1. Department of Molecular and Cellular Biology, and
2. Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1, Canada
3. Department of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada, and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5G 1L5, Canada