Hydrogen bonding in the triple-helix

The increased level of detail obtained from high resolution crystal structu res of triple-helical peptides and the residue specific properties that can be defined by NMR studies on N-15-enriched peptides has given new informat ion on hydrogen bonding in the triple-helix. In particular, it has given de tails about the principle originally posed by Ramachandran to try to maximi ze the hydrogen bonding in the collagen triple-helical structure in the fac e of the lack of direct favorable interactions. Now it can be seen that by the participation of water, and by the summation of many weak hydrogen bond ing patterns, the structure is largely stabilized through hydrogen bonding, as indicated by calorimetry. The CalphaH...O=C hydrogen bonds, the water m ediated NH...CO bonds, and the hydroxyproline-water hydrogen bonds proposed by Ramachandran have been visualized and now defined in the triple-helix.