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

Abstract

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.