THE MICELLE TO VESICLE TRANSITION OF LIPIDS AND DETERGENTS IN THE PRESENCE OF A MEMBRANE-PROTEIN - TOWARDS A RATIONALE FOR 2D CRYSTALLIZATION

The assembly of two-dimensional membrane protein crystals in the prese nce of lipids was analyzed with quasielastic light scattering and elec tron microscopy, Mixtures of detergent-solubilized lipids and/or prote ins were submitted to slow or rapid dilution while measuring the hydro dynamic radii of the aggregates. Lipids alone exhibited lambda-shaped dilution curves with intermediate rod-shaped particles that converted into small vesicles. Depending on the protein-protein and protein-lipi d interactions, detergent-solubilized protein-lipid mixtures showed a sharp transition from micelles to large, densely packed proteoliposome s. Electron microscopy revealed that formation of crystals occurred sh ortly after this phase transition.