Tethered mono- and bilayer lipid membranes on Au and Hg

A simple thiolipid molecule was synthesized by covalent linking of mercapto propionic acid with phosphatidylethanolamine. The integrity of thiolipid se lf-assembled monolayers supported on gold and mercury electrodes was tested by electrochemical techniques both in the absence and in the presence of h ydrophilic redox couples. The organization of the thiolipid monolayer suppo rted on gold was also assessed by surface-enhanced Raman spectroscopy both in air and in aqueous solution. The thiolipid nonolayer was then covered wi th a phospholipid monolayer to form a bilayer lipid membrane tethered to th e electrode surface (t-BLM), and the electrochemical tests were repeated us ing cyclic voltammetry, differential capacitance, impedance spectroscopy (I S), and chronocoulometry. These bilayers possess an exceptionally good mech anical stability while exhibiting electrochemical properties similar to tho se of conventional BLMs. However, no substantial "ionic reservoir" separati ng the t-BLM from the electrode surface was observed by IS. Most probably, this is due to the insufficient length of the mercaptopropionic spacer and its gauche conformation related to the electrode surface.