A physical characterization of some detergents of potential use for membrane protein crystallization

Micellar solutions of lauryldimethylamine oxide, n ‐dodecyl‐β‐D‐maltoside and 1‐dodecanoylpropanediol‐3‐phosphorylcholine were studied by use of small‐angle neutron scattering. These detergents have been selected due to their use as solubilizing agents for membrane proteins. LDAO was found to form a homogeneous, approximately spherical micelle with a radius of 20.7 Å and an M r of 16 000. N ‐Dodecyl‐β‐D‐maltoside forms an inhomogeneous micelle with a core of low scattering density surrounded by a shell of high scattering density. The data are in accord with a micelle forming an oblate ellipsoid and the disaccharide group pointing outward radially from the hydrophobic group. The semi‐axes are 16.8 and 25.5 Å and the M r is 66 000. 1‐Dodecanoylpropanediol‐3‐phosphorylcholine forms a rather homogeneous, roughly spherical micelle. The radius is 24 Å, the M r being 28 700. The data indicate a tangential packing of the phosphorylcholine head groups into a polar layer of 3–4 Å surrounding the micelle core. The use of these detergents as solubilizing agents during membrane protein crystallization is discussed.