1. L. Harrington, R. Oulton, I. Arruda, Ontario Cancer Institute-Amgen Institute, Department of Medical Biophysics, University of Toronto, 620 University Avenue, Toronto, Ontario M5G 2C1, Canada.
2. T. McPhail, V. Mar, W. Zhou, Amgen EST Program, M. B. Bass, M. O. Robinson, Amgen, Inc., 1840 DeHavilland Drive, Thousand Oaks, CA 91320, USA.