The Effect Of Hemin Functionalized Graphene Derivatives On Protein Tyrosine Nitration And The Study On Its Mechanism

Protein tyrosine nitration is implicated in the occurrence and progression of pathological conditions.It has been illuminated that hemin can catalyze protein tyrosine nitration in the presence of nitrite and hydrogen peroxide.It was reported that hemingraphene composites showed high catalytic activity.Herein,we would like to study the effects of hemin-graphene on protein tyrosine nitration and illustrate the potential application of hemin-graphene via investigating its underlying mechanism.In this work,first of all,series of nanocomposites,denoted as hemin-rGO and heminGO,were synthesized through wet-chemical method.Then,Fourier transform infrared spectroscopy(FTIR),dynamic light scattering(DLS)and atomic force microscope(AFM)had been adopted to characterize those nanocomposites.It was confirmed that hemin was successfully immobilized on the surfaces of graphene derivatives.Afterwards,the peroxidase activities of the nanocomposites were evaluated,and the effects of those nanocomposites on protein tyrosine nitration were investigated.The results suggested that hemin showed remarkable increased peroxidase-like activity after functionalization.However,both hemin-rGO and hemin-GO significantly inhibited protein tyrosine nitration in the presence of hydrogen peroxide and nitrite compared with free hemin.Furthermore,the effects of hemin-rGO and hemin-GO on catalyzing tyrosine oxidation to form dityrosine in the presence of hydrogen peroxide were studied.The results showed that those nanocomposites expedited tyrosine oxidation while suppress dityrosine formation.The former was consistent with the consequences of peroxidase-like activity,while the latter was in line with the results of protein tyrosine nitration.Moreover,Griess reaction and high performance liquid chromatograph(HPLC)were applied to measure the content of nitrite and nitrate.The results showed that those nanocomposites accelerated nitrite oxidation.Meanwhile,the content of nitrate increased gradually with higher ratio of graphene derivatives in those nanocomposites.Finally,we illustrated that both hemin-rGO and hemin-GO composites accelerated tyrosine and nitrite oxidation to produce tyrosyl radical and nitrogen dioxide radical respectively.However,on the one hand,the intercalated graphene derivatives served as barrier to inhibit radical-radical coupling reactions.On the other hand,nitrogen dioxide radical was further oxidized to nitrate by those nanocomposites.In consequence,protein tyrosine nitration was remarkably suppressed by both hemin-rGO and hemin-GO.Given the appealing properties of hemin-graphene derivatives that they facilitated the oxidation process while restrained the radical-radical coupling reaction,it may open up new perspectives for their promising potential applications in the alternative oxidation procedures for by-products cleanup.