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

Green Platform Laboratory, Device & Materials Laboratory Fujitsu Laboratories Ltd.,10–1 Morinosato-Wakamiya, Atsugi, Kanagawa 243–0197, JapanKinetic 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 reactiontemperature. The decomposition of LSZ was analyzed by using the first order reaction. The obtained data fairly fit to the firstorder reaction equation, and the rate constant (k) was obtained. Since a good linear relationship was obtained between k valuesand particle weigh of TiHap, it was concluded that the decomposition of LSZ molecules occurs on the surface of TiHap. Theactivation energy of the reaction of LSZ decomposition on the surface of TiHap particles was determined as 30.2kJ/mol byvarying the decomposition temperature from 5 to 45°C. The comparison experiments between 0h UV and 24h UV methodsrevealed that the decomposition of LSZ needs appropriate rates of adsorption and decomposition at the TiHap particle surface. Itwas ascertained that the decomposition temperature at 25­45°C is appropriate to proceed continuous decomposition of LSZ for along time. The LC-MS measurements reveled that LSZ molecules were decomposed to the small molecules with molecular weightof 1/35­1/50 to LSZ one and they converged to the compounds with low molecular weight of 288­316 after a long time UVirradiation.