In both the canonical and tautomeric configurations of A-T, the bond extension under strand separation (see Figure and) is comparable for both individual cases of the extension of the two hydrogen bonds holding the base pair together, defined (see Figure ) as B1 and B2. Bond B1 extends at a much more gradual rate than B2, showing that the bases are rotating with respect to one another. In both canonical and tautomeric cases, the rotation of the bases preferentially limits the extension of the B1 bond. We observe that bond B2 effectively stretches at the same rate at which the DNA strands are separated. The implication of this is that the bond B1 is the stronger bond of the two. Another similarity between the canonical and tautomeric configurations is that the opening angle between the base pair grows steadily until a cut-off point (which is different for each configuration) where the angular interaction of the bases reverts to approximately the original respective opening angle, where θ = 0. This reversion occurs at a lower separation distance for the canonical configuration (∼1.8 Å) than for the tautomeric configuration (∼2.0 Å). By establishing that the bond B1 appears to be stronger than B2, one can go further to say that the tautomeric configuration of the bond B1 is stronger. Figure confirms that the tautomeric version of B1 is stronger since, initially, the bond shortens, momentarily forcing an increase in the rate of angular opening. Once the angular reversions visible in Figure and 2b have occurred, both bonds extend in both the canonical and tautomeric configurations at a very similar rate. This rate is similar to the rate of strand separation.