1. Chemical Process R&D, Amgen, Inc., One Kendall Square, Building 1000, Cambridge, Massachusetts 02139, U.S.A., Chemical Process R&D, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, U.S.A., and Analytical Chemistry, Amgen, Inc., One Amgen Center Drive, Thousand Oaks, California 91320, U.S.A.