Solubilization and activity of proteins in compressible-fluid based microemulsions

We have used the pressure dependency of density in near critical propane to design a novel protein extraction system. Active, structurally intact, proteins have been extracted from an aqueous phase into subcritical propane containing the non-ionic detergent polyoxyethylene sorbitan trioleate (Tween-85). The pressure dependence of protein transfer from the aqueous to organic phase is described for cytochrome C and subtilisin. The effect of the microemulsion and compressible propane on protein structure and function is also discussed. The first determinations of kinetic constants for an enzyme-catalyzed reaction in such a system are also presented.