Proton MAS NMR of a protein in a frozen aqueous solution

1H MAS NMR spectra of α-chymotrypsin in aqueous solution and in ice are presented. The MAS technique allows one to resolve mobile protein polypeptide side chains, even at subzero temperature (248 K). Determination of the amount of non-freezing water at the protein-ice interface using MAS NMR is of advantage in comparison to transverse relaxation time analysis.