1. Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
2. Department of Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
3. Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
4. Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada