Electron Paramagnetic Resonance Spin Trapping Research Articles

Development of a Red-Light-Controllable Nitric Oxide Releaser to Control Smooth Muscle Relaxation in Vivo.

We designed and synthesized a novel Si-rhodamine derivative, NORD-1, as a red-light-controllable nitric oxide (NO) releaser, on the basis of photoredox parameter analysis. Red-light-responsive NO release from NORD-1 was confirmed by ESR spin trapping and quantified with an NO electrode and by means of Griess assay. The NO release cross section (ε656nm·ΦNO) of NORD-1 was calculated to be 3.65 × 102, which is larger than that of a previously reported yellowish-green-light-controllable NO releaser, NO-Rosa5. The photoresponsiveness of NO release from NORD-1 was precise and efficient enough to induce vasodilation ex vivo under Magnus test conditions. Finally, we showed that intracavernous pressure (ICP) could be controlled in rats in vivo with the combination of NORD-1 and a red-light source without increasing systemic blood pressure, which is a serious side effect of usual NO releasers, such as nitroglycerin and isopentyl nitrite. NORD-1 is expected to be a useful chemical tool for NO research, as well as a candidate agent to control the circulatory system.

Heat shock protein 90α increases superoxide generation from neuronal nitric oxide synthases

Neuronal nitric oxide synthase (nNOS) generates superoxide, particularly at sub-optimal l-arginine (l-Arg) substrate concentrations. Heat shock protein 90 (Hsp90) was reported to inhibit superoxide generation from nNOS protein. However, commercially available Hsp90 product from bovine brain tissues with unspecified Hsp90α and Hsp90β contents and an undefined Hsp90 protein oligomeric state was utilized. These two Hsp90s can have opposite effect on superoxide production by NOS. Importantly, emerging evidence indicates that nNOS splice variants are involved in different biological functions by functioning distinctly in redox signaling. In the present work, purified recombinant human Hsp90α, in its native dimeric state, was used in electron paramagnetic resonance (EPR) spin trapping experiments to study the effects of Hsp90α on superoxide generation from nNOS splice variants nNOSμ and nNOSα. Human Hsp90α was found to significantly increase superoxide generation from nNOSμ and nNOSα proteins under l-Arg-depleted conditions and Hsp90α influenced superoxide production by nNOSμ and nNOSα at varying degrees. Imidazole suppressed the spin adduct signal, indicating that superoxide was produced at the heme site of nNOS in the presence of Hsp90α, whereas l-Arg repletion diminished superoxide production by the nNOS-Hsp90α. Moreover, NADPH consumption rate values exhibited a similar trend/difference as a function of Hsp90α and l-Arg. Together, these EPR spin trapping and NADPH oxidation kinetics results demonstrated noticeable Hsp90α-induced increases in superoxide production by nNOS and a distinguishable effect of Hsp90α on nNOSμ and nNOSα proteins.

Catalytic Oxidation of Dyeing Wastewater by Copper Oxide Activating Persulfate: Performance, Mechanism and Application

The effective treatment of dyeing wastewater has been considered as one of the challenges. The sulfate radical (SO4•−)-based technology exhibited great potential in the field of organic wastewater treatment. In this study, copper oxide was synthesized and used to activate persulfate (PS) for removing methylene blue (MB) from aqueous solution. The effects of reaction parameters and coexisting substances on this process were studied. Under the optimal conditions ([CuO] = 0.2 g/L, [PS] = 2 g/L, pH = 7.0–9.0), more than 90% of MB was degraded. Cl− had little effect on MB removal, while SO42− and HCO3− showed inhibitory effect. The activation energy of the reaction was 137.8 kJ/mol at 25 ℃ with an initial MB concentration of 10 mg/L. The mechanisms of PS activated by CuO was elucidated by radical scavenger and electron spin resonance trapping studies. The results found that sulfate radical (SO4·−) and singlet oxygen (1O2) were the primary reactive oxygen species in the CuO/PS system. The recycling experiments showed that MB removal efficiency remained more than 70% after five cycles, which exhibited good stability and high efficiency of the catalyst. The favorable degradation performance of simulated textile wastewater indicated the potential application of CuO/PS for dyeing wastewater treatment.

Unusual Two-Step Claisen-type Rearrangement Reaction under Physiological Conditions.

N-aryl hydroxamic acids, which are best known for their metal-chelating properties in chemical and biomedical research, have been found to markedly detoxify carcinogenic halogenated quinones. However, the exact chemical mechanism underlying such detoxication remains unclear. Here, we show that a very fast reaction took place between N-phenylbenzohydroxamic acid (N-PhBHA) and 2,5-dichloro-1,4-benzoquinone (DCBQ), forming an unexpected new carbon-carbon bonding phenyl-quinone product with high yield. In contrast, no reaction was observed with O-benzoyl N-PhBHA. Analogous results were observed for other N-aryl hydroxamic acids and halogenated quinones, which have an ortho-hydrogen adjacent to the reaction site (DCBQ-type). Interestingly, no free radical intermediates could be detected by both ESR spin-trapping and radical-scavenging methods during the reaction process. Taken together, we proposed that nucleophilic substitution followed by an unusual two-step Claisen-type rearrangement reaction was responsible for the formation of a new C-C bonding compound and the detoxication reaction. This represents the first report of an unusually mild and facile two-step Claisen-type rearrangement, which could take place under normal physiological conditions.

Turning Waste into Useful Products by Photocatalysis with Nanocrystalline TiO2 Thin Films: Reductive Cleavage of Azo Bond in the Presence of Aqueous Formate.

UV-photoexcitation of TiO2 in contact with aqueous solutions of azo dyes does not imply only its photocatalytic degradation, but the reaction fate of the dye depends on the experimental conditions. In fact, we demonstrate that the presence of sodium formate is the switch from a degradative pathway of the dye to its transformation into useful products. Laser flash photolysis experiments show that charge separation is extremely long lived in nanostructured TiO2 thin films, making them suitable to drive both oxidation and reduction reactions. ESR spin trapping and photoluminescence experiments demonstrate that formate anions are very efficient in intercepting holes, thereby inhibiting OH radicals formation. Under these conditions, electrons promoted in the conduction band of TiO2 and protons deriving from the oxidation of formate on photogenerated holes lead to the reductive cleavage of N=N bonds with formation and accumulation of reduced intermediates. Negative ion ESI–MS findings provide clear support to point out this new mechanism. This study provides a facile solution for realizing together wastewater purification and photocatalytic conversion of a waste (discharged dye) into useful products (such as sulfanilic acid used again for synthesis of new azo dyes). Moreover, the use of TiO2 deposited on an FTO (Fluorine Tin Oxide) glass circumvents all the difficulties related to the use of slurries. The obtained photocatalyst is easy to handle and to recover and shows an excellent stability allowing complete recyclability.

First Direct and Unequivocal Electron Spin Resonance Spin-Trapping Evidence for pH-Dependent Production of Hydroxyl Radicals from Sulfate Radicals

Recently, the sulfate radical (SO4•-) has been found to exhibit broad application prospects in various research fields such as chemical, biomedical, and environmental sciences. It has been suggested that SO4•- could be transformed into a more reactive hydroxyl radical (•OH); however, no direct and unequivocal experimental evidence has been reported yet. In this study, using an electron spin resonance (ESR) secondary radical spin-trapping method coupled with the classic spin-trapping agent 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and the typical •OH-scavenging agent dimethyl sulfoxide (DMSO), we found that •OH can be produced from three SO4•--generating systems from weakly acidic (pH = 5.5) to alkaline conditions (optimal at pH = 13.0), while SO4•- is the predominant radical species at pH < 5.5. A comparative study with three typical •OH-generating systems strongly supports the above conclusion. This is the first direct and unequivocal ESR spin-trapping evidence for •OH formation from SO4•- over a wide pH range, which is of great significance to understand and study the mechanism of many SO4•--related reactions and processes. This study also provides an effective and direct method for unequivocally distinguishing •OH from SO4•-.

Au-Cu@PANI Alloy Core Shells for Aerobic Fibrin Degradation under Visible Light Exposure.

Fibrin plays a critical role in wound healing and hemostasis, yet it is also the main case of cardiovascular diseases and thrombosis. Here, we show the unique design of Au-Cu@PANI alloy core-shell rods for fibrin clot degradation. Microscopic (transmission electron microscopy (TEM), scanning transmission electron microscopy-energy-dispersive X-ray (STEM-EDX)) and structural characterizations (powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS)) of the Au-Cu@PANI hybrid material reveal the formation of Au-Cu heterogeneous alloy core rods (aspect ratio = 3.7) with thin Cu2O and PANI shells that create a positive surface charge (ζ-potential = +22 mV). This architecture is supported by the survey XPS spectrum showing the presence of Cu 2p, N 1s, and C 1s features with binding energies of 934.8, 399.7, and 284.8 eV, respectively. Upon photolysis (λ ≥ 495 or 590 nm), these hybrid composite nanorods provide sufficient excited-state redox potential to generate reactive oxygen species (ROS) for degradation of model fibrin clots within 5-7 h. Detailed scanning electron microscopy (SEM) analysis of the fibrin network shows significant morphology modification including formation of large voids and strand termini, indicating degradation of fibrin protofibril by Au-Cu@PANI. The dye 1,3-diphenylisobenzofuran (DPBF) used to detect the presence of 1O2 shows a 27% bleaching of the absorption at λ = 418 nm within 75 min of irradiation of an aqueous Au-Cu@PANI solution in air. Moreover, electron paramagnetic resonance (EPR) spin-trapping experiments reveal a hyperfine-coupled triplet signature at room temperature with intensities 1:1:1: and g-value = 2.0057, characteristic of the reaction between the spin probe 4-Oxo-TEMP and 1O2 during irradiation. Controlled 1O2 scavenging experiments by NaN3 show 82% reduction in the spin-trapped EPR signal area. Both DPBF bleaching and EPR spin trapping indicate that in situ generated 1O2 is responsible for fibrin strand scission. This unique nanomaterial function via use of ubiquitous oxygen as a reagent could open creative avenues for future in vivo biomedical applications to treat fibrin clot diseases.

ESR spin trapping for in situ detection of radicals involved in the early stages of lipid oxidation of dried microencapsulated oils

Different studies have shown that detection of free radicals by ESR spin trapping provides useful information on the susceptibility to oxidation of bulk oils and accordingly on the oxidative stability of different samples for comparative purposes. With the same goal, ESR spin trapping was evaluated in this work for in situ detection of radicals in dried microencapsulated oils (DMOs). By testing different oils, encapsulation matrices and oxidation conditions, results showed that ESR spin trapping can be useful to evaluate the oxidative susceptibility of DMOs, but ESR data should be interpreted cautiously, as the great complexity of the reactions involved may lead to data misinterpretations. Conditions for oxygen availability can have important impacts on the rates of both spin trapping and spin-adduct quenching affecting the levels of radicals observed. The kinetics of oxidation, spin trapping and spin-adduct decay should be known first in bulk oils for correct data interpretation in DMOs.

Drought-induced changes in antioxidant system and osmolyte content of poplar cuttings

Poplars are widely utilized in the intensive and biomass production, as well as in breeding and environment protection programs. This experiment was performed to investigate the effect of drought stress on poplar clones (M-1, PE19/66 and B-229). Poplar clones were grown hydroponically under controlled conditions and exposed to drought stress by applying polyethylene glycol (PEG) 6000. The plant samples were collected and separated into roots and leaves. For estimation of antioxidant status, activities of different antioxidant enzymes were determined (superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), glutathione peroxidase (GPX), glutathione reductase (GR) and ascorbate peroxidase (APX)), as well as antiradical power (ARP) against hydroxyl (˙OH) radical using ESR spin-trapping. The water stress parameters proline (PRO) content, activity of proline dehydrogenase (PDH) and glycine betaine (GB) content were determined. Drought stress had significant effects on PRO and GB contents, SOD, APX and CAT activities when compared to control. All investigated extracts were determined as good inhibitors for ˙OH radical reduction, especially clone M-1where there was an increase of ARP against ˙OH radical in drought condition what could help to prevent or meliorate oxidative damage. Results indicated that the M-1 clone had a greater accumulation of substances for osmotic adjustment and a more efficient enzymatic detoxification cycle for eliminating the negative effects caused by ROS under drought stress than clones B-229 and PE19/66. This study provides valuable information for understanding drought - responsive mechanisms in leaves and roots of poplar clones M-1, B-229 and PE19/66. Key words: antioxidant enzymes, climate change, drought, glycine betaine, proline.

•BMPO-OOH Spin-Adduct as a Model for Study of Decomposition of Organic Hydroperoxides and the Effects of Sulfide/Selenite Derivatives. An EPR Spin-Trapping Approach.

Lipid hydroperoxides play an important role in various pathophysiological processes. Therefore, a simple model for organic hydroperoxides could be helpful to monitor the biologic effects of endogenous and exogenous compounds. The electron paramagnetic resonance (EPR) spin-trapping technique is a useful method to study superoxide (O2•−) and hydroxyl radicals. The aim of our work was to use EPR with the spin trap 5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO), which, by trapping O2•− produces relatively stable •BMPO-OOH spin-adduct, a valuable model for organic hydroperoxides. We used this experimental setup to investigate the effects of selected sulfur/selenium compounds on •BMPO-OOH and to evaluate the antioxidant potential of these compounds. Second, using the simulation of time-dependent individual BMPO adducts in the experimental EPR spectra, the ratio of •BMPO-OH/•BMPO-OOH—which is proportional to the transformation/decomposition of •BMPO-OOH—was evaluated. The order of potency of the studied compounds to alter •BMPO-OOH concentration estimated from the time-dependent •BMPO-OH/•BMPO-OOH ratio was as follows: Na2S4 > Na2S4/SeO32− > H2S/SeO32− > Na2S2 ~Na2S2/SeO32− ~H2S > SeO32− ~SeO42− ~control. In conclusion, the presented approach of the EPR measurement of the time-dependent ratio of •BMPO-OH/•BMPO-OOH could be useful to study the impact of compounds to influence the transformation of •BMPO-OOH.

Changes in Photosynthetic Electron Transport during Leaf Senescence in Two Barley Varieties Grown in Contrasting Growth Regimes.

Leaf senescence is an important process for plants to remobilize a variety of metabolites and nutrients to sink tissues, such as developing leaves, fruits and seeds. It has been suggested that reactive oxygen species (ROS) play an important role in the initiation of leaf senescence. Flag leaves of two different barley varieties, cv. Lomerit and cv. Carina, showed differences in the loss of photosystems and in the production of ROS at a late stage of senescence after significant loss of chlorophyll (Krieger-Liszkay etal. 2015). Here, we investigated photosynthetic electron transport and ROS production in primary leaves of these two varieties at earlier stages of senescence. Comparisons were made between plants grown outside in natural light and temperatures and plants grown in temperature-controlled growth chambers under low light intensity. Alterations in the content of photoactive P700, ferredoxin and plastocyanin (PC) photosynthetic electron transport were analyzed using in vivo near-infrared absorbance changes and chlorophyll fluorescence, while ROS were measured with spin-trapping electron paramagnetic resonance spectroscopy. Differences in ROS production between the two varieties were only observed in outdoor plants, whereas a loss of PC was common in both barley varieties regardless of growth conditions. We conclude that the loss of PC is the earliest detectable photosynthetic parameter of leaf senescence while differences in the production of individual ROS species occur later and depend on environmental factors.

One-pot synthesis of novel ternary Fe3N/Fe2O3/C3N4 photocatalyst for efficient removal of rhodamine B and CO2 reduction

The novel ternary Fe3N/Fe2O3/C3N4 photocatalyst was prepared by thermal pyrolysis of potassium ferricyanide in melamine. The structural, morphological and physico-chemical properties of the photocatalyst were characterized by a multi-technique approach. Photocatalytic experiments supported that 0.04 g of the photocatalyst was able to totally remove 5 ppm of rhodamine B (RhB) solution under acidic condition with the rate constant of 0.1 min−1 in less than 30 min. According to spin-trapping ESR analysis, •OH radicals play a key role in the RhB photodegradation implying Z-scheme mechanism is applicable to our system. Moreover, the evolution rate of CO and CH4 over the photocatalyst was 8.03 and 1.6 μmol g−1 h−1, respectively, which was much higher than the reference photocatalysts under the same conditions. The enhanced photocatalytic performance of this system is attributed to the unique ternary heterojunction between the interfaces of g-C3N4, Fe3N and Fe2O3, which effectively suppressed the charge carriers recombination.

Insights into Interface Charge Extraction in a Noble-Metal-Free Doped Z-Scheme NiO@BiOCl Heterojunction

It is of great significance to thoroughly explore the interface charge extraction and migration in heterojunction systems, which could guide us to synthesize higher-efficiency photocatalytic materials. A novel noble-metal-free doped Z-scheme NiO@BiOCl heterojunction was found in this work. The corresponding heterostructure, interface electron extraction, and electron migration were investigated via first-principles calculation. 5,5′-dimethyl-1-pyrroline-N-oxide (DMPO) spin-trapping electron spin resonance (ESR) and time-resolved photoluminescence (TRPL) tests were implemented to confirm the calculation results, which showed that electrons and holes stayed in the NiO (100) facet and BiOCl (110) facet, respectively. Owing to the large chemical potential of 2.40 V (vs ENHE) for the BiOCl valence-band hole, it possessed super activity to oxidize water into hydroxyl radicals or molecular oxygen. We hope this promising multifunctional photocatalytic material, therefore, NiO@BiOCl can be applied in advanced treatment of organic wastewater and oxygen production from photolysis water.

Are Radicals Formed During Anion-Exchange Membrane Fuel Cell Operation?

In this paper we present a study on stable radicals and short-lived species generated in anion-exchange membrane (AEM) fuel cells (AEMFCs) during operation. The in situ measurements are performed with a micro-AEMFC inserted into a resonator of an electron paramagnetic resonance (EPR) spectrometer, which enables separate monitoring of radicals formed on the anode and cathode sides. The creation of radicals is monitored by the EPR spin trapping technique. For the first time, we clearly show the formation and presence of stable radicals in AEMs during and after long-term AEMFC operation. The main detected adducts during the operation of the micro-AEMFC are DMPO-OOH and DMPO-OH on the cathode side, and DMPO-H on the anode side. These results indicate that oxidative degradation involving radical reactions has to be taken into account when stability of AEMFCs is investigated.

Anti-inflammatory and antioxidant effects of Apium graveolens L. extracts mitigate against fatal acetaminophen-induced acute liver toxicity.

In the present work, antioxidant activity, total phenolics (TP), and total flavonoids (TF) contents of aqueous and methanol extracts of celery were determined, in addition to untargeted metabolites profiling its methanol celery root extract (MCRE) via UPLC-MS. Although MCRE exhibited the lowest TPC and TFC levels, it presented the most potential hydroxyl radical quenching effect using electron paramagnetic resonance spin trapping technique. Treatment of Acetaminophen-induced hepatotoxicity (AAH) rats with MCRE lowered serum levels of AST, ALT, ALP, TNF-α, and IL-1β significantly. Additionally, MCRE significantly increased total antioxidant capacity (TAC) and glutathione (GSH) levels relative to AAH rats. Strikingly, Kaplan-Meier survival analysis of all groups revealed a 100% prevention of acetaminophen-induced mortality of rats by MCRE pretreatment (100mg/kg/day). MCRE prevented AAH-associated severe weight loss and elicited normal behavior in the rescued rats. Our results suggest that pretreatment with MCRE can mitigate against overdosed acetaminophen-induced acute liver failure and warrant further investigations on the potential of postinjury intervention. PRACTICAL APPLICATIONS: Acetaminophen-induced hepatotoxicity (AAH) accounts for alerting numbers of overdose-related acute liver failure and liver transplant cases with increased morbidity and mortality rates. Currently proposed mechanisms implicate mitochondria-mediated oxidative stress and inflammation in the pathogenesis of AAH, which underline current interventions employing antioxidants to combat liver damage by over-dosed acetaminophen. The present work uncovers potent protective effects of some celery extracts (and their fractions) against acetaminophen-induced oxidative stress and inflammation. Treatment of rats with fatal liver injury with methanol extract of celery root significantly reduced secretion of liver enzymes and markedly decreased inflammatory as well as oxidative stress markers in these animals. This, in turn, rescued challenged rats exposed to fatal doses of acetaminophen completely, which establishes methanol extracts of celery roots as effective therapeutic intervention against AAH. The antioxidant capacity of the extracts was determined using EPR technique, and the secondary metabolites related to antioxidant activity were characterized via UPLC-MS.

Efficient visible light photocatalytic antibiotic elimination performance induced by nanostructured Ag/AgCl@Ti3+-TiO2 mesocrystals

Efficient visible light photocatalytic elimination of pharmaceutical factory wastewater is one of widely concerned and greatly significant attempts in dealing with increasingly serious environmental pollution problems. In this work, hybrid Ag/AgCl nanoparticles were successfully introduced into Ti3+ self-doped TiO2 mesocrystals via precipitation and photo-reduction methods for efficient visible light photocatalytic antibiotic elimination. Some characterization measurements, such as XRD, SEM, TEM, XPS, UV–vis DRS spectra, fluorescence emission spectra, time-resolved fluorescence spectra, FT-IR spectra, and electrochemical measurements, were applied to investigate the physico-chemical properties of nanostructured Ag/AgCl@Ti3+-TiO2 mesocrystals. The experiment results showed that nanostructured Ag/AgCl@Ti3+-TiO2-60 composites presented the best visible light photocatalytic performance for tetracycline degradation, which was approximately 3.52 times of Ti3+-TiO2 mesocrystals and 22.43 times of commercial TiO2. Trapping experiments of active species and DMPO spin-trapping ESR experiments further confirmed that the visible light photocatalytic tetracycline degradation by Ag/AgCl@Ti3+-TiO2 mesocrystals were mainly due to the continuous attacks of photo-generated holes, OH and O2− radicals on tetracycline molecules. Besides, nanostructured Ag/AgCl@Ti3TiO composites were also employed in visible light photocatalytic industrial para-ester wastewater degradation. Finally, possible tetracycline transformation pathways and visible light photocatalytic tetracycline degradation mechanism over plasmonic Ag/AgCl@Ti3+-TiO2 composites were also proposed. Current work indicates that defective semiconductor mesocrystals and their composites have huge prospects in the refractory organic elimination.

Artificial Bifunctional Photozyme of Glucose Oxidase-Peroxidase for Solar-Powered Glucose-Peroxide Detection in a Biofluid with Resorcinol-Formaldehyde Polymers.

Photozymes or artificial photosynthesis based on alternative natural enzymes is vital for the sustainable development of next-generation healthcare, energy, and materials science. Herein, we report resorcinol-formaldehyde (RF) resins as a solar-driven metal-free bifunctional glucose oxidase-peroxidase stand-alone photozyme for the colorimetric dual detection of hydrogen peroxide and glucose. The π-bond conjugated benzenoid-ortho/para quinoid RF polymers are efficient for glucose oxidation and hydrogen peroxide reduction with concurrent 3,3',5,5'-tetramethylbenzidine oxidation under natural sunlight. The photoinduced colorimetric process could detect H2O2 up to 3.5 μM at 652 nm with the linear range of 0.1-2 mM. A limit of detection of 9.2 μM was exhibited by the system while measuring glucose with a linearity from 0.2 to 8.5 mM. The formation of hydroxyl radicals (•OH) from glucose oxidation reactions was evidenced by spin trapping electron paramagnetic resonance studies conducted herein. The results indicated that RF resins possessed strong intrinsic glucose oxidase and peroxidase (POx)-like activity under natural sunlight with promising storage and operation. This simple photozyme will definitely have potential uses in biomimetic solar-driven catalysis, bioenergy, and biomedicine.

ATR-IR and EPR spectroscopy for following the membrane restoration of isolated cortical synaptosomes in aluminium-induced Alzheimer’s disease – Like rat model

Synaptosomal membrane peroxidation and alteration in its biophysical properties are associated with Aluminium (Al) toxicity that may lead to cognitive dysfunction and Alzheimer’s disease (AD) like pathogenesis. Here we investigated the therapeutic potential of Lepedium sativum (LS) as a natural anti-inflammatory, antioxidant and as acetyl cholinesterase inhibitor in treating Al induced AD-like in rat model. We utilized ATR-IR spectroscopy to follow the restoration in the damaged membrane structure of isolated rat cortical synaptosomes and its biophysical properties, electron paramagnetic resonance (EPR) spin trapping to follow NADPH oxidase activity (NOX), and EPR spin labelling in response to LS treatment after Al intoxication. We measured the concentration of Ca2+ ions in rat cortical tissue by inductively coupled plasma (ICP), the brain atrophy/curing and hydrocephalus by magnetic resonance imaging (MRI) besides light microscope histopathology. Our results revealed significant increase in synaptosomal membrane rgidification, order, lipid packing, reactive oxygen species (ROS) production and Ca2+ ion concentration as a result of Al intoxication. The dramatic increase in Ca2+ ion concentration detected in AD group associated with the increase in synaptic membrane polarity and EPR-detected order S-parameter suggest that release of synaptic vesicles into synaptic cleft might be hindered. LS treatment reversed these changes in synaptic membranes, and rescued an observed deficit in the exploratory behaviour of AD group. Our results also strongly suggest that the synaptosomal membrane phospholipids that underwent free radical attacks mediated by AlCl3, due to greater NOX activity, was prevented in the LS group. The results of ATR-IR and EPR spectroscopic techniques recommend LS as a promising therapeutic agent against synaptic membrane alterations opening a new window for AD drug developers.

Direct Evidence of Visible Light-Induced Homolysis in Chlorobis(2,9-dimethyl-1,10-phenanthroline)copper(II).

Developments in the field of photoredox catalysis that leveraged the long-lived excited states of Ir(III) and Ru(II) photosensitizers to enable radical coupling processes paved the way for explorations of synthetic transformations that would otherwise remain unrealized. While first row transition metal photocatalysts have not been as extensively investigated, valuable synthetic transformations covering broad scopes of olefin functionalization have been recently reported featuring photoactivated chlorobis(phenanthroline) Cu(II) complexes. In this study, the photochemical processes underpinning the catalytic activity of [Cu(dmp)2Cl]Cl (dmp = 2,9-dimethyl-1,10-phenanthroline) were studied. The combined results from static spectroscopic measurements and conventional photochemistry, ultrafast transient absorption, and electron paramagnetic resonance spin trapping experiments strongly support blue light (λex = 427 or 470 nm)-induced Cu-Cl homolytic bond cleavage in [Cu(dmp)2Cl]+ occurring in <100 fs. On the basis of electronic structure calculations, this bond-breaking photochemistry corresponds to the Cl → Cu(II) ligand-to-metal charge transfer transition, unmasking a Cu(I) species [Cu(dmp)2]+ and a Cl atom, thereby serving as a departure point for both Cu(I)- or Cu(II)-based photoredox transformations. No net photochemistry was observed through direct excitation of the ligand-field transitions in the red (λex = 785 or 800 nm), and all combined experiments indicated no evidence of Cu-Cl bond cleavage under these conditions. The underlying visible light-induced homolysis of a metal-ligand bond yielding a one-electron-reduced photosensitizer and a radical species may form the basis for novel transformations initiated by photoinduced homolysis featuring in situ-formed metal-substrate adducts utilizing first row transition metal complexes.

Synergistic, aqueous PAH degradation by ultrasonically-activated persulfate depends on bulk temperature and physicochemical parameters.

Coupling ultrasound with other remediation technologies has potential to result in synergistic degradation of contaminants. In this work, we evaluated synergisms from adding high-power ultrasound (20kHz; 250W) to activated persulfate over a range of bulk temperatures (20-60°C). We studied the aqueous degradation kinetics of three polycyclic aromatic hydrocarbons (PAHs: naphthalene, phenanthrene, and fluoranthene) treated by ultrasound-alone, heat-activated persulfate, and combined ultrasonically-activated persulfate (US-PS). At 20°C, observed US-PS rate constants strongly correlated with Wilke-Chang diffusion coefficients. This correlation indicates PAH molecules diffuse to the bubble-water interface prior to reaction with sulfate radicals (SO4-) generated at the interface. At higher temperatures, observed US-PS rate constants appear to be a more complicated function of temperature and diffusion coefficients. Synergy indexes for PAHs with fast diffusion coefficients were greatest at 20°C. Fluoranthene, the largest and most hydrophobic PAH, had a maximum synergy index at 30°C; it benefited from additional thermal persulfate activation in bulk solution. Fluoranthene synergy indexes, however, decreased above 30°C and became antagonistic at 60°C. Electron paramagnetic resonance (EPR) spin trapping was used to quantify hydroxyl radical (OH) produced from acoustic cavitation in the absence of persulfate. These data showed consistent OH production from 20 to 60°C, indicating PAH antagonisms at 60°C were not due to lower bubble collapse temperatures. Instead, the results suggest that PAH antagonisms are caused by increased radical-radical recombination as bulk temperature increases. In effort to develop an efficient, combined remediation technology, this work suggests bulk temperatures between 20 and 40°C maximize US-PS synergisms.