¹H NMR relaxation time studies of the hydration of the barley protein C-hordein

NMR proton relaxation time measurements over a range of different water contents and temperatures are reported for the barley protein C-hordein. T₁, T_1ρ and linewidth measurements were made on the protein hydrated with ¹H₂O and ²H₂O. Distinct differences were observed in behaviour which were attributed to the effects of chemical and quantum mechanical spin exchange and to the effects of glutamine amide rotation on spin-lattice relaxation. At higher temperatures and water contents a possible conformational change was observed. It was concluded that the effects of hydration and temperature could be interpreted in terms of the breakdown of amide-amide hydrogen bonds formed by glutamine side chains and their replacement by amide-water hydrogen bonds.