A study on the kinetics of inhibitory effect of 4-hydroxy-3-methoxybenzoic acid on the monophenol- and diphenol-oxidation activity of mushroom tyrosinase has been carried out using enzymological kinetic analysis method in a Na2HPO4-NaH2PO4 buffer solution (pH=6.8) at 30 °C. The results show that 4-hydroxy-3-methoxybenzoic acid efficiently can inhibit both monophenol- and diphenol-oxidation activity of mushroom tyrosinase under experiment conditions. Concentrations of 4-hydroxy-3-methoxybenzoic acid leading to 50 % inhibition rate (IC50) on monophenol- and diphenol-oxidation activity were calculated to be 1.3 mmol/L and 2.6 mmol/L respectively, which are lower than that of arbutin (IC50 = 5.3 mmol/L for diphenol-oxidation activity). The presence of 4-hydroxy-3-methoxybenzoic acid also prolongs the lag period in oxidation of L-tyrosine via tyrosinase — A 4.7-minute lagging was observed in the presence of 4 mmol/L 4-hydroxy-3- methoxybenzoic acid, compared to a 1.1-minute lagging in the absence of inhibitor. The inhibition kinetics analyzed by Lineweaver-Burk plots found 4-hydroxy-3- methoxybenzoic acid to be a mixed-type inhibitor for the oxidation of L-DOPA, the equilibrium constants for inhibitor binding with free enzyme, KI , and with enzyme-substract complex, ＫIS, were 1.76 mmol/L and 8.57mmol/L respectively.

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Nanocomposite microspheres were successfully prepared by grafting TiO2particles to microPCMs by chemical reaction method. The effects of modification of nano TiO2particles, adding time of TiO2dispersion and the amount of TiO2on the surface morphology were investigated. The results indicated that the optional method is adding the TiO2dispersion as soon as all the prepolymer was added to the reaction system, and the optional mass ratio of TiO2to microPCMS is 10wt%.

Methyl ferulate was synthesized by methanol and ferulic acid with strongly acidic cation exchange resin as catalyst under microwave irradiation. The effect of catalyst activity was investigate by single factor experiment. Amount of catalyst, microwave treatment time, microwave output power and methanlo/ ferulic acid ratio were investigate by single factor experiment and orthogonal experiments. The optimal reaction conditions were ferulic acid being 0.1mol, molar radio of ethanol to ferulic acid being 5:1, mass percent of resin being 30％ of the reagent, microwave power being 300W, reaction time being 25 min. The yield of product was 81.2％ under the potimal conditions. The catalytic characteristics of regenerated catalyst were stable and the yield of product may keep greater than 76% after the 732# resin used five times.

Calculating methods of inhibitor concentration leading to yield 50% inhibition (IC50) of competitive inhibitor, noncompetitive inhibitor and mixed inhibitor were proposed on the basis of kinetics of enzyme inhibition, and were applied to calculate IC50 value of concerned compounds, such as cinnamic acid, cinnamaldehyde, benzoic acid and et al. The calculating results of competitive inhibitor, noncompetitive inhibitor and mixed inhibitor are similar to experimental data, and the average errors are only 3.7%, 2.4%, 4.6%, respectively. The calculating method is confirmed to be reliable by the results.