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Water remediation with biomass derivatives has attracted attention for its sustainable impact on the earth. Chemical procedures for new adsorbent and active biomaterials must be implemented to remove organic pollutants more efficiently. Herein, we obtained a sustainable, environmentally, and low‐cost biochar from bamboo Dendrocalamus giganteus (BBC, B400) by thermal treatment at 400 °C without physical and chemical pre‐ and post‐treatments. By electron paramagnetic resonance (EPR), we determined the quantification and ageing of persistent free radicals (PFRs, 1016–1019 spins/g) present in BBC over time. We demonstrated the removal efficiency (R %) of B400 against methylene blue (MB) aqueous solutions without and with different concentrations of H2O2 using a novel B400‐packed column‐flow system. Results demonstrated that the MB removal efficiency via physical adsorption and chemical degradation strongly depended on the concentration of carbon‐centred PFRs and their stability over time. Collectively, a reduced concentration of PFRs and their full passivation by proper treatments led to a remarkable loss of MB removal efficiency, thus evidencing that a PFR‐mediated radical degradation mechanism was predominant in the MB removal process. Experiments with t‐butanol alcohol (TBA) on aged B400 as a radical scavenger of the hydroxyl radical (⋅OH) have evidenced the critical role of PFRs in generating reactive oxygens species (ROSs) in solution, which catalysed the oxidative degradation of MB. Kinetics studies carried out on removal efficiency data vs time by all experiments established that the MB removal profiles of fresh B400 were best described by a pseudo‐second order (PSO) kinetic model, thus suggesting that chemical mechanisms such as electron transfer reactions and PFRs‐mediated degradation were the main contributors to MB removal. On the contrary, MB removal profiles of aged B400 with reduced or insignificant content of PFRs best fitted kinetic models, which describe physical absorption and diffusional nor radical processes, which led to a lower removal efficiency. These findings will be helpful for potential pilot and large‐scale experiments to remove a wide range of contaminants in water. [ABSTRACT FROM AUTHOR]

Copper(II) chloride anionic coordination complexes with different imidazole‐derived ligands due to the potential cytotoxic activity play the important role in protein. By investigating the experimental electron paramagnetic resonance (EPR) and ultraviolet–visible (UV–vis) spectra of [CuCl(C6H10N2)4]Cl, [CuCl(C6H10N2)4]Cl, [CuCl2(C4H6N2)4], and [Cu2Cl2(C5H8N2)6]Cl2·2H2O, the local structure of the corresponding Cu2+ centers and the role of different ligands are obtained. Based on the well‐agreed EPR parameters and the d‐d transitions (10Dq), the four Cu2+ centers show tetragonal and orthorhombic distortion, corresponding to the different anisotropies of EPR signals. In addition, the general rules of governing the impact of methanol in imidazolylalkyl derivatives are also discussed, especially the influence on the local environment (symmetry, distortion, covalency, and crystal field) of above four copper(II) chloride anionic coordination complexes. Therefore, the obtained results in this study will be beneficial to provide a theoretical basis for the experimental design of desired copper‐containing imidazolyl alkyl derivatives. [ABSTRACT FROM AUTHOR]

Bioreduction of spin labels and polarizing agents (generally stable radicals) has been an obstacle limiting the in‐cell applications of pulsed electron paramagnetic resonance (EPR) spectroscopy and dynamic nuclear polarization (DNP). In this work, we have demonstrated that two semiquinone methide radicals (OXQM⋅ and CTQM⋅) can be easily produced from the trityl‐based quinone methides (OXQM and CTQM) via reduction by various reducing agents including biothiols and ascorbate under anaerobic conditions. Both radicals have relatively low pKa's and exhibit EPR single line signals at physiological pH. Moreover, the bioreduction of OXQM in three cell lysates enables quantitative generation of OXQM⋅ which was most likely mediated by flavoenzymes. Importantly, the resulting OXQM⋅ exhibited extremely high stability in the E.coli lysate under anaerobic conditions with 76‐ and 14.3‐fold slower decay kinetics as compared to the trityl OX063 and a gem‐diethyl pyrrolidine nitroxide, respectively. Intracellular delivery of OXQM into HeLa cells was also achieved by covalent conjugation with a cell‐permeable peptide as evidenced by the stable intracellular EPR signal from the OXQM⋅ moiety. Owing to extremely high resistance of OXQM⋅ towards bioreduction, OXQM and its derivatives show great application potential in in‐cell EPR and in‐cell DNP studies for various cells which can endure short‐term anoxic treatments. [ABSTRACT FROM AUTHOR]

Investigation of the physical characteristics of mineral artifacts was undertaken with purpose of development of dating by the electron paramagnetic resonance (EPR) method in a new direction, by means of analysis of spectra of the carbonate probes from the surface of archaeological artifacts. The artifacts – samples of layers from the surface of ceramics and stone tools, containing impurities of quartz and alumosilicates, have been tested. For obtaining the physical characteristics and dating the complex of the methods and equipment has been used which allowed us to reveal specialties of mineral content and structure of the surface. There were chosen optimal conditions for registration, distinguishing and identification of the EPR signals from the paramagnetic centers. Applying of radiation of the ILU-10 accelerator with converter and consequent EPR-studying allowed to estimate the age of artifacts.

The local structures and the spin Hamiltonian parameters (SHPs) for Cu2+ in xBaO–(30–x)TeO2–10TiO2–58B2O3 (BTTB) glasses are theoretically investigated for various BaO concentrations (x = 10, 15, 20, and 25 mol %) in a uniform way. Attributed to the Jahn–Teller effect, the [CuO6]10– groups are found to experience the moderate tetragonal elongation distortions (characterized by the moderate relative tetragonal elongation ratios ρ ≈ 5.1–7.8%) along the C4 axis. With only three adjusted coefficients a, b, and ω, the relevant model parameters (Dq, k, ρ, κ, and H) are suitably described by the quasi-second order harmonic functions, and the measured concentration dependences of the d–d transition bands and SHPs are soundly reproduced. All the model parameters show fluctuations with the concentration x, reflecting the non-monotonic variations of the local crystal-field strength, electron cloud distribution and relative tetragonal elongation distortion with x. [ABSTRACT FROM AUTHOR]

Fullerene derivatives are known radical scavengers and quenchers of reactive oxygen species and have been studied as promising antioxidative agents in biological systems, yet the correlation between the structural features and their efficiency has not been well understood. In this report, we synthesized eight representative water-soluble fullerene derivatives and compared their radical scavenging properties via electron paramagnetic resonance in solution and antioxidative capacity in the H2O2-treated RAW 264.7 macrophage cell model. Through this systematic study, we identified multiple key parameters contributing to their radical scavenging and antioxidative effects, including the number and identity of functional groups on the C60 cage, the size of aggregates, and their cellular uptake in RAW 264.7 cells. [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters and defect structures are theoretically studied for the substitutional Mn2+ at the core of CdSe nanocrystals and in the bulk materials from the perturbation calculations of spin Hamiltonian parameters for trigonal tetrahedral 3d5 clusters. Both the crystal‐field and charge transfer contributions are taken into account in the calculations from the cluster approach. The impurity‐ligand bond angles are found to be about 1.84° larger and 0.10° smaller in the CdSe:Mn2+ nanocrystals and bulk materials, respectively, than those (≈109.37°) of the host Cd2+ sites. The quantitative criterion of occupation (at the core or surface) for Mn2+ in CdX (X = S, Se, Te) nanocrystals is presented for the first time based on the inequations of hyperfine structure constants (HSCs). This criterion is well supported by the experimental HSCs data of Mn2+ in CdX nanocrystals. The previous assignments of signals SI as Mn2+ at the core of CdS nanocrystals are renewed as Mn2+ at the surface based on the above criterion. The present studies would be helpful to achieve convenient determination of occupation for Mn2+ impurities in CdX semiconductor nanocrystals by means of spectral (e.g., HSCs) analysis. [ABSTRACT FROM AUTHOR]

Purpose: Progress toward developing a novel radiocontrast agent for determining pO2 in tumors in a clinical setting is described. The imaging agent is designed for use with electron paramagnetic resonance imaging (EPRI), in which the collision of a paramagnetic probe molecule with molecular oxygen causes a spectroscopic change which can be calibrated to give the real oxygen concentration in the tumor tissue. Procedures: The imaging agent is based on a nanoscaffold of aluminum hydroxide (boehmite) with sizes from 100 to 200 nm, paramagnetic probe molecule, and encapsulation with a gas permeable, thin (10–20 nm) polymer layer to separate the imaging agent and body environment while still allowing O2 to interact with the paramagnetic probe. A specially designed deuterated Finland trityl (dFT) is covalently attached on the surface of the nanoparticle through 1,3-dipolar addition of the alkyne on the dFT with an azide on the surface of the nanoscaffold. This click-chemistry reaction affords 100% efficiency of the trityl attachment as followed by the complete disappearance of the azide peak in the infrared spectrum. The fully encapsulated, dFT-functionalized nanoparticle is referred to as RADI-Sense. Results: Side-by-side in vivo imaging comparisons made in a mouse model made between RADI-Sense and free paramagnetic probe (OX-071) showed oxygen sensitivity is retained and RADI-Sense can create 3D pO2 maps of solid tumors Conclusions: A novel encapsulated nanoparticle EPR imaging agent has been described which could be used in the future to bring EPR imaging for guidance of radiotherapy into clinical reality. [ABSTRACT FROM AUTHOR]

The energy and spin parameters of 3-alkylthiophene oligomers and their composites with aromatic hydrocarbons have been calculated. The coexistence of polarons with different degrees of delocalization in the studied compounds has been identified. It has been revealed that the electronic and spin properties of the composites undergo a periodic change initiated by the interaction of the oligomers with aromatic nanoadditives. The anisotropic parameters of spin Hamiltonians have been obtained for the systems under study, and their high-resolution EPR spectra have been calculated. [ABSTRACT FROM AUTHOR]

The fungicides strobilurins and succinate dehydrogenase inhibitors (SDHIs) are blockers of the electron transport chain (ETC) in fungi. Here, we show that the exposure for 24 h to kresoxym-methyl, a fungicide from the class of strobilurins, alters the mitochondrial respiration in human HepG2 hepatocytes. In addition, we demonstrate an increase in production of mitochondrial superoxide radical anion, a reduction in ATP level, a decrease in the ratio reduced/oxidized glutathione and a decrease in cell viability (assessed by the LDH assay, Presto Blue assay, and Crystal Violet assay). As kresoxym-methyl is associated to boscalid (SDHI) in commercial formulations, we analyzed a potential exacerbation of the induced mitochondrial dysfunction for this combination. For the highest dose at which kresoxym-methyl (5 µM) and boscalid (0.5 µM) did not induce changes in mitochondrial function when used separately, in contrast, when both fungicides were used in combination at the same concentration, we observed a significant alteration of the mitochondrial function of hepatocytes: there was a decrease in oxygen consumption rate, in the ATP level. In addition, the level of mitochondrial superoxide radical anion was increased leading to a decrease in the ratio reduced/oxidized glutathione, and an increase in viability.

Significance: Fundamental to the application of tissue redox status to human health is the quantification and localization of tissue redox abnormalities and oxidative stress and their correlation with the severity and local extent of disease to inform therapy. The centrality of the low-molecular-weight thiol, glutathione, in physiological redox balance has long been appreciated, but direct measurement of tissue thiol status in vivo has not been possible hitherto. Recent advances in instrumentation and molecular probes suggest the feasibility of real-time redox assessment in humans. Recent Advances: Recent studies have demonstrated the feasibility of using low-frequency electron paramagnetic resonance (EPR) techniques for quantitative imaging of redox status in mammalian tissues in vivo. Rapid-scan (RS) EPR spectroscopy and imaging, new disulfide–dinitroxide spin probes, and novel analytic techniques have led to significant advances in direct, quantitative imaging of thiol redox status. Critical Issues: While novel RS EPR imaging coupled with first-generation molecular probes has demonstrated the feasibility of imaging thiol redox status in vivo, further technical advancements are desirable and ongoing. These include developing spin probes that are tailored for specific tissues with response kinetics tuned to the physiological environment. Equally critical are RS instrumentation with higher signal-to-noise ratio and minimal signal distortion, as well as optimized imaging protocols for image acquisition with sparsity adapted to image information content. Future Directions: Quantitative images of tissue glutathione promise to enable acquisition of a general image of mammalian and potentially human tissue health. [ABSTRACT FROM AUTHOR]

Local structures and electron paramagnetic resonance (EPR) parameters (g factors gx, gy, and gz) for the substitutional Ti3+ and W5+ centers in stishovite are theoretically investigated by using the high-order perturbation formulas of these parameters for a d1 ion in rhombically compressed octahedra. In the calculation formulas, the related molecular orbital coefficients are obtained from the cluster approach, and the relevant crystal-field (CF) parameters are determined from the superposition model, which enables to connect these CF parameters and, hence, the studied g factors with the local structures of the Ti3+ and W5+ centers in stishovite. Based on the calculations, the impurity–ligand bond lengths parallel and perpendicular to the C2-axis are found to be R′|| (≈1.751 and 1.717 Å) and R′⊥ (≈1.788 and 1.806 Å) with the planar bond angles θ′ (≈89.0° and 88.2°) for the studied [TiO6]9− and [WO6]7− clusters, respectively. The calculated results are in good agreement with the experimental data, and the validity of the results is discussed. [ABSTRACT FROM AUTHOR]

Identifying the two substrate water sites of nature's water-splitting cofactor (Mn4CaO5 cluster) provides important information toward resolving the mechanism of O-O bond formation in Photosystem II (PSII). To this end, we have performed parallel substrate water exchange experiments in the S1 state of native Ca-PSII and biosynthetically substituted Sr-PSII employing Time-Resolved Membrane Inlet Mass Spectrometry (TR-MIMS) and a Time-Resolved 17O-Electron-electron Double resonance detected NMR (TR-17O-EDNMR) approach. TR-MIMS resolves the kinetics for incorporation of the oxygen-isotope label into the substrate sites after addition of H2 18O to the medium, while the magnetic resonance technique allows, in principle, the characterization of all exchangeable oxygen ligands of the Mn4CaO5 cofactor after mixing with H2 17O. This unique combination shows i) that the central oxygen bridge (O5) of Ca-PSII core complexes isolated from Thermosynechococcus vestitus has, within experimental conditions, the same rate of exchange as the slowly exchanging substrate water (WS) in the TR-MIMS experiments and ii) that the exchange rates of O5 and WS are both enhanced by Ca2+→Sr2+ substitution in a similar manner. In the context of previous TR-MIMS results, this shows that only O5 fulfills all criteria for being WS. This strongly restricts options for the mechanism of water oxidation. [ABSTRACT FROM AUTHOR]

The study and characterization of the biophysical properties of membranes and drug–membrane interactions represent a critical step in drug development, as biological membranes act as a barrier that the drug must overcome to reach its active site. Liposomes are widely used in drug delivery to circumvent the poor aqueous solubility of most drugs, improving systemic bioavailability and pharmacokinetics. Further, they can be targeted to deliver to specific disease sites, thus decreasing drug load, and reducing side effects and poor adherence to treatment. To improve drug solubility during liposome preparation, DMSO is the most widely used solvent. This raises concern about the potential effect of DMSO on membranes and leads us to investigate, using DSC and EPR, the influence of DMSO on the behavior of lipid model membranes of DMPC and DPPC. In addition, we tested the influence of DMSO on drug–membrane interaction, using compounds with different hydrophobicity and varying DMSO content, using the same experimental techniques. Overall, it was found that with up to 10% DMSO, changes in the bilayer fluidity or the thermotropic properties of the studied liposomes were not significant, within the experimental uncertainty. For higher concentrations of DMSO, there is a stabilization of both the gel and the rippled gel phases, and increased bilayer fluidity of DMPC and DPPC liposomes leading to an increase in membrane permeability. [ABSTRACT FROM AUTHOR]

Correlations of electronic and magnetic resonance parameters of spin charge carriers in thiophene oligomers with their polymerization degrees and conformations have been established by comparison of theoretically obtained density functional theory (DFT) and electron paramagnetic resonance (EPR) data with experimental results. [ABSTRACT FROM AUTHOR]

The origin of the common blue 450 nm (2.8 eV) cathodoluminescence (CL) emission in natural and synthetic quartz has been investigated using a combination of CL microscopy and spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and trace-element analysis by electron micro-probe analysis as well as inductively coupled plasma-mass spectrometry (ICP-MS). The study shows that the appearance of the ~450 nm emission band can be attributed to two different defects in quartz. First, a transient luminescence can be explained by structural defects in oxygen deficient quartz. The luminescence model implies self-trapped exciton (STE) emission related to oxygen vacancies. This type of CL emission is frequent in high-purity synthetic quartz and natural quartz of hydrothermal origin. Second, in Ti-rich quartz from natural samples (e.g., quartz phenocrysts in rhyolites) and synthetic quartz of Ti-difusion experiments, an additional 450 nm (2.8 eV) emission was detected, which is stable under the electron beam. The intensity of this ~450 nm emission band correlates with the concentration of trace Ti in quartz, and substitutional Ti4+ at the Si4+ position was proved by EPR spectroscopy. In quartz crystals with elevated Ti concentrations both intrinsic and extrinsic blue CL emissions at ~450 nm can coexist, hindering a thorough characterization and quantification of the CL signal. A reliable distinction of the two diferent CL emission bands is possible by fitting the peaks of the CL spectra, and the peak width of the 450 nm emission can be used to diferentiate the STE from the Ti4+ emission. However, the definitive technique is through the observation of CL peak shape change over time at a point by collecting a time series of CL spectra in conjunction with EPR spectroscopy and trace-element analysis of the Ti concentration. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) is a measurement method to research the microscopic information of magnetic materials. Because early EPR studies were limited by magnetic field strength and microwave frequency, some microscopic information of materials could not be clearly displayed. In recent years, with the development of high magnetic field technology and microwave technology, continuous wave electron paramagnetic resonance (cw-EPR) spectrometer and pulsed electron paramagnetic resonance (pulsed EPR) spectrometer have been fully used under high frequency and high field, and the sensitivity, spectral resolution and other performance indicators of the spectrometer have also been improved. This paper mainly introduces the principle and structure of EPR spectrometer under high frequency and high field, its development history and research status both domestically and internationally, and the latest application in related fields.

Optical thermometers are advantageous for temperature measurement in electromagnetic fields and aggressive environments; however, their composition mostly relies on materials doped with expensive and resource-limited rare earth ions. In this article, we describe the application of calcium aluminate doped with transition metal ions (Mn2+ and Cr3+) in optical thermometry, employing optical fibres for signal transmission. Upon excitation with 450 nm laser diode radiation, changes in the luminescence of Mn2+ ions in the 500–550 nm band are followed along with changes in the Cr3+ band at 750–800 nm. The application has been tested in the temperature range from 20 °C to 800 °C. The temperature dependence of Cr3+ luminescence encompasses the high-temperature range, whereas the luminescence band of Mn2+ ions gives an increase in the total intensity and provides a more consistent change in the range from 400 °C to 550 °C. [ABSTRACT FROM AUTHOR]

Salvia rosmarinus Spenn. is a native Mediterranean shrub belonging to the Lamiaceae family and is well-known as a flavoring and spicing agent. In addition to its classical use, it has drawn attention because its biological activities, due particularly to the presence of polyphenols, including carnosic acid and rosmarinic acid, and phenolic diterpenes as carnosol. In this study, the aerial part of rosemary was extracted with a hydroalcoholic solution through maceration, followed by ultrasound sonication, to obtain a terpenoids-rich Salvia rosmarinus extract (TRSrE) and a polyphenols-rich Salvia rosmarinus extract (PRSrE). After phytochemical characterization, both extracts were investigated for their antioxidant activity through a classical assay and with electron paramagnetic resonance (EPR) for their DPPH and hydroxyl radicals scavenging. Finally, their potential beneficial effects to reduce lipid accumulation in an in vitro model of NAFLD were evaluated. [ABSTRACT FROM AUTHOR]

The study and characterization of the biophysical properties of membranes and drug–membrane interactions represent a critical step in drug development, as biological membranes act as a barrier that the drug must overcome to reach its active site. Liposomes are widely used in drug delivery to circumvent the poor aqueous solubility of most drugs, improving systemic bioavailability and pharmacokinetics. Further, they can be targeted to deliver to specific disease sites, thus decreasing drug load, and reducing side effects and poor adherence to treatment. To improve drug solubility during liposome preparation, DMSO is the most widely used solvent. This raises concern about the potential effect of DMSO on membranes and leads us to investigate, using DSC and EPR, the influence of DMSO on the behavior of lipid model membranes of DMPC and DPPC. In addition, we tested the influence of DMSO on drug–membrane interaction, using compounds with different hydrophobicity and varying DMSO content, using the same experimental techniques. Overall, it was found that with up to 10% DMSO, changes in the bilayer fluidity or the thermotropic properties of the studied liposomes were not significant, within the experimental uncertainty. For higher concentrations of DMSO, there is a stabilization of both the gel and the rippled gel phases, and increased bilayer fluidity of DMPC and DPPC liposomes leading to an increase in membrane permeability.

Many peptide-activated rhodopsin-like GPCRs share a β-hairpin folding motif in the extracellular loop 2 (ECL2), which interacts with the peptide ligand while at the same time being connected to transmembrane helix 3 (TM3) via a highly conserved disulfide bond. Currently, it remains unknown whether the coupling of the specifically shaped ECL2 to TM3 influences the activation of peptide-activated GPCRs. We investigated this possibility in a selection of peptide GPCRs with known structures. Most of the receptors with cysteine to alanine mutations folded like the respective wild-type and resided in the cell membrane, challenging pure folding stabilization by the disulfide bridge. G-protein signaling of the disulfide mutants was retained to a greater extent in secretin-like GPCRs than in rhodopsin-like GPCRs, while recruitment of arrestin was completely abolished in both groups, which may be linked to alterations in ligand residence time. We found a correlation between receptor activity of the neuropeptide Y2 receptor and alterations in ECL2 dynamics using engineered disulfide bridges or site-directed spin labeling and EPR spectroscopy. These data highlight the functional importance of the TM3-ECL2 link for the activation of specific signaling pathways in peptide-activated GPCRs, which might have implications for future drug discovery. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is a very promising platform for quantum information processing, as it can host room temperature solid state defect quantum bits. These room temperature quantum bits are realized by paramagnetic silicon vacancy and divacancy defects in SiC that are typically introduced by irradiation techniques. However, irradiation techniques often introduce unwanted defects near the target quantum bit defects that can be detrimental for the operation of quantum bits. Here, we demonstrate that by adding aluminum precursor to the silicon and carbon sources, quantum bit defects are created in the synthesis of SiC without any post treatments. We optimized the synthesis parameters to maximize the paramagnetic defect concentrations—including already established defect quantum bits—monitored by electron spin resonance spectroscopy. [ABSTRACT FROM AUTHOR]

Corn silk (CS) extracts are reported to contain flavonoids (appx. 59.65 mg quercetin/g), polysaccharides (appx. 58.75 w.%), steroids (appx. 38.3 × 10−3 to 368.9 × 10−3 mg/mL), polyphenols (appx. 77.89 mg/GAE/g) and other functional biological substances. This study investigated the antioxidant activity of corn silk extracts related to their functional compounds. The radical scavenging effect of corn silk extracts was evaluated by the spin-trapping electron paramagnetic resonance (EPR) technique, 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonate) (ABTS•+) free radical measurement, ferric ion-reducing antioxidant power, and copper ion reductive capacity. It was found that the maturity stage of CS plant materials and the applied extraction procedure of their bioactive compounds have a profound effect on the radical scavenging capacity. Differences in the antioxidant activity of the studied corn silk samples based on their maturity were also confirmed. The strongest DPPH radical scavenging effect was observed for the corn silk mature stage (CS-M)stage (CS-MS) (65.20 ± 0.90)%, followed by the silky stage (CS-S) (59.33 ± 0.61)% and the milky stage (CS-M) (59.20 ± 0.92)%, respectively. In general, the final maturity stage (CS-MS) provided the most potent antioxidant effect, followed by the earliest maturity stage (CS-S) and the second maturity stage (CS-M). [ABSTRACT FROM AUTHOR]

The effect of nanosecond electromagnetic pulses on human health, and especially on forming free radicals in human cells, is the subject of continuous research and ongoing discussion. This work presents a preliminary study on the effect of a single high-energy electromagnetic pulse on morphology, viability, and free radical generation in human mesenchymal stem cells (hMSC). The cells were exposed to a single electromagnetic pulse with an electric field magnitude of ~1 MV/m and a pulse duration of ~120 ns generated from a 600 kV Marx generator. The cell viability and morphology at 2 h and 24 h after exposure were examined using confocal fluorescent microscopy and scanning electron microscopy (SEM), respectively. The number of free radicals was investigated with electron paramagnetic resonance (EPR). The microscopic observations and EPR measurements showed that the exposure to the high-energy electromagnetic pulse influenced neither the number of free radicals generated nor the morphology of hMSC in vitro compared to control samples. [ABSTRACT FROM AUTHOR]

The improvement of our living standards puts forward higher requirements for energy storage systems, especially rechargeable batteries. Unfortunately, phenomena such as capacity failure, etc. have been major difficulties in the field of energy storage. Therefore, we need some advanced means to explore the reaction process and mechanisms of the cell. Electron paramagnetic resonance (EPR) has the advantages of a high sensitivity to electrons, lack of damage to samples, quantitative analysis, etc., which can make for a more in-depth exploration of most paramagnetic electrode materials and metal electrode materials. After a brief description of the principle of EPR, this review briefly summarizes the application of EPR to the characterization of transition metal oxide cathode and lithium metal anode electrode materials in recent years, such as showing how to study electrode materials by using EPR in situ and operando. [ABSTRACT FROM AUTHOR]

Ceramics with nominal chemical composition CaCu3Ti4O12 (CCTO), CaCu3Ti3.96Al0.04O11.96F0.04 (CCTOAF), and Ca0.98Mg0.08Cu2.94Ti3.96Al0.04O11.96F0.04 (CCTOMAF) were prepared by the solid-state reactions technique. Using SEM, EDX, XPS, EPR, NMR, and complex impedance spectroscopy, the microstructure, elements distribution, chemical composition of grains and grain boundaries, and the dielectric response of ceramics were investigated. In the ССТО, CCTOAF, and CCTOMAF series, the average grain size increases, the degree of copper segregation at the grain boundaries is inversely related to grain size, and the dielectric loss decreases from 0.071 to 0.047 and 0.030, respectively, while dielectric permittivity ε′ at 1 kHz is 5.6 × 104, 7.1 × 104, and 4.3 × 104, respectively. Additives of Al, Mg, F and milled particles (ZrO2, Al2O3, and SiO2) can either partially introduce into the perovskite structure or form low-melting eutectics at the grain boundaries, causing abnormal grain growth. The presence of copper ions in various oxidation states, as well as evidence of exchange spin interactions between them, was confirmed in all samples.

The enamel matrix protein Ameloblastin (Ambn) has critical physiological functions, including regulation of mineral formation, cell differentiation, and cell–matrix adhesion. We investigated localized structural changes in Ambn during its interactions with its targets. We performed biophysical assays and used liposomes as a cell membrane model. The xAB2N and AB2 peptides were rationally designed to encompass regions of Ambn that contained self-assembly and helix-containing membrane-binding motifs. Electron paramagnetic resonance (EPR) on spin-labeled peptides showed localized structural gains in the presence of liposomes, amelogenin (Amel), and Ambn. Vesicle clearance and leakage assays indicated that peptide–membrane interactions were independent from peptide self-association. Tryptophan fluorescence and EPR showed competition between Ambn–Amel and Ambn–membrane interactions. We demonstrate localized structural changes in Ambn upon interaction with different targets via a multitargeting domain, spanning residues 57 to 90 of mouse Ambn. Structural changes of Ambn following its interaction with different targets have relevant implications for the multifunctionality of Ambn in enamel formation. [ABSTRACT FROM AUTHOR]

Nitroxides are potent tools for studying biological systems by electron paramagnetic resonance (EPR). Whatever the application, a certain stability is necessary for successful detection. Since conventional tetramethyl-substituted cyclic nitroxides have insufficient in vivo stability, efforts have recently been made to synthesize more stable, tetraethyl-substituted nitroxides. In our previous study on piperidine nitroxides, the introduction of steric hindrance around the nitroxide moiety successfully increased the resistance to reduction into hydroxylamine. However, it also rendered the carbon backbone susceptible to modifications by xenobiotic metabolism due to increased lipophilicity. Here, we focus on a new series of three nitroxide candidates with tetraethyl substitution, namely with pyrrolidine, pyrroline, and isoindoline cores, to identify which structural features afford increased stability for future probe design and application in in vivo EPR imaging. In the presence of rat liver microsomes, pyrrolidine and pyrroline tetraethyl nitroxides exhibited a higher stability than isoindoline nitroxide, which was studied in detail by HPLC-HRMS. Multiple metabolites suggest that the aerobic transformation of tetraethyl isoindoline nitroxide is initiated by hydrogen abstraction by P450-FeV = O from one of the ethyl groups, followed by rearrangement and further modifications by cytochrome P450, as supported by DFT calculations. Under anaerobic conditions, only reduction by rat liver microsomes was observed with involvement of P450-FeII. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR) parameters—g factors gi (i = || and ⊥) and hyperfine structure constants Ai (M) and Ai(N), with M and N belonging to isotopes 63Cu2+ and 65Cu2+—and local structure of Cu2+ ion occupying W6+ site in CaWO4 crystal are theoretically studied based on the perturbation formulas of these parameters for a 3d9 ion under tetragonally elongated tetrahedra. In these formulas, the ligand orbital (LO) and spin–orbit coupling (SOC) contributions are included due to the shorter impurity‐ligand distance R (≈1.83 Å) and hence the strong covalency of the studied [CuO4]6− cluster, and the related molecular orbital coefficients are quantitatively determined from the cluster approach in a uniform way; meanwhile, the required crystal field (CF) parameters for the tetragonally distorted tetrahedron (TDT) are estimated from the superposition model and the local structure of the impurity Cu2+ center. According to the calculation, the bond angle θ between the four equivalent Cu2+‐O2− bonds and the C4 axis in the CaWO4:Cu2+ is found to be about 2.1° smaller than that (θ0 ≈ 54.74°) for an ideal tetrahedron due to the Jahn–Teller (JT) effect and the size mismatch. The fitted results agree well with the observed values, and the validity of the present assignment for the local structure of the Cu2+ center is also discussed. [ABSTRACT FROM AUTHOR]

Olea europaea L. is a plant belonging to the Oleaceae family, widely grown around the Mediterranean Basin and its leaves are a source of phenolic compounds with antioxidant and anti-inflammatory capacity. Among these, oleuropein and luteolin-7-O-glucoside represent two major polyphenolic compounds in olive-leaf extract. Herein, a polystyrene resin was used to recover the polyphenolic fraction from the acetone-water leaf extract from Nocellara del Belice cultivar, which showed the higher level of analysed bioactive compounds, compared to Carolea cultivar. The antioxidant activity of the extract concentrated in phenolic compounds (OLECp) was evaluated through a classical assay and electron paramagnetic resonance (EPR) for DPPH and hydroxyl radicals scavenging. Thus, the anti-inflammatory activity and the potential beneficial effects in reducing lipid accumulation in an in vitro model of NAFLD using McA-RH7777 cells exposed to oleic acid (OA) were evaluated. Nile Red and Oil Red O have been used to stain the lipid accumulation, while the inflammatory status was assessed by Cytokines Bioplex Assay. OLECp (TPC: 92.93 ± 9.35 mg GAE/g, TFC: 728.12 ± 16.04 mg RE/g; 1 g of extract contains 315.250 mg of oleuropein and 17.44 mg of luteolin-7-O-glucoside) exerted a good radical scavenging capability (IC50: 2.30 ± 0.18 mg/mL) with a neutralizing power against DPPH and hydroxyl radicals, as confirmed by the decreased signal area of the EPR spectra. Moreover, OLECp at concentration of 25, 50 and 100 μg/mL counteracted the intracellular inflammatory status, as result of decreased intracellular lipid content. Our results highlighted the multiple properties and applications of an O. europaea extract concentrated in polyphenols, and the possibility to formulate novel nutraceuticals with antioxidant properties, destined to ameliorate human health. [ABSTRACT FROM AUTHOR]

According to the high‐order perturbation formulae of 3d5(Mn2+) and 3d9(Cu2+) ions in octahedron, the local structures and electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants A) for Cu2+ and Mn2+ in CdO are theoretically studied in a consistent way. Due to the Jahn–Teller effect, both the substituted sites of Cu2+ and Mn2+ show the tetragonally elongated distortion with different elongation τ. Meanwhile, the crystal field and covalency around doped Cu2+ and Mn2+ are obtained, which can account for the electronic properties in doped CdO. In order to make further investigation of the potential optical and electrical properties, the band structure and density of states (DOS) of pure and transition metal ions (TMs) doped CdO are comparably calculated through density functional theory (DFT). The results show that the band gap of Mn2+‐ and Cu2+‐doped CdO can be effectively reduced, due to the improved covalency between the central ions and ligand ions. [ABSTRACT FROM AUTHOR]

Petroleum asphaltenes are considered the most irritating components of various oil systems, complicating the extraction, transportation, and processing of hydrocarbons. Despite the fact that the paramagnetic properties of asphaltenes and their aggregates have been studied since the 1950s, there is still no clear understanding of the structure of stable paramagnetic centers in petroleum systems. The paper considers the possibilities of various electron paramagnetic resonance (EPR) techniques to study petroleum asphaltenes and their solubility fractions using a carbon-centered stable free radical (FR) as an intrinsic probe. The dilution of asphaltenes with deuterated toluene made it possible to refine the change in the structure at the initial stage of asphaltene disaggregation. From the measurements of samples of bitumen, a planar circumcoronene-like model of FR structure and FR-centered asphaltenes is proposed. The results show that EPR-based approaches can serve as sensitive numerical tools to follow asphaltenes' structure and their disaggregation. [ABSTRACT FROM AUTHOR]

In this work, we theoretically investigate the local structure and electronic paramagnetic resonance (EPR) parameters (g-factors gi and A-constants Ai, i = //, ⊥) of tetragonal Cu2+ centers in phosphate glasses (xCuO⋅(1 – x)[2P2O5⋅Na2O] (0.5< x < 5 mol %)) with the aid of the three-order perturbation formulae of these parameters for 3d9 ions in tetragonally distorted tetrahedra based on the cluster approach. In our calculations, both contributions to EPR parameters from the spin-orbit (SO) coupling interactions of the central Cu2+ ions and the ligand orbital and SO coupling interactions are included. The crystal-field parameters related to the splitting of d-orbitals are calculated from the superposition model and the local structures of the studied Cu2+ centers in the glasses. Based on the calculations, the local bond angle is found to be about 3.78° larger than that of the ideal tetrahedral site, resulting in a slightly compressed ligand tetrahedron. The relative contributions to the g-factors from the ligand orbital and SO coupling interactions are more important than those from the third-order perturbation terms. The theoretical results show good agreement with the experimental values. The signs and the less anisotropy (ΔA = |A//| – |A⊥|) of A-constants for the tetrahedral Cu2+ centers are discussed. [ABSTRACT FROM AUTHOR]

This paper presents the effect of selected alcohols on the fluidity of liposome membranes obtained in sonication of DPPC lecithin. Using the EPR technique, the duality of propanol, n-butanol and pentanol on the behaviour of the aqueous dispersion of liposomes was demonstrated. It was shown that after exceeding a certain concentration, these alcohols initiate dispersion foaming, leading to phase separation: liposome dispersion - lipid foam. The influence of the shape of the molecule and the length of hydrocarbon chains on the effectiveness of destabilisation of the structure of lipid membranes was indicated. [ABSTRACT FROM AUTHOR]

We present a new photoswitchable spin label for light-induced pulsed electron paramagnetic resonance dipolar spectroscopy (LiPDS), the photoexcited triplet state of erythrosin B (EB), which is ideal for biological applications. With this label, we perform an in-depth study of the orientational effects in dipolar traces acquired using the refocused laser-induced magnetic dipole technique to obtain information on the distance and relative orientation between the EB and nitroxide labels in a rigid model peptide, in good agreement with density functional theory predictions. Additionally, we show that these orientational effects can be averaged to enable an orientation-independent analysis to determine the distance distribution. Furthermore, we demonstrate the feasibility of these experiments above liquid nitrogen temperatures, removing the need for expensive liquid helium or cryogen-free cryostats. The variety of choices in photoswitchable spin labels and the affordability of the experiments are critical for LiPDS to become a widespread methodology in structural biology. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the effect of electron beam irradiation (EBI) at a dose of 25 kGy on the stability and antioxidant properties of resveratrol (RSV), a nutraceutical with clinically proven activity. The electron paramagnetic resonance (EPR) method was used to evaluate the concentration of free radicals after irradiation. Minor changes in chemical structure due to free radicals induced by EBI were confirmed by FTIR spectroscopy. HPLC and HPLC-MS analysis ruled out the appearance of degradation products after irradiation. In addition, HPLC analysis confirmed the absence of trans- to cis-resveratrol conversion. Changes in the antioxidant potential of RSV after irradiation were studied using DPPH, ABTS, CUPRAC, and FRAP techniques. It was confirmed that EBI favorably affected the antioxidant properties of tests based on the HAT mechanism (increase in DPPH and CUPRAC tests). [ABSTRACT FROM AUTHOR]

We explored the capability of low-frequency Electron Paramagnetic Resonance (EPR) to noninvasively detect melanin (a stable semiquinone free radical) in the human skin. As previous in vitro studies on biopsies suggested that the EPR signal from melanin was different when measured in skin melanomas or benign nevi, we conducted a prospective first-in-man clinical EPR study in patients with skin lesions suspicious of melanoma. EPR spectra were obtained using a spectrometer operating at 1 GHz, with a surface coil placed over the area of interest. Two clinical studies were carried out: 1) healthy volunteers (n = 45) presenting different skin phototypes; 2) patients (n = 88) with skin lesions suspicious of melanoma (n = 100) requiring surgical resection. EPR data obtained before surgery were compared with histopathology results. The method was not sensitive enough to measure differences in melanin content due to changes in skin pigmentation. In patients, 92% of the spectra were analyzable. The EPR signal of melanin was significantly higher (p < 0.0001) in melanoma lesions (n = 26) than that in benign atypical nevi (n = 62). A trend toward a higher signal intensity (though not significant) was observed in high Breslow depth melanomas (a marker of skin invasion) than in low Breslow lesions. To date, no naturally occurring free radicals have been detected by low-frequency EPR systems adapted for clinical studies. Here, we demonstrated for the first time the ability of this technology to detect an endogenous free radical, opening new avenues for evaluating clinical EPR as a potential aid in the diagnosis of pigmented skin lesions. [Display omitted] • Skin lesion characterization before surgery could accelerate patient management. • Melanin is an endogenous stable semiquinone free radical. • First-in-man clinical EPR study to detect noninvasively melanin in skin lesions. • Study on 100 lesions suspicious of melanoma requiring surgical resection. • EPR signal of melanin was higher in melanoma compared to atypical nevi. [ABSTRACT FROM AUTHOR]

Non-thermal plasma (NTP) induces the generation of reactive oxygen species (ROS) and reactive nitrogen species, such as hydroxyl radicals (•OH), hydrogen peroxide (H2O2), singlet oxygen, superoxide, ozone, and nitric oxide, at near-physiological temperatures. These molecules promote blood coagulation, wound healing, disinfection, and selective cancer cell death. Based on these evidences, clinical trials of NTP have been conducted for treating chronic wounds and head and neck cancers. Although clinical applications have progressed, the stoichiometric quantification of NTP-induced ROS remains unclear in the liquid phase in the presence of FeCl2 or FeCl3 in combination with biocompatible reducing agents, which may modulate the final biological effects of NTP. In this study, we employed electron paramagnetic resonance spectroscopy to quantify ROS using spin-trapping probe, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and H2O2, using luminescent probe in the presence of FeCl2 or FeCl3. NTP-induced DMPO-OH levels were elevated 10–100 µM FeCl2 or 500 and 1000 µM FeCl3. NTP-induced DMPO-OH with 10 µM FeCl2 or FeCl3 was significantly scavenged by ascorbate, α-tocopherol, dithiothreitol, reduced glutathione, or oxidized glutathione, whereas dehydroascorbate was ineffective in 2 mM DMPO. NTP-induced H2O2 was significantly degraded by 100 µM FeCl2 and FeCl3 in an iron-dependent manner. Meanwhile, decomposition of H2O2 by catalase decayed DMPO-OH efficiently in the presence of iron, indicating iron causes DMPO-OH production and degradation simultaneously. These results suggest that NTP-induced DMPO-OH is generated by the H2O2-consuming, iron-dependent Fenton reaction and ferryl intermediates. The potential iron-mediated ROS production by NTP is also discussed to clarify the interaction between NTP-induced ROS and biomolecules. [ABSTRACT FROM AUTHOR]

This study reports, for the first time, the possibility of exploitation of the defect chemistry to suppress the hexagonal phase formation in donor–acceptor co-doped BaTiO3. Systematic Raman and electron paramagnetic resonance spectroscopic investigations have been carried out to understand the mechanism responsible for the suppression of hexagonal phase in Lanthanum and manganese co-doped BaTiO3. Stabilization of the perovskite phase is related to the donor/acceptor ratio and the doping mechanism. Suppression of the hexagonal phase is found to be facile in barium-deficient compositions, whereas in titanium-deficient compositions, coexistence of cubic and hexagonal phase is observed at [La3+] ≥ 0.02. However, in highly B-site acceptor-doped compositions, [Mn3+] ≥ 0.01, h-phase stabilization occurs irrespective of donor/acceptor ratio in both barium- and titanium-deficient compositions. This has opened up a new pathway for the synthesis of hexagonal phase-free donor–acceptor co-doped BaTiO3. [ABSTRACT FROM AUTHOR]

The mammalian fetus thrives at oxygen tensions much lower than those of adults. Gestation at high altitude superimposes hypoxic stresses on the fetus resulting in increased erythropoiesis. We hypothesized that chronic hypoxia at high altitude alters the homeostasis of iron and bioactive nitric oxide metabolites (NOx) in gestation. To test for this, electron paramagnetic resonance was used to provide unique measurements of iron, metalloproteins, and free radicals in the blood and aorta of fetal and maternal sheep from either high or low altitudes (3801 or 300 m). Using ozone-based chemiluminescence with selectivity for various NOx species, we determined the NOx levels in these samples immediately after collection. These experiments demonstrated a systemic redistribution of iron in high altitude fetuses as manifested by a decrease in both chelatable and total iron in the aorta and an increase in non-transferrin bound iron and total iron in plasma. Likewise, high altitude altered the redox status diversely in fetal blood and aorta. This study also found significant increases in blood and aortic tissue NOx in fetuses and mothers at high altitude. In addition, gradients in NOx concentrations observed between fetus and mother, umbilical artery and vein, and plasma and RBCs demonstrated complex dynamic homeostasis of NOx among these circulatory compartments, such as placental generation and efflux as well as fetal consumption of iron-nitrosyls in RBCs, probably HbNO. In conclusion, these results may suggest the utilization of iron from non-hematopoietic tissues iron for erythropoiesis in the fetus and increased NO bioavailability in response to chronic hypoxic stress at high altitude during gestation. [ABSTRACT FROM AUTHOR]

This study reports, for the first time, the possibility of exploitation of the defect chemistry to suppress the hexagonal phase formation in donor–acceptor co-doped BaTiO3. Systematic Raman and electron paramagnetic resonance spectroscopic investigations have been carried out to understand the mechanism responsible for the suppression of hexagonal phase in Lanthanum and manganese co-doped BaTiO3. Stabilization of the perovskite phase is related to the donor/acceptor ratio and the doping mechanism. Suppression of the hexagonal phase is found to be facile in barium-deficient compositions, whereas in titanium-deficient compositions, coexistence of cubic and hexagonal phase is observed at [La3+] ≥ 0.02. However, in highly B-site acceptor-doped compositions, [Mn3+] ≥ 0.01, h-phase stabilization occurs irrespective of donor/acceptor ratio in both barium- and titanium-deficient compositions. This has opened up a new pathway for the synthesis of hexagonal phase-free donor–acceptor co-doped BaTiO3. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes (AOPs) are rapidly evolving but still lack well-established protocols for reliably identifying oxidative reactive species (ORSs). This Perspective presents both the radical and nonradical ORSs that have been identified or proposed, along with the extensive controversies surrounding oxidative mechanisms. Conventional identification tools, such as quenchers, probes, and spin trappers, might be inadequate for the analytical demands of systems in which multiple ORSs coexist, often yielding misleading results. Therefore, the challenges of identifying these complex, short-lived, and transient ORSs must be fully acknowledged. Refining analytical methods for ORSs is necessary, supported by rigorous experiments and innovative paradigms, particularly through kinetic analysis based on in situ spectroscopic techniques and multiple-probe strategies. To demystify these complex ORSs, future efforts should be made to develop advanced tools and strategies to enhance the mechanism understanding. In addition, integrating real-world conditions into experimental designs will establish a reliable framework in fundamental studies, providing more accurate insights and effectively guiding the design of AOPs.

The NAD + -reducing soluble [NiFe] hydrogenase (SH) is the key enzyme for production and consumption of molecular hydrogen (H 2 ) in Synechocystis sp. PCC6803. In this study, we focused on the reductase module of the SynSH and investigated the structural and functional aspects of its subunits, particularly the so far elusive role of HoxE. We demonstrated the importance of HoxE for enzyme functionality, suggesting a regulatory role in maintaining enzyme activity and electron supply. Spectroscopic analysis confirmed that HoxE and HoxF each contain one [2Fe2S] cluster with an almost identical electronic structure. Structure predictions, alongside experimental evidence for ferredoxin interactions, revealed a remarkable similarity between SynSH and bifurcating hydrogenases, suggesting a related functional mechanism. Our study unveiled the subunit arrangement and cofactor composition essential for biological electron transfer. These findings enhance our understanding of NAD + -reducing [NiFe] hydrogenases in terms of their physiological function and structural requirements for biotechnologically relevant modifications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Silicon carbide (SiC) is a very promising platform for quantum information processing, as it can host room temperature solid state defect quantum bits. These room temperature quantum bits are realized by paramagnetic silicon vacancy and divacancy defects in SiC that are typically introduced by irradiation techniques. However, irradiation techniques often introduce unwanted defects near the target quantum bit defects that can be detrimental for the operation of quantum bits. Here, we demonstrate that by adding aluminum precursor to the silicon and carbon sources, quantum bit defects are created in the synthesis of SiC without any post treatments. We optimized the synthesis parameters to maximize the paramagnetic defect concentrations—including already established defect quantum bits—monitored by electron spin resonance spectroscopy.

The spin–Hamiltonian parameters g–factors ( g | | and g ⊥ ) of the Ce3+ paramagnetic centers in BaWO4: Ce and BaWO4: Ce, Na single crystals with axial symmetry are investigated using the superposition model (SPM) via complete diagonalization procedure of energy matrix (CDM method). The calculated g–factors are in reasonable agreement with the experimental values. The fitted intrinsic parameters are comparable with data from other publications for rare-earth paramagnetic centers in a similar environment. The angular distortions of the cerium dodecahedron [CeO8] are also studied. Structural analysis of paramagnetic centers with axial symmetry through the postulated cerium barium tetrahedron [CeBa4] connected via oxygens bridges was carried out. The mechanism of the charge compensation and the role of the second dopant (Na+) is also discussed. [ABSTRACT FROM AUTHOR]

For 3d1 (V4+) impurity in 30PbO‐5Bi2O3‐(65‐x)SiO2 glass systems with different concentrations x of V2O5, the defect structures and gyromagnetic factors are theoretically investigated by using the perturbation formulas of g factors for a tetragonally compressed octahedral 3d1 group. The concentration dependences of d‐d transition band and g factors are suitably explained from the Fourier type concentration functions of the cubic crystal field parameter Dq, covalency factor N and relative tetragonal compression ratio ρ. The above concentration dependences of these quantities are suitably illustrated by the modifications of the local crystal field strength and electron cloud distribution with increasing x. The concentration variations of the electrical conductivity and dielectric relaxation are further analyzed from the stability of the systems in view of two competitive factors (increasing network polymerization and bulk stability at low concentrations and decreasing former SiO2 and stability at high concentrations). [ABSTRACT FROM AUTHOR]