INTRAMOLECULAR HYDROGEN-BONDING IN RIBONUCLEOSIDE SUGAR HYDROXYLS - AN ABINITIO STUDY

Ab initio self-consistent field (SCF) calculations were done for a model of a ribonucleoside where only the ring part of the furanoside form of D-ribose is considered. Full geometry optimization and direct location of stationary points were used in order to characterize the geometry of the minimum energy structure and of the transition state for the proton transfer reaction in the anion. Topological analysis of the charge density and its Laplacian for the minimum energy structure allow us to find clear electronic and geometrical evidence of an intramolecular hydrogen bond. On the other hand, our results show a very low energy barrier for the proton transfer so that the proton jumps easily between the two oxygen atoms.