Probing the interactions between enkephalin peptides and beta-cyclodextrin with NMR spectroscopy

CHED 353

Amy L. Wingert, awingert@carthage.edu and Kevin F. Morris, kmorris@carthage.edu. Department of Chemistry, Carthage College, 2001 Alford Park Drive, Kenosha, WI 53140
Cyclodextrins are cyclic molecules consisting of six (alpha), seven (beta), or eight (gamma) glucose monomers. Drugs, peptides and other biomolecules form stable guest: host complexes with cyclodextrins. As a result, cyclodextrins have found applications in separation science and drug delivery. In this study, the interactions between beta-cyclodextrin and enkephalin peptides were investigated. Enkephalins are neuropeptides that play an important role in the pain response. Job plot analyses showed that all peptides formed 1:1 complexes with beta-cyclodextrin. Two-dimensional NMR spectroscopy showed that the peptides interacted with the macrocycle by inserting either their tyrosine or phenylalanine rings into the cyclodextrin cavity. Finally, NMR diffusion measurements were used to determine guest: host binding constants and free energies of association.