Ionic Solution Conductance Through Oriented Peptide Channels in Supported Hybrid Bilayers
M B. Smith, J Tong, Jan Genzer, Daniel A. Fischer, P K. Kilpatrick
Amphiphilic -helices were formed from designed synthetic peptides comprising alanine, phenylalanine, and lysine residues. The insertion of the - helical peptides into hybrid bilayers assembled on gold was studied by a variety of methods to assess the resulting structural characteristics, such as electrical resistance and molecular orientation. Self-assembled monolayers (SAMs) of dodecanethiol (DDT); octadecanethiol (ODT); and 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) were formed on gold substrates with and without incorporated peptide. Supported hybrid bilayers and multilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were formed on SAMs by the paint-freeze method of bilayer formation. Modeling of electrochemical impedance spectroscopy data using equivalent electrochemical circuits revealed that the addition of peptide decreased dramtically the resistive element of the bilayer films while maintaining the value of the capacitive element, indicating successful incorporation of peptide into a well-formed bilayer. Near-edge X-ray absorption fine structure spectroscopy data provided evidence that the molecules in the SAMs and hybrid multilayers were ordered even in the presence of peptide. The peptide insertion into the SAM was confirmed by observing the * resonance peak correlating with phenylalanine and a peak in the nitrogen K-edge regime attributable to the peptide bond.