The mechanism of electrical breakdown in the membranes ofValonia utricularis

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Abstract
The dielectric breakdown in the membranes of cells ofValonia utricularis was investigated using intracellular electrodes and 500-μsec current pulses. Electrical breakdown, which occurs when the membrane potential reaches a well-defined critical value, is not associated with global damage to the cell or its membranes (the membrane reseals in I–V characteristics observed at different temperatures can be accurately accounted for with no adjustable parameters, by considerations of the mechanical compression of the membrane due to stresses induced by the electric field. Electrical breakdown on this scheme results from an electromechanical instability in the membrane. On this basis the present results indicate that the elastic modulus of the region of the membrane where breakdown occurs, decreases by a factor of 2 with increasing temperature from 4 to 30°C. On the assumption of a thickness of 4.0 nm and a dielectric constant of 5, the elastic modulus is estimated to have a value of 5×106 Nm−2 at 20°C.

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