RESUMEN
Light-harvesting systems are an important way for capturing, transferring and utilizing light energy. It remains a key challenge to develop highly efficient artificial light-harvesting systems. Herein, we report a supramolecular co-assembly based on lower-rim dodecyl-modified sulfonatocalix[4]arene (SC4AD) and naphthyl-1,8-diphenyl pyridinium derivative (NPS) as a light-harvesting platform. NPS as a donor shows significant aggregation induced emission enhancement (AIEE) after assembling with SC4AD. Upon introduction of Nile blue (NiB) as an acceptor into the NPS-SC4AD co-assembly, the light-harvesting system becomes near-infrared (NIR) emissive (675â nm). Importantly, the NIR emitting NPS-SC4AD-NiB system exhibits an ultrahigh antenna effect (33.1) at a high donor/acceptor ratio (250:1). By co-staining PC-3 cells with a Golgi staining reagent, NBD C6 -ceramide, NIR imaging in the Golgi apparatus has been demonstrated using these NIR emissive nanoparticles.
Asunto(s)
Calixarenos/química , Colorantes Fluorescentes/química , Aparato de Golgi/metabolismo , Compuestos de Piridinio/química , Calixarenos/efectos de la radiación , Calixarenos/toxicidad , Transferencia Resonante de Energía de Fluorescencia , Colorantes Fluorescentes/efectos de la radiación , Colorantes Fluorescentes/toxicidad , Humanos , Rayos Infrarrojos , Microscopía Confocal , Microscopía Fluorescente , Nanopartículas/química , Nanopartículas/efectos de la radiación , Nanopartículas/toxicidad , Oxazinas/química , Oxazinas/efectos de la radiación , Oxazinas/toxicidad , Células PC-3 , Compuestos de Piridinio/efectos de la radiación , Compuestos de Piridinio/toxicidadRESUMEN
Thiophenols as high toxic environmental pollutants are poisonous for animals and aquatic organisms. Therefore, it is indispensable to monitor thiophenols in the environment. Herein, a novel near-infrared fluorescent probe was developed for the detection of thiophenols, which was easily prepared by one-step coupling of 2,4-dinitrobenzenesulfonyl chloride with Nile blue. The probe showed a significant near infrared (â¼675â¯nm) fluorescence "turn-on" response to thiophenols with some good features including chromogenic reaction, high sensitivity and selectivity, fast response, near-infrared emission along with low detection limit (1.8â¯nM). The probe was employed to rapidly and visually determine thiophenols in several industrial wastewaters with good recoveries (90-110%). Moreover, this probe has been demonstrated good capability for imaging thiophenol in HeLa cells.
Asunto(s)
Colorantes Fluorescentes/química , Oxazinas/química , Fenoles/análisis , Compuestos de Sulfhidrilo/análisis , Sulfonamidas/química , Aguas Residuales/análisis , Contaminantes Químicos del Agua/análisis , Fluorescencia , Colorantes Fluorescentes/síntesis química , Colorantes Fluorescentes/efectos de la radiación , Colorantes Fluorescentes/toxicidad , Células HeLa , Humanos , Concentración de Iones de Hidrógeno , Rayos Infrarrojos , Límite de Detección , Microscopía Confocal/métodos , Modelos Químicos , Oxazinas/síntesis química , Oxazinas/efectos de la radiación , Oxazinas/toxicidad , Espectrometría de Fluorescencia/métodos , Sulfonamidas/síntesis química , Sulfonamidas/efectos de la radiación , Sulfonamidas/toxicidadRESUMEN
Environmental presence and retention of commonly used neonicotinoid insecticides such as dinotefuran (DNT), imidacloprid (IMD), and thiamethoxam (THM) are a cause for concern and prevention because of their potential toxicity to nontarget species. In the present study the kinetics of the photodegradation of these insecticides were investigated in water and soil compartments under natural light conditions. The results suggest that these insecticides are fairly unstable in both aqueous and soil environments when exposed to natural sunlight. All 3 insecticides exhibit strong first-order degradation rate kinetics in the aqueous phase, with rate constants kDNT , kIMD , and kTHM of 0.20 h(-1) , 0.30 h(-1) , and 0.18 h(-1) , respectively. However, in the soil phase, the modeled photodegradation kinetics appear to be biphasic, with optimal rate constants k1DNT and k2DNT of 0.0198 h(-1) and 0.0022 h(-1) and k1THM and k2THM of 0.0053 h(-1) and 0.0014 h(-1) , respectively. Differentially, in the soil phase, imidacloprid appears to follow the first-order rate kinetics with a kIMD of 0.0013 h(-1) . These results indicate that all 3 neonicotinoids are photodegradable, with higher degradation rates in aqueous environments relative to soil environments. In addition, soil-encapsulated imidacloprid appears to degrade slowly compared with dinotefuran and thiamethoxam and does not emulate the faster degradation rates observed in the aqueous phase. Environ Toxicol Chem 2016;35:1718-1726. © 2015 SETAC.
Asunto(s)
Guanidinas/análisis , Imidazoles/análisis , Modelos Teóricos , Nitrocompuestos/análisis , Oxazinas/análisis , Fotólisis , Contaminantes del Suelo/análisis , Tiazoles/análisis , Contaminantes Químicos del Agua/análisis , Guanidinas/efectos de la radiación , Imidazoles/efectos de la radiación , Cinética , Neonicotinoides , Nitrocompuestos/efectos de la radiación , Oxazinas/efectos de la radiación , Suelo/química , Contaminantes del Suelo/química , Tiametoxam , Tiazoles/efectos de la radiación , Rayos Ultravioleta , Contaminantes Químicos del Agua/efectos de la radiaciónRESUMEN
This paper describes a new LC-MS/TOF method for the degradation products determination when Etifoxine (ETI) is submitted to different stress conditions. Chromatography is performed by using Kromasil C18 column (250mm×4.6mm, 5µm particle size). The selected mobile phase consists of formate buffer 0.02M, pH 3 and methanol (70/30, v/v). ETI is submitted to oxidative, acidic, basic, hydrolytic, thermal and UV light degradations. Detection is made at 254nm by photodiode array detector and mass spectrometry. A number of degradation products (DPs) called DPA, DPB, DPC and DPD are found depending on the stress; DPA with heat, DPA and DPB in acidic media or under UV-light; DPA, DPB and DPC under basic stress; DPA, DPB, DPC and DPD with oxidation. LC-MS/TOF is used to characterize the four DPs of ETI resulting from different stress conditions. (1)H and (13)C NMR are used to confirm the DP structures. The ETI fragmentation pathway is proposed. The method is validated with reference to International Conference on Harmonization guidelines and ETI are selectively determined in presence of its DPs, demonstrating its stability-indicating nature. Finally, for the validation step, specificity, linearity, accuracy and precision are determined for ETI and its DPs.
Asunto(s)
Ansiolíticos/química , Anticonvulsivantes/química , Espectroscopía de Resonancia Magnética con Carbono-13 , Cromatografía Líquida de Alta Presión , Oxazinas/química , Espectroscopía de Protones por Resonancia Magnética , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Ansiolíticos/efectos de la radiación , Anticonvulsivantes/efectos de la radiación , Calibración , Cápsulas , Espectroscopía de Resonancia Magnética con Carbono-13/normas , Cromatografía Líquida de Alta Presión/normas , Estabilidad de Medicamentos , Calor , Concentración de Iones de Hidrógeno , Hidrólisis , Límite de Detección , Estructura Molecular , Oxazinas/efectos de la radiación , Oxidación-Reducción , Estrés Oxidativo , Fotólisis , Espectroscopía de Protones por Resonancia Magnética/normas , Estándares de Referencia , Reproducibilidad de los Resultados , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/normas , Espectrofotometría Ultravioleta , Factores de Tiempo , Rayos UltravioletaRESUMEN
The main purpose of this study was to select an appropriate photochromic dye and to develop a series of photochromic indicators showing ultraviolet (UV) degradation of selected background materials made from different polymers. The photochemistry of a series of photochromic compounds of oxazine and diarylethenes in thin polystyrene films were studied with spectroscopic methods. This paper also discusses the design and results of tests of UV photochromic indicators for high-visibility clothing.
Asunto(s)
Colorantes/efectos de la radiación , Fotólisis , Ropa de Protección/normas , Luz Solar , Rayos Ultravioleta , Color , Ciclopentanos/efectos de la radiación , Oxazinas/efectos de la radiación , Fotoblanqueo , Fotometría , Poliestirenos/efectos de la radiación , Espectrofotometría AtómicaRESUMEN
Photochemical properties and phototoxicity of Pazufloxacin (PAX) were systematically investigated in aqueous solutions using UV-Vis, fluorescence, laser flash photolysis, pulse radiolysis and SDS-PAGE gel electrophoresis techniques. PAX triplet-state ((3)PAX(*)) absorption spectra (λ(max)=570 nm) was determined. (3)PAX(*) was quenched by PAX and O(2), with rate constants of 6.9×10(8) and 3.2×10(8) dm(3) mol(-1) s(-1), respectively. The pK(a) values (5.7 and 8.6) for the protonation equilibrium were determined by UV-Vis and fluorescence techniques. The PAX triplet energy (E(T)=260.3 kJ/mol) was obtained using energy transfer method. The reaction of electron transfer from tryptophan (TrpH) and dGMP to (3)PAX(*) was found with rate constants of 8.8×10(7) and 8.7×10(6) dm(3) mol(-1) s(-1), respectively. The rate constants for reactions of ()OH, SO(4)(-) and hydrated electron with PAX were found to be 5.8×10(8), 2.1×10(9) and 9×10(9)d m(3) mol(-1) s(-1), respectively. Based on the results obtained, a rational scheme for dGMP, TrpH and lysozyme photodamage induced by PAX was proposed.
Asunto(s)
Fluoroquinolonas/química , Fluoroquinolonas/efectos de la radiación , Oxazinas/química , Oxazinas/efectos de la radiación , Nucleótidos de Desoxiguanina/química , Transporte de Electrón , Electroforesis en Gel de Poliacrilamida , Fluoroquinolonas/toxicidad , Rayos Láser , Muramidasa/efectos de los fármacos , Oxazinas/toxicidad , Procesos Fotoquímicos , Fotólisis , Radiólisis de Impulso , Triptófano/efectos de los fármacosRESUMEN
The typical reaction of spironaphthoxazine is the conversion between the non-polar spiro form and polar merocyanine form. Quantum dots (QDs) have unique optical properties and several advantages over conventional organic dyes. In this work, the CdTe QDs containing a water-soluble spironaphthoxazine was used as the optical probe photoisomerization between spiro and merocyanine. The initial bright fluorescence of CdTe QDs was effectively quenched by water-soluble spironaphthoxazine using UV irradiation. Reversible modulation of fluorescence intensity of CdTe QDs was achieved using alternating irradiation with UV and visible light. The possible mechanism is discussed.
Asunto(s)
Compuestos de Cadmio/química , Luminiscencia , Oxazinas/química , Oxazinas/efectos de la radiación , Puntos Cuánticos , Compuestos de Espiro/química , Compuestos de Espiro/efectos de la radiación , Telurio/química , Agua/química , Absorción , Solubilidad , Espectrometría de Fluorescencia , Temperatura , Rayos UltravioletaRESUMEN
This research focused on photocatalytic degradation of imidacloprid, thiamethoxam and clothianidin employing a tailor-made photoreactor with six polychromatic fluorescent UVA (broad maximum at 355 nm) lamps and immobilised titanium dioxide (TiO(2)) on glass slides. The disappearance was followed by high pressure liquid chromatography (HPLC-DAD) analyses, wherein the efficiency of mineralization was monitored by measurements of total organic carbon (TOC). Within 2h of photocatalysis, all three neonicotinoids were degraded following first order kinetics with rate constants k=0.035 ± 0.001 min(-1) for imidacloprid, k=0.019 ± 0.001 min(-1) for thiamethoxam and k=0.021 ± 0.000 min(-1) for clothianidin. However, the rate of mineralization was low, i.e. 19.1 ± 0.2% for imidacloprid, 14.4 ± 2.9% for thiamethoxam and 14.1 ± 0.4% for clothianidin. This indicates that several transformation products were formed instead. Some of them were observed within HPLC-DAD analyses and structures were proposed according to the liquid chromatography-electro spray ionization tandem mass spectrometry analyses (LC-ESI-MS/MS). The formation of clothianidin, as thiamethoxam transformation product, was reported for the first time.
Asunto(s)
Guanidinas/química , Imidazoles/química , Insecticidas/química , Nitrocompuestos/química , Oxazinas/química , Tiazoles/química , Catálisis , Cromatografía Líquida de Alta Presión , Cromatografía Liquida , Guanidinas/efectos de la radiación , Imidazoles/efectos de la radiación , Insecticidas/efectos de la radiación , Cinética , Neonicotinoides , Nitrocompuestos/efectos de la radiación , Oxazinas/efectos de la radiación , Fotólisis , Espectrometría de Masas en Tándem , Tiametoxam , Tiazoles/efectos de la radiación , TitanioRESUMEN
Optimization of photocatalytic degradation of C.I. Basic Blue 3 (BB3) under UV light irradiation using TiO(2) nanoparticles in a rectangular photoreactor was studied. The investigated TiO(2) was Millennium PC-500 (crystallites mean size 5-10 nm) immobilized on non-woven paper. Central composite design was used for optimization of UV/TiO(2) process. Predicted values of decolorization efficiency were found to be in good agreement with experimental values (R(2)=0.9686 and Adj-R(2)=0.9411). Optimization results showed that maximum decolorization efficiency was achieved at the optimum conditions: initial dye concentration 10mg/L, UV light intensity 47.2 W/m(2), flow rate 100 mL/min and reaction time 120 min. Photocatalytic mineralization of BB3 was monitored by total organic carbon (TOC) decrease, and changes in UV-vis and FT-IR spectra. The photodegradation compounds were analyzed by UV-vis, FT-IR and GC-mass techniques. The degradation pathway of BB3 was proposed based on the identified compounds.
Asunto(s)
Nanopartículas/química , Oxazinas/efectos de la radiación , Fotólisis , Titanio/química , Rayos Ultravioleta , Catálisis , Color , Colorantes , Cromatografía de Gases y Espectrometría de Masas , Oxazinas/química , Soluciones , Análisis EspectralRESUMEN
Montmorillonite K-10 and KSF were found to be highly efficient, environmentally friendly and recyclable heterogeneous catalysts for the selective synthesis of a variety of 2-aryl-5,6-dihydro-4H-1,3-oxazines from arylnitriles and 3-amino-1-propanol under ultrasound irradiation. This new methodology provides excellent yields in short reaction times (10-25 min). The reaction work-up is very simple and the catalysts can be easily separated from the reaction mixture and reused several times in subsequent reactions. This catalytic system also exhibits excellent chemoselectivity in the synthesis of mono-oxazines from dinitriles.
Asunto(s)
Silicatos de Aluminio/química , Bentonita/química , Oxazinas/síntesis química , Oxazinas/efectos de la radiación , Solventes/química , Sonicación , Silicatos de Aluminio/efectos de la radiación , Bentonita/efectos de la radiación , Arcilla , Solventes/efectos de la radiaciónRESUMEN
Four hydrogen peroxide detecting probes, 3,3'-diaminobenzidine (DAB), Amplex Red (AR), Amplex Ultra Red (AUR) and a europium-tetracycline complex (Eu(3)Tc) were infiltrated into tobacco leaves and tested for sensitivity to light, toxicity, subcellular localization and capacity to detect H(2)O(2) in vivo. In the absence of leaves, in water solutions, AUR was very much sensitive to strong light, AR showed slight light sensitivity, while DAB and Eu(3)Tc were insensitive to irradiation. When infiltrated into the leaves, the probes decreased the photochemical yield (Phi(PSII)) in the following order of effect AR > DAB > AUR > Eu(3)Tc. With the exception of Eu(3)Tc, all probes stimulated the build-up of non-photochemical quenching either temporally (DAB, AUR) or permanently (AR), showing that their presence may already limit the photosynthetic capacity of leaves, even in the absence of additional stress. This should be taken into account when using these probes in plant stress experiments. Confocal laser scanning microscopy studies with the three fluorescent H(2)O(2) probes showed that the localizations of Eu(3)Tc and AUR were mainly intercellular. AR partly penetrated into leaf chloroplasts but probably not into the thylakoid membranes. Photosynthesis-related stress applications of AR seem to be limited by the low availability of internal leaf peroxidases. Applications of AR for kinetic H(2)O(2) measurements would require a co-infiltration of external peroxidase, imposing another artificial modifying factor and thus taking experiments further from ideal, in vivo conditions. Our results suggest that the studied H(2)O(2) probes should be used in leaf studies with caution, carefully balancing benefits and artifacts.
Asunto(s)
Colorantes Fluorescentes/farmacología , Peróxido de Hidrógeno/metabolismo , Nicotiana/metabolismo , Fotosíntesis/efectos de los fármacos , Hojas de la Planta/metabolismo , 3,3'-Diaminobencidina/farmacología , 3,3'-Diaminobencidina/efectos de la radiación , Clorofila/metabolismo , Cloroplastos/metabolismo , Peróxido de Hidrógeno/análisis , Luz , Microscopía Confocal , Técnicas de Sonda Molecular , Compuestos Organometálicos/farmacología , Compuestos Organometálicos/efectos de la radiación , Oxazinas/farmacología , Oxazinas/efectos de la radiación , Estrés Fisiológico , Tetraciclinas/farmacología , Tetraciclinas/efectos de la radiaciónRESUMEN
Three nitrosyl-dye conjugates, namely, [(Me 2bpb)Ru(NO)(Resf)] ( 1-Resf), [(Me 2bQb)Ru(NO)(Resf)] ( 2-Resf), and [((OMe) 2bQb)Ru(NO)(Resf)] ( 3-Resf) have been synthesized via direct replacement of the chloride ligand of the parent {Ru-NO} (6) nitrosyls of the type [(R 2byb)Ru(NO)(L)] with the anionic tricyclic dye resorufin (Resf). The structures of 1-Resf- 3-Resf have been determined by X-ray crystallography. The dye is coordinated to the ruthenium centers of these conjugates via the phenolato-O atom and is trans to NO. Systematic red shift of the d pi(Ru) --> pi*(NO) transition of the parent nitrosyls [(R 2byb)Ru(NO)(L)] due to changes in R and y in the equatorial tetradentate ligand R 2byb (2-) results in its eventual merge with the intense absorption band of the dye around 500 nm in 3-Resf. Unlike the UV-sensitive parent [(R 2byb)Ru(NO)(L)] nitrosyls, these dye-sensitized nitrosyls rapidly release NO when exposed to visible light (lambda >/= 465 nm). Comparison of the photochemical parameters reveals that direct coordination of the light-harvesting chromophore to the ruthenium center in the present nitrosyls results in a significantly greater extent of sensitization to visible light compared to nitrosyls with appended chromophore (linked via alkyl chains). 1-Resf has been employed as a "trackable" NO donor to promote NO-induced apoptosis in MDA-MB-231 human breast cancer cells under the control of light. The results of this work demonstrate that (a) the d pi(Ru) --> pi*(NO) transition (photoband) of {Ru-NO} (6) nitrosyls can be tuned into visible range via careful alteration of the ligand frame(s) and (b) such nitrosyls can be significantly sensitized to visible light by directly ligating a light-harvesting chromophore to the ruthenium center. The potential of these photosensitive nitrosyl-dye conjugates as (i) biological tools to study the effects of NO in cellular environments and (ii) "trackable" NO donors in photodynamic therapy of malignancies (such as skin cancer) has been discussed.
Asunto(s)
Neoplasias/metabolismo , Donantes de Óxido Nítrico/efectos de la radiación , Óxido Nítrico/metabolismo , Compuestos Organometálicos/efectos de la radiación , Oxazinas/efectos de la radiación , Fotoquimioterapia , Línea Celular Tumoral , Colorantes Fluorescentes/química , Humanos , Luz , Neoplasias/tratamiento farmacológico , Donantes de Óxido Nítrico/química , Donantes de Óxido Nítrico/metabolismo , Compuestos Organometálicos/química , Compuestos Organometálicos/metabolismo , Oxazinas/química , Oxazinas/metabolismo , Fotólisis , Rutenio/química , Neoplasias Cutáneas/tratamiento farmacológico , Neoplasias Cutáneas/metabolismoRESUMEN
Photodegradation of the insecticide thiamethoxam (1), 3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro-4H-1,3,5-oxadiazin-4-imine, in an aqueous medium was monitored by electrospray ionization mass spectrometry in the positive ion mode, ESI(+)-MS. An aqueous solution of (1) was incessantly exposed to a UV radiation source and aliquots were taken after reaction times of 1, 2, 3, and 4 h. Analysis by GC/NCI-MS revealed that (1) was continuously degraded under these experimental conditions. However, the total organic carbon (TOC) content remained practically constant during the exposition period, thereby indicating that 1 was not mineralized but continuously converted into other compounds. ESI(+)-MS monitoring revealed that whereas the intensity of the ions of m/z 292/294 ([1 + H](+)) constantly decreased, there was the emergence of other ions of m/z 247/249, 197, 168, and 116 whose intensities simultaneously increased. Their structures were proposed on the basis of: (1) the data of their ESI(+)-MS/MS; (2) their high resolution m/z values; and (3) a plausible reactivity of the thiamethoxam molecule exposed to UV radiation in aqueous solution. Finally, these data allowed us to suggest a reaction route for the photodegradation of 1 in an aqueous medium.
Asunto(s)
Insecticidas/química , Insecticidas/efectos de la radiación , Nitrocompuestos/efectos de la radiación , Oxazinas/efectos de la radiación , Espectrometría de Masa por Ionización de Electrospray/métodos , Tiazoles/efectos de la radiación , Neonicotinoides , Nitrocompuestos/química , Oxazinas/química , Fotoquímica , Fotólisis , Espectrometría de Masas en Tándem/métodos , Tiametoxam , Tiazoles/química , AguaRESUMEN
A means to control lysozyme conformation with light illumination has been developed using the interaction of the protein with a photoresponsive surfactant. Upon exposure to the appropriate wavelength of light, the azobenzene surfactant undergoes a reversible photoisomerization, with the visible-light (trans) form being more hydrophobic than the UV-light (cis) form. As a result, surfactant binding to the protein and, thus, protein unfolding, can be tuned with light. Small-angle neutron scattering (SANS) measurements were used to provide detailed information of the protein conformation in solution. Shape-reconstruction methods applied to the SANS data indicate that under visible light the protein exhibits a native-like form at low surfactant concentrations, a partially swollen form at intermediate concentrations, and a swollen/unfolded form at higher surfactant concentrations. Furthermore, the SANS data combined with FT-IR spectroscopic analysis of the protein secondary structure reveal that unfolding occurs primarily in the alpha domain of lysozyme, while the beta domain remains relatively intact. Thus, the surfactant-unfolded intermediate of lysozyme appears to be a separate structure than the well-known alpha-domain intermediate of lysozyme that contains a folded alpha domain and unfolded beta domain. Because the interactions between the photosurfactant and protein can be tuned with light, illumination with UV light returns the protein to a native-like conformation. Fluorescence emission data of the nonpolar probe Nile red indicate that hydrophobic domains become available for probe partitioning in surfactant-protein solutions under visible light, while the availability of these hydrophobic domains to the probe decrease under UV light. Dynamic light scattering and UV-vis spectroscopic measurements further confirm the shape-reconstruction findings and reveal three discrete conformations of lysozyme. The results clearly demonstrate that visible light causes a greater degree of lysozyme swelling than UV light, thus allowing for the protein conformation to be controlled with light.
Asunto(s)
Muramidasa/química , Muramidasa/efectos de la radiación , Conformación Proteica , Pliegue de Proteína , Compuestos Azo/química , Compuestos Azo/efectos de la radiación , Luz , Oxazinas/química , Oxazinas/efectos de la radiación , Fotoquímica , Fármacos Fotosensibilizantes/farmacología , Conformación Proteica/efectos de la radiación , Compuestos de Amonio Cuaternario/química , Compuestos de Amonio Cuaternario/efectos de la radiación , Dispersión de Radiación , Espectrometría de Fluorescencia , Espectrofotometría , Espectroscopía Infrarroja por Transformada de Fourier , Tensoactivos/química , Tensoactivos/efectos de la radiaciónRESUMEN
The single crystals of a closed form spirooxazine spiro[azahomoadamantane-isoquinolinoxazine] were found for the first time to undergo photocoloration processes consistent with photochromism in the single crystalline phase.
Asunto(s)
Luz , Oxazinas/química , Oxazinas/efectos de la radiación , Compuestos de Espiro/química , Compuestos de Espiro/efectos de la radiación , Rayos Ultravioleta , Cristalización , Cristalografía por Rayos X , Modelos Moleculares , Estructura Molecular , Fotoquímica , EstereoisomerismoRESUMEN
A versatile molecule is described that performs as a nondestructible read-out optical-storage molecular memory. This molecular memory is composed of two distinct molecules that are chemically bonded to each other to form a single molecule with unique properties. One component is a photochromic fulgimide, and the other is a strongly fluorescing oxazine dye. This composite molecule was specifically designed and synthesized to display, under specific conditions, both the photochromic functions of the first component and the fluorescence properties of the dye. To store information, the polar, closed form of the photochromic component is illuminated with 530-nm light, which converts it to the open, nonpolar form. The information is accessed by excitation at the 650-nm band of the oxazine dye component, causing the dye to fluoresce. However, the dye emits intense fluorescence under a nonpolar environment, which is attained only when the fulgimide component is in its open, nonpolar structure. The ultrafast kinetics, spectroscopy, and mechanism of the photoreaction of this molecule and its photoinduced intermediates have been measured, and fluorescence quantum yields and cross sections were determined.
Asunto(s)
Imidas/química , Equipos de Almacenamiento Óptico , Oxazinas/química , Colorantes/efectos de la radiación , Interacciones Hidrofóbicas e Hidrofílicas , Imidas/efectos de la radiación , Cinética , Rayos Láser , Oxazinas/efectos de la radiación , Fotoquímica , Solventes , Espectrometría de FluorescenciaRESUMEN
An aqueous photolysis study was conducted with radiolabeled thiamethoxam, 4H-1,3,5-oxadiazin-2-imine, 3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro, to establish the relevance of aqueous photolysis as a transformation process for (14)C-[thiazolyl]-thiamethoxam. (14)C-[thiazolyl]-thiamethoxam was applied to sterile sodium acetate pH 5 buffer solution at a dose rate of approximately 10 ppm. The resulting samples were incubated for up to 30 days at 25 degrees C under irradiated and nonirradiated conditions. The irradiated samples were exposed to a 12-hour-on and 12-hour-off light cycle. Volatile fractions accounted for up to an average of 56.76% of the total dose for the irradiated incubations and <0.08% for the nonirradiated incubations. These fractions were proposed to be a mixture of carbonyl sulfide (COS) and isocyanic acid (CONH). Verification of these components was accomplished by trapping with cyclohexylamine and formation of the thiocarbamate and the isocyanic acid derivatives. A similar method of trapping thiocarbamate metabolites was reported (Chen and Casida, 1978) where filter paper saturated with isobutylamine in methanol was arranged to trap (14)COS and (14)CO(2) under a positive flow of O(2) at 25 degrees C. Mass spectroscopy of the derivatized components confirmed the presence of carbonyl sulfide as the cyclohexylamine thiocarbamate and of isocyanic acid as its cyclohexylamine derivative. Evidence from this study indicates that thiamethoxam degrades significantly under photolytic conditions.
Asunto(s)
Insecticidas/química , Nitrocompuestos/química , Oxazinas/química , Insecticidas/efectos de la radiación , Luz , Espectrometría de Masas , Neonicotinoides , Nitrocompuestos/efectos de la radiación , Oxazinas/efectos de la radiación , Fotólisis , Espectrofotometría Ultravioleta , Tiametoxam , TiazolesRESUMEN
Electron donating free radicals NAD(.), (.)CO2(-), MV(.)+, and e(aq)-, generated by pulse radiolysis, reduce resazurin (RNO) with rate constants of 1.9 x 10(9), 2.8 x 10(9), 4.8 x 10(9), and 2.3 x 10(10) M(-1) s(-1), respectively, neutral solution. The semireduced dye (RN(.)-O- disproportionates slowly to RN (resorufin) and RNO. There was little evidence that RN(.)-O- behaves as an oxidizing species capable of initiating chain reactions, for instance via oxidation of NADH to NAD(.). The oxidizing radicals GS(.), (.)OH, and N3(.) interact with RNO via complex consecutive processes, probably by addition-elimination reactions. Stable products generated upon oxidation of RNO by N3(.) exhibit a red-shifted absorption, but GS(.) and (.)OH also cause partial reduction to RN. Neither O2(.)- nor dopa semiquinone nor tyrosine phenoxyl radicals appear to interact with RNO. Radicals formed by reaction of (.)OH with (Gly)3 reduce RNO to RN with stoichiometry near two (gamma-radiolysis), and there is evidence (pulse radiolysis) for direct slow O-atom transfer from RNO to these species. Resazurin is highly photosensitive under anaerobic conditions in presence of H-atom donors like NADH, GSH, or dopa. Under aerobic conditions RNO becomes an efficient catalyst of red light induced photooxidation of these donors; the RN(.)-O- intermediate, formed in the photooxidative process, is apparently recycled to RNO by O2, and by other electron acceptors. Our results suggest that RNO can behave as a photoactive, free radical generating xenobiotic compound.