The research objective of this study is to demonstrate that an ion- selective channel membrane with no counterpart in nature can be used as a biosensor by bringing together the novel combination of highly oriented monolayer films and gramicidin-A. It is the purpose of this proposal to elucidate, through experimentation and computer-modelling, the molecular orientation mechanism of the monolayers and the helix conformation of gramicidin within the monolayer to the transport of monovalent cations through the channel. One particularly successful method to obtain large area, ultrathin monolayer membranes is through polymerizing lipid molecules at the gas/water interface using Langmuir-Blodgett techniques. A summary of the work plan includes preparing monolayer membranes consisting of various aliphatic diacetylenes and phospholipids containing diacetylenes on an aqueous subphase with and without gramicidin-A. Variables will be introduced to the monolayer and subphase to optimize molecular orientation and film density. The channel membranes will be analyzed to verify the structure and the functionality of the monolayer. The lipid monolayers, with and without gramicidin-A will be polymerized with UV irradiation, transferred to suitable planar substrates and tested for selective ion transfer. The transfer of cations and protons will be measured across two aqueous phases that are separated by a partition containing the supported monolayer membrane. The data will provide the basis for comparing the structure-property relationship of the ion selective channel membranes against its theoretical model.
