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. Beijing National Laboratory for Molecular Sciences, Institute of Analytical Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
4. Department of Computer Science, Brandeis University, Waltham, Massachusetts 02454, United States