Theoretical analysis of H/D geometric isotope effect on adenine-thymine base pair using multi-component molecular orbital method

The H/D isotope effect on adenine(A)-thymine(T) DNA base pair has been analyzed at Hartree-Fock/3-21G** level of multi-component molecular orbital (MC_MO) method, which can directly take account of the quantum effect of proton/deuteron. The difference of quantum nature between proton and deuteron in A-T base pair causes the geometric isotope effect (GIE) on the backbone structure of respective monomers, as well as the hydrogen-bonded structure (primary and secondary GIEs). Our MC_MO results clearly suggest the importance of the quantum nature in hydrogen-interacting systems.