Photoionization and Photosensitized Electron-Transfer Reactions of Psoralens and Coumarins

Wood, Paul D.; Johnston, Linda J.

doi:10.1021/jp9802026

Cited by 44 publications

(60 citation statements)

References 51 publications

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“…Apart from that, the offset spectrum of the global fit reveals a relatively large amount of solvated electron absorption. It has previously been shown that this psoralen undergoes rather efficient mono‐ (quantum yield 0.015) and biphotonic ionization in aqueous solution, which rationalizes this observation.…”

Section: Resultssupporting

confidence: 64%

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Photoinduced Electron Transfer between Psoralens and DNA: Influence of DNA Sequence and Substitution

et al. 2015

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Psoralens are heterocyclic compounds which are, among other uses, used to treat skin deseases in the framework of PUVA therapy. In the dark, they intercalate into DNA and can form photoadducts with thymines upon UV-A excitation, which harms the affected cells. We have recently discovered that after excitation of intercalated psoralens, an efficient photoinduced electron transfer (PET) from DNA occurs. Here, the PET is studied in detail by means of femtosecond transient absorption spectroscopy. Using DNA samples that contain either only GC or AT base pairs, we show that only guanine donates the electrons. Additionally, the substituent effects on PET are studied relying on three different psoralen derivatives. The substitution alters spectroscopic and electrochemical properties of the psoralens, which are determined by cyclic voltammetry and steady state spectroscopy. These experiments allow us to estimate the PET energetics, which are in line with the measured kinetics. Implications for the applications of psoralens are discussed.

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Section: Resultssupporting

confidence: 64%

“…The potentiostat was from Princeton Applied Research (Model 263 A). The potentials were measured at a scan rate of 100 mV s −1 and corrected to the internal standard Fc

^{+}

/Fc in acetonitrile ( E

_{1 / 2}^{0 / + 1}

=440 mV) . Psoralen concentrations were around 2 m m .…”

Section: Methodsmentioning

confidence: 99%

Photoinduced Electron Transfer between Psoralens and DNA: Influence of DNA Sequence and Substitution

et al. 2015

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“…CD2 and CD1 exhibit weaker fluorescence than the rest of the compounds. For the compounds we studied, the experimental values of the fluorescence quantum yields agree well with data for compounds with a related structure (for psoralene, ϕ FL = 0.01-0.023 [18][19][20]; for 8-MOP, ϕ FL = 0.003 [18][19][20]; for 5-MOP, ϕ FL = 0.001 [19]). Let us consider the energy deactivation pathways in more detail.…”

Section: Determination Of Fluorescence Quantum Yieldssupporting

confidence: 74%

Fluorescent characteristics of coumarin photosensitizers

et al. 2008

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We present a theoretical and experimental study of the fluorescent ability of new coumarin sensitizers. Using the INDO method, we have drawn the level diagram for the photophysical processes in the coumarin molecules. We have calculated the rate constants for internal conversion and intersystem crossing and the radiative rate constants. We have determined the experimental and theoretical fluorescence yields of the test compounds.Introduction. Coumarins are a group of organic dyes in the blue-green range. These compounds are widely used in different fields of science and technology. For example, many coumarins exhibit intense fluorescence, which is used to design fluorescent labels, optical brighteners, laser active media, and organic light-emitting diodes [1,2]. At the same time, a change in structure can lead to creation of coumarins having good photosensitizing properties.Furocoumarins (psoralenes) are heterocyclic aromatic compounds having photosensitizer properties in the UV radiation range, 320-400 nm [3]. Usually photosensitization is an undesirable phenomenon [4,5], leading to light-induced burns on the skin and eyes for low exposure doses which, under ordinary conditions, do not have a damaging effect. However, sometimes the combined action of light and the photosensitizer causes positive therapeutic effects. Photochemotherapy methods have been devised based on such combination effects of light and dyes on the human body.A number of substances from this group of compounds have properties enabling their use in photochemotherapy of various skin diseases (psoriasis, atopic dermatitis, rheumatoid arthritis, vitiligo) [6,7]. Many substituted coumarins display anticoagulant activity, which is used for therapy of thromboses. In recent years, compounds in this class have also begun to be used for photoinduced modification of nucleic acids, for phototherapy of cancer and viral infections (including HIV infections), and also in transplantology to prevent rejection of transplanted tissues. Despite their widespread popularity, this class of compounds still remains poorly studied.Some compounds in the substituted coumarin series act as bifunctional photoreagents, capable of crosslinking both DNA strands [5,8]. Besides photoreactions of furocoumarins with DNA to form adducts (type III reactions), other types of photochemical reactions are possible [9]. For structurally different furocoumarins, the ratio of the contributions of the different types of photoreactions may vary significantly. The increasingly expanding use of furocoumarins as photosensitizers and photoreagents urgently requires determining the relationship between their structure, spectral luminescence properties, and the primary photoprocesses occurring in them. We may hypothesize that it is specifically the spectral luminescence and photophysical properties and their dependence on the structure of the compound that to a significant extent will determine the later course of both photochemical and photobiological processes, since they all occur with partici...

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“…The values of the photochemical quantum yields in CH 2 Cl 2 were independent of fluorene and oxygen concentrations, consistent with first order photoreactions. Thus, in this case, the main mechanism can be associated with an electron transfer process from the amine group leading to formation of stable cation radicals [68]. This mechanism is nearly independent of oxygen concentration, resulting in many different photoproducts with broad absorption in the visible and near-IR range.…”

Section: Photochemical Properties Of Fluorenes Under One-photon Excitmentioning

confidence: 98%

“…Photodecomposition of the molecules can occur as a result of one-photon, two-photon, or two-step successive absorption within a single pulse of laser excitation. Under these conditions, organic molecules can be excited into high electronic states and undergo different photochemical reactions, such as photoionization and bond fission [68]. In general, these photoprocesses may differ from the reactions of the molecule in its lowest excited state produced by low intensity irradiation.…”

Section: Photochemical Properties Of Fluorene Derivativesmentioning

confidence: 99%