Hydration dynamics of the collagen triple helix by NMR

The hydration of the collagen-like Ac-(Gly-Pro-Hyp)(6)-NH2 triple-helical p eptide in solution was investigated using an integrated set of high-resolut ion NMR hydration experiments, including different recently developed excha nge-network editing methods. This approach was designed to explore the hydr ation dynamics in the proximity of labile groups, such as the hydroxyprolin e hydroxyl group, and revealed that the first shell of hydration in collage n-like triple helices is kinetically labile with upper Limits for water mol ecule residence times in the nanosecond to sub-nanosecond range. This resul t is consistent with a "hopping" hydration model in which solvent molecules are exchanged in and out of solvation sites at a rate that is not directly correlated to the degree of site localization. The hopping model thus reco nciles the dynamic view of hydration revealed by NMR with the previously su ggested partially ordered semi-clathrate-like cylinder of hydration. Ln add ition, the nanosecond to sub-nanosecond upper limits for water molecule res idence times imply that hydration-dehydration events are not likely to be t he rate-limiting step for triple helix self-recognition, complementing prev ious investigations on water dynamics in collagen fibers. This study has al so revealed labile proton features expected to facilitate the characterizat ion of the structure and folding of triple helices in collagen peptides. (C ) 2000 Academic Press.