1. Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA.
2. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
3. Center for Integrative Genomics, University of Lausanne, Génopode, 1015 Lausanne, Switzerland.
4. Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
5. Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.