Figure 4.

Active site of subtilisin Carlsberg in anhydrous dioxane compared with that in water (A) and acetonitrile (B). The catalytic triad, Asn-155 of the oxyanion hole (OH), and solvent molecules in the dioxane structure are shown as balls-and-sticks with carbon, oxygen, and nitrogen shown in white, light-gray, and black, respectively. The water molecules in the aqueous and acetonitrile structures are depicted as dark-gray balls in A and B. The acetonitrile molecules in that structure (B) are also shown as linear balls-and-sticks. The surface of the protein [Connolly algorithm (20)] in the active-site region in the dioxane structure is portrayed by black dots.