The effect of electric fields on brain cephalin and lecithin films

Abstract

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.

The effect of electric fields on brain lipid-cholesterol films

“…The areas of the spectral bands increased with the applied field in the same manner as found with films of the pure PE [7]. Typical results are shown for films of the various mixtures in Figs.…”

“…The bands near 880 cm-1 in the spectra of the mixtures change intensity with applied voltages, but Table 1. A/A o is the ratio of area of band to the area with no field this band does not change its intensity in the spectra of the phospholipids where it appears as a very weak band [7].…”

“…The arrangement and procedure for measuring the effect of the field was identical to that used previously [7]. The direct-current voltage was applied across a cell consisting of two silver chloride plates with the film between the plates.…”

“…The average thickness of a film was evaluated from the weight of the lipid or mixture on the plate and the measured area of the film [7]. A density of 1.07 g/ml was used.…”

“…The behavior of films of lipids may provide information concerning the changes that occur in these substances in the neuronal membrane during excitation. Films are used because they can be considered as models for the lipid structures of the membrane.Previous observations on the effect of direct-current electric fields on films of the brain phospholipids, cephalin and lecithin, have shown that the intensities of certain infrared absorption bands were altered [7]. Since the phospholipids exist in the membrane in combination with cerebroside (CEB) and cholesterol (CHOL), the effect of the interaction between these lipids could be determined by performing similar spectral measurements with mixtures of the lipids and CHOL.…”