1. Department
of Molecular and
Cellular Biology, Harvard University, Cambridge,
Massachusetts 02138, United States
2. Department of Chemistry, Mount Holyoke College, South Hadley, Massachusetts
01075, United States
3. Department of Biological Chemistry
and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, United States
4. Department of Biophysics and
Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
5. Charles Stark Draper Laboratory, Cambridge, Massachusetts 02139, United States