Thymine Hydration

between wireframe and spacefilling models. The wireframe model also displays hydrogen bonds, as calculated by JSmol.

Again we see eleven waters in the "hydration shell." The methyl group of thymine prevents formation of a complete ring around the rim of the flat aromatic ring. Instead, we see a chain of hydrogen bonded water molecules spanning the nonpolar surface of the ring. This bridge is possible because steric crowding by the methyl group forces the two water molecules hydrogen bonded to the adjacent keto group away from the plane of ring. These two waters in turn serve as the abutment for the bridge across the nonpolar surface. Hence the hydrogen bonded bridge spanning the nonpolar face compensates for the weak attraction that water molecules have for nonpolar surfaces.