Abstract
The surface potentials (Δψ) of the mixed micelles composed of arachidonic acid (AA) and nonionic heptaethylene glycol dodecyl ether (HED) were estimated at 25 and 60°C by measuring the fluorescence intensity of 8-anilino-1-naphthalenesulfonate (ANS) as a fluorescent probe. The surface potentials of AA-HED mixed micelles, |-Δψ|, increased with increasing mole fraction of AA (XAA), and decreased with increasing ionic strength (I). These changes are due to the effects of the negative charge of AA and of the ionic atmosphere of Na+, respectively. The surface charge density (σ) was nearly independent of I and proportional to XAA, indicating that the surface state of AA-HED mixed micelles is represented by the Gouy-Chapman theory. The absolute value of σ for AA-HED mixed micelles at 60°C was slightly decreased as compared with that at 25°C.
