Institution: | From the ‡Genome Center of Wisconsin, University of Wisconsin, Madison, Wisconsin 53706; ;§Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706; ;¶Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53706; ;‖Cambridge Isotope Laboratories, Andover, Massachusetts 01810; ;**Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706 |