The peptide hydrates Gly-Gly-Val.2H(2)O (GGV) and Gly-Ala-Leu.3H(2)O (GAL) are known to adopt a-helical configurations containing waters of hydration in which each water is H-bonded to three or four peptide groups. Herein we report a thermodynamic and solid-state NMR (H-2 and O-17) study of these peptides. From TGA and DSC, the average enthalpy per H-bond is 15 U/mol. The dynamics and average orientation of the hydrate are studied by powder and single-crystal 2H NMR. Whereas waters that are shown by the X-ray structure to be coordinated by four hydrogen bonds do not yield observable 2H NMR signals at room temperature, two of the three triply coordinated waters yield residual H-2 quadrupole coupling tensors characteristic of rapid 1800 flip motions and the orientation of the residual tensor is that expected from the X-ray structure-derived H-bonding pattern. At -65 degreesC, the flip motions of triply coordinated water in GGV slow into the H-2 NMR intermediate exchange regime whereas the tetrahedrally coordinated water approaches the slow-exchange limit and yields an observable NMR signal. Extensive isotope exchange between water vapor and crystalline GGV establishes the presence of additional hydrate dynamics and solid-state proton transfer along a chain of water-bridged protonated alpha-amino groups.