1. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138,
2. Surface Logix Inc., 50 Soldiers Field Place, Brighton, MA 02135.
3. Department of Biomedical Engineering, University of Michigan, 2350 Hayward, 3304 GG Brown, Ann Arbor, Michigan 48109-2125.
4. Departments of Surgery and Pathology, Children's Hospital and Harvard Medical School, Enders 1007, Boston, Massachusetts 02115;