The effect of electric fields on brain cephalin and lecithin films.

The effect of a direct-current electric field on cephalin and lecithin films was measured using infrared spectral techniques. The intensities of the spectral bands assigned to the vibrations of the phosphate and the fatty acid chain increased to a maximum as the applied potential was increased. These changes were observed only with brain cephalin and brain lecithin films and not with synthetic lipid films. These observations may be due to changes in the alignments of the phosphate and base dipoles in the lipid molecule as the applied field is changed. The electric field strengths at which the maximum intensities of the spectral bands are observed increase as the thickness decreases. Extrapolation to the thickness of the nerve membrane yields a value of the field strength that is much larger than is to be expected in the neuron. This suggests that only the phosphate group and the hydrocarbon chain change conformation during the passage of the nerve impulse.