13-C NMR investigation of phospholipid membranes with the aid of shift reagents.

13-C NMR spectra of sonicated phospholipid dispersions have been investigated with the aid of paramagnetic ions (Pr-3+) as shift reagents. This method permits discrimination between the outer and the inner surfaces of the vesicular membrane and gives a larger variety of signals than 1-H NMR. The lanthanide induced shifts have been found to depend on other ions present and on the lipid composition of the membrane.