Horizontal 'solvent-free' lipid bimolecular membranes with two-sided access can be formed and facilitate ion channel reconstitution.

We present here an easily used method and apparatus for formation of horizontal 'solvent-free' lipid bilayer membranes affording two-sided access. These horizontal bilayers allow direct delivery of submicroliter volumes of samples onto the membrane upper surface increasing the efficacy of reconstitution by several orders of magnitude, as demonstrated using Staphylococcus aureus alpha-toxin. Also, they permit creation of locally high and transient transbilayer osmotic gradients to initiate fusion of ion-channel containing liposomes with planar membrane, which, following fusion, leaves the membrane and channel in essentially symmetric bathing solutions. This method is especially advantageous for cases where thickness of the membrane, absence of hydrocarbon solvent, or presence of differing lipid compositions in the two monolayers is critical.