1. Department
of Chemistry, Columbia University, New York, New York 10032, United States
2. Department
of Physics, Indian Institute of Technology, Kanpur 208016, India
3. Howard
Hughes Medical Institute, Department of Biochemistry and Molecular
Biophysics, Columbia University, New York, New York 10027, United States
4. Department
of Biology, Columbia University, New York, New York 10027, United States