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In this study, natural tinaksite (K2Ca2NaTi[Si7O18OH]O) and tokkoite (K2Ca4[Si7O18OH](OH,F)) collected in charoite rocks of the Murun alkaline massif (Siberia, Russia) were examined by X-ray diffraction and optical and vibrational spectroscopic methods. A comparative analysis of the experimental diffraction patterns with respect to the calculated X-ray powder diffraction patterns was carried out for tinaksite and tokkoite powders. The shift in the diffraction peaks of tinaksite is explained by the smaller values of the unit cell parameters a and b as compared with those of tokkoite. A similar shift of the peaks is also observed in the Raman and infrared absorption spectra; however, this feature is explained by the difference in the chemical composition of the minerals. The shoulder in the absorption spectra at about 800 nm in tinaksite and 700 nm in tokkoite corresponds to the presence of Mn2+ and Fe3+ absorption bands, the presence of which determines the color of tinaksite and tokkoite. The luminescence band with a maximum at about 540–550 nm in the photoluminescence spectra is related to Mn2+ centers, while an additional band at about 610 nm can be associated with Ti3+ centers in tinaksite. The intensity of the Fe3+ ESR signal increases in both samples after heating, while the intensities of the bands associated with OH groups decrease in tinaksite and tokkoite. This characteristic is the result of iron oxidation and dehydrogenation reaction.

Hypoxia in tumors results in resistance to both chemotherapy and radiotherapy treatments but affords an environment in which hypoxia-activated prodrugs (HAP) are activated upon bioreduction to release targeted cytotoxins. The benzotriazine 1,4-di-N-oxide (BTO) HAP, tirapazamine (TPZ, 1), has undergone extensive clinical evaluation in combination with radiotherapy to assist in the killing of hypoxic tumor cells. Although compound 1 did not gain approval for clinical use, it has spurred on the development of other BTOs, such as the 3-alkyl analogue, SN30000, 2. There is general agreement that the cytotoxin(s) from BTOs arise from the one-electron reduced form of the compounds. Identifying the cytotoxic radicals, and whether they play a role in the selective killing of hypoxic tumor cells, is important for continued development of the BTO class of anticancer prodrugs. In this study, nitrone spin-traps, combined with electron spin resonance, give evidence for the formation of aryl radicals from compounds 1, 2 and 3-phenyl analogues, compounds 3 and 4, which form carbon C-centered radicals. In addition, high concentrations of DEPMPO (5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide) spin-trap the •OH radical. The combination of spin-traps with high concentrations of DMSO and methanol also give evidence for the involvement of strongly oxidizing radicals. The failure to spin-trap methyl radicals with PBN (N-tert-butylphenylnitrone) on the bioreduction of compound 2, in the presence of DMSO, implies that free •OH radicals are not released from the protonated radical anions of compound 2. The spin-trapping of •OH radicals by high concentrations of DEPMPO, and the radical species arising from DMSO and methanol give both direct and indirect evidence for the scavenging of •OH radicals that are involved in an intramolecular process. Hypoxia-selective cytotoxicity is not related to the formation of aryl radicals from the BTO compounds as they are associated with high aerobic cytotoxicity.

Artificial organelles (AnOs) are in the spotlight as systems to supplement biochemical pathways in cells. While polymersome-based artificial organelles containing enzymes to reduce reactive oxygen species (ROS) are known, applications requiring control of their enzymatic activity and cell-targeting to promote intracellular ROS detoxification are underexplored. Here, we introduce advanced AnOs where the chemical composition of the membrane supports the insertion of pore-forming melittin, enabling molecular exchange between the AnO cavity and the environment, while the encapsulated lactoperoxidase (LPO) maintains its catalytic function. We show that H 2 O 2 outside AnOs penetrates through the melittin pores and is rapidly degraded by the encapsulated enzyme. As surface attachment of cell-penetrating peptides facilitates AnOs uptake by cells, electron spin resonance revealed a remarkable enhancement in intracellular ROS detoxification by these cell-targeted AnOs compared to nontargeted AnOs, thereby opening new avenues for a significant reduction of oxidative stress in cells.

Various studies have demonstrated that employing ESR spin trapping to detect free radicals yields valuable insights into the vulnerability of bulk oils to oxidation. Consequently, this method can be employed to assess and compare the oxidative stability of different samples. This study was conducted to investigate the production and transformation of free radicals and trans isomers in linseed oil when subjected to different temperatures and durations of heating. These analyses revealed that the peak levels of free radicals PBN adducts were evident in linseed oil heated to 120 °C, while these levels decreased within 90 min and were absent at a higher temperature of 180 °C. Free radical PBN adducts were readily degraded at 180 °C. Levels of heat-induced trans isomers rose in linseed oil samples with rising temperatures but began to degrade at temperatures exceeding 240 °C partially. The content examination of these trans isomers revealed that the double bonds located at positions 9 and 15 exhibited a higher susceptibility to isomerization compared to the double bond at position 12. Furthermore, the values of k and E a indicated that the synthesis of tri-trans-α-linolenic acid (TALAs) was more challenging compared to double-TALAs, and double-TALAs were more challenging than single-TALAs. This was because the tri-TALAs has a higher E a value than the mono-TALAs and double-TALAs. The study has demonstrated that subjecting linseed oil to high-temperature heating leads to the production of free radicals and trans isomers. And PBN radical adduct is unstable at 180 °C and the double bonds at positions 9 and 15 could be isomerized more easily than that at position 12. These results indicated that controlling the formation of free radicals and single-TALAs isomers may be the key way to reduce the trans isomers of linolenic acid during cooking oil heating. In the follow-up study, we found that VE, VK3, ethyl caffeic acid and resveratrol had significant inhibitory effects on the formation of TALAs of linolenic acid, and the highest inhibitory rate of resveratrol with 5% addition could be reached to 30.86%. The above substances can be applied to the thermal processing of linseed oil to prevent the formation of TALAs., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Li Yongfu reports financial support was provided by Guizhou Provincial Basic Research Program (Natural Science). Li Yongfu reports a relationship with Guizhou Provincial Basic Research Program (Natural Science) that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Reactive oxygen species (ROS) such as superoxide, hydroxyl radical, and hydrogen peroxide play an important role in the maintenance of life. However, production of excessive ROS and/or deficiency of the antioxidant system lead to oxidative stress and cause a variety of diseases. In the present study, we used electron spin resonance (ESR) to detect ROS in vivo to clarify its roles in redox dynamics and organ damage. However, the limited permeability of microwaves and low anatomic resolution of ESR equipment made it difficult to apply clinically. Nitroxide is widely used as a sensitive redox sensor for in vivo ESR analysis. The unpaired electrons of nitroxide are known to cause the T1 relaxation time-shortening effect of water protons, creating magnetic resonance imaging (MRI) effects. The remarkable development of MRI has facilitated the spatiotemporal analysis of nitroxide, which was previously impossible. In a rat model, we have been able to image and analyze the process of nitroxide reduction using MRI. MRI using nitroxide as a contrast medium is considered to be clinically applicable for evaluation of organ redox, imaging of ROS (which cause organ damage), and evaluation of therapeutic effects. In this review, we describe current advances in the analysis of in vivo redox capacity in animals using ESR and MRI equipment. We consider that redox evaluation using MRI can contribute to advances in clinical medicine. [ABSTRACT FROM AUTHOR]

Chemical modification such as intercalation or doping of novel materials is of great importance for exploratory material science and applications in various fields of physics and chemistry. Herein, the systematic intercalation of chemically exfoliated few‐layer graphene with potassium is reported while monitoring the sample resistance using microwave conductivity. It is found that the conductivity of the samples increases by about an order of magnitude upon potassium exposure. The increased number of charge carriers deduced from the electron spin resonance (ESR) intensity also reflects this increment. The doped phases exhibit two asymmetric Dysonian lines in ESR, a usual sign of the presence of mobile charge carriers. The width of the broader component increases with the doping steps; however, the narrow components seem to have a constant line width. [ABSTRACT FROM AUTHOR]

No‐tillage farming combined with temporary cattle grazing is becoming a common practice in parts of South America. We quantified the effects of no‐tillage and winter grazing of annual ryegrass (Lolium multiflorum Lam.) on soil carbon and nitrogen stock, stratification ratio (concentration in 0–5 to 10–20‐cm layer) and lability (based on particulate organic matter, POM), relative to conventional tillage or ungrazed ryegrass. A 9‐year‐old experiment was conducted in a southern Brazilian Ferralsol. Soil under no‐tillage accumulated 1.11 Mg C ha−1 year−1 and 0.10 Mg N ha−1 year−1 to 100‐cm depth relative to conventional tillage when ryegrass was not grazed, and also increased the stratification ratio of carbon (1.48 vs. 1.11) and nitrogen (1.66 vs. 1.17). The carbon and nitrogen lability was also greater in no‐tillage soil, as carbon and nitrogen stocks increased proportionally more in sand‐POM than in silt or clay size fractions (carbon lability index = 1.57 vs. 1.00; nitrogen lability index = 1.57 vs. 1.00). Semiquinone concentrations in physical fractions were 4–28% smaller in no‐tillage, suggesting less organic matter aromaticity in this treatment. Grazing, however, caused no further improvement of stocks of carbon and nitrogen in the 0–100‐cm layer of no‐tillage soil (e.g., 209 vs. 212 Mg C ha−1, ns), or enhancement of stratification or lability of those elements, relative to ungrazed ryegrass. Overall, no‐tillage effectively promoted soil carbon and nitrogen accumulation and lability in this subtropical Ferralsol, whereas grazing did not compromise the gains of no‐tillage. Highlights: Capacity of no‐tillage and grazing to enhance stocks, stratification and lability of soil C and N.C sequestration with no‐tillage is being debated, and little is known when combined with grazing.No‐tillage accumulated 1.11 Mg C ha−1 year−1 but grazing promoted no further C accumulation.No‐tillage effectively accumulated C in soil and grazing did not compromise such gain of no‐tillage. [ABSTRACT FROM AUTHOR]

A series of high iron content boro-phosphate glasses having composition of 30P2O5-70B2O3-xFe2O3);0 ≤ x ≤ 80 wt% was prepared by conventional melt quench method. Mössbauer effect (ME), infrared (IR) and electron spin resonance (ESR) were used to study the behavior of iron brought into borophosphate glass and its effect on the structure of the glass. The results of the glasses containing from 10 to 80 wt% Fe2O3 indicated that iron is present in the glass in the form of Fe3+ and Fe2+, i.e. in tetrahedral and various octahedral symmetric sites. Electron paramagnetic resonance (EPR) spectra were utilized to investigate the glass structure. The analysis shows a well-defined signal at g = 2.04 characteristics for Fe3+ ions and the intensity increases with increasing Fe2O3 concentration before gamma irradiation. After exposing the samples to different doses of gamma irradiation up to 30 kGy; the EPR signal intensity decreases for the samples with a low Fe2O3 concentration (i.e. 10% and 40%), which can be used as radiation indicators. For glass with high iron concentrations above 40%, the intensity of the EPR signal remains approximately constant and therefore, high iron concentrations of this glass can be used for radiation protection purposes. [ABSTRACT FROM AUTHOR]

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In the last couple decades, several viral outbreaks resulting in epidemics and pandemics with thousands of human causalities have been witnessed. The current Covid‐19 outbreak represents an unprecedented crisis. In stopping the virus' spread, it is fundamental to have personal protective equipment and disinfected surfaces. Here, the development of a TiO2 nanowires (TiO2NWs) based filter is reported, which it is believed will work extremely well for personal protective equipment (PPE), as well as for a new generation of air conditioners and air purifiers. Its efficiency relies on the photocatalytic generation of high levels of reactive oxygen species (ROS) upon UV illumination, and on a particularly high dielectric constant of TiO2, which is of paramount importance for enhanced wettability by the water droplets carrying the germs. The filter pore sizes can be tuned by processing TiO2NWs into filter paper. The kilogram‐scale production capability of TiO2NWs gives credibility to its massive application potentials. [ABSTRACT FROM AUTHOR]

The systematic magnetic properties in the zircon‐type GdVO4 single crystal are reported herein. Antiferromagnetic (AFM)‐ordered GdVO4 single crystal presents an upturn below 150 K in the H/M curves. With the decreasing of the field, the upturn behavior enhances which is probably due to spin‐glass‐like behavior that exists in this system. The short‐range order related spin‐glass‐like feature is also observed in the time‐dependent magnetization relaxation. Furthermore, the M (T) and M (H) curves of the single crystal reveal an anisotropic character with two different spin‐flop transitions along the c axis (1 T) and the a, b axes (1.7 T). Combining the high‐frequency electron spin resonance (ESR) measurement and the structure analysis, the main cause of the magnetic anisotropy can be explained as the contribution of the exchange coupling anisotropy due to the asymmetrical environment of the Gd3+ ions. [ABSTRACT FROM AUTHOR]

The behavior of lithium donors in bulk single-crystal isotopically pure Si1 –xGex alloys (x = 0.0039–0.05) enriched in spinless 28Si and 72Ge isotopes (99.998 and 99.984%, respectively) is investigated by electron spin resonance. The fine structure of the spectrum of electrons localized at Li donors is studied at temperatures of T = 3.5–30 K in the expectation that, much like with pure silicon, enriching Si1 –xGex alloys in spinless isotopes (28SiisoGe, where iso = 70, 72, 74, 76) makes it possible to attain a higher resolution in the spectra of electron spin resonance. The results demonstrate that, despite the irregular arrangement of Ge atoms in the lattice of the 28Si1 –x72Gex alloy, the presence of local distortions in their vicinity, and the broadening of the electron-spin-resonance lines of donor electrons due to random strains, the lines of Li donors observed in the spectra of isotopically pure 28Si1 –x72Gex single crystals with x = 0.39, 1.2, and 2.9 at. % are narrower than the corresponding lines in the spectra of similar crystals with the natural composition of silicon and germanium isotopes. Similarly to the case of silicon crystals, this allowed us to study for the first time the angular dependences of the line positions in the electron-spin-resonance spectra of lithium in Si1 –xGex for different values of x. [ABSTRACT FROM AUTHOR]

Nanozymes have been widely applied in bio-assays in the field of biotechnology and biomedicines. However, the physicochemical basis of nanozyme catalytic activity remains elusive. To test whether nanozymes exhibit an inactivation effect similar to that of natural enzymes, we used guanidine chloride (GuHCl) to disturb the iron oxide nanozyme (IONzyme) and observed that GuHCl induced IONzyme aggregation and that the peroxidase-like activity of IONzyme significantly decreased in the presence of GuHCl. However, the aggregation appeared to be unrelated to the quick process of inactivation, as GuHCl acted as a reversible inhibitor of IONzyme instead of a solo denaturant. Inhibition kinetic analysis showed that GuHCl binds to IONzyme competitively with H2O2 but non-competitively with tetramethylbenzidine. In addition, electron spin resonance spectroscopy showed that increasing GuHCl level of GuHCl induced a correlated pattern of changes in the activity and the state of the unpaired electrons of the IONzymes. This result indicates that GuHCl probably directly interacts with the iron atoms of IONzyme and affects the electron density of iron, which may then induce IONzyme inactivation. These findings not only contribute to understanding the essence of nanozyme catalytic activity but also suggest a practically feasible method to regulate the catalytic activity of IONzyme.

Single-molecule measurement techniques have illuminated unprecedented details of chemical behavior, including observations of the motion of a single molecule on a surface, and even the vibration of a single bond within a molecule. Such measurements are critical to our understanding of entities ranging from single atoms to the most complex protein assemblies. We provide an overview of the strikingly diverse classes of measurements that can be used to quantify single-molecule properties, including those of single macromolecules and single molecular assemblies, and discuss the quantitative insights they provide. Examples are drawn from across the single-molecule literature, ranging from ultrahigh vacuum scanning tunneling microscopy studies of adsorbate diffusion on surfaces to fluorescence studies of protein conformational changes in solution.

Abstract We aimed to investigate the biological responses induced by acute and chronic gamma irradiation in colored wheat seeds rich in natural antioxidants. After acute and chronic irradiation, the phenotypic effects on plant growth, germination rate, seedling height, and root length were examined, and the biochemical changes were investigated by analyzing the expression of antioxidant enzyme-related genes, antioxidant enzyme activities, and total antioxidant capacity. High dosages of chronic radiation reduced plant growth compared with the controls. Electron spin resonance measurement and 2,2-diphenyl-1-picrylhydrazyl activity analysis showed lower amount of free radicals in colored wheat seeds on chronic irradiation with low dosage of gamma rays compared to seeds subjected to acute irradiation. Expression levels of anthocyanin biosynthesis genes, antioxidant-related genes, and antioxidant enzyme activity in seeds and young leaves of seedling showed diverse effects in response to different dosages and types of gamma irradiation. This suggests that phenotype is affected by the dosage and type of gamma radiation, and the phytochemicals in colored wheat seeds involved in antioxidant activity to scavenge free radicals respond differently to irradiation types. This provides evidence that acute and chronic exposure to radiation have different effects on seeds and young leaves after germination.

The ability of sodium caprylate and l-menthol to fluidize phospholipid bilayers composed of lipids simulating the buccal epithelium was investigated using electron spin resonance (ESR) to evaluate the action of these agents as permeation enhancers. 5-Doxyl stearic acid (5-DSA) and 16-doxyl stearic acid (16-DSA) were used as spin labels to identify alterations in membrane fluidity near the polar head groups or inner acyl regions of the lipid bilayer, respectively. The molecular motion of both 5-DSA and 16-DSA showed increased disorder near the polar and inner hydrophobic regions of the bilayer in the presence of sodium caprylate suggesting fluidization in both the regions, which contributes to its permeation enhancing effects. L-menthol decreased the order parameter for 16-DSA, showing membrane fluidization only in the inner acyl regions of the bilayer, which also corresponded to its weaker permeation enhancing effects. The rapid evaluation of changes in fluidity of the bilayer in the presence of potential permeation enhancers using ESR enables improved selection of effective permeation enhancers and enhancer combinations based on their effect on membrane fluidization.

This research focused on the identification of parasitic signal sources introduced by sintering under reductive atmospheres of oxide transparent ceramics. The examination encompassed a wide set of materials, like Mg‐spinel, magnesia, alumina. YAG, yttria, zirconia and titania, so as to allow one to detect general rules if operating. The main finding is the dependence between the ability of such ceramics to generate, under reductive conditions, intrinsic parasitic light‐absorbing centers and their composition and structure. Thus it was determined that oxides based on transition element cations have ,in this sense, abilities not present in the case of oxides of elements from the main periodic table groups. The reason is the possibility of non‐absorbing transition cations to be reduced to oxidation states that absorb light. Drive toward reduced oxidation states is motivated by the stabilization energy associated with the ligand fields acting upon the such cations. It has been also found out that YAG lattice distortion, by dopants like tetravalent silicon or zirconium facilitates reduction of Y 3+ to Y 2 + (a light absorbing, d1, cation). Oxygen vacancies do not significantly influence visible light absorption. Carbon atoms penetrate inside ceramics, even dense ones and cause achromatic tints formation. [ABSTRACT FROM AUTHOR]

The solubility of rutin (Rut), which is low in water, was improved by binary amorphous solid with other excipients using a mechanochemical technique. Four potential excipients; L-methionine, naringin hydrate, quercetin dihydrate, and hesperidin (Hes) were used for attempting to preparation of the co-amorphization with Rut. After grinding, the samples were characterized using powder X-ray diffraction, differential scanning calorimetry, electron spin resonance, and ultraviolet-visible spectroscopy. It was found that Hes could suppress the recrystallization of Rut after the mechanochemical process, in contrast to the other excipients. The recrystallization temperature of Hes increased after grinding with Rut, which indicated the possibility of a co-amorphization between Rut and Hes. The produced particles from this process expressed radicals with changes in crystal structure, resulting in a link between structural changes and radical expression. The radical formation may improve the dissolution rate of Rut due to the co-amorphization of Rut and Hes. The radical species identified from the co-amorphization of Rut and Hes would be attributed to the sugar moiety of Hes having coordinated with Rut. [ABSTRACT FROM AUTHOR]