ROLE OF THE INTERFACE IN PROTEIN EXTRACTIONS USING NONIONIC MICROEMULSIONS

The oil-water interface is thought to have a significant role in the e xtraction of proteins into nonionic microemulsions. Several surfactant s, that have a known specificity for particular proteins, have been te sted for their ability to improve the specificity of Neodol 91-2.5 (li near alcohol ethoxylate) microemulsions. Only some of these protein-sp ecific surfactants were capable of improving specificity. In successfu l extractions, a minimum amount of protein-specific surfactant has to be added to Neodol 91-2.5 nonionic microemulsion before any protein is extracted, Above this minimum, all of the protein is removed, It was also observed that below this minimum the protein-specific surfactant is present at the oil-water interface, but is not available for protei n extraction, This is in contrast with affinity-based reverse micellar extraction where the appearance of the ligand at the oil-water interf ace is sufficient to cause protein extraction, The physical structure of the interface plays a role in the protein-surfactant interactions s een in nonionic microemulsions, Two criteria need to be satisfied as a basis for successful protein extraction. A minimum headgroup area of the protein-specific surfactant, and a minimum fractional area coverag e of the protein-specific surfactant at the oil-water interface, are s imultaneously required for protein extraction, A conceptual model has been proposed to explain these observations. (C) 1997 Academic Press