[1] Purdue Univ, Dept Chem, W Lafayette, IN 47907 USA
[2] Purdue Univ, Dept Med Chem, W Lafayette, IN 47907 USA
[3] Univ Calif Santa Cruz, Dept Mol Cell & Dev Biol, Santa Cruz, CA 95064 USA
[4] Univ Calif Santa Cruz, Ctr Mol Biol RNA, Santa Cruz, CA 95064 USA