Kinetic study on the protein decomposition by photocatalytic Ti(IV)-doped calcium hydroxyapatite particles

Abstract

Kinetic study was done for the decomposition process of lysozyme (LSZ) on the surface of Ti(IV)-doped calcium hydroxyapatite (TiHap) particles. The decomposition of LSZ was examined by changing the weight of TiHap particles dispersed and reaction temperature. The decomposition of LSZ was analyzed by using the first order reaction. The obtained data fairly fit to the first order reaction equation, and the rate constant (k) was obtained. Since a good linear relationship was obtained between k values and particle weigh of TiHap, it was concluded that the decomposition of LSZ molecules occurs on the surface of TiHap. The activation energy of the reaction of LSZ decomposition on the surface of TiHap particles was determined as 30.2 kJ/mol by varying the decomposition temperature from 5 to 45°C. The comparison experiments between 0 h UV and 24 h UV methods revealed that the decomposition of LSZ needs appropriate rates of adsorption and decomposition at the TiHap particle surface. It was ascertained that the decomposition temperature at 25–45°C is appropriate to proceed continuous decomposition of LSZ for a long time. The LC-MS measurements reveled that LSZ molecules were decomposed to the small molecules with molecular weight of 1/35–1/50 to LSZ one and they converged to the compounds with low molecular weight of 288–316 after a long time UV irradiation.