1. Department of Chemistry, Department
of Molecular and Cell Biology, and the California Institute for Quantitative
Biosciences (QB3), University of California, Berkeley, Berkeley, California 94720, United States
2. Department of Chemistry and
Biochemistry, University of Colorado, Boulder,
Colorado 80309, United States
3. Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242, United
States
4. Howard Hughes Medical Institute, University of Colorado, Boulder, Colorado 80309, United
States