To do this, we use DFT to calculate the stretching of the hydrogen bonds B1 and B2 and between A-T and the opening angle, θ, of the base separation (see Figure ) as a function of strand separation distance and compute the transition states of the tautomerisation reaction across a range of strand separations. MD was employed to investigate the dynamics of A-T tautomerisation and estimate the timescale of the reaction. A detailed description of the methods used in this investigation can be found in the Supplementary Information document.