1. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
2. Department of Chemical Engineering, MIT, Cambridge, Massachusetts 02142, United States
3. Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10594, United States
4. IBM Thomas J. Watson Research Center, Cambridge, Massachusetts 02142, United States
5. IBM Research Europe, Daresbury, Warrington WA4 4AD, United Kingdom
6. Department of Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts 02142, United States