Unfolding designable structures

Among an infinite number of possible folds, nature has chosen only about 1000 distinct folds to form protein structures. Theoretical studies suggest that selected folds are intrinsically more ``designable'' than others; these selected folds are unusually stable, a property called the designability principle. In this talk we use the 2D hydrophobic-polar lattice model to classify structures according to their designability, and molecular dynamics to account for their time evolution under a gradient of force. We demonstrate that, among all possible folds, the more designable ones require lower gradient of forces to unfold due to their large number of surface-core bonds. Therefore the reduced set of selected folds are, on average, more sensitive to external forces than other folds. This dynamical property might be related to the functional flexibility expected from real protein folds.