1. Department of Biochemistry and Biophysics, 2011 Agricultural and Life Sciences, Oregon State University, Corvallis, Oregon 97331, United States
2. Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania, 3700 Hamilton Walk, Philadelphia, Pennsylvania 19104, United States
3. Department of Chemistry, Portland State University, P.O. Box 751, Portland, Oregon 97207, United States
4. Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States