The determination of polar lipid solubilization boundaries in dilute solutions by light scattering

An apparatus and procedure have been developed which facilitate the acquisition of particle free water by recirculation through a fine membrane filter in a closed system. The system also permits one to vary, independently, composition of two solutes over a few hundred mg/l range, with ± 1 mg/l accuracy, while monitoring scattering intensities.Using these techniques it has been possible to define the phase boundary governing the solubilization of distearoylphosphatidyl choline (DSPC), above its chain melting temperature, by three homologous (C₁₆, C₁₈, C₂₀) ammoniohexanoate (AH) surfactants. The data suggest that negligible (< 1 mg/l) solubilization occurs up to an onset concentration of surfactant, C_on, which for C₁₆AH is 0.77 of the cmc. Beyond C_on finite solubilization occurs with an appreciable efficiency, which peaks at C₁₈AH at 1.35 g/g.