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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]

Local structure and electron paramagnetic resonance (EPR) parameters for Cu2+ center in [Co(nicotinamide)2(H2O)4](saccharinate)2 (CoNAS) crystal are theoretically investigated using high-order perturbation formulas for 3d9 ions in rhombically elongated octahedra. In the calculated formulas, the related molecular orbital coefficients are acquired from the superposition model which enables to correlate the crystal field parameters and hence the EPR parameters with the studied Cu2+ center, the admixtures of d-orbitals in the ground state wave function as well as the ligand orbital and spin–orbit coupling contributions are taken into account. Based on the studies, the [CuO4N2]12− cluster of the studied Cu2+ center are found to suffer the axial and perpendicular bond length variations Δz (≈ 0.0612 Å) along z-axis and δr (≈ 0.0360 Å) along x- and y-axes, respectively, due to the Jahn–Teller effect. [ABSTRACT FROM AUTHOR]

The electronic paramagnetic resonance (EPR) parameters (g factor gi, and hyperfine structure constants Ai, with i = || and ⊥) and tetragonal distortion of the Cu2+ center in Al2O3 are unified interpreted from the perturbation formulas for a 3d9 ion in tetragonally elongated octahedral. In the calculations, the impurity Cu2+ is found to occupy the host trigonally-distorted octahedral Al3+ site with the tetragonal elongation distortion due to the Jahn–Teller effect, despite the original trigonal distortion of the host cation site. The contributions to EPR parameters from both the spin–orbit coupling of the central ion and that of the ligands are taken into account. The defect structure of the Cu2+ center (characterized by the relative tetragonal elongation ratio η ≈ 4.3% along the C4 axis) was determined from the calculation. Furthermore, the calculated results agree well with the experimental data and need fewer adjustable parameters than the previous studies. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) have been well-known and extensively researched due to the high storage /good selectivity for gas molecules. Herein, the structures and electron paramagnetic resonance (EPR) spectra for dicopper paddle wheel MOF compound (Cu2(µ2-O2CCH3)4 with various gas molecule are theoretically investigated by density functional theory (DFT) calculations. The adsorption energies and isotherms (including pure gas molecules and the mixed ones) are calculated for the gas molecules interacting with the unsaturated Cu2(µ2-O2CCH3)4. Both quantities exhibit the roughly consistent orders (e.g. H2S > NH3 > CO2 > CO > H2O > N2 > NO > H2 for isotherms and H2S > NH3 > N2 > CO2 > NO > H2O > H2 > CO for adsorption energies), possibly suggesting that this material may act as a potential adsorbent of these gas molecules. The catalytic property of Cu2(µ2-O2CCH3)4 for oxidation of CO and NO into non-toxic molecules and splitting of H2O into H2 and O2 in the solvent condition are uniformly discussed. Simulation of Grand Canonical Monte Carlo (GCMC) in MS 8.0 and calculations in Langmuir model reveal that Cu2(µ2-O2CCH3)4 has good selectivity for CH4 in natural gas (CH4/CO2/N2) and SO2 in fog (SO2/NO/NO2/H2O/O2), which would exhibit potential environmentally friendly applications. [ABSTRACT FROM AUTHOR]

On the basis of the improved ligand field theory, the electron paramagnetic resonance (EPR) parameters for Cu2+ in rutile TiO2 at low temperature are theoretically investigated by using the improved perturbation formulas of the above EPR parameters for a 3d9 ion in rhombically (D2h) distorted octahedra. In the calculation formulas, the crystal field parameters are determined from the superposition model, and the contributions from the spin–orbit coupling of the ligands and the admixture of d-orbitals in the ground state wave function are also taken into account. Due to the Jahn–Teller effect, the Cu–O bond lengths of the parallel and perpendicular to the C2-axis are, respectively, ≈ 2.081 Å and ≈ 1.898 Å, with the planar bond angle θ' ≈ 82.52°. The calculated results are in agreement with the experimental data, and the reasonableness of these results is discussed. [ABSTRACT FROM AUTHOR]

New, spin-labeled nucleosides, and an efficient synthetic route for a modified uridine amidite, were developed. The spin-labeled part was the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) group, which was linked via an alkynyl chain at the 5 position of uridine. Three typical protecting groups, the t-butyldimethylsilyl (TBDMS) group at 2′, the dimethoxytrityl (DMTr) group at 5′, and the phosphoramidite group at 3′, were introduced to produce an automated nucleic acid synthesizer. The TEMPO group at the 5 position in the uridine structure affected introduction of bulky protecting groups, such as the DMTr group at the 5′ position and the TBDMS group at the 2′ position. The electron paramagnetic resonance (EPR) data revealed a nitroxyl radical in the structure of synthetic nucleoside compounds; however, RNA produced by automated synthesis using a TEMPO-linked uridine phosphoramidite building block was EPR silent. [ABSTRACT FROM AUTHOR]

This review outlines the recent theoretical and computational developments for the prediction of motional electron paramagnetic resonance spectra with introduced spin probes from molecular dynamics simulations. The methodology is illustrated with applications to thermotropic and lyotropic liquid crystals at different phases and aggregate states. [ABSTRACT FROM AUTHOR]

The effect of the spin probe VO2+ in 15BaO-15TeO2-10TiO2-(60-x) B2O3-xV2O5 (x = 0.2, 0.4, 0.6, 0.8 mol %) glasses has been studied by employing Electron Paramagnetic Resonance (EPR) and optical absorption spectroscopic techniques. The observed EPR spectra of VO2+ ions were attributed on the basis of well-known spin-Hamiltonian of C4V symmetry. The simulated EPR spectra for VO2+ ions in the present glass system were drawn using Easy spin software. Both the experimental and simulated spectra were found to be in good agreement with each other. The optical absorption spectra exhibited three d-d transition bands due to crystal and tetragonal fields of VO2+ ions. These bands were assigned to 2B2g→ 2Eg, 2B2g→ 2B1g and 2B2g→ 2A1g transitions. The crystal field parameters Dq, Ds and Dt values are calculated. From the EPR and optical data, the molecular bonding coefficients were evaluated. Employing the higher order perturbation formulae of the g factors for 3d1 ion under tetragonally compressed octahedral fields, theoretical studies were carried out. The spin-Hamiltonian parameters and obtained from both the experimental and theoretical methods were in good agreement with each other. [ABSTRACT FROM AUTHOR]

The local structures and electron paramagnetic resonance (EPR) parameters for Cu2+in 59B2O3–10K2O–(30−x)ZnO–xBaO–1CuO (BKZBC) glasses are theoretically investigated with distinct modifier BaO concentrationsx(= 0, 6, 12, 18, 24 and 30 mol %). Theclusters are found to undergo the relative tetragonal elongations of about 13.5 and 5.0% at zero and higher BaO concentrations. The concentration dependences of the measured d–d transition bands,gfactors andA//are suitably reproduced from the Fourier type functions or sign functions of the relevant quantities withxby using only six adjustable parameters. The features of the EPR parameters and the local structures of Cu2+are analysed in a consistent way by considering the differences in the local ligand field strength and electronic cloud admixtures around Cu2+under addition of Ba2+with the highest ionicity and polarisability. The present theoretical studies would be helpful to the researches on the structures, optical and EPR properties for the similar potassium barium zinc borate glasses containing copper with variation concentration of modifier BaO. [ABSTRACT FROM PUBLISHER]

The spin Hamiltonian parameters and for copper(II) in CuX4 (X = N, S, Cl and Br) tetrahedrons are theoretically investigated within a uniform model by utilizing the perturbation method and cluster approach for 3d9 ions suffering D2d symmetry in view of host structures and angular distortions in terms of a single parameter β. For all the studied polymers, the isotropy of g tensors gav and the hyperine structure constant component A‖ are found, respectively, to undergo an increasing and decreasing trend with the enlarging average X-Cu-X angle β, while the obtained cubic crystal field parameter Dq and isotropic Fermi contact constant κ are experiencing a declining and growing tendency with the rising Cu-X bond length, respectively. The critical angle βc is concluded locating in the range of 109.471°-120° in which the g-isotropy value would reach the maximum, while the hyperine structure factor might vanish that needs to be verified in future X-ray and EPR experiments. This work would be beneficial to the establishment of complete EPR and structure diagram for CuX4 complexes and the synthesis of new compounds possessing novel physical and chemical properties. [ABSTRACT FROM AUTHOR]

We investigated aqueous solutions containing nitrite ions and DMPO (5,5-dimethyl-1-pyrroline-N-oxide) by electron spin resonance (ESR) in the pH range from 1 to 6. A DMPO-OH signal was observed below pH 3.0 in the presence of nitrite ions, whereas in the absence of nitrite ion, an extremely weak signal was observed below pH 1.5. Addition of methanol, a hydroxyl radical scavenger, to this system did not lead to the appearance of a detectable DMPO-CH2OH signal. The possibility of this DMPO-OH signal being due to a genuine spin trapping process with hydroxyl radical was, therefore, ruled out. The reactivities of reactive nitrogen species (RNS) in this system with DMPO have also been investigated by density functional theory (DFT) at the IEFPCM (water)/B3LYP/6–311 + G ** level of theory. On the basis of the pH dependence of the signal intensity and the redox potential E° (versus SHE) calculated by DFT theory, we propose that the origin of this signal is "inverted spin trapping" via one-electron oxidation of DMPO by H2ONO+, followed by the nucleophilic addition of water. Prevention of these false-positive results when detecting hydroxyl radical using ESR spin trapping requires an awareness of both the presence of nitrite ions in the solution and the solution pH. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR)gfactors and local structures for Ni3+in LiAlyCo1–yO2as the cathode materials for lithium-ion batteries are theoretically investigated at various Al concentrationsy(= 0.1, 0.5, 0.8 and 1.0). The [NiO6]9–clusters are subject to the tetragonal elongation distortions along theC4axis owing to the Jahn–Teller effect and the different degrees of distortions are characterised by the slightly increasing relative elongation ratioρ(and also crystal-field strength and covalency) withy. In pure LiAlO2(y = 1.0), the [NiO6]9–cluster exhibits the largestρ(≈1.4%) and an additional relative variation ratioτ(≈1.4%) of the planar bond lengths, responsible for the perpendicularganisotropyδg= (gx–gy). The number of impurity Ni3+centres increases from one aty = 0 and 1.0 to two aty = 0.1 and 0.8 and reaches the maximum four aty = 0.5, in accordance with the increasing degree of disorder of the systems. The distinct impurity centres for the sameymay be accompanied by the comparable energies of the ground and near excited states, similar to ‘resonant states’ with slightly different local elongation distortions and tetragonal level splittings. The present studies will be helpful to understand the relationships between local structures and performances of LiAlyCo1–yO2type cathode materials. [ABSTRACT FROM PUBLISHER]

A water-soluble fullerenol containing porphyrin and isoindoline nitroxide groups APTSPP-C60(OH)10-(TMIO)3was synthesized by the incorporation of 5-(4-amino-phenyl)-10,15,20-tris(4-sulfonatophenyl)-porphyrin (APTSPP) as a tumor-targeting group and 5-formyl-1,1,3,3-tetramethylisoindolin-2-yloxyl (FTMIO) into fullerenol C60(OH)11. This nonmaterial was further characterized by FT-IR, UV, MS, TEM, fluorescence, etc. and its properties in vitro were also evaluated. Electrochemical experiments indicated that APTSPP-C60(OH)10-(TMIO)3retained similar electrochemical properties and redox reaction mechanisms as 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CTMIO). Electron paramagnetic resonance (EPR) spectra of APTSPP-C60(OH)10-(TMIO)3exhibited the hyperfine splittings and characteristic spectra of CTMIO, with typical nitroxide g-values and nitrogen isotropic hyperfine coupling constants. In vitro cytotoxicity assay showed APTSPP-C60(OH)10-(TMIO)3possessed low cytotoxicities to human renal tubular epithelial 293T cells and HepG-2 cells. Therefore APTSPP-C60(OH)10-(TMIO)3may be considered as a potential candidate for novel biological spin probe using EPR spectroscopy. [ABSTRACT FROM AUTHOR]

Leaf extracts ofBryophyllum pinnatum(BPEs) are used in several countries. Contextually, evaluation of the therapeutic potential of these was carried out in this study to explore antioxidant and antityrosinase potential through differentin vitromethods. The radical scavenging properties of BPEs were studied using various techniques, based on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) dot blot thin-layer chromatography (TLC) method, electron paramagnetic resonance (EPR) spectroscopy, metal chelation, β-carotene bleaching, inhibition of DNA breakage on agarose gel, and lipid peroxidation inhibition using liver and brain microsomes. EC50values of the results reflected that aqueous-methanolic BPE was the most active one. Antibrowning potential of the fresh leaf extract showed an antityrosinase property, with EC50values of enzymatic assay of tyrosinase inhibitory activity further advocating the findings. [ABSTRACT FROM PUBLISHER]

The gamma-irradiated single crystals of 2-Bromo-4′-methoxyaceto-phenone (2B4MA) were investigated using electron paramagnetic resonance (EPR) technique. Density-functional theory calculations were employed to investigate and identify the radicals that have been assumed to be formed upon irradiation of 2B4MA single crystals. The EPR spectra of 2B4MA were recorded at different orientations in the magnetic field at room temperature. Taking into account the chemical structure and experimental spectra of irradiated single crystal of 2B4MA, it was assumed that at least two different radicals were produced in the sample. Following this assumption, six possible radicals were modeled and EPR parameters were calculated by using the DFT, B3LYP/6-311+G(d), for the modeled radicals individually. The calculated hyperfine coupling constants and g-tensors were used as initial values for simulation studies. The three crystallographic axes on the simulated spectra were well matched with experimental spectra for the two modeled radicals. Thus, we identified the R1 type radical and R4 type radical as paramagnetic species produced in gamma-irradiated 2B4MA. [ABSTRACT FROM PUBLISHER]

High-order perturbation formulas for a 3d9 ion in rhombically elongated octahedral was applied to calculate the electron paramagnetic resonance (EPR) parameters (the g factors, gi, and the hyperfine structure constants Ai, i = x, y, z) of the rhombic Cu2+ center in CoNH4PO4·6H2O. In the calculations, the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the EPR parameters with the local structure of the rhombic Cu2+ center. Based on the calculations, the ligand octahedral (i.e. [Cu(H2O)6]2+ cluster) are found to experience the local bond length variations ΔZ (≈0.213 Å) and δr (≈0.132 Å) along axial and perpendicular directions due to the Jahn–Teller effect. Theoretical EPR parameters based on the above local structure are in good agreement with the observed values; the results are discussed. [ABSTRACT FROM AUTHOR]

The pyrochlore iridatehas been investigated by means of the electron paramagnetic resonance spectroscopy. A magnetic transition at20 K is found in addition to the transition at130 K, which has not been reported previously. The phase transition at, which corresponds to a resistivity transition, is resulted from the long-range spin ordering ofions in all-in/all-out state. However, the magnetic transition at, which is regardless of resistivity transition, is not caused bybutions. Both of the magnetic transitions are irrelevant to the lattice distortion. We suggest that the competition between the enhanced paramagnetism ofions and thef–dinteraction should be responsible for the magnetic transition at. [ABSTRACT FROM PUBLISHER]

Three fullerene isoindoline nitroxides N-methyl-3,4-fulleropyrrolidine-2-spiro-5′- (1′,1′,3′,3′-tetramethylisoindolin-2′-yloxyl), (C60-(TMIO)m, and C70-(TMIO)n) were synthesized by the covalent bonding of 5-formyl-1,1,3,3-tetramethyl isoindolin-2-yloxyl to the fullerenes C60and C70. Significantly, the X-ray photoelectron spectra indicated the characteristic N 1s signals of NO.at 402 eV. The atomic force microscope morphologies showed that the average particle sizes of C60-(TMIO)mand C70-(TMIO)nwere 38 and 15 nm. The electrochemical experiments indicated that fullerene bound isoindoline nitroxides retained similar electrochemical properties and redox reaction mechanisms as the parent nitroxides. The electron paramagnetic resonance spectra of the fullerene isoindoline nitroxides all exhibited the hyperfine splittings and characteristic spectra of tetramethyl isoindoline nitroxides, with typical nitroxide g-values and nitrogen isotropic hyperfine coupling constants. Therefore, these fullerene isoindoline nitroxides may be considered as potential candidates for novel biological spin probes using electron paramagnetic resonance spectroscopy. [ABSTRACT FROM PUBLISHER]

Reaction of VOSO4with 2-hydroxy-napthaldeyde-S-R-thiosemicarbazones (R: methyl, ethyl, propyl or allyl) and salicyl aldehyde yielded five-coordinate oxovanadium(IV) complexes having a N1,N4-diarylidene-S-R-thiosemicarbazidato structures. The compounds were characterized by elemental analysis, magnetic measurements, electronic, infrared,1H-NMR, and electron paramagnetic resonance (EPR) spectra. The X-band EPR signals were recorded from powder forms and also in solution. All the complexes have a single asymmetric line shape and theoretical fit studies prove the presence of axial symmetry around the paramagnetic vanadium ions. A computer simulation of the EPR spectrum of each complex was carried out to derive the related EPR parameters. Cyclicvoltammogramsof the complexes exhibited two metal-based reversible redox peaks around 500 and −800 mV corresponding to one electron oxidation/reduction of VIVO/VVO and VIVO/VIIIO, respectively. The reductive response in the 50–350 mV region was assigned to ligand reduction. Antioxidant activities of the compounds were determined with CUPric Reducing Antioxidant Capacity, 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, and 1,1-diphenyl-2-picrylhydrazyl assays. The test results indicated that the antioxidant capacity of the compounds increases with the carbon number of saturated hydrocarbon chain on sulfur atom. [ABSTRACT FROM PUBLISHER]

In this work, oxidized multi-walled carbon nanotubes (MWCNTs) and glycine functionalized MWCNTs were synthesized and characterized using ultraviolet-visible (UV-Vis), fourier transform infrared (FT-IR), electron paramagnetic resonance (EPR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques.. UV-Vis spectroscopic study shows a characteristic peak at 276 nm for oxidized MWCNTs, and the red shift was observed for glycine-functionalized MWCNTs at 296 nm. The appearance of another peak at around ∼350 nm is attributed to the formation of glycine-functionalized MWCNTs. FT-IR spectral study confirms that glycine molecules have bonded to MWCNTs. EPR study reveals that the line shape is a Gaussian line shape and the electron spin concentration decreases with increasing concentration of glycine, which indicates that the unpaired electrons undergo a reduction process in the glycine-functionalized MWCNTs. The g-value indicates that the systems are isotropic in nature. The surface morphology of the samples was observed from SEM images. The EDX analysis shows the high purity of both oxidized and glycine-functionalized MWCNTs. [ABSTRACT FROM PUBLISHER]

The local lattice distortions and the electron paramagnetic resonance (EPR) parameters (gfactors, hyperfine structure constants and zero-field splittings) for Cu2+, Mn2+and Fe3+in ZnWO4are theoretically studied based on the perturbation calculations for rhombically elongated octahedral 3d9and 3d5complexes. The impurity centres on Zn2+sites undergo the local elongations of 0.01, 0.002 and 0.013 Å along the C2axis and the planar bond angle variations of 8.1°, 8.0° and 8.6° for Cu2+, Mn2+and Fe3+, respectively, due to the Jahn–Teller effect and size and charge mismatch. In contrast to the host Zn2+site with obvious axial elongation (∼0.31 Å) and perpendicular (angular) rhombic distortion, all the impurity centres demonstrate more regular octahedral due to the above local lattice distortions. The copper centre exhibits significant Jahn–Teller reductions for the spin-orbit coupling and orbital angular momentum interactions, characterised by the Jahn–Teller reduction factorJ(≈0.29 ≪ 1). The calculated EPR parameters agree well with the experimental results. The local structures of the impurity centres are analysed in view of the corresponding lattice distortions. [ABSTRACT FROM AUTHOR]

The improved perturbation formulas of the spin Hamiltonian parameters (zero-field splittingDandgfactors) for a 3d5ion in trigonally distorted tetrahedra are constructed from the cluster approach by including both the crystal-field and charge-transfer contributions. These formulas are applied to the studies of the local structures and the electron paramagnetic resonance (EPR) spectra for Fe3+in CdX (X = S, Se, Te). The impurity Fe3+is found not to occupy exactly the host Cd2+sites but to experience the small outward shifts 0.014 and 0.006 Å away from the ligand triangles along the C3axis in CdS and CdSe, respectively. The charge-transfer contributions to the spin Hamiltonian parameters are important and increase significantly with increasing atomic number of the ligand (i.e., S2−< Se2−< Te2−) arising from the decreases of charge-transfer energy levels and the increases of ligand spin–orbit coupling coefficients. The results are discussed. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance parameters (gfactors and hyperfine structure constants) and local structures are theoretically investigated for Cu2+in alkali lead tetraborate 90R2B4O7·9PbO·CuO (R = Li, Na and K) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9complex. The [CuO6]10−complexes are found to experience the relative tetragonal elongation ratios 18%, 23% and 30% for R = Li, Na and K, respectively, due to the Jahn–Teller effect, much larger than those for similar ARbB4O7(A = Li, Na and K) glasses. This point is attributed to the lattice expansion (longer A–O bond lengths) with doped PbO, yielding lower force constants and more intense Jahn–Teller elongations in the 90R2B4O7·9PbO·CuO glasses. The increasing tendency (Li > Na > K) of the relative elongation ratio λ, covalency and the ratio Δg///Δg⊥forg-shifts are systematically analysed in a uniform way. [ABSTRACT FROM PUBLISHER]

The local structure and the electron paramagnetic resonance (EPR) parameters (gfactors and hyperfine structure constants) for the trigonal Nd3+centre in CdS are theoretically investigated by considering the local lattice relaxation. The impurity Nd3+is found not to occupy exactly the host Cd2+site, but to suffer a shift of about 0.31 Å away from the sulphide triangle along the C3axis due to size and charge mismatch. The theoretical EPR parameters based on the above impurity axial displacement are in good agreement with the observed values. The local structure and the EPR parameters are discussed for this centre. [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters (zero-field splittingD,gfactors and hyperfine structure constants) are theoretically studied for Mn2+in the ZnS nanocrystals and bulks from the perturbation formulae of these quantities for trigonal and cubic tetrahedral 3d5clusters, respectively. The trigonal Mn2+centre in the ZnS nanocrystals is attributed to the impurity–ligand bond angle related to the C3axis about 0.39° larger than that (≈109.47°) of an ideal tetrahedron. Almost the samegfactors and hyperfine structure constants for the nanocrystals and bulks can be ascribed to similar crystal-field environments (i.e. comparable cubic field parametersDq), nearly the same covalency (i.e. the equal covalency factorsN) and the Mn2+3d–3s orbital admixture (i.e. the identical core polarisation constants κ) in both systems. The ligand orbital and spin–orbit coupling contributions are found to be important and should be included in the electron paramagnetic resonance analysis in view of significant covalency. [ABSTRACT FROM AUTHOR]

Cross-linking of the polyethylene was performed with a high-energy electron beam. Electron paramagnetic resonance spectroscopy was used to study the lifetime of unpaired electron in the irradiated samples. Time-dependent electrical parameters are investigated for the cross-linked low-density polyethylene. Both dielectric constant and dielectric strength almost remained unchanged, but for short times, the volume resistivity and loss factor increased and decreased, respectively. It is predicted that for lifetime longer than 48 h, the electrical parameters were constant. It is believed that the variation of some electrical properties during time is due to the effects of trapped electrons. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR) parameters (gfactorsgxx,gyy,gzzand hyperfine structure constantsAxx,Ayy,Azz) are interpreted by taking account of the admixture of d-orbitals in the ground state wave function of the Cu2+ion in a Zn(C3H3O4)2(H2O)2(DABMZ) single crystal. Based on the calculation, local structural parameters of the impurity Cu2+center were obtained (i.e. Ra≈1.92 Å,Rb≈1.96 Å,Rc≈1.99 Å). The theoretical EPR parameters based on the above Cu2+−O2−bond lengths in the DABMZ crystal show good agreement with the observed values and some improvements have been made as compared with those in the previous studies. [ABSTRACT FROM AUTHOR]

Purpose: To study the effects of electromagnetic radiation (EMR) of ultra high frequency (UHF) in the doses equivalent to the maximal permitted energy load for the staffs of the radar stations on the biochemical processes that occur in the cell organelles. Materials and methods: Liver, cardiac and aorta tissues from the male rats exposed to non-thermal UHF EMR in pulsed and continuous modes were studied during 28 days after the irradiation by the electron paramagnetic resonance (EPR) methods including a spin trapping of superoxide radicals. Results: The qualitative and quantitative disturbances in electron transport chain (ETC) of mitochondria are registered. A formation of the iron-nitrosyl complexes of nitric oxide (NO) radicals with the iron-sulphide (FeS) proteins, the decreased activity of FeS-protein N2 of NADH-ubiquinone oxidoreductase complex and flavo-ubisemiquinone growth combined with the increased rates of superoxide production are obtained. Conclusions: (i) Abnormalities in the mitochondrial ETC of liver and aorta cells are more pronounced for animals radiated in a pulsed mode; (ii) the alterations in the functioning of the mitochondrial ETC cause increase of superoxide radicals generation rate in all samples, formation of cellular hypoxia, and intensification of the oxide-initiated metabolic changes; and (iii) electron paramagnetic resonance methods could be used to track the qualitative and quantitative changes in the mitochondrial ETC caused by the UHF EMR. [ABSTRACT FROM AUTHOR]

The spin-Hamiltonian parameters (the anisotropicgfactorsg||andg⊥and the hyperfine structure constantsA||andA⊥) for the impurity Cu2+in Li2B4O7are theoretically investigated using the high-order perturbation formulas of these parameters for a 3d9ion in tetragonally elongated octahedra. In the calculation formulas, the tetragonal field parameters Dsand Dtare determined from the superposition model, by considering the relative axial elongation of the oxygen octahedron around Cu2+due to the Jahn-Teller effect. Based on the calculations, the relative axial elongation of about 0.21 Å for the tetragonal Cu2+center was found. [ABSTRACT FROM PUBLISHER]

Purpose: The ability to estimate individual exposures to radiation following a large attack or incident has been identified as a necessity for rational and effective emergency medical response. In vivo electron paramagnetic resonance (EPR) spectroscopy of tooth enamel has been developed to meet this need. Materials and methods: A novel transportable EPR spectrometer, developed to facilitate tooth dosimetry in an emergency response setting, was used to measure upper incisors in a model system, in unirradiated subjects, and in patients who had received total body doses of 2 Gy. Results: A linear dose response was observed in the model system. A statistically significant increase in the intensity of the radiation-induced EPR signal was observed in irradiated versus unirradiated subjects, with an estimated standard error of dose prediction of 0.9 ±± 0.3 Gy. Conclusions: These results demonstrate the current ability of in  vivo EPR tooth dosimetry to distinguish between subjects who have not been irradiated and those who have received exposures that place them at risk for acute radiation syndrome. Procedural and technical developments to further increase the precision of dose estimation and ensure reliable operation in the emergency setting are underway. With these developments EPR tooth dosimetry is likely to be a valuable resource for triage following potential radiation exposure of a large population. [ABSTRACT FROM AUTHOR]

Single-crystal Electron Paramagnetic Resonance (EPR) and optical absorption studies were performed at room temperature on Cu(II)-ion-doped bis-glycine sodium nitrate, a semiorganic nonlinear optical material (NLO). Spin-Hamiltonian parameters, obtained from single-crystal EPR spectra, recorded in three mutually orthogonal planes, revealed the presence of two magnetically inequivalent Cu(II) sites. Molecular orbital parameters were also evaluated. The optical absorption spectrum at room temperature exhibits the lowering of octahedral symmetry to an axially elongated tetragonal of Cu(II) ion in NLO. [ABSTRACT FROM AUTHOR]

Liposomes are ideal drug-delivery systems because they can alter the pharmacokinetic characteristics and biodistribution profile of the incorporated bioactive molecule. The effect of the aminoglycoside antibiotics, gentamicin (GN), tobramycin (TOB), and amikacin (AMI), on the thermodynamic properties of multilamellar vesicles composed of 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC) was studied by using differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR), and 31P nuclear magnetic resonance (NMR) spectroscopy. The relationship between the structure of aminoglycoside antibiotics and their effect on the physical properties of the liposomal bilayers was investigated. The incorporation of the drugs was achieved and an osmotic gradient created by controlling the mole ratio of the drug inside to that outside of the DPPC vesicles so that [druginside DPPC]/[drugoutside DPPC] was 1:0, 1:0.2, 1:1, or 1:2.5. Incorporation of the drugs into liposomes caused the Tm to shift to a higher temperature and the δHm and δT1/2 values to decrease. The 2Amax and the order parameter (S), obtained from the EPR spectra, indicated that the fluidity of the liposomal membrane was affected by the type of drug and by the concentration used; GN and TOB decreased the fluidity and disturbed chain packing at mole ratios of [druginside DPPC]/[drugoutside DPPC] ranging from 1:0 to 1:0.2, while AMI increased the fluidity and disrupted chain packing at an osmotic gradient of 1:2.5. In conclusion, the molecular organization and thermotropic properties of the multilamellar DPPC vesicles were dependent on the osmotic gradient and structure of the aminoglycoside. [ABSTRACT FROM AUTHOR]

In this review article, we summarize the results of the first investigations of EPR spectra of iron-doped ternary thallium chalcogenides TlInS2, TlGaSe2, and TlGaS2 in a wide temperature interval including previously reported structural phase transitions. In these compounds, Fe ions substituted Ga and/or In sites in crystal structure and served as local probes to study ligand crystal field and its local symmetry around these paramagnetic sites. An overview of our recent EPR studies carried out at room temperature and in the temperature interval including structural phase transitions is provided. The results revealed the fine structure of EPR spectra of the paramagnetic Fe3 + ions and the local symmetry of crystal field (CF) at Fe3 + site and CF parameters. As a result of summarizing the low-temperature EPR investigations a discussion about active atomic groups, possible atomic displacements, and the local symmetry changes during the low-temperature phase transformations is presented. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR) parameters (g factors g//, g⊥ and the hyperfine structure constants) for the interstitial Co2+ center in NH4I are theoretically investigated by the diagonalization of the 6×6 energy matrix of the 4T1 ground state for a 3d7 ion under tetragonal symmetry. The contributions from the admixtures of various J (=1/2, 3/2, 5/2) states and the ligand orbital and spin-orbit coupling interactions, which were normally ignored in previous works, are taken into account in the present treatments. The contributions to the EPR parameters are discussed, and the discrepancies between the calculated hyperfine structure constants and the experimental data are also analyzed. [ABSTRACT FROM AUTHOR]

A prerequisite of dinitrosyl iron complexes (DNIC) formation is the presence of nitric oxide (NO), iron (Fe) and thiol/imidazole groups. The aim of this study was to investigate the influence of Fe chelators on the formation of DNIC in erythroid K562 cells. The cells were treated with lipophilic salicylaldehyde isonicotinoyl hydrazone (SIH) (0.1 mM) and hydrophilic deferoxamine mesylate (DFO) (1 mM), a membrane permeable and non permeable Fe chelator, respectively. Dinitrosyl Fe complexes were generated by addition of 0.07 mM diethylamine NO. The DNIC formation was recorded using electron paramagnetic resonance (EPR). Both chelators inhibited DNIC formation up to 50% after 6 hours of treatment. Taken together, our data suggest that an intracellular low molecular weight labile Fe pool (LIP) and protein-bound Fe participate in DNIC formation in K562 cells to a similar extent. [ABSTRACT FROM AUTHOR]

(50-x/2)Na2O-xCuO-(50-x/2)P2O5 glasses (x=1, 5, 15, or 30 mol%) have been prepared and characterized by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The shape of the Cu2+ EPR spectrum depends on the Cu content, and the corresponding computer simulations suggest that the Cu2+ ions occupy two different sites in these glasses: one of them is preponderant at low Cu content and the other is preponderant at high content, in which the Cu2+-Cu2+ interactions are more important. From EPR parameters, it was found that for the site at low content, the covalency of copper ion bonding with the surrounding ligands is appreciable. The magnetic susceptibility data appear to follow the Curie-Weiss law (χ=C/(T-θp)) with negative paramagnetic Curie temperature θp indicating antiferromagnetic interactions between Cu2+ ions that are more significant in the samples with high Cu content, in agreement with EPR results. [ABSTRACT FROM AUTHOR]

The spin Hamiltonian parameters (g factors g//, g⊥ and hyperfine structure constants A//, A⊥) of Cu2+ in K2SO4-Na2SO4-ZnSO4 glasses are calculated from the high-order perturbation formulas of 3d9 ion in tetragonal octahedral sites. The calculated results are in agreement with the observed values. Since the EPR parameters are sensitive to the local structure of a paramagnetic impurity center, the defect structure of Cu2+ center in K2SO4-Na2SO4-ZnSO4 glasses is estimated. The validity of results is discussed. [ABSTRACT FROM AUTHOR]

The local angular distortions around the impurity Co2+ in CdCl2, CdBr2 and PbI2 are theoretically studied from the perturbation formulas of the electron paramagnetic resonance (EPR) parameters, the g factors g// and g⊥ and the hyperfine structure constants A// and A⊥ for a 3d7 ion in trigonal symmetry. In these formulas, the contributions from the s-orbitals of the ligands, which were often ignored, are taken into account based on the cluster approach. By analyzing the EPR spectra, we find that the impurity-ligand bonding angles β related to the C3 axis in the Co2+ impurity centers are different from the corresponding metal-ligand bonding angles βH in the hosts, characterized by the local angular distortions Δβ (=β-βH). The calculated EPR parameters, especially the anisotropies of the g and A factors for the studied systems based on the local angular distortions Δ β, show reasonable agreement with the observed values. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) spectra of wheat flour show components from Fe(III), Mn(II) and free radicals (FR). The metal signals were higher in the samples from the stressed plants, and reflected the higher total levels of these elements determined analytically. They remained essentially constant throughout the experiment, but the FR signal increased progressively with time over a period of 4-6 months after milling, after which it reached a maximum. The rate of increase in the FR signal during this period was considerably higher in the flour from plants that had been exposed to elevated ozone levels. [ABSTRACT FROM AUTHOR]

Six crystal-field energy levels and three electron paramagnetic resonance (EPR) data [g factor and hyperfine structure constants A(171Yb3+) and A(173Yb3+)] for trivalent ytterbium (Yb3+) ions in the cubic β-lead fluoride (β-PbF2) crystal are calculated by using a diagonalization (of energy matrix) method. In the method, the Zeeman and hyperfine interaction terms are added to the Hamiltonian in the conventional diagonalization method, and so the optical and EPR data can be calculated in a unified way. The calculated results are in reasonable agreement with the experimental values, and the signs of constants A(171Yb3+) and A(173Yb3+) are determined. The results are discussed. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR) parameters (g factors g//, g⊥ and hyperfine structure constants A//, A⊥) for 15MgO-15Na2O-69B2O3 (MNB):Cu2+ ternary glasses were calculated based on the high-order perturbation formulae of 3d9 ion in a tetragonal symmetry. From the calculations, the defect structures of MNB:Cu2+ ternary glasses were obtained and a negative sign for A// and A⊥ for the Cu2+ center is suggested in the discussion. [ABSTRACT FROM AUTHOR]