1. Department
of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
2. Division of Endocrinology, Diabetes & Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, United States
3. Salk
Institute for Biological Studies, Clayton Foundation Laboratories
for Peptide Biology, Helmsley Center for Genomic Medicine, La Jolla, California 92037, United States
4. Small Molecule Mass Spectrometry Facility, FAS Division of Science, Cambridge, Massachusetts 02138, United States