1. National
Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20892, United States
2. High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
3. Laboratory
of Biomolecular Research, Paul Scherrer Institute, 5232 Villigen, Switzerland
4. Department
of Computer Science, Hunter College, The City University of New York, New
York, New York 10065, United States
5. The Graduate Center, The City University of New York, New York, New York 10016, United States
6. Office of
the Director, National Institutes of Health, Bethesda, Maryland 20892, United States