Figure 1.

The three stages of bilayer solubilization by detergents (11). (Top) Schematic depiction of Stages I–III. (Red) Phospholipid headgroups. (Blue) Detergent headgroups. (Bottom) Solubilization of a vesicle preparation (small or large unilamellar vesicles) followed through changes in turbidity. D^sat and D^sol mark, respectively, the beginning and end of Stage II. (Inset) Partial phase diagram of a lipid-detergent-water system. D^sat and D^sol are plotted versus lipid concentration. The slopes of the resulting straight lines correspond to R_e^sat and R_e^sol. The lines define three regions, containing, respectively (from low to high detergent concentration), detergent-containing bilayers, a mixture of detergent-saturated bilayers and lipid-detergent mixed micelles, and lipid-detergent mixed micelles (5).