Professor David Busath
Department of Physiology and Developmental Biology
Brigham Young University
Provo, UT

Monday, October 11, 2004
3:00 pm (CT)
3269 Beckman Institute

Abstract

Simulations and experiments with simple model ion channels exhibit rich and interesting phenomena. A rigid cylindrical atomistic channel will select for cations when current is computed using applied field nonequilibrium molecular dynamics, but not when simple Langevin dynamics are employed. Gramicidin will pass formamidinium readily but not guanidinium, which simulations indicate is due both to exclusion at the mouth of the channel and binding to the center through hydrogen bonds. Force fields for gramicidin tryptophans yield varying axial potentials, and can be accurately distinguished with experiments using native-homolog heterodimers based on perturbation rate-theory. Single channel current measurements with Influenza M2 channels selectively conduct protons in very acidic conditions in spite of NMR-determined pKas suggesting full saturation of inward projecting histidine residues. Ion selectivity therefore involves interactions with water and with the channel, and sometimes escapes easy explanation.

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