Octyl glucoside promotes incorporation of channels into neutral planar phospholipid bilayers. Studies with colicin Ia

Colicin Ia forms voltage-dependent channels in planar phospholipid bilayers containing acidic phospholipids. Addition of the neutral detergent octyl glucoside, at concentrations three orders of magnitude below its critical micelle concentration (CMC), greatly increases channel-forming activity without altering the properties of the channels themselves. Further, octyl glucoside promotes formation of channels by colicin Ia in membranes containing only neutral lipids, making it possible to study the biophysical properties of the channel undistorted by the effects of negative surface charge. In neutral membranes, the macroscopic currents are biphasic with time, the fast component is voltage-dependent and the slow component voltage-independent. The single-channel conductance in 1 M NaCl is 31 pS and the channel is slightly anion selective. The mechanism by which the detergent facilitates channel formation is discussed.