Three main conformations of the hydroxyethyl group are observed, with dihedral values (between atoms C7, C6, methyl carbon of the C6 hydroxyethyl group and hydroxyl oxygen of the C6 hydroxyethyl group, Figure ) of approximately 50, 200 and 290 degrees, referred to here as Positions I, II and III, respectively. These three conformations involve different interactions within the active site. In Position I, the hydroxyl of the 6α-1R-hydroxyethyl group forms a direct hydrogen bond with the DW. In Position II, the methyl group is directed towards DW and Glu166, and the hydroxyl group is rotated away from the active site, hydrogen bonding with the -NH2 of the Asn132 sidechain. In Position III, the hydroxyl group is close to Glu166 and DW, but hydrogen bonds only with Oδ1 of Asn132. .