487 Biochimica et Biophysica Acta, 471 (1977) 487--491 © Elsevier/North-Holland Biomedical Press BBA Report BBA 71322 NMR OBSERVATION OF GRAMICIDIN A' IN PHOSPHATIDYLCHOLINE VESICLES GERALD W. FEIGENSON, PAUL R. MEERS and PETER B. KINGSLEY Section of Biochemistry, Molecular and Cell Biology, Clark Hall, Cornell University, Ithaca, N. Y. (U.S.A.) (Received September 9th, 1977) Summary Dimyristoyl phosphatidylcholine was prepared with perdeuterated hydrocarbon chains and sonicated into bilayer vesicles together with gram- icidin A'. The ~H 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. Peptide-phospholipid interactions have been studied with proton nucle- ar magnetic resonance (1H NMR) spectroscopy using such systems as valino- mycin [ 1] or alamethicin [2] incorporated into aqueous phospholipid dis- persions. The perturbations of the phospholipid resonances induced by the peptides provided information about the properties of the system. Clearly, useful information is contained in the resonances of the peptide. We wish to report the first observation of the 1H NMR signals from a peptide antibiotic, gramicidin A', incorporated into phospholipid vesicles. Gramicidin A' is a mixture of linear pentadecapeptides with antibiotic activity [ 3]. The most abundant component is valine-gramicidin A: HCO-Val-Gly-Ala-Leu-Ala-Val-Val-Val-Trp-Leu-Trp-Leu-Trp-Leu-Trp NHCH~CH2OH. L L D L D L D L D L D L D L This peptide serves as a functional model for ion transport through a mem- brane, the active species being a dimer [4]. The structure of this dimer ion Abbreviation. [2H] dimyristoyl phosphatidylcholine, dimyristoyl phosphatidylcholine with perdeuterated hydrocarbon chains