[Study of Reaction Dynamics between Bovine Serum Albumin and Folic Acid by Stopped-Flow/Fluorescence].

As a kind of coenzyme of one-carbon enzymes in vivo, folic acid belongs to B vitamins, which can interact with other vitamins and has great significance for converting among amino acids, dividing growth of cells and protein synthesis reactions. Half-life, concentration and reaction rate constant of drugs are important parameters in pharmacokinetic study. In this paper, by utilizing fluorescence spectrophotometer and stopped-flow spectrum analyzer, reaction kinetic parameters between bovine serum albumin(BSA) and folic acid in a bionic system have been investigated, which provide references for parameters of drug metabolism related to folic acid. By using Stern-Volmer equation dealing with fluorescence quenching experiments data, we concluded that under 25, 30, and 37 degrees C, the static quenching constants of folic acid to intrinsic fluorescence from bovine serum albumin were 2.455 x 10(10), 4.900 x 10(10) and 6.427 x 10(10) L x mol(-1) x s(-1) respectively; The results of kinetic reaction rate have shown that the reaction rate of BSA and folic acid are greater than 100 mol x L(-1) x s(-1) at different temperatures, pH and buffering media, illustrating that the quenching mechanism between BSA and folic acid is to form composite static quenching process. Reaction concentration of bovine serum albumin and its initial concentration were equal to the secondary reaction formula, and the correlation coefficient was 0.998 7, while the half-life (t1/2) was 0.059 s at physiological temperature. With the increase of folic acid concentration, the apparent rate constant of this reaction had a linear increasing trend, the BSA fluorescence quenching rate constant catalyzed by folic acid was 3.174 x 10(5) mol x L(-1) x s(-1). Furthermore, with different buffer, the apparent rate constant and reaction rate constant of BSA interacting with folic acid were detected to explore the influence on the reaction under physiological medium, which is of great significance to determine the clinical regimen, forecast the efficacy and toxicity of drugs and rational drug.

[Research on the Reaction Dynamics between Peroxynitrite and Tyrosine Catalyzed with Mimic Enzyme through Flow Injection Analyzer].

As a highly active free radical in vivo, peroxynitrite can damage various biological macromolecules and cause a series of major diseases, which is of great significance to determine its content and reactive mechanism. It is very difficult to capture the dynamic process of peroxynitrite due to its active property and fast reacted rate. In this paper, we firstly explored the kinetic characteristics of peroxynitrite and tyrosine with the presence of Hemoglobin and Hemin by using flow injection analyzer. The results showed that the oxidation processes of peroxynitrite and tyrosine catalyzed with hemoglobin and hemin were in accordance with Michaelis-Menten's dynamics law; Based on the Michaelis constant (K(m)) and the maximum initial rate (V(max)), we deduced the reaction mechanism that peroxynitrite, catalyzed by mimic enzymes, directly oxidized tyrosine combined with mimic enzymes, rather than decomposed to · OH and O(-2)·; In addition, we detected the rate constant of the reaction catalyzed by these two kinds of enzymes at different temperature and pH, resulting that the optimum conditions of hemoglobin to catalyze this system were 25 ℃ and pH 8, the rate constant was 1.035×10(6) mol·L(-1) · s(-1), while hemin was 37 ℃ and pH 9.5, the rate constant was 6.842×10(5) mol·L(-1) · s(-1); Comparing the kinetic parameters, K(m)Hb(4.46 µmol·L(-1))V(Hemin)(max)(0.026 ΔIF/s), we discovered that the rate constant of hemoglobin in optimum condition was greater than that in hemin, and the catalytic activity of hemoglobin was higher than that of hemin. All these results have provided kinetic parameters for the study of determining the content of peroxynitrite and exploring its reaction mechanism with enzymatic method. It also laid a theoretical foundation for developing new diagnosis technology to prevent and cure diseases caused by free radicals in vivo.