1. Contribution from the Laboratory for Bioorganic Chemistry, Sloan-Kettering Institute for Cancer Research, 1275 York Avenue, New York, New York 10021, Department of Physiology, Weill Medical College of Cornell University, 1300 York Avenue, New York, New York 10021, Laboratory of Developmental Hematopoiesis, Cell Biology Program, Sloan-Kettering Institute for Cancer Research, New York, New York 10021, Analytical Core Facility, Sloan-Kettering Institute for Cancer Research, 1275 York Avenue, New York, New...