[1] UNIV COLORADO, HLTH SCI CTR, DEPT BIOCHEM, DENVER, CO 80262 USA
[2] UNIV COLORADO, HLTH SCI CTR, DEPT BIOPHYS & GENET, DENVER, CO 80262 USA
[3] UNIV COLORADO, HLTH SCI CTR, DEPT MICROBIOL & IMMUNOL, DENVER, CO 80262 USA
[4] UNIV COLORADO, HLTH SCI CTR, DEPT MED, DENVER, CO 80262 USA
[5] UNIV WASHINGTON, DEPT BIOL STRUCT, SEATTLE, WA 98195 USA