Investigations of conformational structure and enzymatic activity of trypsin after its binding interaction with graphene oxide.

Herein, interaction between graphene oxide (GO) and trypsin was systematically characterized for deep investigations of conformational structure and enzymatic activity of trypsin affected by GO. Results indicated that GO bound with trypsin to form ground state complex with molar ratio of 1 to 1. Intrinsic fluorescence of trypsin was statically quenched by GO through van der Waal interaction, hydrophobic interaction, hydrogen bond, and electrostatic interaction. Both tertiary structure and secondary structure of trypsin were changed obviously after its binding with trypsin, resulting in the structure transformation of trypsin from the β-sheet structure to the α-helix structure. Since GO bound with the allosteric site of trypsin to inhibit its enzymatic activity via non-competitive manner, GO efficiently protected human serum albumin and human cervical carcinoma HeLa cells from the digestion of trypsin. These results explored the exact binding mechanism of GO with protease, which provides more important information for possible biological risk of GO on human beings.