Study of the Interaction Mechanism Between GO/rGO and Trypsin

The mechanism of GO/rGO interaction with trypsin is investigated using multiple methods. UV-Vis reveals that trypsin has a maximum absorption at 278 nm, the absorption intensity increased demonstrating GO/rGO alters the solvent environment of trypsin and exposes the aromatic chromogenic groups. ITC experiments with GO and trypsin provide a negative & UDelta;H of-25.98 KJ mol - 1and the association constant Ka of 4.829 x 10 - 4. The negative & UDelta;S of-23.64 J mol - 1 & BULL;K - 1 is further given by the Gibbs-Helmholtz equation. Combining with the & zeta; potential result, the driving forces for binding include hydrogen bonding, electrostatic interaction forces and van der Waals forces. Fluorescence spectroscopy shows that GO/rGO can significantly quench the fluorescence intensities of trypsin. The equilibrium constant Kd of GO/ rGO-24h / rGO-48h is 4.41 & PLUSMN; 0.07, 5.82 & PLUSMN; 0.53, 7.24 & PLUSMN; 0.25, respectively, which means the reduced content of oxygen-containing groups can weaken the binding forces between GO/rGO and trypsin. CD show that even low concentrations of GO/rGO affect the secondary structure of trypsin, mainly decreasing the a-helix and fl-fold content while increasing the fl-turn and random coil content of trypsin. Overall, GO/rGO can effectively interact with trypsin, the oxidation degree of GO/rGO can affects the combination of trypsin and further influence on protein conformation and function.