Figure 3.

Potential energy landscape of alanine dipeptide in vacuum as a function of the dihedral angles φ and ψ as constructed from the amber force field (18) by constraining φ and ψ and minimizing the energy. The contours are drawn at multiples of 2 kcal/mol above the C_7eq minimum. The large rectangles indicate the stable states. (Lower) The transition state ensemble for the pathways from C_ax to C_7eq is shown as an enlargement of the square region at the saddle point region (Upper).