1. Department of Chemistry, Princeton University, Washington Road, Princeton, New Jersey 08544, United States
2. Department of Chemistry, San José State University, 1 Washington Square, San Jose, California 95192, United States
3. Department of Bioengineering, Stanford University, 443 Via Ortega, Stanford, California 94305, United States
4. Princeton Proteomics and Mass Spectrometry Center, Princeton University, Washington Road, Princeton, New Jersey 08544, United States