NMR observation of gramicidin A' in phosphatidylcholine vesicles

Dimyristoyl phosphatidylcholine was prepared with perdeuterated hydrocarbon chains and sonicated into bilayer vesicles together with gramicidin A'. The 1H NMR resonance from the tryptophan residues in the gramicidin has a linewidth of approximately 80 Hz, indicating significant local mobility for these residues. Paramagnetic lanthanides added to the aqueous medium cause a chemical shift of this signal indicating that some of the tryptophans may be located in the interfacial region of the bilayer.