Sub-picosecond proton tunnelling in deformed DNA hydrogen bonds under an asymmetric double-oscillator model

TL;DR

This paper models proton tunnelling in DNA hydrogen bonds using a double oscillator framework, revealing that under certain deformations, tunnelling occurs in sub-picosecond timescales relevant to biological processes.

Contribution

It introduces a novel asymmetric double oscillator model for proton tunnelling in DNA, showing how geometric deformations significantly reduce tunnelling times to biologically relevant scales.

Findings

Proton tunnelling times can be reduced by up to 40 orders of magnitude with asymmetry.

Tunnelling occurs in less than one picosecond under most planar deformations.

The model links proton tunnelling to biological phenomena like mutations.

Abstract

We present a model of proton tunnelling across DNA hydrogen bonds, compute the characteristic tunnelling time (CTT) from donor to acceptor and discuss its biological implications. The model is a double oscillator characterised by three geometry parameters describing planar deformations of the H bond, and a symmetry parameter representing the energy ratio between ground states in the individual oscillators. If the symmetry parameter takes its maximum value of 1, then we recover a known model which produced CTTs too large to be biologically relevant; but this is reduced by up to 40 orders of magnitude as the symmetry parameter is decreased. We discover that unless the symmetry parameter is close to 1 or 0, the proton's CTT under any planar deformation is guaranteed to be below one picosecond, which is a biologically relevant time-scale. This supports theories of links between proton tunnelling and biological processes such as spontaneous mutation.