X- and γ-radiolysis of Some Tryptophan Dipeptides

Winchester, R. V.; Lynn, K.R.

doi:10.1080/09553007014550681

Cited by 29 publications

(14 citation statements)

References 15 publications

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“…Radiolysis may also damage the neighbours including the cleavage of peptide bonds and a complete loss of amino acids . This was shown for tryptophan dipeptides by Winchester and Lynn (1970) . Busath and Waldbillig (1983) found that photolysis of gramicidin channels .with ultraviolet light leads to a broad distribution of primarily low conductance states .…”

Section: Discussionmentioning

confidence: 72%

Effects of Ionizing Radiation on Artificial (Planar) Lipid Membranes. I. Radiation Inactivation of the Ion Channel Gramicidin A

Strässle

Stark²,

Wilhelm

1987

International Journal of Radiation Biology and Related Studies

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The ion channel formed by the pentadecapeptide gramicidin A in planar lipid membranes is extremely sensitive to ionizing radiation. The membrane conductance may drop by several orders of magnitude under appropriate experimental conditions (low pH and presence of oxygen). The radiation sensitivity is strongly reduced for gramicidin M-. This analogue has the four tryptophan residues replaced by phenylalanines. Experiments performed in the presence of various radical scavengers suggest that the inactivation of the channel is due to a combined action of OH and of HO2 radicals at the tryptophan residues. The shape of the inactivation curves following continuous radiolysis or pulse radiolysis were found to be in fair agreement with a simple model which assumes that the damage of a single tryptophan residue is sufficient for channel inactivation. The conductance of inactivated channels could not be resolved within the experimental accuracy. This is contrary to photolysis of gramicidin channels found by Busath and Waldbilling (1983), where a broad distribution of low conductance states was observed. The inactivation by radiolysis seems to represent an 'all-or-none-process' of the channel conductance.

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Section: Discussionmentioning

confidence: 72%

Effects of Ionizing Radiation on Artificial (Planar) Lipid Membranes. I. Radiation Inactivation of the Ion Channel Gramicidin A

Strässle

Stark²,

Wilhelm

1987

International Journal of Radiation Biology and Related Studies

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“…The reaction of tryptophan with HO • leads to addition of the radical to the indole ring [51] followed partly by dehydration and peroxidation and partly by reaction with dioxygen to give indoyl and peroxyl radicals [52]. Stable products detected in several studies consisted mainly of N-formylkyurenine, kyurenine, 5hydroxytryptophan, 3-indoleacetic acid, 3-indole propionic acid and organic peroxides [52][53][54]. Importantly, similar results were reported for peptides containing tryptophan, suggesting that the decay of the tryptophan radicals in proteins would follow similar routes [54][55][56].…”

Section: Generalmentioning

confidence: 99%

“…Stable products detected in several studies consisted mainly of N-formylkyurenine, kyurenine, 5hydroxytryptophan, 3-indoleacetic acid, 3-indole propionic acid and organic peroxides [52][53][54]. Importantly, similar results were reported for peptides containing tryptophan, suggesting that the decay of the tryptophan radicals in proteins would follow similar routes [54][55][56]. In tyrosine, the principal reaction product with HO • was 3,4-dihydroxyphenylalanine (dopa), regardless of the presence of dioxygen [57,58].…”

Section: Generalmentioning

confidence: 99%

The kinetics of oxidation of GSH by protein radicals

Nauser

Koppenol

Gebicki

2005

Biochemical Journal

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Current studies provide evidence that proteins are initial targets of ROS (reactive oxygen species) in biological systems and that the damaged proteins can in turn damage other cell constituents. This study was designed to test the possibility that protein radicals generated by ROS can oxidize GSH and assess the probability of this reaction in vivo by measurement of the rate constant of this reaction. Lysozyme radicals were generated by hydroxyl and azide radicals in steady-state gamma ray radiolysis. In the absence of dioxygen, a range of protein carbon-centred amino acid radicals were produced by the hydroxyl radicals, and defined tryptophan radicals by the azide radicals. In the presence of dioxygen, each carbon-centred radical was converted to a protein peroxyl radical. Each of the peroxyl radicals was able to oxidize a molecule of GSH, regardless of its location in the protein. The peroxyl radicals were 10 and 20 times more effective GSH oxidants than the carbon-centred radicals produced randomly in the lysozyme, or the defined tryptophan lysozyme radicals respectively. We obtained for the first time the rate constant of reaction between a protein free-radical and GSH. Lysozyme tryptophan carbon radicals generated by nanosecond pulse radiolysis and flash photolysis oxidized GSH with a rate constant of (1.05+/-0.05)x10(5) M(-1) x s(-1). Overall, the results are consistent with the hypothesis that protein radicals may be important intermediates in the pathway linking oxidative stress and damage in living organisms and emphasize the strongly enhancing role of dioxygen in this process.

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“…Tyrosine residues may also react with hydrogen peroxide, yielding 3,4-dihydroxy (dopa) derivative [72,75,76], or bi-tyrosine cross-linked derivatives [73,[77][78][79]. Tryptophan residues are converted to the 2-, 4-, 5-, 6-, or 7-hydroxy derivatives, and also to N-formylkynurenine and kynurenine [72,[80][81][82]. Methionine is readily oxidized to methionine sulfoxide by many different reactive oxygen species [83][84][85].…”

Section: Inactivation Of Enzymes By Modification With Hydrogen Peroxidementioning

confidence: 99%

Hydrogen Peroxide in Biocatalysis. A Dangerous Liaison

Hernández

Berenguer-Murcia²,

Rodrigues³

et al. 2012

COC

140

107

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Hydrogen peroxide is a substrate or side-product in many enzyme-catalyzed reactions. For example, it is a side-product of oxidases, resulting from the re-oxidation of FAD with molecular oxygen, and it is a substrate for peroxidases and other enzymes. However, hydrogen peroxide is able to chemically modify the peptide core of the enzymes it interacts with, and also to produce the oxidation of some cofactors and prostetic groups (e.g., the hemo group). Thus, the development of strategies that may permit to increase the stability of enzymes in the presence of this deleterious reagent is an interesting target. This enhancement in enzyme stability has been attempted following almost all available strategies: site-directed mutagenesis (eliminating the most reactive moieties), medium engineering (using stabilizers), immobilization and chemical modification (trying to generate hydrophobic environments surrounding the enzyme, to confer higher rigidity to the protein or to generate oxidation-resistant groups), or the use of systems capable of decomposing hydrogen peroxide under very mild conditions. If hydrogen peroxide is just a side-product, its immediate removal has been reported to be the best solution. In some cases, when hydrogen peroxide is the substrate and its decomposition is not a sensible solution, researchers coupled one enzyme generating hydrogen peroxide "in situ" to the target enzyme resulting in a continuous supply of this reagent at low concentrations thus preventing enzyme inactivation.This review will focus on the general role of hydrogen peroxide in biocatalysis, the main mechanisms of enzyme inactivation produced by this reactive and the different strategies used to prevent enzyme inactivation caused by this "dangerous liaison". Outlook

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X- and γ-radiolysis of Some Tryptophan Dipeptides

Cited by 29 publications

References 15 publications

Effects of Ionizing Radiation on Artificial (Planar) Lipid Membranes. I. Radiation Inactivation of the Ion Channel Gramicidin A

Effects of Ionizing Radiation on Artificial (Planar) Lipid Membranes. I. Radiation Inactivation of the Ion Channel Gramicidin A

The kinetics of oxidation of GSH by protein radicals

Hydrogen Peroxide in Biocatalysis. A Dangerous Liaison

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