Kinetic Study of Transition Mutations from G−C to A−T Base Pairs in Watson−Crick DNA Base Pairs: Double Proton Transfers

Abstract

According to the Löwdin model [Rev. Mod. Phys. 1963, 35, 724−732], the Watson−Crick guanine−cytosine (G−C) base pair is tautomerized (G*−C*) with a small probability and then replication of G*−C* produces G*−thymine (T) and adenine (A)− C* base pairs. On the basis of this model and our previous work [J. Phys. Chem. B 2020, 124, 1715−1722], we first calculated the intrinsic reaction coordinates from G*−T to G− T* using density functional theory and evaluated the probability of G*−T tautomerization to G−T* by double proton transfer (DPT) on the basis of the transition state theory. Similarly, we calculated the probability of A−C* tautomerization to A*−C by DPT. Then, according to these probabilities, we calculated the probability of transition mutations from G−C to A−T after 2 replications. The calculated probability was 1.31 × 10−8, a value consistent with the mutation rate previously reported by Drake et al. [Proc. Natl. Acad. Sci. U.S.A. 1991, 88, 7160−7164]. Our results suggest that DPT is one cause of the G−C → A−T transition. To investigate differences in the optical properties between G*−T and G−T* and between A−C* and A*−C, we also evaluated the infrared absorption spectra and Raman intensities for these base pairs.