1. Laboratory of Bioorganic Chemistry; National Institute of Diabetes and Digestive and Kidney Diseases; 8 Center Drive Bethesda MD 20892 USA
2. Structural Biology Section; Vaccine Research Center; National Institute of Allergy and Infectious Diseases; 40 Convent Drive Bethesda MD 20892 USA
3. Present address: Department of Biology; SBA School of Science and Engineering; Lahore University of Management Sciences; Lahore 54792 Pakistan
4. Structural Bioinformatics Core Section; Vaccine Research Center; National Institute of Allergy and Infectious Diseases; 40 Convent Drive Bethesda MD 20892 USA