C-nitroso compounds. Part XXII the mechanism of photochemical nitroxide formation from nitroso-monomers

Maassen, J. A.; Hittenhausen, H.; Boer, Th. J. de

doi:10.1016/s0040-4039(01)97136-9

Cited by 14 publications

(3 citation statements)

References 5 publications

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“…In this case, the reaction can also be induced by uv light of longer wave-length, that is 260 nm which is absorbed by the aromatic chromophore (eqs. [6], [7]). …”

Section: Protein Constituentsmentioning

confidence: 99%

“…We studied, but the following reactions (eqs. [2], [3]) have extensively used 2-methyl-2-nitrosopropane are known to occur in organic solvents (6,7): , (MNP) for trapping and characterization of free + + h v radicals generated in protein and nucleic acid 121 tBu-N=N-tBuA I I uv tBu-N=O-tBu't UVorVlS constituents over a wide range of wavelengths of 0-o-(220-313 nm) by direct or sensitized photolyses.…”

Section: Introductionmentioning

confidence: 99%

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Photochemistry of protein and nucleic acid constituents: electron spin resonance and spin-trapping with 2-methyl-2-nitrosopropane

Riesz¹,

Rosenthal²

1982

Can. J. Chem.

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PETER RIESZ and IONEL ROSENTHAL. Can. J. Chem. 60, 1474Chem. 60, (1982. Our recent studies of the direct uv-photolysis of aliphaticand aromatic peptides, DNA constituents, and their 5-haloderivatives in aqueous solution and the photo-induced reactions of benzoylperoxide with amino acids, peptides, fatty acids, and pyrimidines in dimethylsulfoxide-containing solutions are reviewed.2-Methyl-2-nitrosopropane was used for spin-trapping and characterization of free radicals generated photochemically with light in the wavelength range of220-313 nm in aqueous oraprotic solvents. Direct photolysis of aliphatic dipeptides and of phenylalanine peptides produced mostly decarboxylation radicals, while for tyrosine peptides both decarboxylation and deamination radicals were spin-trapped; for tryptophan di-and tripeptides, deamination radicals were predominantly produced, while for long chain polypeptides, main-chain scission was observed.When pyrimidine bases were photolysed, radicals consistent with the addition of an H-atom or an OH-radical at the C(5) position of the 5,Gdouble bond could be detected. The general reaction pattern in the photolyses of 5-chloro, bromo, or iodouracil was the homolytic cleavage of the carbon-halogen bond, while for 5-fluorouracil, the a-fluoro radical was spin-trapped.Dibenzoylperoxide was found to photoinduce the free radical generation in amino acids, peptides, and fatty acids exposed to ultraviolet light, which is not absorbed by these compounds, that is, h = 313 + 10 nm. The most predominant reaction is the decarboxylation of the terminal acid moiety. This process is explained by an electron transfer from the acid to the photoexcited peroxide or its fragmentation products. Pyrimidine bases, such as cytosine and thymine, can be oxidized under these conditions to generate C(5) centered radicals.PETER RIESZ et IONEL ROSENTHAL. Can. J. Chem. 60, 1474Chem. 60, (1982. On passe en revue nos rtcentes Ctudes sur la photolyse direct uv des peptides aromatiques et aliphatiques, des constituants de I'ADN et de leurs dCrivts halogenCs en solution aqueuse ainsi que les riactions photo-induites du peroxyde de benzoyle avec les acides aminks, les peptides, les acides gras et les pyrimidines dans des solutions contenant du dimethylsulfoxyde.Nous avons utilist le methyl-2 nitroso-2 propane comme capteur de spin et pour caracttriser les radicaux libres produits photochimiquement avec une lumiere dont la longueur d'onde vane de 220 a 313 nm dans des solvants aqueux ou aprotiques. La photolyse directe des dipeptides aliphatiques et des peptides contenant de la phCnylalanine produit surtout des radicaux de dtcarboxylation, tandis que dans les cas des peptides contenant la tyrosine, on a captC des radicaux de dtcarboxylation et de dtsamination. Dans le cas des di-et des tripeptides du tryptophane, on obtient surtout des radicaux de dtsamination tandis que I'on observe une scission de la chaine principale dans le cas des longues chaines de polypeptides.Quant on photolyse les bases du type pyrimidine, on dttec...

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“…In this case, the reaction can also be induced by uv light of longer wave-length, that is 260 nm which is absorbed by the aromatic chromophore (eqs. [6], [7]). …”

Section: Protein Constituentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photochemistry of protein and nucleic acid constituents: electron spin resonance and spin-trapping with 2-methyl-2-nitrosopropane

Riesz¹,

Rosenthal²

1982

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…R3C02H and ArC02H, and claim that these amide moieties are excellent photosensitive protective groups for carboxylic acids. Though other 212 Yuan L. Chow photoproducts have not been identified, it has been established that the secondary amide (120, R1 = H) is stable to photoly~is'~', that a nitro oxygen is transferred to the carboxylic acid by 180-labelling e~p e r i m e n t s l~' , and that the carboxylic acid hydrogens can come from substrates 120 and 121 or from the solvent, whichever is the better hydrogen-donating source. Since the intramolecular hydrogen atom abstraction cannot operate in 118 and 121, the reaction must be initiated by an intramolecular attack of the nitro group on the carbonyl group to give an intermediatelJO such as 122 as proposed in equation (89).…”

Section: Ohmentioning

confidence: 99%