An Investigation of Stable Free Radicals in Polyimides Using EPR Spectroscopy

1993 ◽  
Vol 305 ◽  
Author(s):  
Myong K. Ahn ◽  
Thomas C. Stringfellow ◽  
Jianming Lei ◽  
Kenneth J. Bowles ◽  
Michael Meador
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Variable Temperature ◽  
Oxidative Degradation ◽  
High Strength ◽  
Radical Species ◽  
Stable Free Radical ◽  
Paramagnetic Resonance ◽  
Free Radical Species ◽  
Temperature Electron

AbstractPolyimide resins are used as matrix materials in fiber reinforced composites. Such composites are lightweight, have relatively high strength, and can be used at temperatures above 300°C. Postcured PMR-15 produces room temperature electron paramagnetic resonance (epr) spectra from stable free radical species formed during the postcuring stages. The variable temperature EPR spectral intensities indicate the presence of at least two free radical species. The thermo-oxidative degradation involves free radicals generated during the postcuring process in the presence of oxygen gas. These and other recent results including ENDOR and HYSCORE work are discussed.

Involvement of free radicals in the oxidative degradation of indole-3-acetic acid

1969 ◽  
Vol 47 (2) ◽  
pp. 220-224 ◽  
Author(s):  
E. V. Parups
Keyword(s):  
Acetic Acid ◽  
Free Radicals ◽  
Free Radical ◽  
Oxidative Degradation ◽  
Breakdown Product ◽  
Stable Free Radical ◽  
Indole 3 Acetic Acid

The enzymic or nonenzymic oxidation of indole-3-acetic acid (IAA) was promoted in the presence of the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The involvement of DPPH with the IAA free-radicals in the nonenzymic and the peroxidase-catalyzed oxidations was discussed. Methylene-oxindole was identified as a breakdown product of IAA, indicating a pathway operative with this radical.

scholarly journals Free radicals in skin and muscle: damaging agents or signals for adaptation?

1999 ◽  
Vol 58 (3) ◽  
pp. 673-676 ◽  
Author(s):  
Malcom J. Jackson
Keyword(s):  
Gene Expression ◽  
Free Radicals ◽  
Free Radical ◽  
Potential Role ◽  
Biological Effects ◽  
Cell Types ◽  
Radical Species ◽  
Free Radical Species ◽  
The Subject ◽  
Influence Gene Expression

Much of the current literature regarding the biological effects of antioxidant nutrients has concentrated on their potential role in inhibiting or preventing tissue damage induced by free radical species produced during metabolism. Recent findings indicate that antioxidants may also have more subtle roles, regulating changes in gene expression induced by oxidizing free radical species. There is increasing evidence that free radicals act as signals for cell adaptation in a variety of cell types and the nature of the mechanisms by which free radical species influence gene expression is the subject of much current research. Processes such as these may be particularly important in tissues regularly exposed to varying amounts of oxidative stress as part of their normal physiological functions. Examples of such tissues include skin exposed to u.v. light and skeletal muscle subjected to repeated bouts of exercise.

Free radical-mediated skeletal muscle dysfunction in inflammatory conditions

2007 ◽  
Vol 102 (5) ◽  
pp. 2056-2063 ◽  
Author(s):  
Gerald S. Supinski ◽  
Leigh A. Callahan
Keyword(s):  
Skeletal Muscle ◽  
Free Radicals ◽  
Free Radical ◽  
Muscle Weakness ◽  
Muscle Function ◽  
Muscle Dysfunction ◽  
Radical Species ◽  
Inflammatory Conditions ◽  
Skeletal Muscle Dysfunction ◽  
Free Radical Species

Loss of functional capacity of skeletal muscle is a major cause of morbidity in patients with a number of acute and chronic clinical disorders, including sepsis, chronic obstructive pulmonary disease, heart failure, uremia, and cancer. Weakness in these patients can manifest as either severe limb muscle weakness (even to the point of virtual paralysis), respiratory muscle weakness requiring mechanical ventilatory support, and/or some combination of these phenomena. While factors such as nutritional deficiency and disuse may contribute to the development of muscle weakness in these conditions, systemic inflammation may be the major factor producing skeletal muscle dysfunction in these disorders. Importantly, studies conducted over the past 15 years indicate that free radical species (superoxide, hydroxyl radicals, nitric oxide, peroxynitrite, and the free radical-derived product hydrogen peroxide) play an key role in modulating inflammation and/or infection-induced alterations in skeletal muscle function. Substantial evidence exists indicating that several free radical species can directly alter contractile protein function, and evidence suggests that free radicals also have important effects on sarcoplasmic reticulum function, on mitochondrial function, and on sarcolemmal integrity. Free radicals also modulate activation of several proteolytic pathways, including proteosomally mediated protein degradation and, at least theoretically, may also influence pathways of protein synthesis. As a result, free radicals appear to play an important role in regulating a number of downstream processes that collectively act to impair muscle function and lead to reductions in muscle strength and mass in inflammatory conditions.

CYTOTOXIC REACTIONS OF FREE RADICAL SPECIES OF OXYGEN

1978 ◽  
Vol 28 (4-5) ◽  
pp. 887-905 ◽  
Author(s):  
Donald C. Borg ◽  
K. M. Schaich ◽  
J. J. Elmore Jr ◽  
J. A. Bell
Keyword(s):  
Free Radical ◽  
Radical Species ◽  
Free Radical Species
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