93-35-6Relevant articles and documents
Fluorescence detection of hydroxyl radical generated from oxygen reduction on Fe/N/C catalyst
Chen, Li-Na,Yu, Wen-Song,Wang, Tao,Yang, Xiao-Dong,Yang, Hui-Juan,Chen, Zhi-Xin,Wang, Tan,Tian, Na,Zhou, Zhi-You,Sun, Shi-Gang
, p. 198 - 202 (2020)
Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction (ORR) in fuel cells. However, poor stability of Fe/N/C catalyst, mainly attributed to the oxidation corrosion by aggressive ?OH radical, severely hampers its applications. However, the exact mechanism for generation of ?OH is unclear yet. Herein, we developed a fluorescent method to effectively detect ?OH generated from ORR on Fe/N/C catalyst by using coumarin as a fluorescent probe. A great difference in potential dependence between ?OH and H2O2 generated from the ORR was observed, which suggests that ?OH is not generated from the decomposition of H2O2 as traditional viewpoint.
Functional characterization of allelic variants of polymorphic human cytochrome P450 2A6 (CYP2A6*5, *7, *8, *18, *19, and *35)
Han, Songhee,Choi, Seunghye,Chun, Young-Jin,Yun, Chul-Ho,Lee, Chang Hoon,Shin, Hee Jung,Na, Han Sung,Chung, Myeon Woo,Kim, Donghak
, p. 394 - 399 (2012)
Cytochrome P450 2A6 (CYP2A6) catalyzes important metabolic reactions of many xenobiotic compounds, including coumarin, nicotine, cotinine, and clinical drugs. Genetic polymorphisms of CYP2A6 can influence its metabolic activities. This study analyzed the functional activities of six CYP2A6 allelic variants (CYP2A6*5,*7,*8,*18,*19, and *35) containing nonsynonymous single-nucleotide polymorphisms. Recombinant variant enzymes of CYP2A6*7,*8,*18,*19, and *35 were successfully expressed in Escherichia coli and purified. However, a P450 holoenzyme spectrum was not detected for the CYP2A6*5 allelic variant (G479V). Structural analysis shows that the G479V mutation may alter the interaction between the A helix and the F-G helices. Enzyme kinetic analyses indicated that the effects of mutations in CYP2A6 allelic variants on drug metabolism are dependent on the substrates. In the case of coumarin 7-hydroxylation, CYP2A6*8 and *35 displayed increased Km values whereas CYP2A6*18 and *19 showed decreased kcat values, which resulted in lower catalytic efficiencies (kcat/Km). In the case of nicotine 5-oxidation, the CYP2A6*19 variant exhibited an increased Km value, whereas CYP2A6*18 and *35 showed much greater decreases in kcatvalues. These results suggest that individuals carrying these allelic variants are likely to have different metabolisms for different CYP2A6 substrates. Functional characterization of these allelic variants of CYP2A6 can help determine the importance of CYP2A6 polymorphisms in the metabolism of many clinical drugs.
Synthesis of 7-hydroxycoumarins catalysed by solid acid catalysts
Hoefnagel,Gunnewegh,Downing,Van Bekkum
, p. 225 - 226 (1995)
Syntheses of substituted 7-hydroxycoumarins via reactions of 1,3-dihydroxybenzene with ethyl acetoacetate (Pechmann reaction) and with propenoic acid and propynoic acids are reported, in which the production of environmentally harmful waste streams is minimized by the use of solid acid catalysts.
Sn-Doped defect pyrochlore oxide KNbWO6·H2O microcrystals and their photocatalytic reduction of CO2
Zeng, Xu,Chen, Yan,Jiao, Shihui,Fang, Zhenxing,Wang, Boran,Pang, Guangsheng,Feng, Shouhua
, p. 5753 - 5758 (2018)
It is highly desirable to develop new semiconductors for the photocatalytic reduction of CO2 to CH4 and CO to solve greenhouse effect and energy issues. Defect pyrochlore oxides have a flexible composition and the electron/hole mobility can be manipulated by introducing foreign cations into the structure. Through Sn doping into the defect pyrochlore oxide KNbWO6·H2O, we successfully obtained a 2-times higher photocatalytic activity for converting CO2 to CO, CH4 and O2 compared to the original KNbWO6·H2O. According to the data from UV-vis, photoluminescence, and hydroxyl radical amount-related fluorescence spectra, and CO2 adsorption, the improved photocatalytic activity can be attributed to the extended visible light response, the enhanced charge separation and the improved CO2 adsorption due to Sn doping. Our results provide a new strategy for developing high-performance photocatalysts.
LICRED: A versatile drop-in vector for rapid generation of redox-self-sufficient cytochrome P450s
Sabbadin, Federico,Hyde, Ralph,Robin, Aelig,Hilgarth, Eva-Maria,Delenne, Marie,Flitsch, Sabine,Turner, Nicholas,Grogan, Gideon,Bruce, Neil C.
, p. 987 - 994 (2010)
Cytochromes P450 (P450s) are a family of haem-containing oxidases with considerable potential as tools for industrial biocatalysis. Organismal genomes are revealing thousands of gene sequences that encode P450s of as yet unknown function, the exploitation of which will require high-throughput tools for their isolation and characterisation. In this report, a ligation-independent cloning vector "LICRED" is described that enables the high-throughput generation of libraries of redox-self-sufficient P450s by fusing a range of P450 haem domains to the reductase of P450RhF (RhF-Red) in a robust and generically applicable way. Cloning and expression of fusions of RhF-Red with the haem domains of P450cam and P450-XplA resulted in soluble, active, redox-self-sufficient, chimeric enzymes. In vitro studies also revealed that electron transfer from NADPH to haem was primarily intramolecular. The general applicability of the LICRED platform was then demonstrated through the creation of a library of RhF-Red fusion constructs by using the diverse complement of P450 haem domains identified in the genome of Nocardia farcinica. The resultant fusion-protein library was then screened against a panel of substrates; this revealed chimeric enzymes competent for the hydroxylation of testosterone and methyltestosterone, and the dealkylation of 7-ethoxycoumarin.
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Pandya,Sodhi
, p. 381 (1938)
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Microwave Synthesis of Spinel MgFe2O4Nanoparticles and the Effect of Annealing on Photocatalysis
McDonald, Kori D.,Bartlett, Bart M.
, p. 8704 - 8709 (2021)
Through microwave heating in ethanol and with subsequent annealing, crystalline MgFe2O4 nanoparticles are produced rapidly and in high yields >99%. Under varied annealing temperatures, the degree of Mg and Fe site inversion changes the optical, electronic, and composition of the nanoparticles. A small particle size of ～10 nm is achievable with the aid of an ammonium salt mineralizer that caps the particles during nucleation and growth. Particles with the lowest inversion parameter and limited sintering upon annealing (at 600 °C) exhibit the greatest production of hydroxyl radicals under visible light illumination. As such, these particles also facilitate the degradation of methylene blue dye faster than those particles annealed at higher temperature and show a rate constant of 0.061 h-1 for degrading 10 ppm methylene blue with 20 mg of catalyst.
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Kir'yalov
, (1967)
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Improved photoactivities for CO2 conversion and phenol degradation of α-Fe2O3 nanoparticles by co-coupling nano-sized BiPO4 and CuO to modulate electrons
Chen, Shuangying,Mu, Zhiyuan,Yan, Rui,Zhang, Xuliang,Khan, Iltaf,Li, Zhijun,Sun, Ning,Zhang, Qingyang,Jing, Liqiang
, p. 231 - 239 (2019)
It's highly desired to design and fabricate effective α-Fe2O3-based photocatalysts by increasing the surface area, promoting the charge separation and providing catalytic function. Herein, specific surface area-enlarged α-Fe2O3 (SE-FO) nanoparticles have been successfully synthesized by a functional molecule-modulated phase-separated hydrothermal method, with high photocatalytic activities for CO2 conversion and phenol degradation. The photocatalytic activities of SE-FO could be greatly improved by coupling nano-sized BiPO4 via an in-situ introduction method. This is attributed to the coupled BiPO4 as a high-energy platform to accept photogenerated electrons from α-Fe2O3 so as to enhance the charge separation mainly by means of surface photovoltage spectra and fluorescence spectra-related to the amount of produced ?OH species. Moreover, the photocatalytic activities are further improved by introducing a proper amount of nanocrystalline CuO via a simple impregnation process. It is confirmed based on the temperature-programmed desorption and electrochemical reduction measurements that the improved photoactivity is attributed to the introduced CuO as the co-catalyst for promoting electron-induced reduction reactions. Remarkably, the optimized α-Fe2O3 nanocomposite exhibits about 3-time photoactivity improvement compared with the pristine α-Fe2O3. This work would provide a feasible route to fabricate high-activity α-Fe2O3-based photocatalysts for CO2 conversion and phenol degradation.
Development of a highly selective H2S fluorescent probe and its application to evaluate CSE inhibitors
Gu, Xianfeng,Zhu, Huikun,Yang, Suna,Zhu, Yi-Chun,Zhu, Yi-Zhun
, p. 50097 - 50101 (2014)
In this paper, we developed a novel fluorescent probe C359 for highly selective detection of H2S over other relevant biothiols. C359 is designed to contain a thiol-specific cleavable disulfide bond. H2S-mediated the disulfide cleavage and subsequent intramolecular cyclization released the masked 7-hydroxyl coumarin, displaying a remarkable fluorescence enhancement. With the promising features in hand, C359 has been applied to detect the activity of CSE (one of H2S-producing enzyme) and build up an assay for screening CSE inhibitors. We anticipated that the enzyme assay using C359 could provide a powerful methodology for screening more potent and selective enzyme inhibitors. This journal is
Fluorogenic Cyanohydrin Esters as Chiral Probes for Esterase and Lipase Activity
Leroy, Emmanuel,Bensel, Nicolas,Reymond, Jean-Louis
, p. 859 - 865 (2003)
Fluorogenic cyanohydrin esters were prepared that release the fluorescent product umbelliferone by secondary decomposition of the primary cyanohydrin reaction product by cyanide elimination to the aldehyde and subsequent β-elimination. Whereas butyrate 1b and octanoate 1d show the highest reaction rates with enzymes, the highest relative rates above the non-catalyzed background reaction are achieved with pivalate 1c and benzoate 1e. Enantioselective reactions are detected when the conversion stabilizes at 50% of the maximum fluorescence release, and enantioselectivity is confirmed by chiral-phase HPLC analysis of the unreacted cyanohydrin ester substrate.
Co-MOF as an electron donor for promoting visible-light photoactivities of g-C3N4 nanosheets for CO2 reduction
Chen, Qiuyu,Li, Sijia,Xu, Hongyi,Wang, Guofeng,Qu, Yang,Zhu, Peifen,Wang, Dingsheng
, p. 514 - 523 (2020)
A possible mechanism for boosting the visible-light photoactivities of graphitic carbon nitride (g-C3N4) nanosheets for CO2 reduction via coupling with the electron donor Co-metal-organic framework (MOF) is proposed in this study. Specifically, Co-MOF as an electron donor is capable of transferring the photogenerated electrons in the lowest unoccupied molecular orbital (LUMO) to the conduction band of g-C3N4 to facilitate charge separation. As expected, the prepared Co-MOF/g-C3N4 nanocomposites display excellent visible-light-driven photocatalytic CO2 reduction activities. The CO production rate of 6.75 μmol g?1 h?1 and CH4 evolution rate of 5.47 μmol g?1 h?1 are obtained, which are approximately 2 times those obtained with the original g-C3N4 under the same conditions. Based on a series of analyses, it is shown that the introduction of Co-MOF not only broadens the range of visible-light absorption but also enhances the charge separation, which improves the photocatalytic activity of g-C3N4 to a higher level. In particular, the hydroxyl radical (?OH) experiment was operated under 590 nm (single-wavelength) irradiation, which further proved that the photogenerated electrons in the LUMO of Co-MOF can successfully migrate to g-C3N4. This work may provide an important strategy for the design of highly efficient g-C3N4-based photocatalysts for CO2 reduction.
Drastic enhancement on Fenton oxidation of organic contaminants by accelerating Fe(III)/Fe(II) cycle with l-cysteine
Luo, Lianshun,Yao, Yuyuan,Gong, Fei,Huang, Zhenfu,Lu, Wangyang,Chen, Wenxing,Zhang, Li
, p. 47661 - 47668 (2016)
The development of a highly efficient and pH-tolerant Fenton system has been one of the most important and challenging goals in water remediation. Herein, a green natural organic ligand, l-cysteine (Cys), was innovatively introduced into Fenton's reagent to construct an excellent catalytic oxidation system. The introduction of Cys into the Fenton system expanded the effective pH range up to 6.5 and achieved a superior oxidation efficiency, representing about 70% higher removal ratio and 12 times higher reaction rate constant with methylene blue dye as the probe compound. The Cys-driven Fenton reaction presented an outstanding pH adaptability and oxidative activity compared with other common organic ligands or reducing agent-modified Fenton reactions. An investigation of the reaction mechanism indicated that the addition of Cys into the system accelerated the Fe(iii)/Fe(ii) cycle, and led to a relatively steady Fe(ii) recovery, which enhances the generation of hydroxyl radicals (OH). The presence of Cys in the Fenton system remarkably reduced the apparent activation energy from 95.90 to 47.93 kJ mol-1. The findings from this study provide a feasible approach for a highly efficient and pH-tolerant wastewater treatment process with environmentally benign characteristics, and initiates an inspiring research domain of amino acids in the environmental catalysis field.
Ethnic-related differences in coumarin 7-hydroxylation activities catalyzed by cytochrome P4502A6 in liver microsomes of Japanese and Caucasian populations
Shimada,Yamazaki,Guengerich
, p. 395 - 403 (1996)
Interethnic differences in cytochrome P4502A6 (CYP2A6) levels and coumarin 7-hydroxylation activities were determined in liver microsomes of 30 Japanese and 30 Caucasians. Although CYP2A6 levels and coumarin 7-hydroxylation activities varied very significantly in the 60 human samples examined, both CYP2A6 levels and coumarin 7-hydroxylation activities were found to be higher in Caucasian than Japanese population. Interestingly, eight of the 30 Japanese examined showed very low or undetectable levels of coumarin 7-hydroxylation activities as well as of CYP2A6 in liver microsomes. All of the Caucasians, however, had significant CYP2A6 levels and variable 7-hydroxylation activities. Kinetic analysis of coumarin 7-hydroxylation activities in liver microsomes of various human samples suggested that although there were ~260-fold differences in V(max)'s in 10 human samples examined, the K(m)'s were very similar (2.1 ± 0.7 μM); a value consistent with that obtained (1.2 μM) with purified CYP2A6 in reconstituted system. The results suggest that CYP2A6 is actually involved in the 7-hydroxylation of coumarin in human liver microsomes, and that interethnic differences in coumarin 7-hydroxylation activities in Japanese and Caucasian population may be ascribed to the differences in expression of CYP2A6 protein.
Purified fusion enzyme between rat cytochrome P4501A1 and yeast NADPH-cytochrome P450 oxidoreductase
Hara, Masayuki,Miyake, Jun,Asada, Yasuo,Ohkawa, Hideo
, p. 21 - 28 (1999)
A genetically engineered fusion enzyme between rat P4501A1 and yeast P450 reductase in the microsomal fraction of the recombinant yeast AH22/pAFCR1 was purified. The purified enzyme showed a typical CO-difference spectrum of P4501A1 and a single band with an apparent molecular weight of 125,000 on sodium dodecyl sulfate polyacrylamide gel electrophoresis. This agreed with the molecular weight of 131,202 calculated from the amino acid sequence. The purified enzyme showed both 7-ethoxycoumarin o-deethylase activity and horse heart cytochrome c reductase activity in the presence of NADPH. The 7-ethoxycoumarin o-deethylase activity depended on the species of lipid used for the reconstitution of the purified fusion enzyme although the purified enzyme showed the activity without reconstitution. The purified fusion enzyme had the Km value of 26 μM for 7-ethoxycoumarin and the maximal turnover rate of 29 mol product/min/mol enzyme at 30°C.
7-Ethoxycoumarin O-deethylase kinetics in isolated rat, dog and human hepatocyte suspensions
Bayliss,Bell,Wilson,Park
, p. 231 - 241 (1994)
A comparative study of the kinetics of the O-deethylation of 7-ethoxycoumarin has been carried out in freshly isolated rat, dog and human hepatocytes. Biphasic kinetics were observed for all three species with apparent K(m) and V(max) values of 11.5, 2.2 and 3.9 μM and 0.30, 0.21, 0.007 nmol/min/106 cells from rat, dog and man, respectively, for the high affinity-low capacity component, and 560, 40, 470 μM and 1.52, 0.74, 0.057 nmol/min/106 cells, respectively, for the low affinity-high capacity component. These observed kinetic parameters in hepatocytes from rat and man were similar to published values for microsomes for the same two species. Values for intrinsic clearance of 7-ethoxycoumarin for the three species calculated from the K(m) and V(max) data were 152, 631 and 6 ml/min/kg for rat, dog and human hepatocytes, respectively. These intrinsic clearance values predict that 7-ethoxycoumarin would be subject to a high hepatic clearance in rat and dog, and low hepatic clearance in man. These values are supported by published data on rat which show that 7-ethoxycoumarin is subject to high clearance.
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Kir'yalov
, (1969)
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Carbon-centered radicals can transfer hydrogen atoms between amino acid side chains
Raffy, Quentin,Buisson, David-Alexandre,Cintrat, Jean-Christophe,Rousseau, Bernard,Pin, Serge,Renault, Jean Philippe
, p. 2960 - 2963 (2012)
Radical migration between aliphatic amino acid side chains can occur in solution and intramolecularly in peptides. The kinetic constant of the hydrogen transfer reaction was measured by using competition kinetics, and the half-life as well as the distance that a radical can move within a protein was calculated. Copyright
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Zhukov,Prokopenko
, (1967)
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A sensitive and selective high-throughput screening fluorescence assay for lipases and esterases
Nyfeler, Erich,Grognux, Johann,Wahler, Denis,Reymond, Jean-Louis
, p. 2919 - 2927 (2003)
Long-chain fatty acid esters of 7-(3,4-dihydroxybutyloxy)-2H-1-benzopyran-2-one (6) such as octanoate 2a are shown to be exceptionally sensitive and selective fluorogenic substrates for lipases and esterases. Umbelliferone (8) is released upon hydrolysis of the ester function in 2a in the presence of bovine serum albumin and sodium periodate. These substrates are at least by one order of magnitude more sensitive to lipases than the commercial fluorogenic substrate 4-methylumbelliferyl heptanoate. Furthermore, they are stable to a broad range of pH-induced- and thermal-hydrolysis conditions and do not react with non-catalytic proteins such as bovine serum albumin (BSA).
Preparation and photocatalytic performance of Bi nanoparticles by microwave-assisted method using ascorbic acid as reducing agent
Cui, Zhankui,Zhang, Yange,Li, Senlin,Ge, Suxiang
, p. 97 - 100 (2015)
Bismuth nanoparticles (NPs) were prepared by using microwave (MW) as heating source and ascorbic acid as reducing agent. Pure phase of Bi NPs was obtained and the size was uniform with the mean value of 70 nm. The visible light absorption was good and the optical band gap was 1.77 eV. The photocatalytic efficiency was 2.7 times that of the sample by solvothermal method for degradation of methyl blue (MB) under visible light irradiation. The hydroxyl radicals during photocatalysis were detected due to the transition of Bi from semimetal to semiconductor. The small size effect was considered to contribute a lot to the efficient photocatalytic activity.
In vitro evaluations for pharmacokinetic drug-drug interactions of a novel serotonin-dopamine activity modulator, brexpiprazole
Sasabe, Hiroyuki,Koga, Toshihisa,Furukawa, Masayuki,Matsunaga, Masayuki,Sasahara, Katsunori,Hashizume, Kenta,Oozone, Yoshihiro,Amunom, Immaculate,Torii, Mikako,Umehara, Ken,Kashiyama, Eiji,Takeuchi, Kenji
supporting information, p. 522 - 535 (2021/03/19)
Brexpiprazole, a serotonin-dopamine activity modulator, is indicated for the treatment of schizophrenia and also adjunctive therapy to antidepressants for the treatment of Major Depressive Disorder. To determine the drug–drug interaction risk for cytochrome P450, and SLC and ABC transporters, brexpiprazole and its metabolite, DM-3411 were assessed in this in?vitro investigation. Brexpiprazole exhibited weak inhibitory effects (IC50 >13 μmol/L) on CYP2C9, CYP2C19, CYP2D6 and CYP3A4 activities, but had moderate inhibitor activity on CYP2B6 (IC50 8.19 μmol/L). The ratio of systemic unbound concentration (3.8 nmol/L) to the Ki value was sufficiently low. DM-3411 had comparable inhibitory potentials with brexpiprazole only for CYP2D6 and CYP3A4. The mRNA expressions of CYP1A2, CYP2B6 and CYP3A4 were not changed by the exposure of brexpiprazole to human hepatocytes. Brexpiprazole and DM-3411 exhibited weak or no inhibitory effects for hepatic and renal transporters (OATPs, OATs, OCTs, MATE1, and BSEP), except for MATE-2K (0.156 μmol/L of DM-3411), even for which the ratio to systemic unbound concentration (5.3 nmol/L) was sufficiently low. Brexpiprazole effected the functions of P-gp and BCRP with IC50 values of 6.31 and 1.16 μmol/L, respectively, however, the pharmacokinetic alteration was not observed in the clinical concomitant study on P-gp and BCRP substrates. These in?vitro data suggest that brexpiprazole is unlikely to cause clinically relevant drug interactions resulting from the effects on CYPs or transporters mediating the absorption, metabolism, and/or disposition of co-administered drugs.
Boronic acid with high oxidative stability and utility in biological contexts
Graham, Brian J.,Windsor, Ian W.,Gold, Brian,Raines, Ronald T.
, (2021/03/16)
Despite their desirable attributes, boronic acids have had a minimal impact in biological contexts. A significant problem has been their oxidative instability. At physiological pH, phenylboronic acid and its boronate esters are oxidized by reactive oxygen species at rates comparable to those of thiols. After considering the mechanism and kinetics of the oxidation reaction, we reasoned that diminishing electron density on boron could enhance oxidative stability. We found that a boralactone, in which a carboxyl group serves as an intramolecular ligand for the boron, increases stability by 104-fold. Computational analyses revealed that the resistance to oxidation arises from diminished stabilization of the p orbital of boron that develops in the rate-limiting transition state of the oxidation reaction. Like simple boronic acids and boronate esters, a boralactone binds covalently and reversibly to 1,2-diols such as those in saccharides. The kinetic stability of its complexes is, however, at least 20-fold greater. A boralactone also binds covalently to a serine side chain in a protein. These attributes confer unprecedented utility upon boralactones in the realms of chemical biology and medicinal chemistry.
