Alteration of the conformational and dynamic properties of peptides in the presence of micelles mimics the cellular events that take place during insertion and translocation of peptides in biological membranes. We have recently reported the alteration of the conformation of neuropeptides Leu- and Met-enkephalins in the presence of ganglioside GM1 micelles.(41) Here, using pulsed-field gradient-stimulated echo diffusion NMR studies, we observe that the diffusion coefficients of the peptides are greatly reduced in the presence of GM1 micelles. Partition coefficient calculations indicate a nearly total incorporation of the peptides into the micelles. The binding epitope of the enkephalins, as established from the saturation transfer difference NMR spectroscopy, indicates involvement of the Tyr(1), Gly(3), and Phe(4) residues. The involvement of the aromatic side chains of the Tyr(1) and Phe(4) indicates a possible hydrophobic nature of the interaction.