In this paper, tyrosine was modified by the benzotriazole structure through the coupling reaction with the diazonium salt to form the intermediate and the ring-closing reaction of the intermediate to form the benzotriazole structure. Structure of intermediate and modified tyrosine was characterized via high performance liquid chromatography (HPLC), fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (1H-NMR) and mass spectra (MS) methods; then the photo-degradation curve under ultraviolet (UV) exposure of the modified tyrosine was measured and compared with the tyrosine; UV and fluorescence spectrum were used to analyze the photo-stabilization mechanism of the modified tyrosine. Results showed that the photo-degradation rate of modified tyrosine was less than one fifth of tyrosine after UV irradiation for 2 h and far less than that of tyrosine in the whole irradiation experiment in this work, proving that the photo-stability of the tyrosine was greatly improved by introducing the benzotriazole structure after the modification. From the analysis of UV and fluorescence spectrum, the photo-stabilization mechanism of the modified tyrosine was revealed.

Zongqian Wang, Yinchun Fang and Jun Li