A Kinetic Study on Dismutation of Superoxide Ion by Macrocyclic Dioxotetramine-Copper(Ⅱ) Complex by Using Pulse Radiolysis

We studied the reaction kinetics of dismutation for superoxide ion by copper (Ⅱ) complex of macrocycllc dioxotetramine ligand 12- ( 4' - nitro )- benzyl-1,4,7,10- tetraazacy-clotridecane-11,13-dionato copper (Ⅱ) by using pulse radiolysis. The rate constants of dismutation kcat's were measured to be 1. 78×106 mor-1 . L.s-1(at pH 7. 0) and 1. 06×106 mol-1. L. s-1(at pH 7. 8). The reaction mechanism is similar to that catalyzed by super-oxide dismutase.

THE DISMUTATION OF SUPEROXIDE ANION BY COPPER(Ⅱ)COMPLEX OF 1,4,7,10-TETRAAZACYCLOTRIDECANE-11,13-DIONE—A KINETIC STUDY BY MEANS OF PULSE RADIOLYSIS

The dismutation kinetics of superoxide anion by copper complex of 1,4,7,10-tetranza- cyctotridecane-11,13-dione was studied by pulse radiolysis.The dismutation rate constants at various pH and concentration of complex were obtained.

Development of picosecond pulse radiolysis system at Waseda University

A compact pulse radiolysis apparatus using a BNL-type s-band photocathode RF gun is now under development at Waseda University.The laser pulse is used for excitation of the photocathode and for generation of white light,which is used for analyzing light in the pulse radiolysis.

Pulse radiolysis study on gatifloxacin——A fluoroquinolone antibiotic

The reactions between gatifloxacin(GFX) and various one-electron oxidants,such as ˙OH,N3˙,Br2˙ˉ,and SO4˙ˉ,have been studied by pulse radiolysis techniques.The GFX radical anion formed in the reaction of GFX with eaqˉ could either be protonated or deprotonated,and the absorption of GFX radical anion was located at 390 nm.The transient species produced by the reaction of GFX with ˙OH radical shows a broad band in the 380?600 nm region with a shoulder,while the oxidation by N3˙,SO4˙ˉ,and Br2˙ˉ results in an absorption band with λmax = 370 nm.At neutral condition(pH 7),the rate constants of GFX reacting with ˙OH,N3˙,Br2˙ˉ,SO4˙ˉ and eaqˉ are estimated to be 1.0 × 1010,3.1 × 109,2.8 × 109,3.0 × 109,and 1.8 × 1010 dm3 mol?1 s?1,respectively.From the pH dependence on the formation of electron adducts and on the rate constant of GFX with eaqˉ,the pKa of GFX radical anion is estimated to be 5.5 and 9.3.

Pulse radiolysis study on the mechanisms of reactions of CCl_3OO radical with quercetin,rutin and epigallocatechin gallate

The mechanisms of reactions between CC13OO? radical and quercetin, rutin and epigallocatechin gallate (EGCG) have been studied using pulse radiolytic technique. It is suggested that the electron transfer reaction is the main reaction between CC13OO? radical and rutin, EGCG, but there are two main pathways for the reaction of CC13OO? radical with quercetin, one is the electron transfer reaction, the other is addition reaction. The reaction rate constants were determined. It is proved that quercetin and rutin are better CC13OO? radical scavengers than EGCG.

Reactions of Hydroxyl Radical with Salicylic Acid Derivatives： A Pulse Radiolysis Study

Based on pulse radiolysis of aqueous solutions of two salicylic acid derivatives including ethyl salicylate and benzylsalicylate the transient absorption spectra and the rate constants of hydroxyl radical with salicylic acid derivatives were determined for the first time. The results indicated that ethyl salicylate and benzylsalicylate have efficient activities to scavenge hydroxyl radical.

Oxidative Splitting of a Pyrimidine Cyclobutane Dimer: A Pulse Radiolysis Study

The oxidative splitting process of cis-syn 1,3-dimethyluracil cyclobutane dimer (DMUD) in aqueous solution was investigated using pulse radiolysis technique. The results indicated that DMUD can be splitted into 1,3-dimethyluracil (DMU) by OH radicals (OH ·) and Br_2 radical anions (Br ·-_2), but not by azide radicals (N ·_3). The oxidative mechanisms that an H-abstracted from DMUD for OH · oxidative splitting and an electron transfer from DMUD to Br ·-_2, were suggested. Related kinetic parameters were determined.

Pulse radiolysis study of rapid electron transfer from electron adduct and reducing OH adduct of dAMP to riboflavin and flavin adenine dinucleotide (FAD)

Rapid electron transfer from electron adduct and reducing OH adduct of 2-deoxyadenosine-5′-monophosphate acid (dAMP) to riboflavin (RF) and flavin adenine dinucleotide (FAD) was studied using the time-resolved pulse radiolysis techniques. Both spectroscope and kinetic analyses showed that transient absorption spectrum of electron adduct or OH adduct of dAMP formed at first, and men changed to that of radical anion of RF or FAD after several microseconds of pulse. The evidence indicated that electron transfer from electron adduct and reducing OH adduct of dAMP to RF or FAD did occur. From buildup or bleaching kinetics of radical anions of RF and FAD, the rate constants for electron transfer were determined, respectively.

Photosensitive damage of lysozyme caused by pazufloxacin and the protective effect of ferulic acid

Laser flash photolysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) experiments were carried out to study the photosensitive damage induced by pazufloxacin(PAX) and the protection of lysozyme(Lyso) by ferulic acid(FCA), an active antioxidant. Transient absorption spectra revealed electron transfer from Lyso and FCA to 3PAX*, with respective bimolecular reaction rate constants of 6.3×107 and 1.4×1010 dm3/(mol s). A pulse radiolysis study was also performed to investigate the formation of Lyso radical cations. Results showed that FCA effectively inhibited the cross-linking of protein induced by fluoroquinolones. Finally, a mechanism of the protective effect of FCA on Lyso was proposed.

Interactions of oxidative radicals with N-phosphoryl dipeptide derivatives

The interactions of oxidative radicals (Br2?-, HO?etc.) with N-phosphoryl dipeptide derivatives (NDM-TrpOMe and NDT-MetOMe) have been investigated by using pulse radiolysis at different pH values. It has been found that Br2?- and HO? radicals oxidize the Met-site and Trp-site in the dipeptide derivatives via formation of the three-electron-bonded intermediate and indolyl radical simultaneously. Then the intramolecular electron transfer along the peptide backbone occurs. The rate constants of electron transfer, k, have been determined and the reaction mechanism has been deduced.