1. Department of Physiology, Sol Sherry Thrombosis Research Center, Fels Research Institute for Cancer and Molecular Biology, Temple University, School of Medicine, 3400 North Broad Street, Philadelphia, Pennsylvania 19140, Instituto de Biomedicina, CSIC, Valencia, Spain, Institute of Peptide Research, Hannover, Germany, Cardeza Foundation for Hematological Research, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, and Biogen Inc., Cambridge, Massachusetts 02142