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Lung surfactant is a mixture of lipids and proteins and is essential for air breathing in mammals. The hydrophobic surfactant proteins B and C (SP-B and SP-C) assist in reducing surface tension in the lung alveoli by organizing the surfactant lipids. SP-B deficiency is life-threatening, and a lack of SP-C can lead to progressive interstitial lung disease. B-YL (41 amino acids) is a highly surface-active, sulfur-free peptide mimic of SP-B (79 amino acids) in which the four cysteine residues are replaced by tyrosine. Mammalian SP-C (35 amino acids) contains two cysteine-linked palmitoyl groups at positions 5 and 6 in the N-terminal region that override the β-sheet propensities of the native sequence. Canine SP-C (34 amino acids) is exceptional because it has only one palmitoylated cysteine residue at position 4 and a phenylalanine at position 5. We developed canine SP-C constructs in which the palmitoylated cysteine residue at position 4 is replaced by phenylalanine (SP-Cff) or serine (SP-Csf) and a glutamic acid-lysine ion-lock was placed at sequence positions 20-24 of the hydrophobic helical domain to enhance its alpha helical propensity. AI modeling, molecular dynamics, circular dichroism spectroscopy, Fourier Transform InfraRed spectroscopy, and electron spin resonance studies showed that the secondary structure of canine SP-Cff ion-lock peptide was like that of native SP-C, suggesting that substitution of phenylalanine for cysteine has no apparent effect on the secondary structure of the peptide. Captive bubble surfactometry demonstrated higher surface activity for canine SP-Cff ion-lock peptide in combination with B-YL in surfactant lipids than with canine SP-Csf ion-lock peptide. These studies demonstrate the potential of canine SP-Cff ion-lock peptide to enhance the functionality of the SP-B peptide mimic B-YL in synthetic surfactant lipids.

Flavor plays an essential role in the sensory and consumer acceptance of complementary food products for infants and young children. To improve the quality of infant complementary food nutrition powder, the volatile flavor substances in nutrition powder and those with kiwifruit powder, orange powder and quinoa flour were analyzed by headspace-gas chromatography-ion migration spectrometry. A total of 61 compounds were identified in the nutrition powder of two different formulations, of which 58 could be clearly identified. The study showed that supplementation with kiwifruit powder, orange powder and quinoa flour could inhibit the production of (E)-2-nonenal, 2-octanone, delta-nonalactone, ethyl disulfide. The inhibitory rate of (E)-2-nonenal was the highest, achieving 37.00 ± 3.07%, delta-Nonalactone was 28.86 ± 3.69% and 2-octanone was 14.12 ± 0.46%. It may delay their conversion to acids, aldehydes, ketones, and other compounds. In addition, the intensity of the saturated acids signal in the YYB-300 was different significantly than the YYBS-300, which was 1.99 ± 0.07 cm−1 in the YYB-300 group, 1.941 ± 0.12 cm−1 in the YYBS-300 group, severally. The results of electron spin resonance (ESR) showed that the free radical content material of the YYB-300 group was 6.57 × 105, but the free radical content material of YYBS-300 group was low significantly, which used to be 6.18 × 105. The consequence of Fourier transforms infrared spectroscopy (FTIR), and electron spin resonance (ESR) confirmed that the addition of kiwifruit powder, orange powder and quinoa flour maybe delay the lipid oxidation. The results also provided a theoretical basis for improving the flavor quality and nutritional quality of infant nutrition powder. [ABSTRACT FROM AUTHOR]

In recent times, there has been growing interest in free radicals due to their close association with human aging and various illnesses. Cooking processes, particularly those involving smoked meat, used oil, and fat are external factors that produce free radicals. Foods rich in proteins, lipids, and carbohydrates, as well as those containing reactive ingredients, serve as primary sources of these compounds. When free radicals accumulate in the body without proper removal, oxidative stress occurs. This buildup is linked to chronic and degenerative conditions such as cancer, autoimmune diseases, aging, cataracts, rheumatoid arthritis, cardiovascular diseases, and neurological disorders. The purpose of this study was to use electron spin resonance (ESR) to detect the presence of free radicals in various meat products as a potential human threat. Twenty-five randomly selected ready-to-eat fried chicken samples were collected from several supermarkets to assess the presence of free radicals using electron spin resonance (ESR). Our results showed that free radicals were present in the examined samples at various concentrations. [ABSTRACT FROM AUTHOR]

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]

When ionizing radiations interact with polymers, free radicals are generated and are known to be the initiating species for the modification in materials. Monitoring and identifying free radicals after irradiation allow assessing the impact of X‐rays and gamma rays on materials. A comparative study has been performed on materials made from polypropylene and polyethylene after irradiation by the two irradiation technologies. Electron spin resonance (ESR) signal has been monitored up to 380 days when signal was still present. ESR signals, concentration profiles, and kinetics were observed after X‐rays and gamma rays. [ABSTRACT FROM AUTHOR]

Background: Anesthetic agents, particularly intravenous anesthetics, may affect immune function and tumorigenic factors. We herein investigated whether the anti‐inflammatory effects of anesthetic agents are attributed to their antioxidant properties. The antioxidant and anti‐inflammatory effects of remimazolam, a new anesthetic, remain unclear. We hypothesized that remimazolam exerts anti‐inflammatory effects due to its antioxidant properties, which may affect the postoperative inflammatory response. This retrospective clinical study examined this hypothesis using laboratory and clinical approaches. Methods: The antioxidant effects of remimazolam and dexmedetomidine were assessed by electron spin resonance (ESR) spectroscopy, and postoperative inflammatory responses were compared in 143 patients who underwent transcatheter aortic valve replacement at Kindai University Hospital between April 2021 and December 2022. The primary endpoint was the presence or absence of the antioxidant effects of the anesthetics themselves using ESR. Results: Remimazolam at clinical concentrations exerted antioxidant effects, whereas dexmedetomidine did not. Increases in C‐reactive protein (CRP) levels on POD3 from preoperative values were significantly smaller in the remimazolam group than in the dexmedetomidine group (1.33 ± 1.29 vs. 2.17 ± 1.84, p =.014). Conclusions: Remimazolam exerted stronger anti‐inflammatory effects than dexmedetomidine, and these effects were enhanced by its antioxidant properties, which may have affected postoperative CRP production. [ABSTRACT FROM AUTHOR]

Xylanases are of significant interest for biomass conversion technologies. Here, we investigated the allosteric regulation of xylan hydrolysis by the Bacillus subtilis GH11 endoxylanase. Molecular dynamics simulations (MDS) in the presence of xylobiose identified binding to the active site and two potential secondary binding sites (SBS) around surface residues Asn54 and Asn151. Arabinoxylan titration experiments with single cysteine mutants N54C and N151C labeled with the thiol‐reactive fluorophore acrylodan or the ESR spin‐label MTSSL validated the MDS results. Ligand binding at the SBS around Asn54 confirms previous reports, and analysis of the second SBS around N151C discovered in the present study includes residues Val98/Ala192/Ser155/His156. Understanding the regulation of xylanases contributes to efforts for industrial decarbonization and to establishing a sustainable energy matrix. [ABSTRACT FROM AUTHOR]

Abstract Background Anesthetic agents, particularly intravenous anesthetics, may affect immune function and tumorigenic factors. We herein investigated whether the anti‐inflammatory effects of anesthetic agents are attributed to their antioxidant properties. The antioxidant and anti‐inflammatory effects of remimazolam, a new anesthetic, remain unclear. We hypothesized that remimazolam exerts anti‐inflammatory effects due to its antioxidant properties, which may affect the postoperative inflammatory response. This retrospective clinical study examined this hypothesis using laboratory and clinical approaches. Methods The antioxidant effects of remimazolam and dexmedetomidine were assessed by electron spin resonance (ESR) spectroscopy, and postoperative inflammatory responses were compared in 143 patients who underwent transcatheter aortic valve replacement at Kindai University Hospital between April 2021 and December 2022. The primary endpoint was the presence or absence of the antioxidant effects of the anesthetics themselves using ESR. Results Remimazolam at clinical concentrations exerted antioxidant effects, whereas dexmedetomidine did not. Increases in C‐reactive protein (CRP) levels on POD3 from preoperative values were significantly smaller in the remimazolam group than in the dexmedetomidine group (1.33 ± 1.29 vs. 2.17 ± 1.84, p = .014). Conclusions Remimazolam exerted stronger anti‐inflammatory effects than dexmedetomidine, and these effects were enhanced by its antioxidant properties, which may have affected postoperative CRP production.

To study the new type of dosimeter with a dose up to the ultra-high dose range of MGy, the electron spin resonance (ESR) method is used to measure the signal intensity of the sample irradiated by gamma rays or electron beams. Preliminary studies have been carried out through the selection of sensitive materials, linearity after irradiation, and stability. The results showed that the quartz can be used as a raw material for ultra-high dosimeters. After 15 min 300 ℃ proper heat treatment, the signal intensity of the irradiated quartz sample can maintain good stability within one year with a change of less than 3%. The radiation dose and the E′ signal intensity of quartz are proportional to the dose range of 10-103 kGy. The fitting coefficient is above 0.99. Compared with the high-purity quartz sample without heat treatment, the stability and R2 of fitting function of quartz sample are significantly improved. Therefore, the quartz dosimeter is suitable as a working dosimeter in the ultra-high dose range.

Currently, extensive research activities are devoted to developing persistent phosphors which extend beyond the visible range. In some emerging applications, long-lasting emission of high-energy photons is required; however, suitable materials for the shortwave ultraviolet (UV–C) band are extremely limited. This study reports a novel Sr2MgSi2O7 phosphor doped with Pr3+ ions, which exhibits UV–C persistent luminescence with maximum intensity at 243 nm. The solubility of Pr3+ in the matrix is analysed by X-ray diffraction (XRD) and optimal activator concentration is determined. Optical and structural properties are characterised by photoluminescence (PL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) spectroscopy techniques. The obtained results expand the class of UV–C persistent phosphors and provide novel insights into the mechanisms of persistent luminescence. [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 purpose of this study is to investigate the thermo-oxidative degradation behavior of polypropylene (PP) by comparing three types of pristine PP granules (consisting of homopolymer, random copolymer, and block copolymer) with their corresponding oxidized analogues. These analogues were intensely oxidized under oxygen at 90 °C for 1000 h by using the electron spin resonance (ESR) spin trapping method that can detect short-lived radical intermediates during the degradation. The degrees of oxidation could be evaluated by chemiluminescence (CL) intensity, which was related to the concentration of hydroperoxide groups generated in the PP chain. In the pristine PP samples, a small amount of hydroperoxides were found to be formed unintentionally, and their homolysis produces alkoxy radicals, RO•, which then undergo β-scission to yield chain-end aldehydes or chain-end ketones. These oxidation products continue to take part in homolysis to produce their respective carbonyl and carbon radicals. On the other hand, in the oxidized PP granules, because of their much higher hydroperoxide concentration, the two-stage cage reaction and the bimolecular decomposition of hydroperoxides are energetically favorable. Carbonyl compounds are formed in both reactions, which are then homolyzed to form the carbonyl radical species, •C(O)–. PP homopolymer produced the largest amount of carbonyl radical spin adduct; thus, it was found that the homopolymer is most sensitive to oxygen attack, and the presence of ethylene units in copolymers enhances the oxidation resistance of PP copolymers. [ABSTRACT FROM AUTHOR]

Study of the segmental mobility of polymer chains is important when the polymer is used as drag reduction agents of crude oil. Electron spin resonance (ESR) spectroscopy can provide important information about segmental dynamics of polymer chains, which is related to their microenvironment. In this article, we employed an amphiphilic polymer to study the effect of hydrophilic/hydrophobic balance of the polymers on the segmental motion of polymer chains. Poly(styrene-co-maleic acid) (PSMA) was spin labeled with 4-amino TEMPO radicals by increasing the concentration of radical moiety on the polymer chains. The PSMA and spin labeled-PSMAs (SL-PSMAs) were characterized by nuclear magnetic resonance (NMR), Fourier transform infrared (FT-IR) spectroscopy, Cyclic voltammetry (CV) and ESR techniques. Inter-polymer complexes (IPCs) of SL-PSMA-2 were prepared by employing polyethylene glycols (PEGs) of varying molecular weights. The results showed that the increased hydrophobic interactions of nitroxide radicals on the SL-PSMAs’ chains reduced the rotational mobility of spin labels and the random coil-to-globular transition of polymer chains occurred at higher pH value for SL-PSMAs, which showed a slow motion component in the ESR spectra of SL-PSMAs. Further, by increasing the molecular weight of PEGs in IPCs the complexation was increased, which also reduced the rotational motion of spin labels due to interpolymer hydrogen bonding causing a slow motion component in the ESR spectra.

[Display omitted] • NiFe 2 O 4 /Ag 2 WO 4 improved TC-HCl photocatalytic degradation under visible light. • NiFe 2 O 4 /Ag 2 WO 4 demonstrated enhanced photodegradation upto 92.3% against tetracycline. • NiFe 2 O 4 /Ag 2 WO 4 showed excellent rate constant values (k) of 0.0315 min−1. The use of tetracycline (TC-HCl) antibiotics is harmful to ecosystems worldwide. Herein, NiFe 2 O 4 /Ag 2 WO 4 nanocomposite (NC) was synthesized via the hydrothermal method for the degradation of tetracycline. The photodegradation efficiency of TC-HCl reached 92.3% after being exposed to visible light for 90 min. Additionally, the stability of the NiFe 2 O 4 /Ag 2 WO 4 nanocomposite is maintained during the photodegradation of tetracycline, as verified by the recyclability test. Degradation efficiency up to 83% was still present after six cycles. The presence of DMPO- ∙ O 2 - and DMPO-•OH is confirmed by the ESR study, when the visible exposure period expanded to 15 min. High photocatalytic performance, strong recyclability, and stability make NiFe 2 O 4 /Ag 2 WO 4 a potential antibiotic photodegradation candidate. [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 radical mechanisms of the thermal degradation of polyamide 66 (PA66) occurring under a vacuum at a temperature range between 80 °C and 240 °C (which includes the temperature of practical applications) were investigated using a spin-trapping electron spin resonance (ST-ESR) technique, as well as FTIR, TG-DTA, and GPC methods. No significant weight loss and no sign of thermal degradation are observed at this temperature range under oxygen-free conditions, but a slight production of secondary amine groups is confirmed by FTIR. GPC analysis shows a small degradation by the main chain scission. ST-ESR analysis reveals two intermediate radicals which are produced in the thermal degradation of PA66: (a) a ●CH2− radical generated by main chain scission and (b) a −●CH− radical generated by hydrogen abstraction from the methylene group of the main chain. The ST-ESR result does not directly confirm that a −NH−●CH− radical is produced, although this reaction has been previously inferred as the initiation reaction of the thermal degradation of PA; however, the presence of −●CH− radicals strongly suggests the occurrence of this initiation reaction, which takes place on the α-carbon next to the NH group. The ST-ESR analysis reveals very small levels of reaction, which cannot be observed by common analytical methods such as FTIR and NMR. [ABSTRACT FROM AUTHOR]

In order to restrain the spontaneous combustion of coal and ensure the safety of coal mine, an environment-friendly whole-processinhibiting hydrogel-tea polyphenols-halloysite nanotubes (HNTs) physicochemical composite inhibitor was prepared. The optimal ratio was determined by response-surface experiment, namely, tea polyphenol 2.42%, neutralization degree 80%, initiator dosage 1.68%, crosslinking agent 1%, and crossing point temperature 159.74°C. Compared with pure hydrogel inhibitor and tea polyphenol hydrogel inhibitor, the composite inhibitor performed superior whole-process inhibition effect, with the lowest oxygen consumption rate, CO, and CO2 production rate. The overall inhibition rate was stable at approximately 55% and its highest value was 58%, which indicated that tea polyphenols and HNTs effectively improved the thermal stability. The radical concentration treated with composite inhibitor was the lowest with the reduction of 2.784 × 1017/g lower than that of raw lignite, which proved that the composite inhibitor improved the inhibiting effect microscopically. Finally, inhibition mechanisms of the composite inhibitor were proposed. The results of this work suggest that composite inhibitor is an effective inhibitor of coal oxidation. [ABSTRACT FROM AUTHOR]

Calcium phosphates hold paramount importance as the constituents of hard tissue of living organisms. Among them, brushite (CaHPO 4 ·2H 2 O), also known as dicalcium phosphate dihydrate (DCPD), is a common precursor in phosphate synthesis and is becoming increasingly appealing as a biomaterial for bone regeneration applications. This study presents a comparative analysis of structural, morphological, thermal, and spectroscopic properties of synthetic brushite prepared by the wet precipitation method with several brushite products available from commercial vendors. Electron paramagnetic resonance (EPR) spectroscopy revealed that Mn2+ and Fe3+ ions are common trace impurities in commercial products. Following exposure to X-rays, EPR signals of several phosphorous-related radicals emerge. The annealing of the irradiated samples gives rise to broad thermally stimulated luminescence (TSL) signals in the 40–120 °C range, which correlates with the annealing kinetics of the radicals. The stability of radiation-induced EPR and TSL signals is limited by the phase transformation temperature from brushite to monetite (CaHPO 4). The results of this study provide novel insights into the formation and stability of phosphorous-related radicals and demonstrate how minuscule amounts of impurity ions can strongly influence the spectroscopic properties of brushite. • Mn2+ and Fe3+ are identified as common paramagnetic impurities in brushite. • X-ray-irradiation causes the formation of PO 4 2- and other phosphorous radicals. • TSL peaks in the 40–120 °C range are detected with maximum emission at 600 nm. • Annealing of the radicals, partially correlated with TSL, occurs in 20–150 °C range. • Radical stability is limited by the phase transformation from brushite to monetite. [ABSTRACT FROM AUTHOR]

The effects of ion-track overlapping on the ion-track grafting reactivity, which governs the properties of the resulting functional films, were investigated using a model reaction of a vinyl benzyl chloride monomer into poly(ethylene- co -tetrafluoroethylene) base films irradiated with 560 MeV 129Xe and 330 MeV 40Ar. Electron spin resonance analysis showed that a higher linear energy transfer of 560 MeV 129Xe led to a lower radical concentration, probably due to the high probability of radical recombination. The radical concentration showed a linear relationship as a function of the dose, whereas the degree of grafting (DG) showed a saturated trend at higher doses for both Xe and Ar ions. The local grafting density, defined by dividing the DG by the fluence, began to decrease from a certain fluence, which signified a higher probability of track overlapping. [ABSTRACT FROM AUTHOR]

The possibility of EPR dating for sediments using Al-h signals of fine (4–11 μm) grains of quartz has not been previously discussed. Here, the Al-h and peroxy EPR spectra of fine (4–11 μm) and coarse (63–90, 125–180 μm) sedimentary quartz from thoroughly investigated loess sites in Eastern Europe were examined. By comparing experimental spectra with a simulated signal, we evaluated the overestimation observed when using the standard approach established by Toyoda and Falguères to measure Al-h intensity for different doses of radiation, up to 40,000 Gy. This overestimation, caused by the presence of peroxy signals, was much more pronounced for fine grains. Fine grains exhibited some additional dose-dependent signals, which, for some samples, caused a complete distortion of the Al-h spectra at high doses, making it impossible to measure the standard amplitude. We propose a new approach to measuring Al-h signal intensity, focusing on the peak-to-baseline amplitude of the part of the signal at g ≈ 2.0603, which is not affected by the peroxy signals and therefore has the potential of providing more accurate results. The shapes of dose response curves constructed for coarse and fine grains using the new approach show considerable similarity, suggesting that Al-h centre formation in fine and coarse grains upon artificial radiation at room temperature follows the same pattern. [ABSTRACT FROM AUTHOR]

Quartz is one of the most common rock-forming minerals and crystallizes over a wide range of temperature and pressure conditions. This diversity of quartz crystallization environments is reflected by trace-element compositional variations, which can be used to distinguish between different source sediments. Trace elements that are incorporated into the quartz lattice form corresponding paramagnetic centers (impurity centers, such as Al and Ti centers), which can be detected using the electron spin resonance (ESR) method. However, whether the quartz impurity center ESR signal intensity (quartz ESR-SI) can be used for quartz sediment provenance tracing remains uncertain. In the present study, five present-day (modern) fluvial sediments from the Songhua, Yellow, Yangtze, Huai, and Pearl rivers in China and eight ancient fluvial sand lenses from the Yichang Gravel Layer (YGL) located in the middle Yangtze River were sampled for major- and trace-element determinations by ICP-OES and ICP-MS for the purpose of provenance discrimination. A total of 1404 ESR spectra were also collected to evaluate the effect of γ-ray dose (varying from 50 to 50 000 Gy) on quartz ESR-SI to establish the relationship between quartz element contents and quartz ESR-SIs and thereby to assess the potential utility of quartz ESR-SI for sediment provenance analysis. Results indicate that: (1) quartz collected from the different studied locations can be distinguished by element contents; (2) the quartz Al center ESR-SI increases with increasing γ-ray dose from 50 to 50 000 Gy; (3) the quartz Ti center ESR-SI increases within a γ-ray dose of 10 000 Gy and decreases beyond 10 000 Gy; (4) quartz Al and Ti center ESR-SIs are closely related to the contents of Al and Ti in quartz; and (5) a plot of quartz Ti center ESR-SI vs. Al center ESR-SI using data for a γ-ray dose range of 4000–7000 Gy is the best indicator of fluvial sediment provenance using the ESR method. [ABSTRACT FROM AUTHOR]

DC magnetometry and electron spin resonance (ESR) studies of Ni2FeVO6 powder samples obtained by the traditional calcination method are presented. As our X-ray diffraction study of Ni2FeVO6 has revealed an orthorhombic crystal structure and not previously reported rhombohedral FeTiO3-type structure (ilmenite), a new magnetic structure was proposed. As a consequence, the role of magnetic ions had to be re-evaluated. The transition to ferromagnetic (FM)-like phase was found at $T_{C} $ = 200 K in weak magnetic fields, while spin freezing dynamics in the superparamagnetic (SPM) regime was observed below $T_{C}$. Above 260 K, the Curie–Weiss paramagnetic (PM) phase with a large effective magnetic moment $\mu _{\mathrm {eff}} $ = $11.7 ~\mu _{B}$ /f.u was found. Interestingly, the Griffiths phase (GP) above $T_{C}$ was also detected. The important role of magnetic spin clusters with different sizes has been inferred from magnetization measured in different magnetic fields and at different temperatures. Although the main bulk ferromagnetic phase was not registered in the ESR spectra, they were analyzed in terms of Lorentzian and Gaussian components and attributed to different types of PM spin clusters with FM and antiferromagnetic (AFM) interactions. [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.

Dynamic nuclear polarization (DNP) is a method for achieving high levels of nuclear spin polarization by transferring spin polarization from electrons to nuclei by microwave irradiation, resulting in higher sensitivity in NMR/MRI. In particular, DNP using photoexcited triplet electron spins (triplet-DNP) can provide a hyperpolarized nuclear spin state at room temperature and in low magnetic field. In this review article, we highlight recent developments in materials and instrumentation for the application of triplet-DNP. First, a brief history and principles of triplet-DNP will be presented. Next, important advances in recent years will be outlined: new materials to hyperpolarize water and biomolecules; high-sensitivity solution NMR by dissolution triplet-DNP; and strategies for further improvement of the polarization. In view of these developments, future directions to widen the range of applications of triplet-DNP will be discussed., 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 Author(s). Published by Elsevier B.V. All rights reserved.)

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.

Trapped charge techniques of luminescence and electron spin resonance (ESR) are classic tools for dating Quaternary deposits. Over the past decade, these techniques have been routinely applied to investigate provenance and/or the sedimentary history of quartz grains based on their different luminescence and ESR characteristics. Of these, optically stimulated luminescence (OSL) sensitivity is one of the most widely investigated parameter for luminescence-based provenance approach. A majority of studies on this parameter are based on evaluation of multi-grain quartz OSL sensitivity of the samples. This is particularly concerning because single-grain quartz luminescence studies have shown that the luminescence signal of a multi-grain aliquot is contributed by less than ∼1–10% of the total grains. Since the sole criteria for discrimination of sources based on luminescence sensitivity relies on its intensity, therefore the results based on multi-grain analysis will most likely be skewed depending on the 'proportion' and 'brightness' of a few grains. This demands a need to evaluate the potential of single-grain quartz OSL sensitivity in provenance studies. In this study, we investigate single and multi-grain quartz OSL sensitivity from compositionally different sandstones with well-characterised sources based on U–Pb zircon ages. We further complement this analysis with characterisation of ESR centres commonly used in quartz provenance, namely E′ 1 and [AlO 4 ]0 centres. Our study shows that single-grain quartz OSL sensitivity can help distinguish between sediments that have a predominant input from a single source as compared to those with contribution from multiple sources, which otherwise cannot be inferred from multi-grain studies. Moreover, our results on characterisation of quartz-based ESR intensity of E′ 1 and saturated [AlO 4 ]0 centres successfully differentiates between sandstones and further complements the luminescence-based characterisation. [ABSTRACT FROM AUTHOR]

Silica clathrates have polyhedral cage structures with guest molecules and are naturally found under various forms such as melanophlogite, chibaite, or bosoite. Although electron spin resonance (ESR) could be potentially used to date their formation, the evaluation of the thermal stability of the radiation-induced radicals is not simple, like in the case of chibaite. Decay mechanism of the radical should be understood to ensure reliable ESR dating results. To investigate the behavior of radiation-induced radical in silica clathrate, isopropylamine silica clathrate was synthesized from mixed solutions of orthosilicic acid and isopropylamine. Hydrogen atom and (CH 3) 2 C·(NH 2) radical are mainly formed by γ-ray irradiation at 77 K. Hydrogen atom decay around 230 K by following a first-order kinetics and its activation energy is 65 ± 4 kJ/mol. Since the amount of hydrogen atom decrease was similar to that of the (CH 3) 2 C·(NH 2) radical increase, it is hypothesized that hydrogen atom abstracts hydrogen from isopropylamine in the silica clathrate. • Isopropylamine silica clathrate was successfully synthesized. • Hydrogen atom and (CH 3) 2 C·(NH 2) radical were mainly induced in isopropylamine silica clathrate after γ-irradiation at 77 K. • Hydrogen atom decayed with a first-order kinetics and would abstract hydrogen from isopropylamine in the silica clathrate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co 0.5 Mg 0.5 Fe 2 O 4 /rGO degraded TC-HCL (93 %) when exposed to visible light. • Photodegradation of TC-HCL was also explored via the LC-MS approach. • Co 0.5 Mg 0.5 Fe 2 O 4 /rGO displayed higher stability and recyclability. • Nanocomposite showed potential as a suitable photocatalyst for wastewater treatment. This study investigated cobalt-magnesium ferrite (Co 0.5 Mg 0.5 Fe 2 O 4) with reduced graphene oxide (rGO) as a dominant photocatalyst for the photo-degradation of tetracycline. Co 0.5 Mg 0.5 Fe 2 O 4 /rGO nanocomposite degraded 93 % of the tetracycline (TC-HCL) after 120 min of visible radiation, which can be attributed to the improved adsorption capacity and the significantly better transfer and separation of photoexcited ( e - h + ) pairs. Additionally, the Co 0.5 Mg 0.5 Fe 2 O 4 /rGO nanocomposite had higher stability and recyclability. Based on observed intermediates, possible processes of tetracycline degradation were proposed, where the •OH and • O 2 - played a major part. Photodegradation of TC-HCL was also provided using the LC-MS approach. The Co 0.5 Mg 0.5 Fe 2 O 4 /rGO nanocomposite was found to have a new potential for enhanced photocatalytic performance, making it a suitable photocatalyst for wastewater treatment. [ABSTRACT FROM AUTHOR]

Coordination compounds containing the Fe3+ ions like sodium salt Na[FeO6(C10H8N)3], kaolinite Al2[Si2O5]⋅(OH)4, metalloproteins (Ferritin, Maltofer, and Ferrum Lek) find a wide application. The analysis of the properties of these compounds has demonstrated a developed crystal structure. The diffractogram of Ferritin included an amorphous component. Within the temperature range of 4.2–300 К, all the compounds are characterized by transformation and mutual transfer of the lines of electron paramagnetic resonance spectrum of the Fe3+ ions (EPR). This fact allows estimation of a dynamical characteristic of the nearest neighbor environment of Fe3+. [ABSTRACT FROM AUTHOR]

The possibility of EPR dating for sediments using Al-h signals of fine (4–11 μm) grains of quartz has not been previously discussed. Here, the Al-h and peroxy EPR spectra of fine (4–11 μm) and coarse (63–90, 125–180 μm) sedimentary quartz from thoroughly investigated loess sites in Eastern Europe were examined. By comparing experimental spectra with a simulated signal, we evaluated the overestimation observed when using the standard approach established by Toyoda and Falguères to measure Al-h intensity for different doses of radiation, up to 40,000 Gy. This overestimation, caused by the presence of peroxy signals, was much more pronounced for fine grains. Fine grains exhibited some additional dose-dependent signals, which, for some samples, caused a complete distortion of the Al-h spectra at high doses, making it impossible to measure the standard amplitude. We propose a new approach to measuring Al-h signal intensity, focusing on the peak-to-baseline amplitude of the part of the signal at g ≈ 2.0603, which is not affected by the peroxy signals and therefore has the potential of providing more accurate results. The shapes of dose response curves constructed for coarse and fine grains using the new approach show considerable similarity, suggesting that Al-h centre formation in fine and coarse grains upon artificial radiation at room temperature follows the same pattern.

(BaSnO3)x/Cu0.5Tl0.5Ba2Ca2Cu3O10-δ superconducting composites (0.00 ≤ x ≤ 1.50 wt.%) were prepared by the solid-state reaction technique. The crystalline structure and superconducting transition temperature were investigated by X-ray powder diffraction (XRD) and dc-electrical resistivity measurements, respectively. X-Band electron spin resonance (ESR) measurements were carried out at different temperatures 103 ≤ T ≤ 298 K. ESR spectra are dominated by a single asymmetric line corresponding to Cu2+ ions at the rhombic site. The temperature dependence of the g factors allowed the determination of the pseudo-gap onset temperature T*. The results of T* are compatible with those obtained from resistivity and thermoelectric power measurements. The contribution of delocalized electrons from Cu2+ ions in the disordered part of the impurity phases BaCuO2 and Ba2CuO3 is significant for the high addition of nanoparticles. Moreover, the number of spins N participating in ESR and the activation energy Ea were enhanced with the addition of BaSnO3. [ABSTRACT FROM AUTHOR]

The presence of titanium in ground granulated blast‐furnace slags (GGBS) has been suspected to modify cement properties. This study provides the first evidence of a relation between the TiO2 content of slags and the mechanical properties of mortars based on slag cements. It is observed that only the slags containing less than 1%TiO2 show a compressive strength at 28 days that remains within the 52.5 MPa norm with CEM III cements complying with the European Standard NF EN 197‐1. The structural origin of this chemical dependence of the performance of cements is investigated by determining directly the titanium speciation in various European slags by spectroscopic methods. Electron paramagnetic resonance indicates that about 76% of Ti in slag occurs as Ti4+. The atomic structure around Ti was determined by Ti K‐edge X‐ray absorption near edge structure, which shows that Ti is mainly five‐fold coordinated in square‐based pyramid geometry. Five coordinated Ti acts as network‐stabilizer of the silicate network as it increases the polymerization. Requiring Ca2+ for charge‐compensation of the titanyl bond, it reduces the availability of Ca2+ during glass alteration in a modified random model of glass structure, where Ca2+ atoms are clustered in percolating cationic domains. As a consequence, the presence of five‐coordinated Ti results in a slower dissolution of the slag. These peculiar structural properties of titanium may explain the detrimental role of Ti above a 1% concentration, for many physical and chemical slag properties. This work provides a scientific ground for the technological acceptability of the upper limit of the Ti‐content of GGBS. [ABSTRACT FROM AUTHOR]

Aloe vera (Aloe barbadensis Miller) has been used as topical and oral therapeutic. This research highlights the phenolic constituents’ profile and antioxidant activity of 70% ethanol extracts of Aloe vera flower for the first time. The ethanol-based extracts showed the inhibition for linoleic acid oxidation and free radical-induced DNA damage. Among about 11 phenolic constituents of the extract, identified by using high performance liquid chromatography (HPLC), the content of vanillic acid was highest, corresponding to strong antioxidant activities of the extract. The extracts elevated superoxide dismutase, catalase, and glutathione peroxidase enzymes activities in the liver tissue of hydrogen peroxide-treated BALB/c mice. The radical-scavenging activities of the extracts were well-correlated to the total phenolic content. Therefore, Aloe bardadensis flower might be an effective source of natural antioxidant.

The quartz electron spin resonance (ESR) signal intensity (SI) of the Al and Ti–Li centers in sediment samples collected from the mainstream and major tributaries of the Yangtze River Basin were measured to determine whether they can be used as fluvial sediment provenance indicators. The results show significant spatial variation in the ESR-SI between the bulk, coarse (200–355 μm), and fine (75–154 μm) grain-size fractions. For all three size fractions, the ESR-SIs of sediment from the mid-lower-reaches of the basin were higher than those of the upper reaches, demonstrating that the ESR-SI can be used to distinguish between quartz contributed by the upper and mid-lower reaches of the basin. Furthermore, the quartz ESR-SI of the major tributaries exhibited distinct spatial variation, according to the distribution of the type of bedrock. Thus, the quartz ESR-SI can be used to trace the provenance of fluvial sediments, even in large river systems. Additionally, the upper Yangtze River Basin contributed a large amount of material to the lower-mid mainstream, and even the fine fraction of sediment in the lower Yangtze River originated mainly from the upper Yangtze River Basin. [ABSTRACT FROM AUTHOR]

Aminoxyl radicals (nitroxides) are a class of compounds with important biomedical applications, serving as antioxidants, spin labels for proteins, spin probes of oximetry, pH, or redox status in electron paramagnetic resonance (EPR), or as contrast agents in magnetic resonance imaging (MRI). However, the fast reduction of the radical moiety in common tetramethyl-substituted cyclic nitroxides within cells, yielding diamagnetic hydroxylamines, limits their use in spectroscopic and imaging studies. In vivo half-lives of commonly used tetramethyl-substituted nitroxides span no more than a few minutes. Therefore, synthetic efforts have focused on enhancing the nitroxide stability towards reduction by varying the electronic and steric environment of the radical. Tetraethyl-substitution at alpha position to the aminoxyl function proved efficient in vitro against reduction by ascorbate or cytosolic extracts. Moreover, 2,2,6,6-tetraethyl-4-oxo(piperidin-1-yloxyl) radical (TEEPONE) was used successfully for tridimensional EPR and MRI in vivo imaging of mouse head, with a reported half-life of over 80 min. We decided to investigate the stability of tetraethyl-substituted piperidine nitroxides in the presence of hepatic microsomal fractions, since no detailed study of their "metabolic stability" at the molecular level had been reported despite examples of the use of these nitroxides in vivo. In this context, the rapid aerobic transformation of TEEPONE observed in the presence of rat liver microsomal fractions and NADPH was unexpected. Combining EPR, HPLC-HRMS, and DFT studies on a series of piperidine nitroxides — TEEPONE, 4-oxo-2,2,6,6-tetramethyl(piperidin-1-yloxyl) (TEMPONE), and 2,2,6,6-tetraethyl-4-hydroxy(piperidin-1-yloxyl) (TEEPOL), we propose that the rapid loss in paramagnetic character of TEEPONE is not due to reduction to hydroxylamine but is a consequence of carbon backbone modification initiated by hydrogen radical abstraction in alpha position to the carbonyl by the P450-Fe(V)=O species. Besides, hydrogen radical abstraction by P450 on ethyl substituents, leading to dehydrogenation or hydroxylation products, leaves the aminoxyl function intact but could alter the linewidth of the EPR signal and thus interfere with methods relying on measurement of this parameter (EPR oximetry). Image 1 • Tetraethyl-substituted aminoxyl radicals are valuable probes for biological EPR. • They are indeed more resistant to reduction than their tetramethyl analogs. • Here, the metabolic stability of three piperidine nitroxides was studied in vitro. • Surprisingly TEEPONE rapidly decayed in contrast to TEMPONE or TEEPOL. • The trigger is hydrogen abstraction by P450-FeV=O on the lipophilic probe. [ABSTRACT FROM AUTHOR]

In the present paper, we numerically simulate fractional-order model of the Bloch equation by using the Jacobi polynomials. It arises in chemistry, physics and nuclear magnetic resonance (NMR). It also arises in magnetic resonance imaging (MRI) and electron spin resonance (ESR). It is used for purity determination, provided that the molecular weight and structure of the compound is known. It can also be used for structural determination. By the study of NMR, chemists can determine the structure of many compounds. The obtained numerical results are compared and simulated with the known solutions. Accuracy of the proposed method is shown by providing tables for absolute errors and root mean square errors. Different orders of the time-fractional derivatives results are illustrated by using figures. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study is to clarify the antioxidative effects of orengedokuto (OGT) and its crude drug components in the human oral cavity. Method: In healthy subjects, the amount of change between the oxidation–reduction potential (ORP) value of saliva when gargled with water or with Kampo extract was compared to verify the antioxidant capacity of Kampo extract (OGT and excluding each single constituent in OGT) in the oral cavity. Moreover, the superoxide radical in this Kampo extract was measured by electron spin resonance (ESR) spectrometry to determine its inherent antioxidative capacity. Results: In this protocol using saliva, the antioxidative capacity of OGT extract was dose‐dependent. The OGT extract showed a significantly higher antioxidative capacity compared to the byakkokaninjinto extract, and the effect was almost equivalent to that of the green tea extract. In the comparison of excluding each single crude drug from OGT, excluding the Scutellaria Root extract showed the lowest antioxidative capacity. In the comparison of crude drug constituting of OGT, the Scutellaria Root extract showed the highest antioxidant ability. These results showed very similar behavior to the superoxide scavenging activity of Kampo extract itself measured by ESR. Conclusion: This almost noninvasive test method can easily evaluate the intraoral antioxidative capacity and was effective in verifying the antioxidative capacity of Kampo medicines. In OGT, Scutellaria Root made a significant contribution in the antioxidative capacity of the crude drug extract itself in vitro and the intraoral antioxidative capacity in vivo. [ABSTRACT FROM AUTHOR]

A detailed electron spin resonance (ESR) analysis of mechanically induced free radicals (mechanoradicals) formation of glucose-based polysaccharides, dextran (Dx) and glycogen (Gly) was performed in comparison with amylose mechanoradicals. The ESR spectra of the samples mechanically fractured at room temperature were multicomponent. The radical concentration of Dx and Gly mechanoradicals gradually decreased during vibratory milling after reaching the maximum value. Although the molecular weight of Dx or the particle diameter of Gly steeply diminished until reaching the each maximum value of radical concentration, after that the molecular weight or the particle diameter slowly decreased. These results suggested that Dx and Gly mechanoradicals might be more unstable than amylose radicals possessing an intramolecular helical structure due to the branched structure.