1. Center for Biomedical Research Support, Biological Mass Spectrometry Facility, The University of Texas at Austin, Austin, Texas 78712, United States
2. Center for Vaccines and Immunology, University of Georgia, Athens, Georgia 30602, United States
3. Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
4. Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia 30602, United States
5. Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, United States