1. Department
of Chemistry and
Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712, United States
2. Department of Chemistry, Virginia Tech, MC 0212, Blacksburg, Virginia 24061,
United States
3. Jack Skirball Chemical Biology
and Protein Laboratory, The Salk Institute, 10010 N. Torrey Pines Rd., La Jolla, California 92037, United States