CERTAIN SINGLET OXYGEN QUENCHERS AFFECT THE PHOTOREACTION BETWEEN 8‐MOP and DNA

Bordin, F.; Conconi, Maria Teresa; Capozzi, A.

doi:10.1111/j.1751-1097.1987.tb04770.x

Cited by 16 publications

(9 citation statements)

References 15 publications

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“…Despite widespread clinical application of PUVA therapy, there is evidence that its long-term use may be associated with a variety of harmful side effects, including carginogenicity, mutagenicity and immune system modulation (2,6,7). In addition to their DNA-specific chemistry, psoralens and related compounds have been shown to generate singlet oxygen (8)(9)(10)(11)(12), to bind to proteins (13)(14)(15)(16)(17) and to undergo photocycloaddition reactions with unsaturated fatty acids (18,19). DNA adducts in which the psoralen is attached to the sugar rather than to the base have also been characterized (20).…”

Section: Introductionmentioning

confidence: 99%

Reactions of Psoralen Radical Cations with Biological Substrates†¶

Wood¹,

Mnyusiwalla²,

Chen³

et al. 2007

Photochemistry and Photobiology

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The reactions of several psoralen and coumarin radical cations with biological substrates such as nucleotides, amino acids and alkenes that serve as models for unsaturated fatty acids have been examined. The radical cations were generated by laser photoionization of the parent psoralen or coumarin in aqueous buffer in most cases. Easily oxidized substrates such as tyrosine, tryptophan and guanosine monophosphate react with the 8-methoxypsoralen and several methoxy-substituted coumarin radical cations with rate constants in excess of 2 ؋ 10 9 M Ϫ1 s Ϫ1 . In each case reaction occurs via electron transfer, as demonstrated by the observation of quencher-derived radical cations or radicals by transient absorption spectroscopy. For other substrates such as histidine, methionine and adenosine monophosphate the measured rate constants are significantly slower and vary with the oxidation potential of both the parent psoralen or coumarin and the quencher, again indicative of electron transfer reactivity. Most of the alkenes studied also react with the psoralen or coumarin radical cations via electron transfer, although there is some evidence for addition for linoleic acid. Product studies carried out using both lamp and laser irradiation in the presence of deoxyguanosine as a radical cation trap lead to the formation of characteristic base-derived Type-I (electron transfer) products. This lends support to our previous hypothesis that photoionization occurs via a monophotonic process and is thus relevant to conditions used in clinical phototherapeutic applications of psoralens. The results demonstrate the relevance of electron transfer chemistry to the use of psoralens and related compounds as photoactivated drugs.

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Section: Introductionmentioning

confidence: 99%

Reactions of Psoralen Radical Cations with Biological Substrates†¶

Wood¹,

Mnyusiwalla²,

Chen³

et al. 2007

Photochemistry and Photobiology

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“…It is also clear that reactions other than DNA cross-linking are important in both the beneficial and deleterious effects of PUVA therapy. Photoaddition to membrane components, singlet oxygen-mediated chemistry, and reaction with amino acids and proteins have all been postulated, on the basis of a variety of studies both in model systems and in a cellular environment (7)(8)(9)(10)(11)(12)(13)(14)(15).…”

Section: Introductionmentioning

confidence: 99%

Psoralen and Coumarin Photochemistry in HSA Complexes and DMPC Vesicles†

Chen

Rinco

Popov

et al. 2006

Photochem Photobiol

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The photochemistry and photophysics of several psoralens and coumarins have been examined in human serum albumin (HSA) complexes and dimyristoylphosphatidylcholine (DMPC) vesicles. Fluorescence spectroscopy indicates that there are multiple binding sites with polarities that are intermediate between those of acetonitrile and water for the substrates complexed to HSA. In the case of the 6,7-dimethoxycoumarin-HSA complex, laser flash photolysis experiments provide evidence for the formation of radical cation in addition to triplet. Radical cations are not detected for other coumarin-HSA complexes, either due to a lower yield of formation or to rapid reaction of an initial radical cation with adjacent amino acids. Fluorescence spectra for coumarins indicate that they are primarily solubilized in the polar headgroup region in DMPC vesicles. Consistent with this, radical cations generated by photoionization are detected in transient experiments. For dimethoxycoumarins the radical cation is long-lived, indicating rapid exit from the vesicle and decay in the aqueous phase. However, 4,5',8-trimethylpsoralen and 7-ethoxy-4-hexadecylcoumarin radical cations are much shorter-lived, presumably due to rapid decay by electron recombination in the vesicle. The results for both HSA complexes and vesicles indicate that radical ions may play a role in psoralen and coumarin photochemistry in a cellular environment.

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“…[2][3][4][5] Photochemical properties of 5,7-dimethoxycoumarin (DMC), such as photodimerization, 2,6 photoaddition, 7,8 photoionization, and photosensitized electron-transfer reactions, 9 have been investigated under one-photon excitation by IR, UV, NMR and mass spectrometry, 3 transient absorption spectroscopy 9 and measurement of singlet oxygen yields. 10 Coumarin derivatives continue to be investigated as photorecording materials 11 and as photolabile protecting groups for single-and two-photon uncaging (release) of biologically active substances in cells and tissues. 12 Dimers of the photocycloaddition of DMC have been isolated and characterized after irradition in a number of solvents, including acetonitrile (ACN), and the stereochemical and regiochemical configuration of the dimers was elucidated (Fig.…”

Section: Introductionmentioning

confidence: 99%

Photophysical and photochemical properties of 5,7‐dimethoxycoumarin under one‐ and two‐photon excitation

Belfield¹,

Bondar²,

Liu³

et al. 2002

J of Physical Organic Chem

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The spectroscopic and photochemical properties of 5,7-dimethoxycoumarin (DMC) in acetonitrile (ACN) were investigated at room temperature under one-and two-photon excitation. Two-photon induced [2 2] photocycloaddition of DMC was investigated with 650 nm laser excitation (120 fs pulse width). GC and GC-MS analysis confirmed dimer formation, while HPLC analysis allowed specific photodimer identification through comparison with samples prepared via one photon irradiation. Photodimer products formed via two-photon excitation correlated with those formed via UV irradiation. Syn head-to-head and syn head-to-tail photodimers were formed in 1:3.0 and 1:2.8 ratios under one-photon (broadband UV) and two-photon (650 nm, 120 fs) irradiation in anisole, respectively. The quantum yield for the photoreaction of DMC solution (10 À4 M) under broadband UV irradiation was of the order of 1 Â 10 À3 and increased dramatically to 1 Â 10 À2 under two-photon excitation. The spectral investigation of the photochemical products of DMC revealed efficient fluorescence emission in the spectral region 290-340 nm, attributed to the syn-head-to-tail dimers of DMC. Evidence for an additional manifold for the photochemical reaction of DMC was found, resulting in the production of photochemical products that exhibited low fluorescence emission intensity along with dependences on excitation wavelength.

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CERTAIN SINGLET OXYGEN QUENCHERS AFFECT THE PHOTOREACTION BETWEEN 8‐MOP and DNA

Cited by 16 publications

References 15 publications

Reactions of Psoralen Radical Cations with Biological Substrates†¶

Reactions of Psoralen Radical Cations with Biological Substrates†¶

Psoralen and Coumarin Photochemistry in HSA Complexes and DMPC Vesicles†

Photophysical and photochemical properties of 5,7‐dimethoxycoumarin under one‐ and two‐photon excitation

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