1. Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
2. Department of Chemistry, University of Virginia, Charlottesville, VA 22908, USA
3. Department of W. M. Keck Biomedical Mass Spectrometry Laboratory, University of Virginia, Charlottesville, VA 22908, USA
4. Department of Microbiology, University of Virginia, Charlottesville, VA 22908, USA
5. Department of Pathology, University of Virginia, Charlottesville, VA 22908, USA