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1.
Toxicon ; 168: 49-57, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31207350

RESUMO

Ozone plays an increasingly important role in food processing for its antimicrobial ability and degradation effects on mycotoxins. The mycotoxin deoxynivalenol (DON) was treated with saturated aqueous ozone for different amounts of time, and by-products were collected for compounds annotation and cytotoxicity evaluation. To investigate the cytotoxicity of ozone degradation by-products, untargeted GC-TOFMS-based metabolomics were utilized. Caco-2 cells were dosed with 0.1 µg/mL DON and saturated aqueous ozone-treated DON (treatment time: 1 min, 3 min, 5 min) for 24 h followed by cytotoxicity tests (cell viability assay, ROS assay, and apoptosis assay), and intracellular metabolic analysis. Cytotoxicity test results revealed that ozone treatment could degrade DON structure; however, its degradation products and cellular toxicity existed under different treatment time of ozone. Metabolomics analysis indicated that ozone-treated DON degradation products weakened DON-induced metabolic disorder, such as purines-related nucleotide metabolism; Krebs cycle-related fuel and energy metabolism; and lipid, alkaloid and amino acid metabolism. By contrast, the catecholamine pathway, which is related to latent inflammation and oxidative stress effects, was unaltered in the ozone-treated DON group, indicating that the potential cytotoxicity still existed. These findings provide a comprehensive safety evaluation for ozone-treated DON in vitro and propose a new strategy for studying the effects of ozone-treated food.


Assuntos
Oxidantes Fotoquímicos/farmacologia , Ozônio/farmacologia , Tricotecenos/química , Tricotecenos/toxicidade , Apoptose/efeitos dos fármacos , Células CACO-2 , Sobrevivência Celular/efeitos dos fármacos , Manipulação de Alimentos/métodos , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Metaboloma , Oxidantes Fotoquímicos/química , Ozônio/química , Espécies Reativas de Oxigênio/metabolismo , Tricotecenos/metabolismo
2.
Chemosphere ; 230: 406-415, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31112863

RESUMO

Norfloxacin (NOR) is an emerging antibiotics contaminant due to its high resistance to microbial degradation and natural weathering. In this study, Fe-doped ZnS photocatalyst (Zn0.9Fe0.1S) was deposited on nickel foam (Ni-foam) to improve photocatalytic activity under visible light irradiation. The mass ratio of Zn0.9Fe0.1S and Ni-foam was optimized to be 0.03 g catalyst versus per g Ni-foam (0.03 Zn0.9Fe0.1S/Ni-foam), which led to the highest removal rate of 95%. The optimal degradation condition for NOR over 0.03 Zn0.9Fe0.1S/Ni-foam was pH at 7.0, initial NOR concentration of 5 mg L-1, and initial photocatalyst concentration of 11.7 g L-1, with the highest first-order reaction rate constant of 0.025 min-1 and mineralization rate of 63.1%. The NOR removal rate on 0.03 Zn0.9Fe0.1S/Ni-foam photocatalyst (95%) was approximately four times of that obtained on Zn0.9Fe0.1S photocatalyst (25%). The increased photocatalytic performance could be attributed to the function of Ni-foam as excellent electron collectors that provided efficient photoinduced charge separation from Zn0.9Fe0.1S. The reactive species responsible for the degradation of NOR were photo-generated holes, hydroxyl radical, and superoxide radicals. Nearly 90% of the photocatalytic efficiency was retained over seven cycles and the released metal ion concentrations were <0.3% of the total mass of photocatalyst, suggesting high stability of the photocatalyst during the photocatalytic reactions. The aqueous/solid mass transfer and intraparticle mass transfer for Zn0.9Fe0.1S/Ni-foam were not limiting factors for the degradation of NOR. Therefore the Zn0.9Fe0.1S/Ni-foam photocatalyst could be applied in the degradation of hazardous pollutants.


Assuntos
Ferro/química , Luz , Níquel/química , Norfloxacino/análise , Oxidantes Fotoquímicos/química , Sulfetos/química , Poluentes Químicos da Água/análise , Compostos de Zinco/química , Catálise , Norfloxacino/efeitos da radiação , Oxirredução , Poluentes Químicos da Água/efeitos da radiação
3.
J Nanobiotechnology ; 17(1): 58, 2019 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-31036008

RESUMO

BACKGROUND: Iron oxide nanocomposites have received a great attention for their application in various fields like physics, medicine, biology, and material science etc., due to their unique properties, such as magnetism, electrical properties, small size, biocompatibility and low toxicity. METHODS: Fe3O4/Ag3PO4@WO3 nanocomposites with different weight percent of Ag3PO4 were successfully prepared through fabricated Ag3PO4/Fe3O4 with WO3 via in situ fabrication method, electrospinning involved precursor solution preparation and spinning to enhance photocatalyst performance under simulated sunlight for the degradation of methylene blue (MB) and antibacterial activity against Staphylococcus aureus (S. aureus). RESULTS: The photocatalytic degradation of methylene blue (MB) under simulated light irradiation indicated that the nanocomposite with 0.25 mg of Ag3PO4 has the best activity. An additional advantage of these photocatalysts is magnetic recoverability, using external magnetic field and photocatalytic stability of the nanocomposites was evaluated for three cycles. In addition, using different scavengers, holes (h+) and superoxide radical (O 2 ·-) radicals and hydroxide radical (·OH) were identified the main oxidative species in the degradation reaction of methylene blue. CONCLUSIONS: The results reveal that Fe3O4/Ag3PO4@WO3-0.25 nanocomposites have photocatalytic and antibacterial activity against S. aureus. The photocatalyst and mechanism based on the enhancement of electron transfer processes between Ag3PO4 and WO3 nanoparticles.


Assuntos
Antibacterianos/química , Óxido Ferroso-Férrico/química , Nanopartículas Metálicas/química , Nanocompostos/química , Oxidantes Fotoquímicos/química , Óxidos/química , Compostos de Prata/química , Tungstênio/química , Catálise , Transporte de Elétrons , Hidróxidos/química , Luz , Magnetismo/métodos , Azul de Metileno/química , Oxirredução , Tamanho da Partícula , Staphylococcus aureus , Superóxidos/química , Poluentes Químicos da Água/química
4.
Chemosphere ; 225: 434-442, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30889407

RESUMO

TiO2 is one of the most cheap materials which can both adsorb arsenic and oxidize arsenite [As(III)] to arsenate [As(V)]. In this study, anatase TiO2 crystals with different main facets such as {101}, {001} and {100} are synthesized and used to investigate arsenic adsorption kinetics, adsorption isotherms, photocatalytic oxidation (PCO) process and the pH effects. The adsorption kinetics of arsenic on TiO2 crystals can be described by the pseudo second-order kinetic model. For the adsorption isotherms, the Langmuir model is better than the Freundlich model for arsenic on these TiO2 crystals. For the PCO process, the rate of As(III) oxidation can be denoted by the pseudo first-order kinetic model. It should be noted that at neutral condition the adsorption and PCO rates of the three kinds of TiO2 crystals follow the order of {101} > {001} > {100}. The pH effect is above all important for both the arsenic adsorption and its PCO. The highest PCO speed appears at high pH values such as at pH 11 or 12.


Assuntos
Arseniatos/química , Arsênico/química , Arsenitos/química , Oxidantes Fotoquímicos/química , Titânio/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Oxirredução
5.
Biochim Biophys Acta Biomembr ; 1861(3): 660-669, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30605637

RESUMO

Lipid rafts display a lateral heterogeneity forming membrane microdomains that hold a fundamental role on biological membranes and are indispensable to physiological functions of cells. Oxidative stress in cellular environments may cause lipid oxidation, changing membrane composition and organization, thus implying in effects in cell signaling and even loss of homeostasis. The individual contribution of oxidized lipid species to the formation or disruption of lipid rafts in membranes still remains unknown. Here, we investigate the role of different structures of oxidized phospholipids on rafts microdomains by carefully controlling the membrane composition. Our experimental approach based on fluorescence microscopy of giant unilamellar vesicles (GUV) enables the direct visualization of the impact of hydroperoxidized POPC lipid (referred to as POPCOOH) and shortened chain lipid PazePC (1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine) on phase separation. We found that the molecular structure of oxidized lipid is of paramount importance on lipid mixing and/or demixing. The hydrophobic mismatch promoted by POPCOOH coupled to its cylindrical molecular shape favor microdomains formation. In contrast, the conical shape of PazePC causes disarrangement of lipid 2D organized platforms. Our findings contribute to better unraveling how oxidized phospholipids can trigger formation or disruption of lipid rafts. As a consequence, phospholipid oxidation may indirectly affect association or dissociation of key biomolecules in the rafts thus altering cell signaling and homeostasis.


Assuntos
Bicamadas Lipídicas/metabolismo , Microdomínios da Membrana/efeitos dos fármacos , Microdomínios da Membrana/metabolismo , Fosfatidilcolinas/metabolismo , Fosfatidilcolinas/farmacologia , Bicamadas Lipídicas/química , Peroxidação de Lipídeos/fisiologia , Microdomínios da Membrana/química , Oxidantes Fotoquímicos/química , Oxidantes Fotoquímicos/farmacologia , Oxirredução , Fosfatidilcolinas/química , Fosforilcolina/análogos & derivados , Fosforilcolina/química , Fosforilcolina/metabolismo , Lipossomas Unilamelares/química , Lipossomas Unilamelares/metabolismo
6.
Environ Pollut ; 243(Pt B): 1679-1688, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30300873

RESUMO

The oxidative potential (OP) and chemical characteristics of fine particles collected from urban, roadside, rural, and industrial sites in Korea during spring, summer, fall, and winter seasons and an urban site in the Philippines during dry and wet seasons were examined. Significant differences in the OP of fine particles among sites and seasons were found. The industrial site yielded the highest OP activity (both mass and volume-normalized OP) among the sites, suggesting the strongest reactive oxygen species (ROS)-generating capability of industry source-dominant PM2.5. Seasonal data show that OP activities increased during the spring and summer possibly due to increased heavy metals caused by dust events and secondary organic aerosols formed by strong photochemical activity, respectively. The strength of the OP association with the chemical components highlights the influence of organic carbon and transition metals on the OP of ambient fine particles. The two OP assays (dithiothreitol (DTT) and electron spin resonance (ESR)) having different ROS-generating mechanisms were found to have different sensitivities to the chemical components facilitating a complementary analysis of the OP of ambient fine particles. Multiple linear regression model equations (OP as a function of chemical components) which were dependent on the sites were derived. A comparison of the daily OP and hazard index (HI) (the ratio of the measured mass concentration to the reference mass concentration of fine particles) suggests that the HI may not be sufficient to accurately estimate the health effects of fine particles, and a direct or indirect measurement of toxicity such as OP should be required in addition to the concentration level.


Assuntos
Poluentes Atmosféricos/química , Poeira/análise , Monitoramento Ambiental/métodos , Oxidantes Fotoquímicos/química , Material Particulado/química , Aerossóis/análise , Poluentes Atmosféricos/análise , Ditiotreitol/química , Espectroscopia de Ressonância de Spin Eletrônica , Oxirredução , Estresse Oxidativo , Tamanho da Partícula , Material Particulado/análise , Filipinas , Espécies Reativas de Oxigênio/química , República da Coreia , Estações do Ano
7.
Sci Rep ; 8(1): 12888, 2018 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-30150642

RESUMO

In the present study, we evaluated the prooxidative mode of action of photoirradiated (+)-catechin at 400 nm in relation to reactive oxygen species generation and its possible application to disinfection. Photoirradiation of (+)-catechin at a concentration of 1 mg/mL yielded not only hydrogen peroxide (H2O2) but hydroxyl radical (·OH) in a total amount of approximately 20 µM in 10 min. As a result, photoirradiated catechin killed Staphylococcus aureus, and a > 5-log reduction in viable bacteria counts was observed within 20 min. Liquid chromatography-high-resolution-electrospray ionization-mass spectrometry showed that photoirradiation decreased the (+)-catechin peak (molecular formula C15H14O6) whilst it increased two peaks of a substance with the molecular formula C15H12O6 with increasing irradiation time. Nuclear magnetic resonance analysis revealed that the two C15H12O6 peaks were allocated to intramolecular cyclization products that are enantiomers of each other. These results suggest that photoirradiation induces oxidation of (+)-catechin resulting in the reduction of oxygen to generate H2O2. This H2O2 is then homolytically cleaved to ·OH, and alongside this process, (+)-catechin is finally converted to two intramolecular cyclization products that are different from the quinone structure of the B ring, as proposed previously for the autoxidation and enzymatic oxidation of catechins.


Assuntos
Catequina/metabolismo , Oxidantes Fotoquímicos/metabolismo , Oxirredução , Antibacterianos/química , Antibacterianos/farmacologia , Catequina/química , Catequina/farmacologia , Cromatografia Líquida , Peróxido de Hidrogênio/metabolismo , Radical Hidroxila/metabolismo , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Oxidantes Fotoquímicos/química , Oxirredução/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/metabolismo , Espectrometria de Massas em Tandem
8.
Food Res Int ; 112: 90-97, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30131162

RESUMO

This study investigated a novel method of photosensitizer-induced cross-linking (using riboflavin as a sensitizer) to improve the structural and physicochemical properties of gelatin-based edible films with different glycerol concentrations (25% and 50%) during different UV exposure times (2, 4 and 6 h). The films' tensile strength was enhanced significantly for both glycerol concentrations with increasing UV exposure times compared to the control film, so that the highest tensile strength was observed for films with 25% glycerol and 6 h of UV exposure (25%-6 h). The films' tensile strength declined and the elongation at break increased about three times when the glycerol concentration was increased to 50% with 6 h exposure. The photosensitizer-induced cross-linking significantly reduced the films' solubility and permeability. The UV-treated films exhibited very good barrier properties against UV, with zero light transmission at a wavelength of 200 to 350 nm. Moreover, no toxicity was found in any of the films. In addition, Fourier transform infrared spectroscopy and differential scanning calorimetry findings revealed a good interaction between functional groups of riboflavin (as the sensitizer) and gelatin in the 25%-6 h film. Therefore, this new method can be a suitable alternative to chemical methods of cross-linking biopolymers.


Assuntos
Embalagem de Alimentos/métodos , Gelatina/efeitos da radiação , Oxidantes Fotoquímicos/química , Riboflavina/química , Raios Ultravioleta , Animais , Varredura Diferencial de Calorimetria , Sobrevivência Celular/efeitos dos fármacos , Gelatina/química , Gelatina/toxicidade , Glicerol/química , Humanos , Camundongos , Células NIH 3T3 , Oxidantes Fotoquímicos/toxicidade , Oxirredução , Permeabilidade , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Resistência à Tração , Fatores de Tempo
9.
Chemistry ; 24(49): 12902-12911, 2018 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-29675830

RESUMO

ReI -polypyridyl complexes have interesting and distinctive photochemical and photosensitizing properties. This work describes the capability to induce (or photoinduce) DNA damage of three ReI -complexes with a naturally occurring alkaloid called norharmane (nHo) as ligand: [Re(CO)3 (nHo)(L)]CF3 SO3 where L=2,2'-bipyridine (ReBpy), phenanthroline (RePhen) or dipyrido[3,2-a:2',3'-c]phenazine (ReDppz). The interaction of the complexes with DNA was investigated by steady-state and time-resolved spectroscopy. Data show that the mode and strength of interaction depend on the chemical structure of the bidentate ligand. The complexes show a major static contribution to the overall interaction, giving rise to the formation of noncovalent adducts with DNA, and the particular trend observed was RePhen>ReDppz>ReBpy. Photo-oxidation at the purine bases represents the major DNA damaging mechanism. RePhen also induces single-strand breaks in a yield similar to that of base damage, suggesting an additional photosensitizing pathway. We also performed the Ames test to evaluate the cytotoxic and mutagenic properties of both non-irradiated and photoexcited complexes. RePhen, but not the other complexes, turned out to be both toxic and phototoxic for the bacteria.


Assuntos
2,2'-Dipiridil/química , Carbolinas/química , Complexos de Coordenação/química , Dano ao DNA/efeitos dos fármacos , DNA/química , Rênio/química , Complexos de Coordenação/toxicidade , Ligantes , Luz , Testes de Mutagenicidade , Oxidantes Fotoquímicos/química , Oxirredução , Espécies Reativas de Oxigênio/química , Salmonella typhimurium/efeitos dos fármacos , Oxigênio Singlete/química
10.
Acta Biomater ; 71: 460-473, 2018 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-29555461

RESUMO

Acellular tumor extracellular matrices (ECMs) have limitations when employed as three-dimensional (3D) scaffolds for tumor engineering. In this work, methylene blue-mediated photooxidation was used to crosslink acellular tumor ECMs. Photooxidative crosslinking greatly increased the stiffness of acellular tumor ECM scaffolds but barely altered the Amide III band of the secondary structure of polypeptides and proteins. MCF-7, HepG2 and A549 cells cultured on photooxidatively crosslinked acellular tumor ECM scaffolds exhibited greater cell number per scaffold, more IL-8 and VEGF secretion, and increase migration and invasion abilities than cells cultured on uncrosslinked acellular tumor ECM scaffolds. The three tumor cell lines cultured on the stiffer photooxidatively crosslinked acellular matrices acquire mesenchymal properties (mesenchymal shift) and dedifferentiated phenotypes. Furthermore, the malignant phenotypes induced in vitro when cultured on the crosslinked scaffold promoted the in vivo tumor growth of BALB/c nude mice. Finally, the dedifferentiated cancer cells, including MCF-7, HepG2 and A549 cells, were less sensitive to chemotherapeutics. Thus, photooxidatively crosslinked acellular tumor ECMs have potentials as 3D tumor engineering scaffolds for cancer research. STATEMENT OF SIGNIFICANCE: Natural material scaffolds have been successfully used as 3D matrices to study the in vitro tumor cell growth and mimic the in vivo tumor microenvironment. Acellular tumor ECMs are developed as 3D scaffolds for tumor engineering but have limitations in terms of elastic modulus and cell spheroid formation. Here we use methylene blue-mediated photooxidation to crosslink acellular tumor ECMs and investigate the influence of photooxidative crosslinking on structural, mechanical and biological characteristics of acellular tumor ECM scaffolds. It is the first study to evaluate the feasibility of photooxidatively crosslinked acellular tumor ECMs as 3D scaffolds for cancer research and the results are encouraging. Moreover, this study provides new research areas in regard to photodynamic therapy (PDT) for Cancer.


Assuntos
Matriz Extracelular , Neoplasias , Engenharia Tecidual , Tecidos Suporte/química , Células A549 , Animais , Matriz Extracelular/química , Matriz Extracelular/metabolismo , Matriz Extracelular/patologia , Células Hep G2 , Xenoenxertos , Humanos , Interleucina-8/metabolismo , Células MCF-7 , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Proteínas de Neoplasias/metabolismo , Transplante de Neoplasias , Neoplasias/química , Neoplasias/metabolismo , Neoplasias/patologia , Oxidantes Fotoquímicos/química , Fator A de Crescimento do Endotélio Vascular/metabolismo
11.
Toxicol In Vitro ; 47: 238-248, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29223573

RESUMO

Recently, designed platelet shaped micron particles that are composed of nano primary particles, called MicNo (=Micron+naNo) particles, have been developed to exploit the benefits of nano size, while removing the adverse effects of nanoparticles. It has been shown that MicNo-ZnO particles exhibit both micron and nanosized particle characteristics. Although physical and chemical properties of MicNo-ZnO particles have been studied, their biocompatibility has not yet been evaluated. Accordingly, the research objective of this study was to evaluate in vitro cytotoxicity, genotoxicity and phototoxicity behaviors of designed MicNo-ZnO particles over human epidermal keratinocyte (HaCaT) cells. MicNo-ZnO particles exhibit much less cytotoxicity with IC50 concentrations between 40 and 50µg/ml, genotoxicity above 40µg/ml and lower photo genotoxicity under UVA on HaCaT than the ZnO nanoparticles. Although their chemistries are the same, the source of this difference in toxicity values may be attributed to size differences between the particles that are probably due to their ability to penetrate into the cells. In the present study, the expansive and detailed in vitro toxicity tests show that the biocompatibility of MicNo-ZnO particles is much better than that of the ZnO nanoparticles. Consequently, MicNo-ZnO particles can be considered an important active ingredient alternative for sunscreen applications due to their safer characteristics with respect to ZnO nanoparticles.


Assuntos
Queratinócitos/efeitos dos fármacos , Lisossomos/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Modelos Biológicos , Oxidantes Fotoquímicos/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Óxido de Zinco/toxicidade , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Ensaio Cometa , Humanos , Concentração Inibidora 50 , Queratinócitos/citologia , Queratinócitos/metabolismo , Queratinócitos/efeitos da radiação , Lisossomos/metabolismo , Lisossomos/efeitos da radiação , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Potencial da Membrana Mitocondrial/efeitos da radiação , Nanopartículas Metálicas/química , Nanopartículas Metálicas/efeitos da radiação , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Varredura , Microscopia de Fluorescência , Testes de Mutagenicidade , Oxidantes Fotoquímicos/química , Estresse Oxidativo/efeitos da radiação , Tamanho da Partícula , Espécies Reativas de Oxigênio/metabolismo , Propriedades de Superfície , Raios Ultravioleta/efeitos adversos , Óxido de Zinco/química , Óxido de Zinco/efeitos da radiação
12.
Crit Rev Food Sci Nutr ; 58(13): 2176-2201, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-28394634

RESUMO

The food contamination issue requires continuous control of food at each step of the production process. High quality and safety of products are equally important factors in the food industry. They may be achieved with several, more or less technologically advanced methodologies. In this work, we review the role, contribution, importance, and impact of ozone as a decontaminating agent used to control and eliminate the presence of microorganisms in food products as well as to extend their shelf-life and remove undesirable odors. Several researchers have been focusing on the ozone's properties and applications, proving that ozone treatment technology can be applied to all types of foods, from fruits, vegetables, spices, meat, and seafood products to beverages. A compilation of those works, presented in this review, can be a useful tool for establishing appropriate ozone treatment conditions, and factors affecting the improved quality and safety of food products. A critical evaluation of the advantages and disadvantages of ozone in the context of its application in the food industry is presented as well.


Assuntos
Contaminação de Alimentos , Manipulação de Alimentos/métodos , Oxidantes Fotoquímicos/farmacologia , Ozônio/farmacologia , Conservação de Alimentos/métodos , Humanos , Oxidantes Fotoquímicos/química , Ozônio/administração & dosagem
14.
Chemistry ; 23(43): 10344-10351, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-28543779

RESUMO

Key to the development of DNA-targeting phototherapeutic drugs is determining the interplay between the photoactivity of the drug and its binding preference for a target sequence. For the photo-oxidising lambda-[Ru(TAP)2 (dppz)]2+ (Λ-1) (dppz=dipyridophenazine) complex bound to either d{T1 C2 G3 G4 C5 G6 C7 C8 G9 A10 }2 (G9) or d{TCGGCGCCIA}2 (I9), the X-ray crystal structures show the dppz intercalated at the terminal T1 C2 ;G9 A10 step or T1 C2 ;I9 A10 step. Thus substitution of the G9 nucleobase by inosine does not affect intercalation in the solid state although with I9 the dppz is more deeply inserted. In solution it is found that the extent of guanine photo-oxidation, and the rate of back electron-transfer, as determined by pico- and nanosecond time-resolved infrared and transient visible absorption spectroscopy, is enhanced in I9, despite it containing the less oxidisable inosine. This is attributed to the nature of the binding in the minor groove due to the absence of an NH2 group. Similar behaviour and the same binding site in the crystal are found for d{TTGGCGCCAA}2 (A9). In solution, we propose that intercalation occurs at the C2 G3 ;C8 I9 or T2 G3 ;C8 A9 steps, respectively, with G3 the likely target for photo-oxidation. This demonstrates how changes in the minor groove (in this case removal of an NH2 group) can facilitate binding of RuII dppz complexes and hence influence any sensitised reactions occurring at these sites. No similar enhancement of photooxidation on binding to I9 is found for the delta enantiomer.


Assuntos
Complexos de Coordenação/química , DNA/química , Inosina/química , Oxidantes Fotoquímicos/química , Rutênio/química , Sequência de Bases , Sítios de Ligação , Transporte de Elétrons , Guanina/química , Substâncias Intercalantes/química , Modelos Moleculares , Estrutura Molecular , Oxirredução , Espectrofotometria Ultravioleta/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Estereoisomerismo , Relação Estrutura-Atividade , Termodinâmica
15.
Chemosphere ; 181: 337-342, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28456035

RESUMO

Photooxidation of As(III) in ternary As(III) - Fe(III) - Fulvic acid system at pH 4 was investigated by optical spectroscopy, steady-state photolysis (365 nm) and atomic-emission spectrometry with inductively coupled plasma techniques. It was found that at all values of [FA]/[Fe] ratio the main photoactive species is OH radical formed by photolysis of Fe(III) hydroxocomplexes. Addition of fulvic acid leads to mainly negative effect on As(III) photooxidation due to the following reasons: (i) slow dark reduction of photoactive Fe(III) species with formation of scattering particles and photoinert Fe(II) species; (ii) formation of photoreductive Fe(III)-FA complexes incapable to oxidize As(III), (iii) competition of both FA and Fe(III)-FA complexes for UVA quanta with FeOH2+ complex and for OH radicals with As(III). Aging of ternary system is also very important parameter leading to one order decrease of quantum yields of both Fe(II) formation and As(III) photooxidation.


Assuntos
Arsênico/efeitos da radiação , Ferro/química , Raios Ultravioleta , Arsênico/química , Benzopiranos , Oxidantes Fotoquímicos/química , Oxirredução , Fotólise/efeitos da radiação
16.
J Pharm Sci ; 106(5): 1310-1316, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28108379

RESUMO

Forced degradation studies are an important tool for a systematic assessment of decomposition pathways and identification of reactive sites in active pharmaceutical ingredients (APIs). Two methodologies have been combined in order to provide a deeper understanding of singlet oxygen-related degradation pathways of APIs under light irradiation. First, we report that a "dark" singlet oxygen test enables the investigation of drug reactivity toward singlet oxygen independently of photolytic irradiation processes. Second, the photosensitizing properties of the API producing the singlet oxygen was proven and quantified by spin trapping and electron paramagnetic resonance analysis. A combination of these techniques is an interesting addition to the forced degradation portfolio as it can be used for (1) revealing unexpected degradation pathways of APIs due to singlet oxygen, (2) clarifying photolytic drug-drug interactions in fixed-dose combinations, and (3) synthesizing larger quantities of hardly accessible oxidative drug degradants.


Assuntos
Preparações Farmacêuticas/química , Fotólise , Oxigênio Singlete/química , Detecção de Spin/métodos , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Luz/efeitos adversos , Oxidantes Fotoquímicos/química , Oxidantes Fotoquímicos/metabolismo , Oxirredução , Preparações Farmacêuticas/metabolismo , Oxigênio Singlete/metabolismo
17.
Angew Chem Int Ed Engl ; 56(8): 2097-2100, 2017 02 13.
Artigo em Inglês | MEDLINE | ID: mdl-28105772

RESUMO

Halofunctionalization of alkenes is a classical method for olefin difunctionalization. It gives rise to adducts which are found in many natural products and biologically active molecules, and offers a synthetic handle for further manipulation. Classically, this reaction is performed with an electrophilic halogen source and leads to regioselective formation of the halofunctionalized adducts. Herein, we demonstrate a reversal of the native regioselectivity for alkene halofunctionalization through the use of an acridinium photooxidant in conjunction with a copper cocatalyst.


Assuntos
Acridinas/química , Alcenos/química , Cobre/química , Oxidantes Fotoquímicos/química , Alcenos/síntese química , Catálise , Oxirredução , Estereoisomerismo
18.
Environ Sci Process Impacts ; 19(3): 324-338, 2017 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-27942650

RESUMO

Quantitative structure-activity relationships (QSARs) for prediction of the reaction rate constants of phenols and phenolates with three photochemically produced oxidants, singlet oxygen, carbonate radical, and triplet excited state sensitizers/organic matter, are developed. The predictive variable is the one-electron oxidation potential (E1), which is calculated for each species using density functional theory. The reaction rate constants are obtained from the literature, and for singlet oxygen, are augmented with new experimental data. Calculated E1 values have a mean unsigned error compared to literature values of 0.04-0.06 V. For singlet oxygen, a single linear QSAR that includes both phenols and phenolates is developed that predicts experimental rate constants, on average, to within a factor of three. Predictions for only 6 out of 87 compounds are off by more than a factor of 10. A more limited data set for carbonate radical reactions with phenols and phenolates also gives a single linear QSAR with prediction of rate constant being accurate to within a factor of three. The data for the reactions of phenols with triplet state sensitizers demonstrate that two sensitizers, 2-acetonaphthone and methylene blue, most closely predict the reactivity trend of triplet excited state organic matter with phenols. Using sensitizers with stronger reduction potentials could lead to overestimation of rate constants and thus underestimation of phenolic pollutant persistence.


Assuntos
Oxidantes Fotoquímicos/química , Fenóis/química , Relação Quantitativa Estrutura-Atividade , Carbonatos , Cinética , Oxirredução , Oxigênio Singlete/química
19.
Inorg Chem ; 55(7): 3218-28, 2016 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-26974004

RESUMO

UV-vis spectral titrations of a manganese(III) corrolazine complex [Mn(III)(TBP8Cz)] with HOTf in benzonitrile (PhCN) indicate mono- and diprotonation of Mn(III)(TBP8Cz) to give Mn(III)(OTf)(TBP8Cz(H)) and [Mn(III)(OTf)(H2O)(TBP8Cz(H)2)][OTf] with protonation constants of 9.0 × 10(6) and 4.7 × 10(3) M(-1), respectively. The protonated sites of Mn(III)(OTf)(TBP8Cz(H)) and [Mn(III)(OTf)(H2O)(TBP8Cz(H)2)][OTf] were identified by X-ray crystal structures of the mono- and diprotonated complexes. In the presence of HOTf, the monoprotonated manganese(III) corrolazine complex [Mn(III)(OTf)(TBP8Cz(H))] acts as an efficient photocatalytic catalyst for the oxidation of hexamethylbenzene and thioanisole by O2 to the corresponding alcohol and sulfoxide with 563 and 902 TON, respectively. Femtosecond laser flash photolysis measurements of Mn(III)(OTf)(TBP8Cz(H)) and [Mn(III)(OTf)(H2O)(TBP8Cz(H)2)][OTf] in the presence of O2 revealed the formation of a tripquintet excited state, which was rapidly converted to a tripseptet excited state. The tripseptet excited state of Mn(III)(OTf)(TBP8Cz(H)) reacted with O2 with a diffusion-limited rate constant to produce the putative Mn(IV)(O2(•-))(OTf)(TBP8Cz(H)), whereas the tripseptet excited state of [Mn(III)(OTf)(H2O)(TBP8Cz(H)2)][OTf] exhibited no reactivity toward O2. In the presence of HOTf, Mn(V)(O)(TBP8Cz) can oxidize not only HMB but also mesitylene to the corresponding alcohols, accompanied by regeneration of Mn(III)(OTf)(TBP8Cz(H)). This thermal reaction was examined for a kinetic isotope effect, and essentially no KIE (1.1) was observed for the oxidation of mesitylene-d12, suggesting a proton-coupled electron transfer (PCET) mechanism is operative in this case. Thus, the monoprotonated manganese(III) corrolazine complex, Mn(III)(OTf)(TBP8Cz(H)), acts as an efficient photocatalyst for the oxidation of HMB by O2 to the alcohol.


Assuntos
Complexos de Coordenação/química , Manganês/química , Metaloporfirinas/química , Oxidantes Fotoquímicos/química , Oxigênio/química , Derivados de Benzeno/química , Catálise , Cristalografia por Raios X , Modelos Moleculares , Oxirredução , Prótons , Sulfetos/química
20.
Chemistry ; 22(15): 5142-5, 2016 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-26887904

RESUMO

A novel metal-free composite (GN) composed of two types of carbon-based nanomaterials, graphite oxide (GO) and 2D oxidized carbon nitride (OCN) nanodots was produced. Chemical and morphological characterizations reveal that GN contains a main component of GO with well-dispersed 2D OCN nanodots. GN shows enhanced photocatalytic performance for degrading an organic pollutant, Rhodamine B, under visible light.


Assuntos
Grafite/química , Nanopartículas/química , Nitritos/química , Oxidantes Fotoquímicos/química , Óxidos/química , Catálise , Oxirredução
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