1. Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
2. Department of Molecular Biology and Biochemistry, Center for Advanced Biotechnology and Medicine, and Northeast Structural Genomics Consortium, Rutgers University, Piscataway, NJ 08854, USA.
3. Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA.
4. Department of Chemistry and Biochemistry and Northeast Structural Genomics Consortium, Miami University, Oxford, OH 45056, USA.
5. Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260, USA.
6. Howard Hughes Medical Institute (HHMI) , Seattle, WA 98195, USA.