[1] UNIV CALIF LOS ANGELES, DEPT CHEM, LOS ANGELES, CA 90024 USA
[2] UNIV CALIF LOS ANGELES, INST MOLEC BIOL, LOS ANGELES, CA 90024 USA
[3] UNIV PENN, SCH MED, JOHNSON RES FDN, PHILADELPHIA, PA 19174 USA
[4] UNIV AMSTERDAM, BCP JANSEN INST, BIOCHEM LAB, AMSTERDAM, NETHERLANDS
[5] UNIV PENN, SCH MED, DEPT BIOPHYS & PHYS BIOCHEM, PHILADELPHIA, PA 19174 USA
[6] CORNELL UNIV, BIOCHEM MOLEC & CELL BIOL SECT, ITHACA, NY 14853 USA
[7] UNIV STOCKHOLM, ARRHENIUS LAB, DEPT BIOCHEM, S-10691 STOCKHOLM, SWEDEN
[8] GLYNN RES LABS, CORNWALL PL30 4AV, ENGLAND