Preparation and electrochemical behavior of gramicidin-bipolar lipid monolayer membranes supported on gold electrodes

Abstract

Gramicidin-containing synthetic bolalipid membranes comprised of 2,2'-di-O-decyl-3,3'-O-1,20-eicosanyl-bis-rac-glycero-1,1'-diphosphocholine (C20BAS) have been synthesized and supported on gold electrodes. Supported membranes were prepared by first depositing a partial bolalipid layer on the electrode using a thioctic acid-modified bolalipid (1'-O-omega-thioctamidetetraethylene glycol-2,2'-di-O-decyl-3,3'-di-O-1,20-eicosanyl-bis-rac-glycero-1-phosphate, SSC20BAS) as an anchoring group, followed by a vesicle fusion step using either pure C20BAS or gramicidin-containing C20BAS (C20BAS-GA) vesicles. The latter configuration was designed to immobilize single, continuously-on channels of gramicidin in the C20BAS membrane. Vesicle deposition to form supported bolalipid monolayer membranes was monitored by impedance spectroscopy and cyclic voltammetry. Impedances were observed to increase with vesicle deposition time. Pretreatment of the impedance electrode with SSC20BAS accelerated the supported monolayer membrane deposition rate. Impedances decreased in a gramicidin concentration-dependent manner when gramicidin was incorporated into the C20BAS membrane. These supported bolalipid membranes are also surprisingly inert to organic solvent exposure (CH(3)CH(2)OH;CH(2)Cl(2)), suggesting that they may serve as robust host matrices for integral membrane protein-based sensors.