Professor Alex Levine
Department of Physics
University of Massachusetts
Amherst, MA 01003

Monday, October 25, 2004
3:00 pm (CT)
3269 Beckman Institute

Abstract

In this talk I introduce a minimal extension of the worm-like chain model to describe polypeptides having alpha-helical secondary structure. Due to the coupling of chain conformational degrees of freedom to "internal" secondary structure variables, the mechanical response of the molecule in thermal equilibrium is highly nonlinear. Using this model I compute both the extensional and bending moduli of the chain as well as thenonlinear interaction between applied forces and torques. In particular I demonstrate a buckling transition under applied torque and the denaturation of the molecule under tensile stress. This inherent instability of alpha helices may play a role in protein conformational change in vivo.

Tea and coffee will be served in R3151 Beckman Institute at 2:15pm.