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 ΔH of -25.98 KJ mol −1 and the association constant Ka of 4.829 × 10 −4 . The negative ΔS of -23.64 J mol −1 ∙K −1 is further given by the Gibbs–Helmholtz equation. Combining with the ζ 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±0.07, 5.82±0.53, 7.24±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 α -helix and β -fold content while increasing the β -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.