Room temperature phosphorescence of selected pteridines

Parker, R.T.; Freelander, Richard S.; Schulman, E. M.; Dunlap, R. Bruce

doi:10.1021/ac50048a007

Cited by 56 publications

(14 citation statements)

References 33 publications

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“…To further investigate the possible participation of the pterin triplet state, experiments in the presence of iodide (I -) were performed. This anion enhances the non-radiative decay of the lowest triplet state of pterins 46 and has been used as a selective quencher to investigate the role of pterin triplet states in different photochemical processes. [47][48][49] It has been demonstrated for several pterin derivatives that I -, over the concentration range of 100 to 500 mM, does not quench the pterin singlet excited state.…”

Section: Photolysis Of Pteglu In Air and O 2 -Saturated Solutionsmentioning

confidence: 99%

Mechanism of photooxidation of folic acid sensitized by unconjugated pterins

Dántola

Denofrio

Zurbano

et al. 2010

Photochem Photobiol Sci

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Folic acid, or pteroyl-l-glutamic acid (PteGlu), is a precursor of coenzymes involved in the metabolism of nucleotides and amino acids. PteGlu is composed of three moieties: a 6-methylpterin (Mep) residue, a p-aminobenzoic acid (PABA) residue, and a glutamic acid (Glu) residue. Accumulated evidence indicates that photolysis of PteGlu leads to increased risk of several pathologies. Thus, a study of PteGlu photodegradation can have significant ramifications. When an air-equilibrated aqueous solution of PteGlu is exposed to UV-A radiation, the rate of the degradation increases with irradiation time. The mechanism involved in this "auto-photo-catalytic" effect was investigated in aqueous solutions using a variety of tools. Whereas PteGlu is photostable under anaerobic conditions, it is converted into 6-formylpterin (Fop) and p-aminobenzoyl-l-glutamic acid (PABA-Glu) in the presence of oxygen. As the reaction proceeds and enough Fop accumulates in the solution, a photosensitized electron-transfer process starts, where Fop photoinduces the oxidation of PteGlu to Fop, and H(2)O(2) is formed. This process also takes place with other pterins as photosensitizers. The results are discussed with the context of previous mechanisms for processes photosensitized by pterins, and their biological implications are evaluated.

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Section: Photolysis Of Pteglu In Air and O 2 -Saturated Solutionsmentioning

confidence: 99%

Mechanism of photooxidation of folic acid sensitized by unconjugated pterins

Dántola

Denofrio

Zurbano

et al. 2010

Photochem Photobiol Sci

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“…Besides melanins and bilurubins, which absorb in a broad range of the spectrum from UV to the visible region (300 to 600 nm), the chromophores such as urocanic acids (250 to 300 nm), porphyrin (protoporphyrins) (320 to 400 nm), flavins (345 to 375 nm), and pterins (345 to 375 nm) absorb particularly in the UV region of the spectrum. [18][19][20] The absorption of UV radiation by these chromophores initiates photosensitization, which leads to the formation of ROS either by type I or type II reaction. 36,37 As a consequence, there is a development in human skin of both photoaging, characterized by deep Fig.…”

Section: Discussionmentioning

confidence: 99%

“…17 On the other hand, other chromophores such as the urocanic acid (250 to 300 nm), riboflavins (355 nm), and pterins (345 to 375 nm) have an absorption maximum in the UV range with almost no absorption in the visible region of the spectrum. [18][19][20] The excited photosensitizer undergoes electron transport and energy transfer, leading to the formation of radical (superoxide anion radical, O 2…”

Section: Introductionmentioning

confidence: 99%

Ultraweak photon emission induced by visible light and ultraviolet A radiation via photoactivated skin chromophores: <italic>in vivo</italic> charge coupled device imaging

Prasad

Pospı́šil

2012

J. Biomed. Opt

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Abstract. Solar radiation that reaches Earth's surface can have severe negative consequences for organisms. Both visible light and ultraviolet A (UVA) radiation are known to initiate the formation of reactive oxygen species (ROS) in human skin by photosensitization reactions (types I and II). In the present study, we investigated the role of visible light and UVA radiation in the generation of ROS on the dorsal and the palmar side of a hand. The ROS are known to oxidize biomolecules such as lipids, proteins, and nucleic acids to form electronically excited species, finally leading to ultraweak photon emission. We have employed a highly sensitive charge coupled device camera and a low-noise photomultiplier tube for detection of two-dimensional and one-dimensional ultraweak photon emission, respectively. Our experimental results show that oxidative stress is generated by the exposure of human skin to visible light and UVA radiation. The oxidative stress generated by UVA radiation is claimed to be significantly higher than that by visible light. Two-dimensional photon imaging can serve as a potential tool for monitoring the oxidative stress in the human skin induced by various stress factors irrespective of its physical or chemical nature.

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“…Se veral authors reported on the fluorescence spectra of folic acid (18,19) and riboflavin (vitamin B 2 ) (9). Parker et al (20) investigated the phosphorescence properties of several pteridines at room temperature and at 77 K. The fluorescence of flavins was found to depend on the structure of the side chain (21 , 22) . Also, Fritz et al (23) demonstrated that the triplet lifetimes of flavins at room temperature vary widely with the substituent.…”

Section: Introductionmentioning

confidence: 99%

Solvent Effects upon the Electronic Absorption and Fluorescence Spectra of Pteridines and Riboflavin and Their Ground and First Excited Singlet State Dipole Moments

et al. 1991

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The electronic absorption. fluorescence excitation, and fluorescence emission spectra of a series of pteridines (lumazine, xanthopterin. isoxanthopterin, biopterin) and riboflavin (vitamin B 2 ) were measured at room temperature (298 K) in a number of solvents covering a wide range of polarities (dioxane, ethyl ether, chloroform, ethyl acetate, I-butanol. 2-propanol, ethanol, methanol, dimethylformamide, acetonitrile, and dimethyl sulfoxide) . The effects of the solvent upon the spectral properties are discussed . Experimental groundstate dipole moments were measured for selected compounds and were used in combination with the spectral data to evaluate their first excited singlet-state dipole moments by means of the solvatochromic shift method (Bakhshiev's and Kawski-Chamma-Viallet's equations based on the variation of the Stokes shift with the solvent dielectric constant-refractive index term). The theoretical ground and excited singlet-state dipole moments for all pteridines and riboflavin were calculated as a vector sum of the rt-component (obtained by the PPP method) and the a-component (obtained from a-bond moments). A second set of theoretical values was obtained by using the CNDO j2 method. A good agreement was observed between the experimental and the theoretical values. Excited singlet-state dipole moments are higher than the ground state values by 1 to 6 Debye units for all the pteridines under study with the exception of xanthopterin .

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Room temperature phosphorescence of selected pteridines

Cited by 56 publications

References 33 publications

Mechanism of photooxidation of folic acid sensitized by unconjugated pterins

Mechanism of photooxidation of folic acid sensitized by unconjugated pterins

Ultraweak photon emission induced by visible light and ultraviolet A radiation via photoactivated skin chromophores: <italic>in vivo</italic> charge coupled device imaging

Solvent Effects upon the Electronic Absorption and Fluorescence Spectra of Pteridines and Riboflavin and Their Ground and First Excited Singlet State Dipole Moments

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