The Theory Studies On Anodic Reaction Of Biofuel Cell Assembled With Glucose Oxidase

Enzyme biofuel cells（EBFC）with a wide range of fuel sources,excellent biocompatibility,mild reaction conditions,have potential application prospects in many fields.In recent years,a large number of studies focus on enhancing the direct electron transfer between the enzyme active center and inorganic electrode,increasing the enzyme load,and extending the life of enzymes with experimental method to improve enzyme biological fuel cell performance.Although a large number of achievements have been made,the widespread use of enzyme biofuel cells still faces the defects of insufficient performance.How to further improve the performance of enzyme biofuel cells,it is necessary to study the nature of the microscopic reaction mechanism of the EBFC electrode.The development of quantum chemistry provides a powerful tool for us to understand the electronic reaction mechanism of biofuel at the molecular and atomic level.Therefore,with the help of high-precision theoretical methods,this paper deeply studies the role of the protein environment around the enzyme activity center in the EBFC,as well as the influence of electrode materials on the enzyme activity,which plays an important role in guiding the reasonable construction of high-performance enzyme biofuel cell.The research contents of this work mainly include:（1）The effect of protonated state of His505/His548 on proton/electron transfer in reduced half-reaction of active center of glucose oxidase.We used the ONIOM method to study the synergistic regulation of different protonated His505,His548 and Arg210 on the proton/electron transfer process of GOx active center at the ONIOM（M06-2X/6-31G（d,p）:PM6）level.The GOx reductive half-reaction involves the transfer of two electrons and two protons fromβ-D-glucose,in which one proton from the hydroxyl group at C₁and one proton from C₁ transfer to His505（or His548）and the isoalloxazine at N₅,respectively,while the isoalloxazine gains two electrons fromβ-D-glucose.Through detailed analysis the structures of reactant,transition state,product in different protonated states of His505,His548 and Arg210,combining with corresponding electronic states and potential energy diagrams,it is found that the activation energy of the reaction has reduced.Because of the electrostatic effect of protonated His505 can effectively promote the transfer of two protons onβ-D-glucose,and it has a synergistic effect with electron absorption capacity of Arg210,that promotes the proton/electron transfer in the catalytic reaction process of GOx active center.Due to the electrostatic attraction of the protonated His548 and Arg210 to isoalloxazine from opposite directions,respectively,the competitive effect has generated,which is not conducive to the electron transfer in the catalytic reaction process of the active center of GOx.（2）Regulation of B,N,S doped graphene electrode materials on proton/electron transport in active sites of glucose oxidase.The structures of reactant,transition state and product of B,N and S doped graphene in the catalytic oxidation ofβ-D-glucose reaction at the glucose oxidase were optimized at the M06-2X/6-31G（d,p）level,and the structural changes of the reaction sites,electronic states and corresponding potential energy diagrams were analyzed in detail.It is found that due to the different electronegativity of B,N and S atoms,they act as the center of positive charge or negative charge in the corresponding doped graphene,respectively,while theπ-conjugated system in graphene weakens the function of the center of charge.B atom is less electronegative,and S atom has a larger atomic radius and much electrons.Under the action ofπ-conjugated system,both B and S atoms in the corresponding doped graphene lose electrons,and the plane of doped graphene bears a negative potential,which is not conducive to electron transfer to the electrode.N atom has high electronegativity,and the corresponding doped graphene plane with positive potential.But N atom acquires fewer electrons in theπ-conjugated system,therefore,the strong electron absorption ability of N atom survived.The positive potential on the plane of N-doped graphene and the electron-absorbing action of N atoms themselves effectively promote electron transfer to the electrode.In addition,we have also investigated the effects of the graphite structure and pyridine structure of N-doped graphene and BN doped graphene on proton/electron transfer in the reductive half-reaction of GOx,it is found that the graphite structure of N-doped graphene and a certain doping proportion of BN doped graphene are conducive to promoting electron transfer to the electrode.