Figure 10.

2D (θ₁,χ) PMF surface predicted for 1×1 UU base pairs by umbrella sampling calculations. The results include 11 minima, where (g) is the global minimum conformation (anti–anti). Three transformation pathways for syn–anti ↔ anti–anti are predicted. Energy barriers, such as the ones seen in b ↔ e and j ↔ g transformations, might be the reason why we could not see any syn–anti ↔ anti–anti transformation in regular MD simulations at 300 K. See Figure S7 for a comparison with the results previously obtained for 1×1 AA base pairs.⁴⁸