1. Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, Livermore, California 94550, Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, Biosystems Research Department, Sandia National Laboratory, Livermore, California 94551-0969, and Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143