SPECIFIC CAPACITANCE OF METAL SUPPORTED LIPID-MEMBRANES

A model for the structure of supported bilayer lipid membranes (s-BLM) is assumed based on the measurement of specific capacitance, electros triction and surface potential of the s-BLM formed on the tip of fresh ly cut Teflon or polymer coated stainless steel wire and of the electr olyte-metal interface, depending on the frequency of AC voltage. We ha ve shown that s-BLM does not represent a continuous bilayer on a metal support. Its structure is like that of a continuous monolayer, three layers, or in certain case, also like that of a bilayer interrupted by 'islands' of metal support. The former ones are characterized by a sm aller resistance in comparison with a lipid bilayer and with specific capacitance 20-50 times higher than that of conventional; free standin g BLM. The assumed model allows us to understand the nature of a numbe r of effects observed on s-BLM, particularly the behavior of current f luctuations. The nature of current fluctuations can be easily explaine d by fluctuations of the size of the 'islands' both towards increase a nd/or decrease of their diameter due to removal and/or appearance of n ew lipid molecules on a metal support.