¹³C NMR Spectra of Lecithin Vesicles and Erythrocyte Membranes

Abstract

UNLIKE proton nuclear magnetic resonance (NMR) spectroscopy, ¹³C NMR has the potential advantages in studies of macromolecular systems of a wider range of chemical shifts (∼200 p.p.m.) and of reduced resonance broadening in structures with restricted molecular motion. Thus we have been able to observe ¹³C NMR spectra of unsonicated lecithin and erythrocytes, which do not yield high resolution proton spectra. We also report T₁ relaxation times for ¹³C nuclei in the polar headgroup of the lecithin molecule and at both ends of the alkyl chains, in sonicated vesicles in D₂O buffer and in deuterochloroform. The results are consistent with increasing chain motion towards the terminal methyl group of the alkyl chains for both systems, in agreement with relaxation data for stearic acid derivatives specifically labelled with ¹⁹F nuclei in lecithin vesicles¹, and with the results of similar spin label experiments of Hubbell and McConnell².