Peroxides radicals

Morel, D.W., Hessler, J.R. and Chisolm, G.M. (1983a). Low density lipoprotein cytotoxicity induced by free radical peroxidation of lipid. J. Lipid Res. 24, 1070-1076. 

Detoxification of pro-oxidatively active molecules (radicals, peroxides) is ensured by enzymatic and nonenzymafic compounds. 

Taking into account that ROS produced by irradiated fullerenes C60 may act only in the radius of their short diffusion existence, one may suppose that cytotoxic effect is determined by the interaction of fullerene C60 with the surface of cells and initiation of chain reactions of free radical peroxidation in membranes. That is why the influence of photoexcited fullerene C60 on the course of LPO process was studied and evaluated by the content of generated primary (diene conjugates) and final (Schiff bases) products. The content of diene conjugates in thymocytes was 17.7 4.2, inEAC cells was 21.1 1.3, andinL1210 was 12.8 3.1 nM/mg protein, and Schiff bases -56 7.9,46.5 4.5, and 36.6 4.6 rel. units/mg protein, respectively, and did not alter during 1 h incubation of the cells. 

Based on the original commercial processes from the 1940s, this route runs at pressures as high as 50,000 psi and temperatures of 400—650 F. The process has its limitations since free radical peroxide-base catalysts cannot yield linear, highly crystalline polymers. They create branched chains. Today the process is used for LDPE,... 

Free Radical Peroxides (monomers cyclic ketene acetals)... 

Additionally, free radical peroxidation can convert arachidonic acid nonenzymati-cally to yield isoprostanes (6). 

A. J. Moye (California State College, Los Angeles, Calif.) An alternative mechanism to the intramolecular hydrogen transfer could be the transfer of a single electron to give a radical-anion intermediate in place of the radical-peroxide of Reaction 4. Have you considered this possibility ... 

A discussion of this relation was contained in a paper presented in April 1951 (7). It was there pointed out that these facts are consistent with the free radical peroxidation theory of combustion, if it is assumed that the free radicals add at the carbon-to-carbon double bond. The assumption is justified on the basis of experimental evidence. 

Lipid peroxidation has often been regarded simply as an undesirable side reaction, but it is also a normal part of metabolism. Initiated by enzymatically generated radicals, peroxidation occurs as specific metabolic pathways, such as the arachidonate cascade, which leads to a variety of local hormones and other substances (Eq. 21-16).254 2563... 

Polymer modifications -peroxide fiee radicals [PEROXIDES AND PEROXIDE COMPOUNDS - ORGANIC PEROXIDES] (Vol 18)... 

It seems that the cavities enclose a vapor of the solute because of the high vapor pressure of these compounds. The primary reaction pathway for these compounds appears to be the thermal dissociation in the cavities. The activation energy required to cleave the bond is provided by the high temperature and pressure in the cavitation bubbles. This leads to the generation of radicals such as hydroxyl radical, peroxide radical, and hydrogen radical. These radicals then diffuse to the bulk liquid phase, where they initiate secondary oxidation reactions. The solute molecule then breaks down as a result of free-radical attack. The oxidation of target molecules by free radicals in the bulk liquid phase under normal operating pressures and temperatures can be presented by a second-order rate equation ... 

Being primary, stable, intermediate oxidation products and owing to the simplicity of their dissociation to free radicals, peroxide compounds HOOH, ROOH, ROOR (where R is alkyl, acyl, arylacyl fragments or their derivatives) possess favorable initiation properties in chain oxidation and polymerization reactions. 

Other silanes led to an increase in the formation of alcohols 341 and free hydroperoxides 340b. Tokuyasu et al. extended the investigations to Co-catalyzed tandem radical peroxidation/peroxyl radical cyclization sequences to give oxygenated endoperoxides, such as 342 [378]. 

Since both cyclooxygenase and lipoxygenase catalyze stereospecific free radical peroxidations of arachidonic acid at their active sites, it is widely believed that the dual COX and LOX inhibition activities of flavonoids derive from their non-selective free radical scavenging or iron chelating functions rather than specific enzyme inhibition. However, Laughton et al. 

Fig. 2.7. The sequential reduction of oxygen via superoxide radical, peroxide and hydroxyl radical to water.

Radicals are formed from covalent bonds by adding energy in the form of heat (A) or light (hv). Some radical reactions are carried out in the presence of a radical initiator, a compound that contains an especially weak bond that serves as a source of radicals. Peroxides, compounds with the general structure RO OR, are the most commonly used radical initiators. Heating a peroxide readily causes homolysis of the weak 0-0 bond, forming two RO- radicals. 

Many peroxides and azo compounds can be heated to generate radicals. Peroxides decompose readily because of the weak O — O bond, whereas azo compounds cleave readily because of the driving force provided by the formation of the stable nitrogen molecule. Common examples of these decompositions follow. (The tj/2 is the time it takes one-half of the material to decompose.)... 

V.Z. Lankin, A.K. Tikhase and Yu.G. Osis, Simulation of the enzymic reactions sequence in liposomes including free radical peroxidation, reduction and hydrolysis of polyenic acyls of phospholipids for investigation of this processes influence on the membrane structure. Biochemistry (Moscow) 2001(in press). 

V.Z.Lankin, A.N.Zakirova, B.Kh.Akhmetova, N.V.Kotelevtseva, A.K.Tikhaze and L.V. Kasatkina, Lipid peroxides and atherosclerosis. Free radical peroxidation of polyene lipids in the blood in coronary heart disease, Kardiologiia (Cardiology) 20 (1980) 96-99. [Article in Russian]... 

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