Preferred conformation, orientation, and accumulation of dynorphin A-(1-13)-tridecapeptide on the surface of neutral lipid membranes

Abstract

Infrared attenuated total reflection (IR-ATR) spectroscopy and capacitance minimization (CM) were used to study the secondary structure, orientation, and accumulation of dynorphin A-(1-13)-tridecapeptide (dynorphin1-13) molecules on the surface of planar membranes prepared from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. The peptide assumed a helical structure oriented perpendicularly on the membrane surface. Binding from aqueous solutions containing 10 mM KCl saturated reversibly at about a bilayer area of 110 nm2 per peptide molecule, an apparent dissociation constant of 11 microM, and rate constants of 2 X 10(2) s-1 (adsorption) and 2 X 10(-3) s-1 (desorption). The results complement those obtained by vesicle-mediated hydrophobic labeling [Gysin, B., & Schwyzer, R. (1983) Arch. Biochem. Biophys. 225, 467-474]. They indicate that the behavior of this amphiphilic peptide in contact with neutral lipid membranes may be quite different from that in molecularly disperse or micellar solutions of detergents or lysolecithins and that, in the case of dynorphin1-13, primary amphiphilicity overrules secondary amphiphilicity.