1. From the Departments of Biological Regulation (M.V., K.V., R.O., S.M., M.N.) and Chemical Physics (A.L.), Weizmann Institute of Science, Rehovot, Israel; Department of Physiology and Biomedical Engineering, University of Kentucky, Lexington (M.V.); and Molecular Biotechnology Center, University of Torino, Torino, Italy (D.D.C., S.A.).