1. Lawrence Berkeley National Laboratory, Berkeley, California 94720;
2. Department of Bioengineering, University of California at Berkeley, Berkeley, California 94720
3. Department of Biochemistry, University of Washington, Seattle, Washington 98195;,
4. Howard Hughes Medical Institute; Departments of Molecular and Cellular Physiology, Neurology and Neurological Sciences, Structural Biology, and Photon Science
5. Departments of Biochemistry and Physics, Stanford University, Stanford, California 94305;
6. Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Cambridge CB2 0XY, United Kingdom;
7. Department of Biochemistry, Duke University, Durham, North Carolina 27710;
8. Los Alamos National Laboratory, Los Alamos, New Mexico 87545;