Water-in-Carbon Dioxide Microemulsions: An Environment for Hydrophiles Including Proteins

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Science  02 Feb 1996:
Vol. 271, Issue 5249, pp. 624-626
DOI: 10.1126/science.271.5249.624


Carbon dioxide in the liquid and supercritical fluid states is useful as a replacement for toxic organic solvents. However, nonvolatile hydrophilic substances such as proteins, ions, and most catalysts are insoluble. This limitation was overcome by the formation of aqueous microemulsion droplets in a carbon dioxide-continuous phase with a nontoxic ammonium carboxylate perfluoropolyether surfactant. Several spectroscopic techniques consistently indicated that the properties of the droplets approach those of bulk water. The protein bovine serum albumin (BSA) with a molecular weight of 67,000 is soluble in this microemulsion and experiences an environment similar to that of native BSA in buffer.