From surfactant binding to understanding stability of membrane proteins

Membrane proteins are often characterized by poor stability when solubilized in surfactant solutions. Understanding how surfactants self-assemble around these proteins and affect their stability is the key to increase success rates in crystallization and functional studies of these proteins. Sedimentation equilibrium and small-angle neutron scattering with contrast variation are used to quantify binding of alkyl polyglucoside surfactants to bacteriorhodopsin. Results indicate that the mode of binding shifts from monolayer to larger shell with increasing the surfactant chain length and does not correlate with micellar aggregation number even for small and predominantly hydrophobic membrane proteins. In addition, stability studies show that the monolayer type of binding directly links to limited stability of bacteriorhodopsin under different solution conditions, including light illumination.