Nuclear magnetic resonance studies of erythrocyte membranes

The use of nuclear magnetic resonance spectroscopy for studying molecular interactions in biological membranes has been investigated using erythrocyte membrane fragments. Sonic dispersion of these fragments produces a sharp and well-defined high-resolution nuclear magnetic resonance spectrum. The spectrum shows peaks which can be assigned to various groups of the lipid, sugar and protein. The choline N+ (CH3)3 signal of the membrane lipid is prominent but the signal due to (CH2)n protons of the hydrocarbon chains is broadened as a result of interaction. This signal narrows at higher temperatures or when exposed to increasing concentrations of sodium deoxycholate. Signals due to amino acids of the membrane protein are unresolved in the spectrum but appear as well-defined peaks after treatment with urea or trifluoroacetic acid. Co-dispersion of the membrane fragments with lysolecithin gives a spectrum which indicates the formation of an additive complex.