1. Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, Biomedical Mass Spectrometry and Functional Proteomics Facility, Department of Biochemistry and Molecular Biology, Mayo Clinic/Foundation, Rochester, Minnesota 55905, and Biomedical Sciences Department, Dental School, University of Maryland at Baltimore, 666 West Baltimore Street, Baltimore, Maryland 21201