Ion binding study by [sup.17.O] solid-state NMR spectroscopy in the model peptide Gly-Gly-Gly at 19.6 T

[Li.sup.+] and [Ca.sup.+] binding to the carbonyl oxygen sites of a model peptide system is studied by [sup.17.O] solid-state NMR spectroscopy and [sup.17.O] chemical shift (CS) and quadrupole coupling (QC) tensors are determined in four Gly-(Gly-[sup.17.O])-Gly polymorphs by a combination of stationary and fast magic-angle spinning (MAS) methods at high magnetic field, 19.6 T. The effects of the ion binding are found to be almost an order of magnitude greater than those induced by hydrogen bonding.