Figure 4.

(A) Conformation of the amide moiety. The image depicts a superimposition of the four independent amide linkages with average values of torsion angles indicated on the right. (B and C) Major and minor groove hydration in the central portion of the RNA13 duplex. Two views of the overlay of four strands (only residues 5–8 are shown) depict (B) major groove hydration and (C) minor groove hydration (obtained after rotation by 90? around the vertical). Carbon atoms of strands 1, 2, 3 and 4 are colored in beige, pink, salmon and gray, respectively. The small spheres represent water molecules with colors matching their respective strands and dashed lines indicate hydrogen bonds. The amide carbonyls and the adjacent linking carbon atoms are colored in green and C-NH-CO-C linkages are highlighted in ball and stick mode.