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/metabolismoRESUMO
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/químicaRESUMO
A set of mesoporous delaminated montmorillonites containing iron(III)-titanium oxide species was synthesized using two minerals: a bentonite as support and an ilmenite as source of Fe-TiO2 species. Several values of both sulphuric acid concentration and temperature were employed to extract Fe-TiO2 species from an ilmenite. Analyses by X-ray fluorescence, X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption confirmed the successful formation of delaminated (or exfoliated) mesoporous structures. Optical properties of solids were determined by UV-Vis diffuse reflectance spectroscopy, and their band gap energy values were also calculated. A small UV-shift of band gap values regarding that of commercial photo-active TiO2 was detected as consequence of the quantum size effect, suggesting that photocatalytic experiments should be performed under UV-radiation assistance. The synthesized solids showed good activity in the photocatalytic oxidation of a textile dye (reactive yellow 145: RY 145), achieving conversions higher than 70% and chemical oxygen demand removal between 60% and 80%.
Assuntos
Compostos Azo/isolamento & purificação , Bentonita/química , Corantes/isolamento & purificação , Ferro/química , Oxidantes Fotoquímicos/química , Titânio/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Catálise , Compostos Férricos/química , Têxteis/análise , Raios UltravioletaRESUMO
SOx and NOx are emissions resulting from combustion processes and are the main agents that contribute to the formation of acid rain, which causes harm to humans and the environment. Several techniques for removing these pollutants are applied in i.e. oil refineries, thermoelectric that use petroleum oils and vehicular pollution. Among these, highlight the adsorption of contaminants by the usage of activated carbon fibers and activated carbon, which are characterized by high surface area and uniform distribution of pores, providing appropriate conditions for application in processes of removing environmental contaminants. In the present work, activated viscose fibers (AVF) were prepared and applied in adsorption experiments of NO and SO2. The materials produced showed high values of surface area, with a predominance of micro pores with diameters in the range of 1.0 nm. The AVF had satisfactory performance in the removal of contaminants and are compatible with other synthetic fibers. Thus, the formation of active sites of carbon provides contaminants adsorption, demonstrating that carbon fibers cloth can be applied for the removal of pollutants.
Assuntos
Poluentes Atmosféricos/química , Carbono , Celulose , Óxidos de Nitrogênio/química , Dióxido de Enxofre/química , Adsorção , Poluentes Atmosféricos/isolamento & purificação , Fibra de Carbono , Carvão Vegetal , Recuperação e Remediação Ambiental/métodos , Óxidos de Nitrogênio/isolamento & purificação , Oxidantes Fotoquímicos/química , Ozônio/química , Dióxido de Enxofre/isolamento & purificaçãoRESUMO
Textile industry wastes raise a great concern due to their strong coloration and toxicity. The objective of the present work was to characterize the degradation and mineralization of textile effluents by advanced oxidative processes using either TiO(2) or TiO(2)/H(2)O(2) and to monitor the toxicity of the products formed during 6-h irradiation in relation to that of the in natura effluent. The results demonstrated that the TiO(2)/H(2)O(2) association was more efficient in the mineralization of textile effluents than TiO(2), with high mineralized ion concentrations (NH (4) (+) , NO (3) (-) , and SO (4) (2-) ) and significantly decreased organic matter ratios (represented by the chemical oxygen demand and total organic carbon). The toxicity of the degradation products after 4-h irradiation to Artemia salina L. was not significant (below 10 %). However, the TiO(2)/H(2)O(2) association produced more toxicity under irradiation than the TiO(2) system, which was attributed to the increased presence of oxidants in the first group. Comparatively, the photogenerated products of both TiO(2) and the TiO(2)/H(2)O(2) association were less toxic than the in natura effluent.
Assuntos
Resíduos Industriais , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/toxicidade , Purificação da Água/métodos , Animais , Artemia , Peróxido de Hidrogênio/química , Oxidantes Fotoquímicos/química , Processos Fotoquímicos , Indústria Têxtil , Titânio/química , Testes de Toxicidade , Raios Ultravioleta , Poluentes Químicos da Água/químicaRESUMO
In this work, the photocatalytic degradation of aqueous microcystin-LR was studied using TiO(2) and ZnO as photocatalysts. The process was optimised and characterised at the bench scale (200 mL); both semiconductors exhibited a high degradation capacity at reaction times of 1 min (degradation greater than 95%). The transient species that were observed indicate that the degradation occurs via the multiple hydroxylation and elimination of the labile peptide residues of the molecule. When photocatalysis was applied in a continuous treatment system (20-50 L), the photocatalytic process exhibited a high degradation efficiency, which resulted in residual microcystin-LR concentrations that were less than 1 µg L(-1) (C(0)=5 µg L(-1)).
Assuntos
Microcistinas/química , Processos Fotoquímicos , Poluentes Químicos da Água/química , Purificação da Água/métodos , Recuperação e Remediação Ambiental/métodos , Toxinas Marinhas , Microcistinas/análise , Oxidantes Fotoquímicos/química , Titânio/química , Raios Ultravioleta , Poluentes Químicos da Água/análise , Óxido de Zinco/químicaRESUMO
When ozone is used during caries treatment, bond strength can be compromised by the release of oxygen. The use of antioxidant agents neutralizes the free oxygen. The aim of this study was to evaluate the effects of ozone and sodium ascorbate on resin-dentin microtensile bond strength (µTBS). Forty human third molars were divided into four groups: Group 1, not treated with ozone; Group 2, ozone application followed by acid etching; Group 3, acid etching followed by ozone application; and Group 4, ozone and application of sodium ascorbate. Bonded beams (1.0 mm(2)) were tested under tension (0.5 mm min(-1)). The µTBS values were analyzed using one-way analysis of variance (ANOVA) and the Tukey test (p=0.05). All beams that fractured were analyzed under stereomicroscopy (40×). Group 1 had significantly higher µTBS values than Group 2 or 3. The µTBS values of Groups 1 and 4 were similar and higher than those of Group 2. The use of ozone in Group 2 resulted in lower values of µTBS in all conditions evaluated. The predominant failure mode was adhesive. The application of ozone decreased the µTBS of the dentin-composite resin interface. These values were reversed when compared with Groups 1 and 2 when sodium ascorbate was used.
Assuntos
Resinas Compostas/química , Colagem Dentária , Materiais Dentários/química , Dentina/ultraestrutura , Oxidantes Fotoquímicos/química , Ozônio/química , Cimentos de Resina/química , Condicionamento Ácido do Dente/métodos , Adesividade , Antioxidantes/química , Ácido Ascórbico/química , Cimentos Dentários/química , Análise do Estresse Dentário/instrumentação , Humanos , Teste de Materiais , Camada de Esfregaço , Estresse Mecânico , Propriedades de Superfície , Temperatura , Resistência à Tração , Fatores de Tempo , Água/químicaRESUMO
Novel photo-Fenton catalysts were prepared by immobilizing iron species on commercial bentonite plates via two methods: (1) ion exchange reaction (Fe(3+) vs. Na(+)) by aqueous suspension powder-clay/FeCl(3) followed by plate preparation, and (2) forced hydrolysis of Fe(NO(3))(3) onto a prefabricated clay plate. The last method led to a more photo-active Fe-oxide/bentonite plate. This material allowed, at a non-adjusted initial pH of 5.5 and in the presence of H(2)O(2), the total degradation of resorcinol and 55% mineralization in 80 and 100 min of irradiation, respectively. The reached degradation percentages were correlated to the presence of dissolved iron, demonstrating that in these processes, the homogeneous photo-Fenton reactions were mainly responsible for the resorcinol elimination. Likewise, in slurry system, where clay has normally an increased surface area, there was no increase in activity because of a reduced leached iron probably due to the diminished light penetration in the suspension. Despite the lower surface area, in comparison to that of the slurry, the clay plates have the advantage, as heterogeneous photo-catalysts, that separation of the reaction media after treatment is not needed, and thus, a potential use for batch and continuous reaction systems is proposed.
Assuntos
Bentonita/química , Ferro/química , Compostos Orgânicos/química , Poluentes Químicos da Água/química , Silicatos de Alumínio/química , Catálise , Argila , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Oxidantes Fotoquímicos/química , Resorcinóis/química , Eliminação de Resíduos Líquidos/métodosRESUMO
UV radiation induces damages to the DNA molecule and its components through photosensitized reactions. Among these processes, photosensitized oxidations may occur through electron transfer or hydrogen abstraction (type I mechanism) and/or the production of singlet molecular oxygen ((1)O(2)) (type II mechanism). Lumazines are an important family of heterocyclic compounds present in biological systems as biosynthetic precursors and/or products of metabolic degradation. To evaluate the capability of lumazines to act as photosensitizers through type I mechanism, we have investigated the oxidation of 2'-deoxyadenosine 5'-monophosphate (dAMP) photosensitized by the specific compound called lumazine (pteridine-2,4(1,3H)-dione; Lum) in aqueous solutions under UV irradiation. The photochemical reactions were followed by UV/vis spectrophotometry, HPLC, electrochemical measurement of dissolved O(2), and an enzymatic method for H(2)O(2) determination. The effect of pH was evaluated and the participation of oxygen was investigated. In aerated solutions, oxidation of dAMP photoinduced by the acid form of Lum (pH 5.5) takes place through a type I mechanism, in which the excitation of Lum is followed by an electron transfer from dAMP molecule to the Lum triplet excited state. During the process, O(2) is consumed and H(2)O(2) is generated, whereas the photosensitizer is not consumed. In contrast, no evidence of a photochemical reaction induced by the basic form of Lum (pH 10.5) was observed.
Assuntos
Nucleotídeos de Desoxiadenina/química , Oxidantes Fotoquímicos/química , Fármacos Fotossensibilizantes/química , Pteridinas/química , Cromatografia Líquida de Alta Pressão , Dano ao DNA/efeitos da radiação , Peróxido de Hidrogênio/análise , Concentração de Íons de Hidrogênio , Modelos Químicos , Oxigênio/análise , Processos Fotoquímicos , Fotoquímica , Oxigênio Singlete/química , Espectrofotometria Ultravioleta , Raios UltravioletaRESUMO
BACKGROUND: Ozone water can be used to eliminate micro-organisms from the water systems in dental offices. OBJECTIVES: To determine if ozone water diminishes the bond strength of orthodontic adhesives. METHODS: One hundred and twenty bovine mandibular incisors were randomly divided into four equal groups. The teeth were cleaned with pumice and washed either with tap water (Groups 1 and 3) or with ozone water Groups (2 and 4) before bonding stainless steel orthodontics brackets to the teeth with either a composite resin (Groups 1 and 2; Transbond XT, 3M Unitek, Monrovia, CA, USA) or a resin-modified glass ionomer cement (Groups 3 and 4; Fuji Ortho LC, GC America Corporation, Tokyo, Japan). The manufacturers' recommendations for bonding were followed. All samples were subjected to thermal cycling and the shear bond strengths were determined with a universal testing machine. The Adhesive Remnant Index (ARI) was used to score the amount of resin remaining on the teeth after debonding the brackets. RESULTS: There were no statistical differences in the shear bond strengths of the brackets debonded from enamel washed with either ozone water or tap water or between the groups bonded with the two adhesive resins (p = 0.595). The ARIs in Groups 2 and 3 were significantly different from the ARIs in Groups 3 and 4 (p = 0.030). CONCLUSION: Ozone water did not alter the bond strength of brackets bonded with composite resins, but it did alter the sites of resin fracture when Fuji Ortho LC was used.