1. Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1, Canada
2. Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada
3. Centre for Structural Biology, McGill University, Montreal, Quebec H3G 0B1, Canada
4. Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4L8, Canada