THE INTEGRATED SYSTEM FOR ELECTROCHEMICAL INVESTIGATIONS OF BILAYER LIPID MEMBRANES

Sławomir Kalinowski

Warsaw University, Białystok Branch, Institute of Chemistry, Al. J. Piłsudskiego 11/4, 15-443 Białystok, Poland

The measurement system for carrying the complex studies of electrical properties of bilayer lipid membranes was constructed. This system is controlled by the PC computers with Windows environment. The system makes possible carrying out different types of experiments using voltage and current clamp techniques, membrane potential measurements and capacitance measurements. The measurements can be made in two-, three- or four-electrode arrangement.

The investigations of the electrical phenomena in planar bilayer lipid membranes consist of a few stages. The first stage is the membrane formation. The best method for controlling this process is recording the membrane capacitance. This metod allows to observe the membrane thickness, bilayer area and its stability. The membrane quality can be also tested by measurements of the resistance (voltammetric curves) and electrocompressibility (capacitance-voltage curves). The classical electroanalytical techniques as cyclic voltammetry, chronoamperometry, potentiometry can be used for studies e.g. transport processes, redox reactions, photoeffects, membrane fusion. While the current clamp techniques can be used for investigations of the membrane electroporation.

A new method for simultaneous recording the several parameters of the membranes is in developing. This method is based on the capacitance minimization method. After each cycle the measurement points are fitted to the parabola equation. Next the following parameters are calculated: minimum capacitance, minimum capacitance potential (difference between surface membrane potentials), hysteresis voltage, and electrocompressibility. These parameters describe phenomena on the membrane surfaces and inside the bilayer.