Micellar Properties of the Zwitterionic Detergents 'CHAPS' and 'CHAPSO' used in Membrane Biochemistry

Centre for Cellular and Molecular Biology, Hyderabad-500 007

The micellar properties of the zwitterionic detergent 3-[(3-cholamidopropyl)- dimethylammonio]-1-propane-sulphonate (common name CHAPS) and its 2-hydroxy derivative, CHAPSO, are described. These form micelles above 8 mM in water, have a molecular area at the interface of around 160 Ų (CHAPS) and 120 A² (CHAPSO), and appear to be arranged in stacks, similar to the bile salts. CHAPS is shown to be totally inert towards a globular protein, and to be able to essentially quantitatively solubilise liver microscome cytochrome P-450.