with ultrasoft pseudo-potential method has been used within the local density approximation (LDA) for the exchange correlation functional. Electron densities of the bp steps corresponding to HOMO and LUMO level have been calculated to understand the difference in stacking energies of the bp steps. The variation of HOMO–LUMO gap (g) of all possible bp steps on twist angle has been studied. We have observed that out of the 10 bp steps, 4 purine–purine bp steps (d(AA), d(GG), d(AG) and d(GA)), show significant variation of [Formula: see text] on twist angle. The observed variation on twist angle of d(AA) bp step has been explained by the calculated DOS and electron densities.