1. Department of Biochemistry, McMaster University, Health Sciences Centre, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5, Laboratoire de Chimie Physique des Macromolecules aux Interfaces, Université Libre de Bruxelles, Campus Plaine CP 206/2, Boulevard du Triomphe 1050, Bruxelles, Belgium, and Biophysics Department, Roswell Park Cancer Institute, Buffalo, New York 14263