Membrane solubilization with and reconstitution from surfactant solutions: a comparison of phosphatidylserine and...

Most structural and functional studies of membrane proteins eventually require that the protein be solubilized from its original membrane, isolated and reconstituted into a membrane composed of native or specific phospholipids. The conditions comprising a successful reconstitution protocol often seem both arbitrary and elusive. The solubilization steps as the neutral surfactant octyl glucoside (OG) is added to the negatively charged lipid phosphatidylserine (PS) were followed by several optical techniques. Vesicle leakage, changes in resonance energy transfer between lipid probes and micelle formation were determined as a function of (PS) and temperature. The (OG) needed at these transitions was linear with (PS) so that average compositions and the free (OG) could be calculated for each point. More OG is needed to solubilize at 15 compared to 35 degrees C reflecting the temperature dependence of pure OG solubility. Although similar, the average compositions of the mixed surfactant-lipid structure and their temperature dependence were not identical to similar points determined for egg phosphatidylcholine and OG.