[1] Yale Univ, Dept Mol Biophys & Biochem, New Haven, CT 06520 USA
[2] Panum Inst, Lab B, Dept Med Biochem & Genet, Ctr Biomol Recognit, DK-2200 Copenhagen, Denmark
[3] Yale Univ, Dept Chem, New Haven, CT 06520 USA
[4] Yale Univ, Dept Mol Cellular & Dev Biol, New Haven, CT 06520 USA