For the molecular dynamics investigation, we find that the DNA strand separation occurs at a speed of ∼1.25 Å ps -1 . If we assume that, at a separation distance of 2.0 Å, the tautomerisation reaction does not reverse back to the canonical state, the lifetime of the tautomer need only exceed ∼1.6 ps. This assumption is very reasonable since, at separations >1.56 Å, the reverse energy barrier would require temperatures of >3.5