title: The electrostatic interactions between nano-TiO(2) and trypsin inhibit the enzyme activity and change the secondary structure of trypsin.
abstract: In this work, the interaction between nano-TiO(2) and trypsin was investigated, and the mechanisms of the interaction were explored by the methods of UV-vis detection, circular dichroism (CD), and fluorescence. The results clearly demonstrated that nano-TiO(2) had an inhibitory effect on the enzyme activity. The activity was decreased to 64% of the untreated trypsin in the presence of 300 μg/ml nano-TiO(2). UV spectrometry proved that nano-TiO(2) had a strong physical absorption effect on trypsin, and the CD spectra revealed that the secondary structure of trypsin was partly destroyed while bound together with nano-TiO(2). The ratio of α-helix increased from 7.9% to 12.8% in the presence of 100 μg/ml TiO(2) while the ratio of β-sheet decreased from 48.7% to 36.4%. Furthermore, the fluorescence spectrometry indicated that nano-TiO(2) could quench the intrinsic fluorescence of trypsin through static quenching. Meanwhile, the binding constant was calculated to be 1, and the process of binding of trypsin on nano-TiO(2) was a spontaneous molecular interaction procedure in which electrostatic interaction plays a major role. Our study was to provide a useful approach for evaluating the health risk of nanomaterials on level of proteins.
authors.affiliation: Shanghai key laboratory of cell signaling and diseases, School of Life Science and Technology, Tongji University, 1239 Siping Road, Shanghai 200092, People's Republic of China.
authors.forename: Wen-Rui
authors.initials: WR
authors.lastname: Wang
authors.forename: Rong-Rong
authors.initials: RR
authors.lastname: Zhu
authors.forename: Rong
authors.initials: R
authors.lastname: Xiao
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.forename: Shi-Long
authors.initials: SL
authors.lastname: Wang
mesh_terms: D002942:Circular Dichroism; D005453:Fluorescence; D017433:Protein Structure, Secondary; D014025:Titanium / Q000737:chemistry*; D014357:Trypsin / Q000737:chemistry* / Q000378:metabolism*
chemical_list: C009495:titanium dioxide; D014025:Titanium; D014357:Trypsin