Studies on reaction of amino acids and triplet thioxanthone derivatives by laser flash photolysis

Zhu, Hongping; Wang, Wenfeng; Yao, Side

doi:10.1007/s10637-006-7073-4

Cited by 7 publications

(8 citation statements)

References 20 publications

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“…The reduction potential for NAT, E °(NAT •+ /NAT), should not be so different from those reported for tryptophan and some methylindole derivatives, ranging between 1.23 and 0.93 V. − These values are in the same E ° range of amines that we previously used to photoreduce 3-phenylquinoxalin-2-one derivatives. , Therefore, it is reasonable to expect a SET from NAT to the substituted quinoxalin-2-one. For NAT derived radicals, transient absorptions are expected near 560 nm for the radical cation NAT •+ and close to 510 nm for the deprotonated neutral radical NAT-H • , similar to those reported for tryptophan radicals. ,− …”

Section: Introductionsupporting

confidence: 76%

Spectral and Kinetic Study of 3-Methylquinoxalin-2-ones Photoreduced by Amino Acids: N-Phenylglycine Radical Chain Reactions and N-Acetyltryptophan Decarboxylation

Fuente

Cañete²,

Carathanassis

et al. 2016

J. Phys. Chem. A

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Transient intermediates were identified in the photoreduction of 3-methylquinoxalin-2-one derivatives by N-phenylglycine, NPG, and N-acetyltryptophan, NAT. For both reductants it can be postulated a sequence of reaction comprising first a photoinduced single electron transfer followed by a proton transfer from the radical cation of the electron donor to the radical anion of the 3-methylquinoxalin-2-one giving rise to the reported products. The effect of the concentrations of NPG and the quinoxalin-2-one on the rate of photoconsumption of this last were quantified, and the lifetimes of the possible intermediates estimated. In the photoreduction by NAT, processes leading to the decarboxylation of NAT and radical adduct product compete with the expected SET from the indoyl N to the excited triplet of quinoxalin-2-ones as revealed by the detection of the deprotonated N-acetyltryptophan radical [NAT-H](•). This radical is formed almost instantly after the laser pulse and has a secondary delayed growth via a delayed proton transfer from the indoyl radical cation NAT(•+) to the quinoxalin-2-one radical anions. The decarboxylation of NAT that mimics C-terminus tryptophan in proteins is biologically relevant because might cause damages at cellular and the whole organism level. As far as we know this is the first report of a radical decarboxylation of N-acetyltryptophan leading to photoproducts.

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Section: Introductionsupporting

confidence: 76%

Spectral and Kinetic Study of 3-Methylquinoxalin-2-ones Photoreduced by Amino Acids: N-Phenylglycine Radical Chain Reactions and N-Acetyltryptophan Decarboxylation

Fuente

Cañete²,

Carathanassis

et al. 2016

J. Phys. Chem. A

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“…13 Recently, the photoinduced electron-transfer reactions between the triplet excited state of TX with indolic and phenolic derivatives have been reported. 5,6,14 In most of the TX photochemistry, the long-lived lowest triplet state has been attributed to be responsible for the photosensitization reactions. It has also been shown that the photochemical reaction efficiency and relaxation behavior of carbonyl compounds can be correlated with the electronic state configuration (ππ* or nπ*) of the lowest triplet excited state.…”

Section: ' Introductionmentioning

confidence: 99%

Time-Resolved Resonance Raman Spectroscopic Studies on the Triplet Excited State of Thioxanthone

Pandey

Umapathy

2011

J. Phys. Chem. A

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Thioxanthone has been investigated extensively owing to its unique photochemical and photophysical applications and its solvatochromic behavior. Here, we report the time-resolved resonance Raman studies on the structure of the lowest triplet excited state of thioxanthone in carbon tetrachloride. In addition, FT-IR and FT-Raman techniques have been used to study the vibrational structure in the ground state. To corroborate the experimental findings, density functional theory calculations have been carried out. Isotopic calculations and normal coordinate analysis have been used to help in assigning the observed bands to Raman vibrational modes. Structural information derived from this study is expected to help in better understanding the triplet state photochemistry of thioxanthone.

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“…ring, 12,17,18 and the chelated Mg 2＋ had little influence on the two absorptions at 550 and 700 nm according to the literature. 19 TDBP had a series of weak absorptions in 500-700 nm region.…”

Section: Steady-state Uv-vis Absorptions Of Mg-purpurin-18 M-tcpp Amentioning

confidence: 65%

Studies on the Photodynamic Mechanism of Tetrapyrrole Compounds by Laser Flash Photolysis

et al. 2008

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Photodynamic therapy (PDT) is a promising new treatment technique which can potentially destroy unwanted and malignant tissues, such as those of cancer. The photodynamic mechanisms of three tetrapyrrole compounds: Mg-purpurin-18, tetra(meso-chlorophenyl)porphyrin (m-TCPP) and 2,7,12,18-tetramethyl-3,8-di[(1-isobutoxyl)ethyl]-13,17-bis[3-di(2-chloroethyl)aminopropyl]porphyrin (TDBP) in acetonitrile were investigated by 355 nm laser flash photolysis. It was found that after laser flash photolysis (LFP), the excited states of TDBP and Mg-purpurin-18 could react with O 2 and 1 O 2 was produced, which proved that TDBP and Mg-purpurin-18 took effects through type II mechanism in PDT. This suggested that TDBP and Mg-purpurin-18 should be suitable for target tissues containing enough O 2 . Mg-purpurin-18 has two extra absorptions at 550 and 700 nm, which means it has broad choices of laser wavelength in PDT. It was also found that m-TCPP could be photoionized when excited with 355 nm laser under N 2 -saturated condition. It could also react with O 2 to produce reactive oxygen species such as superoxide and the peroxide anions, but not 1 O 2 . These were known as the Type I mechanism. So m-TCPP could be used even at low oxygen concentration or more polar environments with good behavior in PDT. From the above studies on the three different tetrapyrrole compounds it could be concluded that the structure of porphin ring takes a main role in PDT. And there was important impact on the photodynamic mechanism for the functional group directly connecting with porphin ring, while little influence for the functional group indirectly connecting with porphin ring. These will be of great value in the discovery of new PDT drugs.

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Studies on reaction of amino acids and triplet thioxanthone derivatives by laser flash photolysis

Cited by 7 publications

References 20 publications

Spectral and Kinetic Study of 3-Methylquinoxalin-2-ones Photoreduced by Amino Acids: N-Phenylglycine Radical Chain Reactions and N-Acetyltryptophan Decarboxylation

Spectral and Kinetic Study of 3-Methylquinoxalin-2-ones Photoreduced by Amino Acids: N-Phenylglycine Radical Chain Reactions and N-Acetyltryptophan Decarboxylation

Time-Resolved Resonance Raman Spectroscopic Studies on the Triplet Excited State of Thioxanthone

Studies on the Photodynamic Mechanism of Tetrapyrrole Compounds by Laser Flash Photolysis

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