Electron-transfer processes induced by the triplet state of pterins in aqueous solutions

Dántola, M. Laura; Vignoni, Mariana; González, C.; Lorente, Carolina; Vicendo, Patricia; Oliveros, Esther; Thomas, Andrés H.

doi:10.1016/j.freeradbiomed.2010.06.011

Cited by 33 publications

(35 citation statements)

References 57 publications

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“…Iodide ions (I − ) at micromolar concentrations efficiently and selectively quench the triplet excited states of pterins . We performed experiments to study the effect of iodide (250 μ m KI) on the photosensitizing activity of Bip in H 4 Bip oxidation.…”

Section: Resultsmentioning

confidence: 99%

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Photooxidation of Tetrahydrobiopterin under UV Irradiation: Possible Pathways and Mechanisms

Buglak

Телегина

Lyudnikova

et al. 2014

Photochem & Photobiology

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Tetrahydrobiopterin (H4 Bip) is a cofactor for several key enzymes, including NO synthases and aromatic amino acid hydroxylases (AAHs). Normal functioning of the H4 Bip regeneration cycle is extremely important for the work of AAHs. Oxidized pterins may accumulate if the H4 Bip regeneration cycle is disrupted or if H4 Bip autoxidation occurs. These oxidized pterins can photosensitize the production of singlet molecular oxygen (1)O2 and thus cause oxidative stress. In this context, we studied the photooxidation of H4 Bip in phosphate buffer at pH 7.2. We found that UV irradiation of H4 Bip affected its oxidation rate (quantum yield Φ300 = (2.7 ± 0.4) × 10(-3)). The effect of UV irradiation at λ = 350 nm on H4 Bip oxidation was stronger, especially in the presence of biopterin (Bip) (Φ350 = (9.7 ± 1.5) × 10(-3)). We showed that the rate of H4 Bip oxidation linearly depends on Bip concentration. Experiments with KI, a selective quencher of triplet pterins at micromolar concentrations, demonstrated that the oxidation is sensitized by the triplet state biopterin (3) Bip. Apparently, electron transfer sensitization (Type-I mechanism) is dominant. Energy transfer (Type-II mechanism) and singlet oxygen generation play only a secondary role. The mechanisms of H4 Bip photooxidation and their biological meaning are discussed.

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Section: Resultsmentioning

confidence: 99%

“…These results indicate that O 2 •− is involved in the photosensitized oxidation process, although its participation is minimal. Therefore, Reaction 5 is, indeed, very unlikely to occur with Bip, particularly because this reaction does not occur with pterin .…”

Section: Resultsmentioning

confidence: 99%

Photooxidation of Tetrahydrobiopterin under UV Irradiation: Possible Pathways and Mechanisms

Buglak

Телегина

Lyudnikova

et al. 2014

Photochem & Photobiology

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“…Since these latter species participate in the physiopathology of many diseases (19), the photochemical production of these species by pterins is biologically relevant. Aromatic pterins are able to generate O 2 ·-and H 2 O 2 through two different photochemical mechanisms: a) In neutral or slightly acidic aqueous solutions, photoinduced electron transfer from the pterin moiety itself (Pt), to the triplet excited state of Pt ( 3 Pt*) may initiate a series of reactions leading to the formation of O 2 ·-and H 2 O 2 (20). The main results supporting this mechanism are: EPR analysis in the presence of the spin trap DMPO shows the characteristic signal of the adduct between DMPO and O 2 ·-; the formation of H 2 O 2 has been proven by a colorimetric method and its amount increased in the presence of superoxide dismutase (SOD) which catalyzes the O 2 ·-disproportionation; it also increased with the pterin concentration and decreased when the O 2 concentration increased.…”

Section: Production Of Superoxide Anion and Hydrogen Peroxidementioning

confidence: 99%

“…Although, an electron transfer process must be involved in the photoreduction of pterins, the overall mechanism should be different from that proposed for the photosensitized oxidation of nucleotides. In a very recent work it was explained why, in some cases, photooxidation of a substrate take place without photosensitizer (Pt) consumption, whereas in other cases photoreduction of pterins occurs (20).…”

Section: Photoreduction Of Pterinsmentioning

confidence: 99%

Electron Transfer Initiated Reactions Photoinduced by Pterins

et al. 2011

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Interest in the photochemistry and photophysics of pterins has increased since the participation of this family of compounds in different photobiological processes has been suggested or demonstrated in recent decades. Pterins participate in relevant biological processes, such as metabolic redox reactions, and can photoinduce the oxidation of biomolecules through both electron transfer mechanisms (Type I) and singlet oxygen production (Type II). This article describes recent findings on electron transfer-initiated reactions photoinduced by the triplet excited state of pterins and connects them in the context of photosensitized processes of biological relevance.

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“…Es importante mencionar que el consumo de Ptr observado en ausencia de dT5 no se debe exclusivamente a su fotoquímica, sino también a la presencia de TRIS en el medio de reacción. Cuando se irradia Ptr en condiciones anaeróbicas y en presencia de un buen donor de electrones, como es el caso del TRIS, puede reducirse y generar los correspondientes dihidroderivados [Dántola, 2010]. Cuando se irradió la disolución de oligonucleótido a 350 nm en ausencia de Ptr, no se observaron cambios espectrales y el análisis de HPLC reveló que no hay consumo del sustrato (Figura 92).…”

Section: Fotosensibilización De Un Oligonucleótido Deunclassified

Generación fotoquímica y caracterización de aductos pterina-pirimidina en nucleósidos, oligonucleótidos y ADN

Ruiz¹

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El objetivo general de esta tesis doctoral es investigar los procesos fotosensibilizados por pterinas de bases pirimidínicas que forman parte de diferentes sustratos en condiciones aneróbicas. Para ello se trabajó con Ptr, que es el compuesto modelo no sustituido de las pterinas oxidadas. Como sustratos se emplearon nucleótidos, nucleósidos, oligonucleótidos y ADN eucariota. A continuación se detallan los objetivos específicos que han dirigido el desarrollo de la tesis: - Estudiar el proceso fotosensibilizado del nucleósido de timina por Ptr bajo diferentes condiciones experimentales y dilucidar el mecanismo de reacción. - Comparar la eficiencia de los procesos fotosensibilizados en nucleótidos y nucleósidos por Ptr en condiciones anaeróbicas. Concretamente, realizar un estudio sobre la generación de aductos fluorescentes entre el fotosensibilizador y el sustrato. - Caracterizar estructuralmente dichos aductos. - Analizar las propiedades fotofísicas de aductos pterina-timina. - Investigar la generación de aductos fluorescentes en oligonucleótidos, tanto de hebra simple como de hebra doble. - Estudiar el daño sufrido por moléculas de ADN eucariota en procesos fotosensibilizados por Ptr. - Realizar un análisis acerca de la formación de aductos pterina-timina en moléculas de ADN.

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Electron-transfer processes induced by the triplet state of pterins in aqueous solutions

Cited by 33 publications

References 57 publications

Photooxidation of Tetrahydrobiopterin under UV Irradiation: Possible Pathways and Mechanisms

Photooxidation of Tetrahydrobiopterin under UV Irradiation: Possible Pathways and Mechanisms

Electron Transfer Initiated Reactions Photoinduced by Pterins

Generación fotoquímica y caracterización de aductos pterina-pirimidina en nucleósidos, oligonucleótidos y ADN

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