Radiation‐Induced Radical Reactions

Bobrowski, Krzysztof

doi:10.1002/9781119953678.rad005

Cited by 4 publications

(4 citation statements)

References 343 publications

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“…The reduced AOC of the Tyr-Tyr and Tyr-Trp dipeptides compared with the combined AOC of the comprising amino acids appears to result from the interactions of the redox-active amino acid residues with each other. Also for Met-Tyr, Tyr-His and His-Tyr a synergic effect was revealed ( Figure 3 a), caused, apparently, by the processes of intramolecular tunneling electron transfer from methionine or histidine residues to the Tyr phenoxyl radical, which was earlier observed by different authors for His-, Met-, and Tyr-containing peptides [ 33 , 34 , 35 , 36 , 37 , 38 ].…”

Section: Resultssupporting

confidence: 60%

Structure-Functional Study of Tyrosine and Methionine Dipeptides: An Approach to Antioxidant Activity Prediction

Týčová

Королева

Khrameeva

et al. 2015

IJMS

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Quantum chemical methods allow screening and prediction of peptide antioxidant activity on the basis of known experimental data. It can be used to design the selective proteolysis of protein sources in order to obtain products with antioxidant activity. Molecular geometry and electronic descriptors of redox-active amino acids, as well as tyrosine and methionine-containing dipeptides, were studied by Density Functional Theory method. The calculated data was used to reveal several descriptors responsible for the antioxidant capacities of the model compounds based on their experimentally obtained antioxidant capacities against ABTS (2,2′-Azino-bis-(3-ethyl-benzothiazoline-6-sulfonate)) and peroxyl radical. A formula to predict antioxidant activity of peptides was proposed.

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Section: Resultssupporting

confidence: 60%

Structure-Functional Study of Tyrosine and Methionine Dipeptides: An Approach to Antioxidant Activity Prediction

Týčová

Королева

Khrameeva

et al. 2015

IJMS

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“…Radiolysis of water provides a very convenient source of one-electron oxidizing radicals characterized by a very broad range of reduction potentials which is very useful for studying oxidation reactions of molecules of biological significance [ 68 , 69 ]. In the current study, we selected two inorganic radicals (SO 4 ●− , CO 3 ●− ) and Tl 2+ ions, with reduction potentials higher than the reduction potential of N 3 ● , and one radical (SCN) 2 ●− with a nearly equal, however lower, reduction potential as that of N 3 ● (vide Table S1 ).…”

Section: Introductionmentioning

confidence: 99%

Spectral Probe for Electron Transfer and Addition Reactions of Azide Radicals with Substituted Quinoxalin-2-Ones in Aqueous Solutions

Skotnicki

Ostrowski

Dobrowolski

et al. 2021

IJMS

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The azide radical (N3●) is one of the most important one-electron oxidants used extensively in radiation chemistry studies involving molecules of biological significance. Generally, it was assumed that N3● reacts in aqueous solutions only by electron transfer. However, there were several reports indicating the possibility of N3● addition in aqueous solutions to organic compounds containing double bonds. The main purpose of this study was to find an experimental approach that allows a clear assignment of the nature of obtained products either to its one-electron oxidation or its addition products. Radiolysis of water provides a convenient source of one-electron oxidizing radicals characterized by a very broad range of reduction potentials. Two inorganic radicals (SO4●−, CO3●−) and Tl2+ ions with the reduction potentials higher, and one radical (SCN)2●− with the reduction potential slightly lower than the reduction potential of N3● were selected as dominant electron-acceptors. Transient absorption spectra formed in their reactions with a series of quinoxalin-2-one derivatives were confronted with absorption spectra formed from reactions of N3● with the same series of compounds. Cases, in which the absorption spectra formed in reactions involving N3● differ from the absorption spectra formed in the reactions involving other one-electron oxidants, strongly indicate that N3● is involved in the other reaction channel such as addition to double bonds. Moreover, it was shown that high-rate constants of reactions of N3● with quinoxalin-2-ones do not ultimately prove that they are electron transfer reactions. The optimized structures of the radical cations (7-R-3-MeQ)●+, radicals (7-R-3-MeQ)● and N3● adducts at the C2 carbon atom in pyrazine moiety and their absorption spectra are reasonably well reproduced by density functional theory quantum mechanics calculations employing the ωB97XD functional combined with the Dunning’s aug-cc-pVTZ correlation-consistent polarized basis sets augmented with diffuse functions.

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“…These solvents are well-known for pulse radiolysis generation of radical cation precursors. 39 We have initiated primarily this study to generate isolated oxoisoaporphine radical cations and to study their spectra and kinetic behavior. Semiempirical quantum mechanical calculations PM3 and ZINDO/S have been performed to assist in the interpretation of the data and compared with the spectra obtained in the thermally induced and radiation-induced reactions.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Additional insight into the details of the oxidation mechanism of oxoisoaporphines (A1–A6, Chart ) was gained by comparing the spectral and kinetic behaviors of radical cations derived from oxoisoaporphines formed as a result of radiation-induced charge transfer between oxoisoaporphines and radical cations derived from organic solvents of various polarity (1,2-dichloroethane (1,2-DCE), acetone, and acetonitrile). These solvents are well-known for pulse radiolysis generation of radical cation precursors . We have initiated primarily this study to generate isolated oxoisoaporphine radical cations and to study their spectra and kinetic behavior.…”

Section: Introductionmentioning

confidence: 99%

Spectral and Kinetic Properties of Radical Cations Derived from Oxoisoaporphines: Relevance to Electron-Transfer Processes Involving Phytoalexins

et al. 2014

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The thermally induced intermolecular electron transfer reaction in acetonitrile between the tetracyanoethylene (TCNE), a π-electron acceptor with a large electron affinity, and six oxoisoaporphines (2,3-dihydro-7H-dibenzo[de,h]quinolin-7-one, 5-methoxy-2,3-dihydro-7H-dibenzo[de,h]quinolin-7-one, 1-azabenzo[de]anthracen-7-one, 5-methoxy-1-azabenzo[de]anthracen-7-one, 7H-benzo[e]perimidin-7-one, and 2-methyl-7h-benzo[e]perimidin-7-one) is reported. Spectral and kinetic characteristics are presented for radical cations derived from these six oxoisoaporphines either generated by a thermal reaction or generated radiolytically in argon-saturated 1,2-dichloroethane, oxygen-saturated acetone, and acetonitrile. The radical cations of oxoisoaporphines are insensitive to oxygen and are mostly characterized by absorption maxima of their most intense bands located at λ = 400-410 nm, except of the radical cations derived from 2,3-dihydrooxoisoaporphines. For the latter compounds, the absorption maxima of the most intense absorption bands are located at λ = 290-295 nm. Their locations are independent of the presence of functional groups and the solvents used. They are formed in bimolecular processes with pseudo-first-order rate constants ranging from 2.1 × 10 to 1.5 × 10 s (in solutions containing 10 M of the substrate), depending on the derivative and the solvent used. They are stable either when formed via the electron-transfer reaction with TCNE or when generated in isolation in pulse radiolysis of Ar-saturated 1,2-dichloroethane. In acetone and acetonitrile they decay predominantly by first-order kinetics with the first-order rate constants ranging from 2.3 × 10 to 5.1 × 10 s. Formation of dimeric radical cations for all of the oxoisoaporphines studied was observed in acetonitrile solutions, and for azaoxoisoaporphines also in acetone solutions. The experimental spectra show a reasonably good agreement with the ZINDO/S semiempirical quantum mechanical calculations of radical cation absorptions.

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Radiation‐Induced Radical Reactions

Cited by 4 publications

References 343 publications

Structure-Functional Study of Tyrosine and Methionine Dipeptides: An Approach to Antioxidant Activity Prediction

Structure-Functional Study of Tyrosine and Methionine Dipeptides: An Approach to Antioxidant Activity Prediction

Spectral Probe for Electron Transfer and Addition Reactions of Azide Radicals with Substituted Quinoxalin-2-Ones in Aqueous Solutions

Spectral and Kinetic Properties of Radical Cations Derived from Oxoisoaporphines: Relevance to Electron-Transfer Processes Involving Phytoalexins

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