January 23 , 2008
3pm in Howey Physics Lecture Room 5

 

Benjamin Smith
Departments of Physics and Pathology
University of British Columbia, Vancouver, BC

 

"Dynamic Strength of Lipid Membranes Exposed to Antimicrobial Peptides"

Many dynamic functions of cellular membranes and membrane-associated proteins are critically regulated by the composition and material properties of the lipid bilayer. To understand such regulatory mechanisms we must first identify the molecular determinants of bilayer elastic strength, permeability and stability under dynamic stress (both physical and chemical). I will show how advanced techniques of micropipette aspiration can probe the kinetic process of membrane failure, understood via a simple model of nucleation and growth of a single aqueous pore in the fluid lipid bilayer. Antimicrobial peptides of the innate immune defense system induce a dramatic weakening of the bilayers dynamic strength, quantified with extreme sensitivity (1:10000 peptide:lipids) by a reduction in pore edge energy. Alternatively, cholesterol provides a protective resistance to host (eukaryotic) membranes against the potentially toxic effects of these novel antibiotics. These studies employ thermodynamic models, statistical mechanics, and kinetic reaction rate theory to describe biological function and therefore should be of interest to the broad scientific community.