Abstract: ObjectiveTo explore the infrared fluorescence of the gold nano-particles （AuNPs） and their labeled Cytochrome P450 at 811 nm, and to explore its mechanism. MethodDifferent sizes AuNPs were obtained by adding different amount of tri-sodium citrate to reduce the chloroauric acid in a boiled and stirred condition, and then the protein was labeled by AuNPs. The AuNPs and its labeled Cytochrome P450 were observed by the UV-visible light absorption spectrum, transmission electron microscopy (TEM) and fluorescence spectrum. ResultsWith an increase of the tri-sodium citrate， the AuNPs became smaller under TEM. The absorption peak of the larger AuNPs was at 250nm under the UV-visible spectrum, and when the AuNPs were reduced to 21nm, the absorption peak was at 525nm. When it was excited at 538nm, the emission peak was at 811nm. and the intension was enhanced after it was labeled by the protein. Conclusion Infrared fluorescence of the AuNPs can be used as a probe to determinate Cytochrome P450.

Key words: Gold nano-particles（AuNPs）, Infrared fluorescence, Cytochrome P450