The effect of low molecular weight chelators on iron chelation and free radical generation as studied by ESR measurement
IRG/WP 00-10367
Yuhui Qian, B Goodell
The focus of this work was to improve our current knowledge of the non-enzymatic mechanisms involved in brown-rot decay. Electron Spin Resonance (ESR), also known as Electron Paramagnetic Resonance (EPR), is an attractive technique for the identification and study of chemical species containing unpaired electrons (such as radicals and certain transition metal species). ESR spin-trapping techniques are also commonly used to study very reactive and short-lived free radical species. It has been proposed that low MW chelators as well as Fenton reagents are involved in wood brown-rot decay, at least in early non-enzymatic stages. In this work, the binding between a chelator model compound and ferric iron was studied by ESR spectroscopy. The effects of the chelator model compound, Fenton reagents, as well as the reaction conditions on free radical generation were also studied using ESR spin-trapping techniques. The results indicate: 1. The relative amount of ferric iron bound to chelators is directly related to the chelator / iron ratio in the system. The relative quantity of the chelator-iron complex can be determined by measuring the intensities of the characteristic g4.3 ESR signal. 2. The effects of the chelator/iron ratio, the pH, and other reaction parameters on the hydroxyl radical generation in a Fenton type system could be determined using ESR spin-trapping techniques. 3. Data support the hypothesis that superoxide radicals are involved in the chelator mediated Fenton processes.
Keywords: WOOD DECAY; SUPEROXIDE; RADICAL; OXYGEN; ELECTRON SPIN RESONANCE; HYDROXYL; IRON; REDUCTION; BROWN ROT; GLOEOPHYLLUM TRABEUM