Hydrogen peroxide in biology

Perhaps the most significant aspect of the superoxide-, hydroxide-, or electron-induced auto-oxidation of donor molecules (1,2-diphenylhydrazine, dihydrophenazine, dihydro-lumiflavin, and reduced flavoproteins) is the activation of dioxygen to hydrogen peroxide in biological matrices. Thus, within the normal cytochrome P-450 metabolic cycle, either hydroxide ion or an electron-transfer co-factor acts as an initiator (probably to produce Fl -) and reduced flavoproteins act as the H-atom donor. In contrast, the introduction of 02 - or hydrated electrons (from ionizing radiation or a disease state) into a biological matrix that contains donor molecules leads to the uncontrolled formation of hydrogen peroxide. If reduced metal ions are present, Fenton... 

Fluorescent probes for the detection of hydrogen peroxide in biological systems 13COC654. 

Nathan, C.F. (1987). Neutrophil activation on biological surfaces. Massive secretion of hydrogen peroxide in response to products of macrophages and lymphocytes. J. Clin. Invest. 80, 1550-1560. 

Puppo, A. and Halliwell, B. (1988). Formation of hydroxyl radicals from hydrogen peroxide in the presence of iron. Is haemoglobin a biological Fenton catalyst Biochem. J. 249, 185-190. 

Ortmans I, Moucheron C, Kirsch-De Mesmaeker A (1998) Ru(ll) polypyridine complexes with a high oxidation power. Comparison between their photoelectrochemisty with transparent SnC>2 and their photochemistry with desoxyribonucleic acids. Coord Chem Rev 168 233-271 Ozawa T, Ueda J, Flanaki A (1993) Copper(ll)-albumin complex can activate hydrogen peroxide in the presence of biological reductants first ESR evidence for the formation of hydroxyl radical. Biochem Mol Biol Int 29 247-253... 

Let us now consider the questions of the biological oxidation of various substrates with hydrogen peroxide in the presence of catalases and peroxidases. As Pratt notes [82], this group of enzymes is unique in that it is the only one in which intermediates are detected, and all stages of catalytic process are determined, identified and studied. Of special value is the characteristic that catalase consists of four subunits, whereas peroxidase possesses only one subunit. Using special technique, it is also shown that every iron atom (heme) binds one H202 molecule [83 ]. 

Despite the differences between the functions implemented by hydrogen peroxide in gas, liquid and biological oxidation processes, they are united by a specific feature H202 first transforms to a higher reactive form in which the donor-acceptor properties of the original compound are preserved, and then only (in this new form) oxidizes the substrate according to the conjugated mechanism. 

Forman NJ, Boveris A. Superoxide radical and hydrogen peroxide in mitochondria. In Pryor A, ed., Free Radicals in Biology, Vol 5. New York Academic Press, 1982 65. 

Traces of fluoride can be separated from aqueous solutions by extraction with triethylchlorsilane in m-xylene The conditions were optimized and co-precipitation (for enrichment) reactions were tested Adsorption on hydroxyl apatite was found most suitable. From acidified solutions of biological materials fluoride was selectively extracted with a solution of trimethylchlorsilane in benzeneOrganic material or blood was destroyed by heating with hydrochloric acid and hydrogen peroxide in a closed distilling apparatus. The resulting distillates were extracted by triethylchlorsilane in tetrachloroethylene ... 

The main source of hydrogen peroxide in natural waters is through its photochemical production [113]. Elowever, as will be discussed below, other processes also affect concentrations of H2O2 in the water column. These include dry and wet atmospheric deposition, and biological release. 

---