Observation of polymerlike phase separation of protein-surfactant complexes in solution

Protein solution at appropriate pH and ionic strength has been shown to phase separate upon addition of suitable amount of anionic surfactant, sodium dodecylsulfate (SDS). We determine a series of cloud-point curves for bovine serum albumin-SDS complexes in aqueous solutions at different pH. Small angle neutron-scattering and light-scattering studies give strong evidence that these denatured proteins in solution are multicomponent polymerlike objects. We show that the generalized Flory-Huggins theory for polydisperse polymers can describe the cloud-point curves satisfactorily.