- A new mechanism of the photochemical oxidation of tryptophan sensitised with the uranyl ion
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It has been found that tryptophan oxidation sensitised with the uranyl ion occurs as a chain reaction of Trp+ cation radicals with O2.
- Ostakhov, Sergey S.,Kazakov, Valerii P.,Osina, Irina O.
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- Polymer-Based Sensitizers for Photochemical Reactions. Silica gel as a Support
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Silica gel has been converted to silylated derivatives which can be converted to sensitizers for singlet oxygen formationn.The silica gel sensitizers, Si>-rose bengals, are versatile and useful in both polar and nonpolar media. Si>-Rose bengal has been studied as a source of singlet oxygen and its uses in reactions of sulfite ion, tryptophan, and 2,3-diphenyldioxene are reported.Results are compared with unbound and polystyrene-based rose bengal (-rose bengal).
- Tamagaki, Seizo,Liesner, Cathy E.,Neckers, Douglas C.
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- The mechanism of formation of N -formylkynurenine by heme dioxygenases
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Heme dioxygenases catalyze the oxidation of l-tryptophan to N-formylkynurenine (NFK), the first and rate-limiting step in tryptophan catabolism. Although recent progress has been made on early stages in the mechanism, there is currently no experimental data on the mechanism of product (NFK) formation. In this work, we have used mass spectrometry to examine product formation in a number of dioxygenases. In addition to NFK formation (m/z = 237), the data identify a species (m/z = 221) that is consistent with insertion of a single atom of oxygen into the substrate during O2-driven turnover. The fragmentation pattern for this m/z = 221 species is consistent with a cyclic amino acetal structure; independent chemical synthesis of the 3a-hydroxypyrroloindole-2-carboxylic acid compound is in agreement with this assignment. Labeling experiments with 18O2 confirm the origin of the oxygen atom as arising from O2-dependent turnover. These data suggest that the dioxygenases use a ring-opening mechanism during NFK formation, rather than Criegee or dioxetane mechanisms as previously proposed.
- Basran, Jaswir,Efimov, Igor,Chauhan, Nishma,Thackray, Sarah J.,Krupa, James L.,Eaton, Graham,Griffith, Gerry A.,Mowat, Christopher G.,Handa, Sandeep,Raven, Emma Lloyd
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- Dye-sensitized Photo-oxygenation of Tryptophan to give N'-Formylkynurenine
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Exclusive conversion of the tricyclic hydroperoxide (1) into N'-formylkynurenine (2) has been found to occur in Na2CO3-AcOH (pH 7) and the methylene blue-sensitized photo-oxygenation of tryptophan in the same system has given N'-formylkynurenine as the sole product, in contrast with the reaction in water, which gave compound (1).
- Nakagawa, Masako,Kato, Shiro,Nakano, Kumiko,Hino, Tohru
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- UVA photoinduced yeast protein modifications by methylene blue and naproxen
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UVA photosensitization by methylene blue (MB) or by naproxen (NAP) towards cell proteins in yeast Saccharomyces cerevisiae was investigated in order to compare this system with two simpler models, such as free Trp in solution and as a component of bovine and human serum albumin. The process was studied by monitoring protein tryptophan (Trp) residue integrity. The sensitized photodegradation of proteins resulted in different degrees of Trp damage with different Trp (photo)-products. Indeed, many of these Trp derivatives are diagnostic for the photosensitization mechanism and some of them were obtained from cells by UVA photosensitization for the first time in this work. The analysis of quantum yields of photoproduct distribution allowed us to weigh up the type I/II contribution on a UVA photosensitization mechanism. The UVA mediated generation of these Trp derivatives is consistent with the occurrence of singlet oxygen formation (almost dominant in MB), and photoionization (significant in NAP) within the protein matrix. The results obtained in the case of this more complex system (cell) are in agreement with the two simpler models recently studied in our lab. The quantum yields of Trp photoinduced degradation, as well as of its photoproducts formation, decrease with increasing the complexity of the investigated target. The Royal Society of Chemistry and Owner Societies 2013.
- Bracchitta, Giuseppina,Catalfo, Alfio,De Guidi, Guido
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- Formation of fluorophores from the kynurenine pathway metabolite N-formylkynurenine and cyclic amines involves transamidation and carbon-carbon bond formation at the 2-position of the amine
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Background Tryptophan catabolism along the kynurenine pathway is associated with a number of pathologies including cataract formation and cancer. Whilst the chemical reactions of kynurenine are well studied, less is known about the reactivity of its precu
- Tomek, Petr,Palmer, Brian D.,Kendall, Jackie D.,Flanagan, Jack U.,Ching, Lai-Ming
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- Inhibitory substrate binding site of human indoleamine 2,3-dioxygenase
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(Graph Presented) Human indoleamine 2,3-dioxygenase (hIDO) is an intracellular heme-containing enzyme, which catalyzes the initial and rate-determining step of L-tryptophan (L-Trp) metabolism via the kynurenine pathway. Due to its immunosuppressive function, hIDO has been recognized as an important drug target for cancer. Here we report evidence supporting the presence of an inhibitory substrate binding site (Si) in hIDO that is capable of binding molecules with a wide variety of structures, including substrates (L-Trp and 1-methyl-L-tryptophan), an effector (3-indole ethanol), and an uncompetitive inhibitor (Mitomycin C). The data offer useful guidelines for future development of more potent hIDO inhibitors; they also call for the re-evaluation of the action mechanism of Mitomycin C (MtoC), a widely used antitumor chemotherapeutic agent.
- Lu, Changyuan,Lin, Yu,Yeh, Syun-Ru
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- Nitrobenzofurazan derivatives of N′-hydroxyamidines as potent inhibitors of indoleamine-2,3-dioxygenase 1
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Tryptophan metabolism through the kynurenine pathway is considered as a crucial mechanism in immune tolerance. Indoleamine 2,3-dioxygenase 1 (IDO1) plays a key role in tryptophan catabolism in the immune system and it is also considered as an important therapeutic target for the treatment of cancer and other diseases that are linked with kynurenine pathway. In this study, a series of nitrobenzofurazan derivatives of N′-hydroxybenzimidamides (1) and N′-hydroxy-2-phenylacetimidamides (2) were synthesized and their inhibitory activities against human IDO1 enzyme were tested using in-vitro and cellular enzyme activity assay. The optimization leads to the identification of potent compounds, 1d, 2i and 2k (IC50 = 39-80 nM), which are either competitive or uncompetitive inhibitors of IDO1 enzyme. These compounds also showed IDO1 inhibition potencies in the nanomolar range (IC50 = 50-71 nM) in MDA-MB-231 cells with no/negligible amount of cytotoxicity. The stronger selectivity of the potent compounds for IDO1 enzyme over tryptophan 2,3-dioxygenase (TDO) enzyme (312-1593-fold) also makes them very attractive for further immunotherapeutic applications.
- Paul, Saurav,Roy, Ashalata,Deka, Suman Jyoti,Panda, Subhankar,Trivedi, Vishal,Manna, Debasis
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p. 364 - 375
(2016/06/13)
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- Associative chemosensing by fluorescent macrocycle-dye complexes-a versatile enzyme assay platform beyond indicator displacement
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A label-free in situ method to monitor reactions in real time by using fluorescent supramolecular chemosensors based on cucurbit[8]uril is presented. It allows sensing of enzymatic activity, inhibitor and activator screening, and analyte detection with unprecedented versatility and high sensitivity.
- Biedermann, Frank,Hathazi, Denisa,Nau, Werner M.
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supporting information
p. 4977 - 4980
(2015/03/30)
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- PHOTOOXIDATION OF L(-)-TRYPTOPHAN BY URANYL IONS
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The uranyl-sensitized photodecomposition of L(-)-tryptophan has been carried out.Kynurenin and N-formylkynurenin have been characterized as the products of photooxidation of L(-)-tryptophan, and a tentative mechanism for the photooxidation af L(-)-tryptophan has been proposed.
- Bhatt, Rachana,Shrimali, P. S.,Ameta, S. C.,Chowdhry, H. C.
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p. 388 - 390
(2007/10/02)
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- DYE-SENSITIZED PHOTO-OXYGENATION OF TRYPTOPHAN
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Dye-sensitized photo-oxygenation of L-triptophan (1) has been studied at various pH and in various buffers.Disappearance of 1 in both acetate and phosphate buffers was rapid at higher pH.The tricyclic hydroperoxide (8) was the sole product in the oxidatio
- Nakagawa, Masako,Yokoyama, Yukio,Kato, Shiro,Hino, Tohru
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p. 2125 - 2132
(2007/10/02)
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- CERTAIN RELATIONSHIPS OF FORMATION OF THE PRODUCTS OF OZONIZATION OF TRYPTOPHAN.
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In order to elucidate the role of radical reactions in ozonization of tryptophan, the authors carried out a comparative study of ozonization and radiolysis of tryptophan in dilute aqueous solutions, and also of its oxidation by OH radicals generated in the Fenton reaction. Formation of products of decomposition, polymerization, and deamination of the amino acid was observed during ozonization of tryptophan. As in the case of radiolysis and oxidation by Fenton's reagent, an important part in the formation of final products of tryptophan ozonization in aqueous solution is played by homolytic processes involving OH radicals.
- Sikorskaya,Ignatenko,Cherenkevich
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p. 1910 - 1914
(2007/10/02)
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- DYE-SENSITIZED PHOTOOXYGENATION OF TRYPTOPHAN: 3a-HYDROPEROXYPYRROLOINDOLE AS A LABILE PRECURSOR OF FORMYLKYNURENINE
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The isolation, structure determination, and reactivity of the tricyclic labile hydroperoxides 10 and 2 obtained by dye-sensitized photooxygenation of L-, D-, and DL-tryptophan and Nb-methoxycarbonyltryptophan ester are reported.The tricyclic hydroperoxide 10, under apprpopiate conditions, was easily convertible to formylkynurenine.Plausible mechanisms for these transformations are discussed.Keywords-tryptophan and its derivatives; dye-sensitized photooxygenation; formylkynurenine; hydroperoxypyrroloindoles; 3-hydroperoxyindolenines; 1,3-benzoxazines; CD spectra; rearrangement; ring-chain tautomerism; biological oxidation
- Nakagava, Masako,Kato, Shiro,Kataoka, Shigehiro,Kodato, Shinichi,Watanabe, Hideyuki,et al.
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p. 1013 - 1026
(2007/10/02)
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