1. Department of Chemistry, Texas A&M University-Kingsville, MSC 161, 700 University Blvd., Kingsville, Texas 78363, U.S.A.
2. Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, U.S.A.
3. Department of Biological and Health Sciences, Texas A&M University-Kingsville, MSC 158, 700 University Blvd., Kingsville, Texas 78363, U.S.A.
4. Chemical Biology Research Group, Texas A&M University-Kingsville, MSC 161, 700 University Blvd., Kingsville, Texas 78363, U.S.A.