| Abstract
| - We report the first results on an enzyme-induced reaction within the water core of reverse micelles thathave been formed in supercritical CO2 (scCO2). By using a perfluoropolyether ammonium carboxylate(PFPE) surfactant, we form reverse micelles in scCO2 with water cores and we show that the oxidationof cholesterol by cholesterol oxidase (ChOx) obeys Michaelis−Menten kinetics. The results of our experimentsalso show that (1) the optimum ChOx activity occurs when the molar ratio of H2O-to-PFPE (R) exceeds∼12, (2) the rate constant describing the conversion of the ChOx−cholesterol complex to product (kcat,app)is similar to values reported using reverse micelle systems formed in liquid alkanes, (3) the equilibriumconstant that describes the ChOx−cholesterol complex dissociation (Km,app) is optimal at high R values,(4) the best-case Km,app is ∼2-fold better than the value reported using reverse micelles formed in liquidalkanes, (5) there is little change in the ChOx kcat,app and Km,app as we adjust the CO2 pressure between100 and 260 bar, and (6) the ChOx was active within the PFPE water pool for at least 5 h; however, after8 or more hours within the PFPE water pool, ChOx became temporarily inactive.
|
