A Novel Thermooptical Detection Method for Enzyme Reaction Based on the Optical Beam Deflection Induced by Reaction Heat

Abstract

A novel thermooptical detection method for enzyme reaction based on the optical beam deflection induced by reaction heat is proposed. A probe beam passes through a CCl4 phase above which a model enzyme reaction occurs. The enzyme reaction medium is arranged to be either interfaced directly with the CCl4 phase or separated from the CCl4 phase by a thin gold film. The decomposition reaction of hydrogen peroxide catalyzed by catalase is used as a model enzyme reaction. In the arrangement that the reaction medium is interfaced directly with the CCl4 phase, both the reaction heat and the reaction product O2 diffuse into the CCl4 phase, and thus generate temperature and concentration gradients, respectively. Since both the temperature and concentration gradients induce the deflections of the probe beam, two peaks are observed in the deflection signal. On the other hand, in the arrangement that the reaction medium is separated from the CCl4 phase by the gold film, only the deflection signal generated by the temperature gradient is detected. The quantitative relations between the deflection signals induced by the reaction heat and the concentrations of catalase and H2O2 are investigated. Under the present batch experimental conditions, deflection signals are linear in the concentration ranges of 4 × 10−3-4 × 10−2 mol/liter for H2O2, and 11-550 μg/ml (activity, 11-550 unit/ml) for catalase solution, respectively. The detection limits for H2O2 and catalase solution are 4 × 10−3 mol/liter and 11 μg/ml (activity, 11 unit/ml), respectively. In addition, the possibilities of development as a new thermooptical biosensor and application to the determination of activity distribution of this method are also discussed.