Heterocyclic Resonant Radicals

Simic, Michael G.; Jovanović, Slobodan V.; Al-Sheikhly, M.

doi:10.3109/10715768909073444

Cited by 12 publications

(5 citation statements)

References 4 publications

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“…which leads indirectly to free radical formation, ROOH + Fe(II) -RO + OH" + Fe(III) (17) Alkoxyl radicals, RO, are in many respects similar to OH radicals, although they are not as reactive (Table I).…”

Section: Initiationmentioning

confidence: 97%

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Mechanisms of Lipid Oxidative Processes and Their Inhibition

Simic

Jovanović

Niki

1992

ACS Symposium Series

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A concise overview of the kinetics, energetics, and mechanisms of oxidative processes involving fatty acids in simple model systems relevant to autoxidation of foods is presented. Endogenous and exogenous factors that initiate oxidative processes in biochemical systems are reviewed and elements of and conditions for propaga tion of chain peroxidation processes are defined. Mechanistic aspects of chain-breaking antioxidants, including redox potentials, are presented. Biomarkers of fatty acid peroxidation are briefly reviewed and their relevance and specificity assessed.Food quality, excluding bacterial and enzymatic spoilage, deteriorates on standing due to oxidative processes induced and propagated by atmospheric oxygen (1). The appearance, texture, flavor, and odor of foods are affected by oxidative processes. The extent of these changes depends on the type of food and conditions. The rancidity of fats, which is unpleasant, can be reduced by storing fats at lower temperatures. Although low-temperature storage efficiently preserves saturated and lower unsaturated fats, reduced temperature alone is not sufficient to protect polyunsaturated fish oils against oxidation. For example, refrigeration of ham at 4 ° C preserves its quality for days or even weeks. On the other hand, refrigerated cooked mackerel is inedible after only two days.In addition to the undesirable sensory characteristics of autoxidized foods, questions have been raised regarding the safety of oxidation products in foods (2). Can hydroperoxides, epoxides, and their decomposition products (diverse carbonyl compounds) contribute to carcinogenesis through the stages of initiation, promotion, or progression? Hydroperoxides are known to damage DNA. Carbonyl compounds, although unreactive with DNA, may affect cellular signal transduction.Foods are complex systems with numerous components. Hence, oxidative mechanisms are often difficult, if not impossible, to study directly. The very short

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Section: Initiationmentioning

confidence: 97%

“…Because of the resonant character of unsaturated and polyunsaturated fatty acid (PUFA) radicals, the rate constants for reactions with oxygen are lower (17). For example, the bisallylic radical (HL-) of linoleic acid (H 2 L), reacts with oxygen an order of magnitude slower, HL-+ 0 2 HLOO-(25) k = 1.8 x 10 8 M" 1 s" 1…”

Section: Initiationmentioning

confidence: 99%

Mechanisms of Lipid Oxidative Processes and Their Inhibition

Simic

Jovanović

Niki

1992

ACS Symposium Series

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“…With guanine as base, the situation is analogous. In this case the oxyl radical at position 6 of guanine is formed with a yield of -50% per reacting OH radical (O'Neill and Chapman, 1985), but with a 100% yield on oxidation with Br;, SO: , or Tl(I1) (Candeias and Steenken, 1990;Jovanovic and Simic, 1989). Ionization of guanosine does not lead to 8-hydroxyguanosine; this may indicate that the laser-induced radical cations of the purines do not decay by reaction with water at position 8 (Steenken, personal commun.).…”

Section: Comparison Of Ssb Formation Induced By Laser Pulses and By Omentioning

confidence: 99%

“…The guanine radical cation and its neutral successor do not react with oxygen (O'Neill and Chapman, 1985;Simic and Jovanovic, 1986;Simic et al, 1989;Steenken, 1989). In double-stranded DNA G t will rapidly deprotonate since the attached cytosine is a sufficiently strong base to accept a proton from the guanine radical cation, which is a strong acid with pK, = 3.9 (Candeias and Steenken, 1989).…”

Section: Comparison Of Ssb Formation Induced By Laser Pulses and By Omentioning

confidence: 99%

“…In double-stranded DNA G t will rapidly deprotonate since the attached cytosine is a sufficiently strong base to accept a proton from the guanine radical cation, which is a strong acid with pK, = 3.9 (Candeias and Steenken, 1989). The guanine oxyl radical thus expected has recently been observed spectroscopically as a transient for single-stranded DNA (Jovanovic and Simic, 1989) and for double-stranded DNA in aqueous solution at room temperature in the absence and presence of oxygen by EPR (Hildenbrand and Schulte-Frohlinde, 1990). In contrast, a long-lived guanine radical has not been detected with singlestranded DNA by EPR under the same conditions.…”

Section: Comparison Of Ssb Formation Induced By Laser Pulses and By Omentioning

confidence: 99%

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