Mechanistic aspects of the Fenton reaction under conditions approximated to the extracellular fluid.
The Fenton reaction was investigated, in a medium approximating to that of the extracellular fluid (ECF), by rapid-mixing stopped flow experiments and HPLC analysis using sodium terephthalate (TA(2-)). The reactive intermediate of the Fenton reaction hydroxylates the essentially nonfluorescent, TA(2-) to the brilliant fluorophor 2-hydroxy-terephthalate (OH-TA), which allows the Fenton reaction to be monitored in stopped-flow experiments. There was no artefactual quenching of the fluorescence by substances present in the Fenton-reaction mixture or in the artificial cerebrospinal fluid (aCSF) that might have influenced OH-TA quantification. A mathematical model based on kinetic considerations was developed. This explains the observed independence of the OH-TA concentration on the amount of TA(2-) present in aCSF as well as its dependence on TA(2-) concentration in potassium acetate buffer. A mechanism based on this model, involving complex formation between Fe(II), TA(2-) and H(2)O(2), followed by an intra-molecular hydroxylation accompanied by an intra-molecular electron transfer was developed. The results are consistent with a reactive intermediate, which causes oxidative stress in vivo, not being a free hydroxyl radical, but a ferryl species or a "crypto" radical. The biological implications of these results are discussed.
Institute for Applied Synthetic Chemistry, Vienna University of Technology, Vienna, Austria.
Wolfhardt
W
Freinbichler
Keith F
KF
Tipton
Laura Della
LD
Corte
Wolfgang
W
Linert
D045604:Extracellular Fluid / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism*; D017665:Hydroxyl Radical / Q000378:metabolism*; D006900:Hydroxylation; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D010795:Phthalic Acids / Q000378:metabolism*
C045076:Fenton's reagent; D010795:Phthalic Acids; D017665:Hydroxyl Radical; C011363:terephthalic acid; D006861:Hydrogen Peroxide; D007501:Iron