The extent to which structural modifications affect the topography of complex molecular energy landscapes is largely unknown. Through quantitative mapping of the potential energy surfaces of two related hexapeptides, we find that a conformational constraint can completely alter the character of the molecular energy landscape. The linear peptide exhibits a single-funnel potential topography, while its cyclic analog exhibits a shallow energy landscape with competing basins and unevenly distributed roughness.

• Received 18 February 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.1126