Synthesis and characterization of SAMs and tethered bilayer membranes from unsymmetrically substituted 1,2-dithianes

The synthesis of a series of new membrane-forming compounds, based on previously established components used in an ion-channel switch (ICS) biosensor (Nature 1997, 387, 580) is described. All new compounds are derived from 4,5-dihydroxy-1,2-dithiane, and contain a hydrophilic reservoir section (based on ethylene glycol units) and a lypophilic section (based on the natural lipid phytanol). Ellipsometry and contact angle measurements indicate that self-assembled monolayers (SAMs) formed from the new materials possess thicknesses and membrane packing comparable to previously reported biosensor components. Tethered bilayer lipid membranes (t-BLMs) incorporating the novel materials were studied using impedance spectroscopy with the ion-carrier valinomycin. The electrical behavior and calculated membrane thickness of the t-BLMs are comparable to those derived from the standard ICS components and this demonstrates that the novel membrane-forming compounds form stable membranes that are sufficiently fluid to transport potassium ions in the presence of valinomycin.