The Effect Of Oxidative Damage Of Fibrinogen On Fibrosis

Reactive oxygen species(ROS) mediated biochemical mechanisms of protein oxidation. ROS can directly induce protein, resulting in the body's physiological and pathological changes, and even accelerate the aging process. Hydrogen peroxide(H2O2) and hydroxyl radical(OH.) is one kind of ROS, and both of them have strong oxidizing power. They can modify process of protein post-translation modification under physiological or pathological conditions. Such modifications can cause oxidation of the protein, induce a series of reactions and may eventually lead to various diseases.Fibrinogen is an important protein and essential for homeostasis. During coagulation, the soluble fibrinogen is converted to insoluble fibrin polymers. The process is initiated by thrombin, which catalyzes the cleavage first of two fibrinopeptides from the amino termini of the ?-chains and then two fibrinopeptides from the amino termini ?-chains. It has been shown that oxidative fibrinogen may induce various diseases.In this paper, free radical oxidative damage of fibrinogen was studied and use antioxidant assay with TiO2 nanoparticles. The main work are as the following: 1. Effects of Oxidative Stress Induced by H2O2 on Fibrillization of Fibrinogen:Circular dichroism(CD) spectrum, UV-vis spectroscopy, ?-potential, size distribution and conductivity were applied to study the structure and properties of fibrinogens oxidized with H2O2 in the solution. Atomic force microscopy(AFM) was used to characterize the oxidized fibrinogen and the formed fibrin. The results demonstrated that oxidized damage can influence the conformations, the aggregation behavior and the surface properties. CD spectrum usually can be used to study the secondary structures of protein. CD spectrum demonstrated that H2O2 can modify the conformation of fibrinogen molecule. The results show that H2O2 can change the conformation of fibrinogens. 2. Effects of Oxidative Stress Induced by hydroxyl radical on Fibrillization of Fibrinogen:Circular dichroism spectrum, UV-vis spectroscopy, ?-potential, size distribution and conductivity were applied to study the structure and properties of fibrinogens oxidized with OH. in the solution. The UV spectrum of protein is originated from the absorption of side chains of Trp residue and Tyr residue to UV light and the strong absorption of peptide bonds. The result shows that Trp and Tyr residues were not substantially cleaved from the fibrinogen molecules. ?-Potential indicates the degree of repulsion between adjacent, similarly charged particles in a dispersed solution.The variation of solution conductivity indicated that oxidative stress of OH. to fibrinogen can alter the electrical charges of fibrinogen molecules. The results show that OH. can chang conformation of fibrinogens. 3. Antioxidant assay with TiO2 nanoparticles:A method based on the photogeneration of OH radicals in water from TiO2 nanoparticles has been developed to study the kinetics of oxidation of organic molecules used as biological antioxidants. The kinetic of oxidation of terephthalic acid taken here as a reference probe is monitored by fluorescence measurements of the concentration of its oxidized form, 2-hydroterephthalic acid. The kinetic of oxidation of other antioxidant molecules is then deduced from the radical scavenging competition.