Free Radicals In Biological Systems Research Articles

Control of the generation and reactions of free radicals in biological systems by kinetic and thermodynamic factors.

Quantifiable redox properties are useful predictors of substrate reactivity in enzyme-catalysed redox reactions of e.g. nitroreductases or peroxidases. Redox properties may also control the rates of electron-transfer reactions between radical products of reduction and oxidation, and endogenous oxidants and reductants respectively. However, in numerous instances prototropic properties of substrate or radical may have profound kinetic consequences, protonation of radicals frequently slowing down electron-transfer reactions. Further, reactions which are thermodynamically extremely unfavourable may still proceed if radical products are removed from the pre-equilibrium efficiently. Thus kinetic considerations often outweigh the purely thermodynamic viewpoint.

Effect of spin traps in isolated rat hepatocytes and liver microsomes

Spin traps are increasingly employed in the detection of free radicals in biological systems, including liver microsomes and isolated hepatocytes. Two spin traps phenyl- t-butyl nitrone (PBN) and 4-pyridyl-1-oxide- t-butyl nitrone (4-POBN) have been tested for their effects on hepatocyte viability and mixed-function oxidase activity. High concentration of PBN but not of 4-POBN proved to moderately affect liver cell integrity, without interfering with intracellular ATP or cytochrome P-450 content. PBN also decreased hepatocyte GSH content, probably as the result of its metabolism to benzaldehyde. The two spin traps were found to inhibit aminopyrine demethylase and ethoxycoumarin deethylase activity in hepatocytes and microsomes. At low concentrations (1–5 mM) PBN enhanced aniline hydroxylase while high concentrations of the spin trap inhibited this activity. The inhibition of the monooxygenase system was not caused by damage of microsomal enzymes, but rather by competition with other substrates for the binding to the haemoprotein. The effects of spin traps on mixed function oxidase systems should be taken into account when evaluating the results of spin trapping experiments.

27] High-pressure liquid chromatography-electrochemical detection of oxygen free radicals

The presence of superoxide, hydrogen peroxide, and a catalytic amount of iron complexed to an appropriate liquid, such as di- or triphosphate nucleotides, will lead to the production of hydroxyl free radicals (OH·). Hydroxyl free radicals are extremely reactive and thus would be present at any specific time in at most very low amounts in biological systems even under conditions of severe oxidative stress. Detection of hydroxyl free radicals per se by electron paramagnetic resonance (EPR) in biological systems is virtually impossible; however, the use of spin-trapping techniques offers possibilities. The results presented illustrate that the hydroxyl-free-radical adduct of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) (DMPO-OH·) and its one-electron reduction product (DMPO-OH 2 ) can be separated out and detected by high-pressure liquid chromatography (HPLC)-electrochemical detection. It is clear, because biological systems tend to reduce DMPO-OH· to the diamagnetic DMPO-OH 2 and because HPLC-electrochemical detection offers extreme sensitivity as well as selective separation that this method has excellent potential of being very useful as a tool for studying oxygen free radicals in biological systems.

Flash photolysis, pulse radiolysis — Contribution the chemistry of free radicals in biological systems

Bulletin des Sociétés Chimiques BelgesVolume 92, Issue 6-7 p. 615-622 Article Flash photolysis, pulse radiolysis — Contribution the chemistry of free radicals in biological systems R.V. Bensasson , R.V. Bensasson Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, INSERM U201, CNRS ERA 951, 61 rue Buffon, 75005 PARISSearch for more papers by this author R.V. Bensasson , R.V. Bensasson Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, INSERM U201, CNRS ERA 951, 61 rue Buffon, 75005 PARISSearch for more papers by this author First published: 1983 https://doi.org/10.1002/bscb.19830920606Citations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume92, Issue6-71983Pages 615-622 RelatedInformation

Aicardi syndrome in a male infant

1. Pascale JA, Mims LC, Greenberg MH, Gooden DS, and Chronister E: Riboflavin and bilirubin response during phototherapy, Pediatr Res 10:854, 1976. 2. Speck WT, Chen CC, and Rosenbrang HS: In vitro studies of effects of light and riboflavin on DNA and hela cells, Pediatr Res 9:150, 1975. 3. Sanvordeker DR, and Kostenbauder HB: Mechanisms for riboflavin enhancement of bilirubin photodecomposition in vitro, J Pharm Sci 631:404, 1974. 4. Kostenbauder HB, and Sanvordeker RR: Riboflavin enhancement of bilirubin photocatabolism in vivo, Experientia 29:282, 1973. 5. Straight R, and Spikes JD: Sensitized photooxidation of amino acids: Effects on the reactivity of their primary amine groups with fluorescamine and o-phthalaldehyde, Photochem Photobiol 27:565, 1978. 6. Spikes JD, and Straight R: Sensitized photochemical processes in biological systems, Annu Rev Phys Chem 18:409, 1967. 7. Benassi CA, Scoffane E, Craliazzo G, and Jori G: Proftavinesensitized photooxidation of tryptophan and related peptides, Photochem Photobiol 6:857, 1967. 8. Weft L, Gordon, WG, and Buchert AR: Photooxidation of amino acids in the presence of methylene blue, Arch Biochem Biophys 33:90, 1951. 9. Eoote CS: Free radicals in biological systems, in Pryor WA, editor: Free radicals in biology, vol 2, New York, 1976, Academic Press Inc., pp 69-145. 10. Litwin J: The effect of light on the aging of human diploid fibroblasts, Exp Gerontol 7:381, 1972. 11. Branda RF, and Eaton JW: Skin color and nutrient photob lysis: An evolutionary hypothesis, Science 201:625, 1978. 12. Wang RJ, and Nixon BT: Identification of hydrogen peroxide as a photoproduct toxic to human cells in tissueculture medium irradiated with daylight fluorescent light, In Vitro 14:715, 1978.

Free radicals in biological systems

Free Radicals in Biology. Vol. 1: Pp. xv + 287. Vol 2: Pp. xiv + 303. Edited by W. A. Pryor. (Academic: New York and London, 1976.) £19.55; $27.50 each volume.

Free radicals in biological systems.

Free radicals in biological systems.

Reactivity of Trapped Free Radicals in Biological Systems

IRRADIATED poly-crystalline amino-acids lend themselves to the kinetic investigation of radical stabilities, because radicals can be induced readily in solid amino-acid by irradiation and because radical concentrations at different temperatures can be followed conveniently by electron spin resonance spectroscopy. In this study, radicals were formed in a number of amino-acids containing sulphur by irradiation at 2537 A with a low-pressure mercury-vapour germicidal lamp1. Electron spin resonance spectra were determined on a JEOL–3BX electron spin resonance spectrometer. Samples were usually irradiated continuously at room temperature until the concentration of radicals remained constant and decay rates were then studied at higher temperatures; it was assumed that the radical concentration present was proportional to the signal strength, which was estimated directly from the recorded spectral trace using a planimeter.

Manganese free radicals in cobalt-60 gamma-irradiated strawberries.

THE formation of free radicals in biological systems exposed to ionizing radiation is well established1–7. Some of the induced radicals, as well as some of those occurring naturally8, have long lives9–11. The surprising stability of the induced radicals may have far-reaching biological implications. As an example of stability, cystine, on irradiation in vacuo at room temperature, gave electron paramagnetic resonance signals even after 35 days12. Numerous investigations in connexion with irradiation damage of proteins and amino-acids confirm the stability of these radicals13–18. This stability must be considered carefully in assessing the wholesomeness of foods preserved by ionizing radiation. Such assessment involves the concepts of stored chemical energy and consequent radio-mimetic hazard19–20. Chromosomal aberrations have been shown to occur in germinating barley and onion seeds following treatment with orange or apple juice, which had been irradiated with 200 Krad of γ-rays21. Although the radiomimetic precursors generated by irradiation of fruit juices have not been ascertained, preliminary studies indicate that peroxides may be implicated.

Free Radicals in Biological Systems

Free Radicals in Biological Systems

Free Radicals in Biological Systems.

Free Radicals in Biological Systems.

Free Radicals in Biological Systems

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Free Radicals in Biological Systems

Free Radicals in Biological Systems

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Free Radicals in Biological Systems

Free Radicals in Biological Systems

Electron spin resonance investigations of rat liver and rat hepatoma.

STUDIES concerning the role of free-radical reactions in biological processes have long been hampered by the lack of a method for detecting free radicals in biological systems. The recent investigations of Commoner1 have shown that electron spin resonance techniques offer considerable promise for this purpose. This communication describes, first, an investigation of sample preparation and handling methods, and second, a qualitative comparison of electron spin resonance signal intensities from normal rat liver tissue with Novikoff rat hepatoma.