1. Harvard-MIT Division of Health Sciences and Technology, MIT, Cambridge, Massachusetts 02139, United States
2. Program in Biophysics, Harvard University, Boston, Massachusetts 02115, United States
3. Microsoft Research New England, Cambridge, Massachusetts 02142, United States
4. Department of Biological Engineering, MIT, Cambridge, Massachusetts 02139, United States
5. Department of Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts 02139, United States
6. Howard Hughes Medical Institute, Cambridge, Massachusetts 02139, United States