pH dependence of phosphatidic acid transition temperatures

Phosphatidic acids (PA) are normally minor components in natural membranes but there is increasing evidence that these components play a key role in aggregation, fusion and transport processes in cellular membranes. The aim of this research was to investigate the influences of pH on the transition temperatures and hentalpies of aqueous PA dispersions. The phase transition temperatures (Tt) of aqueous phosphatidic acid dispersions at different degrees of dissociation were measured using differential scanning calorimetry. The Tt vs pH diagrams of the four phosphatidic acids are quite similar and of a characteristic shape. Our experimental data are compared with measurements of different authors. A decrease of the transition temperatures was observed increasing pH and decreasing the chain lenght.