1. The Clayton Foundation Laboratories for Peptide Biology, Structural Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Berne, CH 3010, Switzerland, Psychiatry/Neuroscience Research, WSJ-386/745, Novartis Institutes for Biomedical Research, Basel, CH 4002 Basel, Switzerland