[1] NHLBI,BETHESDA,MD 20014
[2] OAK RIDGE NATL LAB,OAK RIDGE,TN 37830
[3] MIT,DEPT BIOL,CAMBRIDGE,MA 02139
[4] ROCHE INST MOLEC BIOL,NUTLEY,NJ 07110
[5] MAX PLANCK INST MOLEK GENET,D-1000 BERLIN 33,FED REP GER
[6] UNIV CHICAGO,DEPT BIOCHEM,CHICAGO,IL 60637