1. Center for Biomedical Mass Spectrometry, Boston University School of Medicine, Boston, Massachusetts 02118, United States
2. Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States
3. Department of Chemistry and Biochemistry, Montclair State University, Montclair, New Jersey 07043, United States
4. Department of Computer Science, Brandeis University, Waltham, Massachusetts 02453, United States