Determination of hydrophobicity of myelinic, synaptosomal, and mitochondrial surfaces in the rat brain.

The hydrophobicity of myelinic, synaptosomal and mitochondrial surfaces in the rat brain was measured using the nonionic surfactant, C18H37O(CH2CH2O)13H. This method is based on the adsorption of the hydrophobic alkyl group of the surfactant by the hydrophobic sites on the surfaces. Each preparations was mixed with an excess of the surfactant and the surfactant remaining in the supernatants was determined spectrophotometrically by measuring the absorbance of tetrabromophenolphthalein ethylester at 690 nm. The greatest amount was adsorbed by myelin, followed by synaptosomes and mitochondria. The hydrophobicity is shown to be a reflection of the surface lipids. This method showed good reproducibility and was useful for the quantitative determination of hydrophobicity.