The proposed study will test the feasibility of using a capacitive biosensor based on an interdigitated electrode array to monitor the interaction of volatile anesthetics with cardiac membrane proteins that play a role in calcium homeostasis and are thought to be sties at which the volatile anesthetics act to depress cardiac contractility. A biosensor can be defined as a system in which a biological recognition system is coupled with a transducing device to give an electrical output that is directly usable for either measurement or control purposes. If it can be shown that such biosensors are sufficiently sensitive and that the outputs can be related to specific bimolecular processes, then this technology has enormous potential for testing pharmacologic activity and the interaction of agents that ct on membrane receptors. The voltage-dependent Ca2+ channel and Ca2+/Mg2+-ATPase from cardiac muscle will be reconstituted into membrane-like structures at the surface of a planar capacitive biosensor. The capacitance response of the system to the application of agonists, antagonists, halothane, and to various combinations of these agents will be measured. Membrane assemblies prepared by the same technique will be studied by Fourier transform infrared (FTIR) spectroscopy through use of attenuated total reflectance (ATR) techniques for obtaining spectral data from surface films. Biomembranes incorporating membrane proteins as well as assemblies formed from phospholipids alone will be observed by FTIR in order to identify the sites at which the agents bind and their effects on protein or lipid structure. Structural information obtained by FTIR will be correlated with electrical response from the biosensor to determine whether this type of biosensor can contribute to mechanistic studies and/or rapid monitoring of drug and anesthetic interactions.
