1. Departments of biology, physics, and medicine of Brookhaven National Laboratory, Upton, New York 11973.
2. Departments of biology, physics, and medicine of Brookhaven National Laboratory, Upton, New York 11973; National Science Foundation.
3. Departments of biology, physics, and medicine of Brookhaven National Laboratory, Upton, New York 11973; Health Sciences Center of the State University of New York at Stony Brook.