Inorganic Free Radicals in Solution.

Uri, N.

doi:10.1021/cr60157a003

Cited by 268 publications

(61 citation statements)

References 177 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The impurities were shown to be octahedral Fe(II1) hydroxychloro complexes ([Fe(H,O), (OH),])()) where X is a chloride or hydroxyl ion. These salts have broad electronic absorptions that extend from the UV to the visible region of the spectrum (-250-450 nm) (43). F~~+ -xundergoes photoreduction to yield iron(I1) and a free radical X according to eq.…”

Section: Methodsmentioning

confidence: 99%

Solid-state photochemistry of π-conjugated poly(3-alkylthiophenes)

Abdou¹,

Holdcroft²

1995

Can. J. Chem.

View full text Add to dashboard Cite

Films of poly(3-alkylthiophenes) undergo simultaneous photobleaching, cross-linking, and chain scission when irradiated in air with UV or visible light. The quantum yields of the latter two processes were determined using Chalesby-Pinner theory. Under the irradiation conditions employed the cross-linking density is -4.5 times greater than the fracture density (chain scission). This corroborates the observation that poly(3-alkylthiophenes) are negative-type photoresists. Although the quantum yield of cross-linking is relatively low, the polymer maintains a relatively high degree of IT-conjugation following irradiation. The mechanism of crosslinking and insolubilization proceeds via a classical photooxidation route that is initiated by photolysis of residual iron impurities. Photobleaching involves photosensitization, and reaction of singlet oxygen. '0, undergoes a 1,4 Diels-Alder addition to thienyl units which results in a loss of IT-conjugation, a blue shift in the absorption spectrum of the polymer, and a decrease in the optical density. Photobleaching, cross-linking, and chain scission are considerably reduced in the absence of oxygen.Key words: photochemistry, polymers, thin films, degradation, cross-linking.RCsumC : Lorsqu'on les soumet B une irradiation UV ou visible dans l'air, les films de poly(3-alkylthiophbnes) subissent des photoblanchiments, des rtticulations et des scissions de chaines simultants. Utilisant la thCorie de Chalesby-Pinner, on a determink les rendements quantiques des deux derniers processus. Dans les conditions d'irradiation employtes, la densitk de la rkticulation est environ 4,5 fois plus grande que la densitk de fracture (scission des chaines). Ces rksultats corroborent l'observation que les poly (3-alkylthiophbnes) sont des photorksistances de type nkgatif. M&me si le rendement quantique de la rkticulation est relativement bas, le polymbre maintient un degrk relativernent klevk de conjugaison IT aprbs l'irradiation. Le mkcanisme de rkticulation et d'insolubilisation procbde par le biais d'une photooxydation classique qui est initike par la photolyse d'impuretks ferriques rksiduelles. Le photoblanchiment irnplique une photosensibilitation et la reaction d'un oxygbne singulet. Le '0, subit une addition-1,4 de Diels-Alder sur les unites thiknyles qui provoquent une perte de conjugaison IT, un dkplacement vers le bleu dans le spectre d'absorption du polymbre et une diminution de la densitk optique. Les rkactions de photoblanchiment, rkticulation et scission de chaine sont forternent rtduites en l'absence d'oxygbne.

show abstract

Section: Methodsmentioning

confidence: 99%

Solid-state photochemistry of π-conjugated poly(3-alkylthiophenes)

Abdou¹,

Holdcroft²

1995

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…Harman (127) postulated that even at normoxia, oxygen utilization causes subtle tissue damage due to production of free radicals. He integrated evidence from the electron spin resonance study, post-Hiroshima studies of radiation damage, Fenton's findings, and contemporary theories that proposed free radical mechanisms for the oxidation of organic compounds and dismutation of hydrogen peroxide by iron salts (358). Harman proposed that physiological iron and other metals would cause ROS to form in the cell via Haber-Weiss chemistry as a by-product of normal redox reactions.…”

Section: A Mitochondrial Free Radical Productionmentioning

confidence: 99%

Life and Death: Metabolic Rate, Membrane Composition, and Life Span of Animals

Hulbert¹,

Pamplona²,

Buffenstein

et al. 2007

Physiological Reviews

754

725

View full text Add to dashboard Cite

Maximum life span differences among animal species exceed life span variation achieved by experimental manipulation by orders of magnitude. The differences in the characteristic maximum life span of species was initially proposed to be due to variation in mass-specific rate of metabolism. This is called the rate-of-living theory of aging and lies at the base of the oxidative-stress theory of aging, currently the most generally accepted explanation of aging. However, the rate-of-living theory of aging while helpful is not completely adequate in explaining the maximum life span. Recently, it has been discovered that the fatty acid composition of cell membranes varies systematically between species, and this underlies the variation in their metabolic rate. When combined with the fact that 1) the products of lipid peroxidation are powerful reactive molecular species, and 2) that fatty acids differ dramatically in their susceptibility to peroxidation, membrane fatty acid composition provides a mechanistic explanation of the variation in maximum life span among animal species. When the connection between metabolic rate and life span was first proposed a century ago, it was not known that membrane composition varies between species. Many of the exceptions to the rate-of-living theory appear explicable when the particular membrane fatty acid composition is considered for each case. Here we review the links between metabolic rate and maximum life span of mammals and birds as well as the linking role of membrane fatty acid composition in determining the maximum life span. The more limited information for ectothermic animals and treatments that extend life span (e.g., caloric restriction) are also reviewed.

show abstract

“…This follows from the fact that it has been known for many years that iron salts catalyze the air oxidation of organic compounds (5,6,14,15); OH radicals are believed to be involved in these reactions (13) . Iron salts also catalyze the decomposition of hydrogen peroxide to water and oxygen-a reaction that involves OH and HO, radicals (16) . Further, recent studies in this laboratory on the inactivation of rat liver catalase suggest that the OH radical is involved .…”

mentioning

confidence: 99%

Aging: A Theory Based on Free Radical and Radiation Chemistry

Harman¹

1956

Journal of Gerontology

7,448

4,045

View full text Add to dashboard Cite

The phenomenon of growth, decline and death-aging-has been the source of considerable speculation (1,8,10) . This cycle seems to be a more or less direct function of the metabolic rate and this in turn depends on the species (animal or plant) on which are superimposed the factors of heredity and the effects of the stresses and strains of life-which alter the metabolic activity.The universality of this phenomenon suggests that the reactions which cause it are basically the same in all living things . Viewing this process in the light of present day free radical and radiation chemistry and of radiobiology, it seems possible that one factor in aging may be related to deleterious side attacks of free radicals (which are normally produced in the course of cellular metabolism) on cell constituents. ' Irradiation of living things induces mutation, cancer, and aging (9). Inasmuch as these also arise spontaneously in nature, it is natural to inquire if the processes might not be similar. It is believed that one mechanism of irradiation effect is through liberation of OH and HO, radicals (12) . There is evidence, although indirect, that these two highly active free radicals are produced normally in living systems. In the first place, free radicals are present in living cells; this was recently demonstrated in vivo by a paramagnetic resonance absorption method (3) . Further, it was shown that the concentration of free radicals increased with increasing metabolic activity in conformity with the postulates set forth some years ago that free radicals were involved in biologic oxidation-reduction reactions (11,13) . Are some of these free radicals OH and/or HO or radicals of a similar high order of reactivity, and where might they arise in the cell?The most likely source of OH and HO, radicals, at least in the animal cell, would be the interaction of the respiratory enzymes involved Submitted. forpobiintion Much 2 3, 1956.7ûie research was performed under the auspices of the Atomic Fmeru Commtnlon.Published on a gttnt from the Forest Park Foundation to the journal of Gerontology .in the direct utilization of molecular oxygen, particularly those containing iron, and by the action of catalane on hydrogen peroxide. This follows from the fact that it has been known for many years that iron salts catalyze the air oxidation of organic compounds (5, 6, 14, 15); OH radicals are believed to be involved in these reactions (13) . Iron salts also catalyze the decomposition of hydrogen peroxide to water and oxygen-a reaction that involves OH and HO, radicals (16) . Further, recent studies in this laboratory on the inactivation of rat liver catalase suggest that the OH radical is involved . The catalane activity of the homogenates both in the presence and absence of hydrogen donors such as sodium bisulfite, sodium hypophosphite, pyrogallol, and mercaptans remains relatively constant under an atmosphere of nitrogen. However, in the presence of air, catalane activity rapidly decreases and the rate of decrease is accelerated in the presence ...

show abstract

Inorganic Free Radicals in Solution.

Cited by 268 publications

References 177 publications

Solid-state photochemistry of π-conjugated poly(3-alkylthiophenes)

Solid-state photochemistry of π-conjugated poly(3-alkylthiophenes)

Life and Death: Metabolic Rate, Membrane Composition, and Life Span of Animals

Aging: A Theory Based on Free Radical and Radiation Chemistry

Contact Info

Product

Resources

About