ESR Signal Amplitude Research Articles

Paramagnetic properties of Cuban red mud at low temperatures

The electron spin resonance (ESR) spectra of Cuban red mud have been measured at three different temperatures: 295 K, 150 K and 77 K. The broad absorption line with resonance fields ∼(1.7–1.8) kOe was observed at all temperatures with values of g-factor from 3.602 to 4.020. The temperature decrease resulted in an absorption line appearance with resonance fields of 3.252 kOe (g = 2.067) at 150 K and 3.339 kOe (g = 2.086) at 77 K. The ESR-signal amplitude with resonance fields ∼(1.7–1.8) kOe decreases and the ESR-signal amplitude in the field ∼3.3 kОе increases with reduction in temperature.

Copper-induced change in the ESR signal of hemoglobin nitrosyl complexes in wound by the action of copper nanoparticles

The results concerning changes in the ESR signal of hemoglobin nitrosyl complexes in wound tissues in the course of healing by the action of ointments with copper nanoparticles (patent N2460532, Russia) are presented. It is shown that the wound healing process modified by the influence of copper nanoparticles demonstrates the increase in the ESR signal amplitude for :hemoglobin nitrosyl complexes as compared with controls (the ointment base without nanoparticles). Planimetric measurements of wound area through reparation course indicate an active process of wound healing for injuries treated with copper nanoparticles in the ointment, resulting in lessening half-reparation time up to 5.0 times as compared with controls (treatment with the ointment base). The paper discusses the role of copper nanoparticles, NO and their potential synergistic effect on the skin wound regeneration.

Dosimetry and application of the alanine-polymer film dosimeter

Alanine/ESR dosimetry has been developed mainly for reference and transfer dosimetry. The dosimetric properties of the alanine-polymer film dosimeter have been studied. It is found that the dose-response curves have very good linearity in double logarithm coordinates in the range 10 2–10 4 Gy for both 60Co γ-rays and electron beam, and a slight sublinearity in higher dose region. The dispersivity of the ESR signal amplitude is investigated and its standard deviation is ±1.2%. The effect of irradiation temperature on the ESR signal amplitude of the irradiated samples is studied. And the correction factor 0.0026°C −1 is obtained for 800 Gy dose irradiated with 60Co γ-ray. The overall uncertainty of this dosimeter system is less than ±4.8% (2 σ) at a dose of 800 Gy for 60Co γ-rays, and less than ±5% (2 σ) at a dose of 1.8 kGy for 4 MeV electron beam. The dosimeters have been used for radiation processing at 3–5 MeV linear electron accelerator.

The reaction of lanthanide ions with n-doxyl stearic acids and its utilization for the ESR study on the permeability of lipid-bilayer of erythrocyte membrane to gadolinium ions

The reaction of lanthanide ions with n-doxyl stearic acid ( nDS) spin labels ( n=5,7,12,16) was investigated by the electron spin resonance technique in aqueous solution. Among the lanthanides, the Gd 3+, Tb 3+, Tm 3+ and Ce 3+ ions strongly quenched the ESR signal of spin labels, but the effects of La 3+, Eu 3+ and Lu 3+ are very weak. The quenching effects are featured by: (1) the dependence on the concentration of lanthanide ions; (2) no obvious changes of the ESR line shape in the presence of lanthanide ions; (3) the quenching constant decreases in the order: Gd 3+ > Tb 3+ > Tm 3+ > Ce 3+; (4) the quenching effects of lanthanide ions are found to strikingly correlate with their magnetic properties. These findings indicate that the interaction of lanthanide ions with nitroxide oxygen leading to the reduction of ESR signal amplitude is dominated by their magnetic characteristics rather than the coordination effect. By labeling erythrocyte membrane with nDS, n=5,7,12,16 at different depths, we studied the diffusion of Gd 3+ into the lipid-bilayer of erythrocyte membrane by monitoring the reduction processes of the ESR signals of nitroxide spin labels located at different depths of membrane lipid-bilayer after addition of Gd 3+. These results revealed that the Gd 3+ ions can penetrate into the lipid-bilayer, though the entry rate is slow. It was shown that the Gd 3+ ions bind to the membrane and enhance the permeability of extracellular ascorbate into erythrocyte membrane. The transport mechanism of Gd 3+ ions through the lipid-bilayer might be involved in the Gd 3+ cation-induced pore formation in the surface of membrane.

Structural identification of point defects in amorphous silicon oxynitrides

The nature and the behaviour of point defects in amorphous hydrogenated silicon oxynitrides SiO x N y H z are reviewed and compared to that in plasma-enhanced chemical vapour deposition silicon dioxide and silicon nitrides. These defects are studied by electron spin resonance measurements after the ESR signal amplitude saturation by VUV illumination. The influences of the chemical composition (atomic ratio O O + N in the SiO x N y H z ) and of the hydrogen density on the type and density of defects are investigated. This is achieved by working on usual silicon oxynitrides containing high hydrogen densities (HHD) and on a new family of materials, the low hydrogen densities (LHD) silicon oxynitrides. Two defects are found in LHD silicon oxynitrides, the silicon dangling bond (Si db) and a new type of nitrogen related defect, the N x defect. By contrast, three defects are found in the usual HHD silicon oxynitrides, the Si db, the nitrogen dangling bond (N b) and the N x defect. The N x defect is described by an axially symmetrical paramagnetic centre with g ‖ = 2.0030, g ⊥ = 2.0017, A iso = 18.9 G and A aniso = 9.7 G. Compared to the situation observed in the silicon nitride where the nitrogen defects are only observed after rough treatments, the nitrogen defects are easily detected in the silicon oxynitrides.

ESR Dosimetry with Magnesium Sulphate

Abstract The aim of the investigation is to enhance the ESR dosemeter sensitivity in the therapy dose range below 10 Gy, where the ESR spectrum of the a-alanine radical becomes increasingly difficult to evaluate for dosimetry. Anhydrous magnesium sulphate, MgSO4, appears to be an excellent candidate from the spectrometric point of view. On irradiation with 60Co ? rays the stable radical SO3 is produced whose ESR signal amplitude increases linearly with dose up to about 105 Gy. Ignoring the abundant isotopes 17O (0.04%) and 33S (0.74%), the spectrum of SO3 is a single line at g = 2.0036 of width 0.5 mT which is stable at temperatures up to at least 120 oC. Using the conventional peak-to-peak method of dosemeter readout, the MgSO4 dosemeter is somewhat more sensitive than the traditional alanine dosemeter of the same mass. Its main advantage over the alanine dosemeter is, however, the ease of computer enhancement and the possibility of integration which the single-line spectrum offers.

Spin-label assay for phospholipase A 2

A rapid and continuous method for measuring phospholipase A 2 activity using electron spin resonance spectroscopy and a spin-labeled phospholipid as a substrate has been developed. The substrate, 1-palmitoyl-2-(4-doxylpentanoyl)glycerophosphocholine, gives rise principally to a broad ESR line in aqueous solution due to strong spin-spin interactions, probably resulting from its micellar formation. Upon addition of bee venom phospholipase A 2, the water-soluble product, 4-doxylpentanoic acid, is released which brings about a sharp three-line spectrum. Thus, the kinetics of phospholipase A 2 activity can be followed by monitoring the increase in the ESR signal amplitude of the three-line spectrum, which is linearly proportional to the amount of 4-doxylpentanoic acid produced; no separation of the product from the substrate is needed during the measurement. The rate of hydrolysis of 1 nmol min −1 can be accurately measured within a 5-min period of time in a sample volume of 100 μl. This new method should be useful for assaying phospholipase A 2 activities in various biological systems.

Spin trap determination of free radical burst kinetics in stimulated neutrophils.

Electron spin resonance spin-trapping methods were used to investigate the free radical production kinetics of neutrophils stimulated with phorbol myristate acetate (PMA) and opsonized zymosan (OPZ). Using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide, the principle spin adduct observed is DMPO-OH (trapped hydroxyl radical). The DMPO-OH ESR signal amplitude was observed to decay exponentially. In such cases a simple method may be used to analyze the raw kinetics amplitude data to yield true production rate and net production data. The method, pitfalls, and self-consistency criteria are illustrated with PMA and OPZ-stimulated neutrophils at 25 and 37 degrees C under varying oxygen tensions, and with noise-free simulated data. The simulations demonstrate that rate results are relatively insensitive to the precise choice of decay time constant, tc, while net production results are very sensitive to the choice of tc used to analyze the raw data. OPZ (0.6-2.4 mg/ml) yields a strong, sharp neutrophil burst which peaks in 2 min or less while PMA yields a slower burst which peaks in 3.4-14 min for PMA concentrations of 500-50 ng/ml, respectively. Increased oxygen tension during the PMA experiments increased the spin adduct lifetime. The methods presented are applicable to other cell systems or spin adducts which exhibit first order decay.

Magnetic resonance experiments on the radical cation salt (fluoranthenyl) 2+ PF 6−. Correlation of proton-NMR, fluorine-NMR and ESR

The longitudinal relaxation rates of the protons and the fluorine were determined for the radical cation salt (fluoranthenyl) 2 +PF 6 − as a function of the temperature. These data are compared with the temperature dependence of the pulsed ESR signal amplitude at the same Larmor frequency (44 MHz). Whereas the fluorines are relaxed mainly by the reorientational motion of the anions and by the interaction with fixed paramagnetic impurities, the protons are relaxed additionally above 150 K predominantly by highly mobile paramagnetic species, whose concentration could be determined directly via the signal amplitudes of the NMR and ESR signals in the same set up. The Pauli susceptibility χ c s = 3.1 ×10 −5 cm 3/mole which is derived from this experiment and the Korringa relation ( T 1H 4 −) −1 = constant of the proton relaxation leads to the assumption of a metal-like behavior of the salt above 183 K. The observation that the protons of the cation stacks, rather than the fluorines on the anions are relaxed by the mobile paramagnetic species favors the assumption of one-dimensional spin transport within the fluoranthenyl stacks, which is further supported by an ω −1 2 dependence of T 1H −1.

Association between onset of generative phase and amplitude of ESR signal I in wheat leaves

Association between onset of generative phase and amplitude of ESR signal I in wheat leaves

Spin polarization in the lowest triplet state of chlorophyll

Chlorophyll-b in glassy solution has a spin-polarized lowest triplet state at and above 77 K. The magnitude of the effect is different for MTHF and ethanol as solvents, in contrast to what is found for the porphin free base. Chlorophyll-a does not exhibit spin-polarization under identical conditions as for chlorophyll-b. Zero-field parameters are found to be: chlorophyll-a (MTHF) D = (281 ± 6) × 10 −4 cm −1; E = (39 ± 3) × 10 −4 cm −1; chlorophyll-b (MTHF) D = (289 ± 4) × 10 −4 cm −1; E = (49 ± 3) × 10 −4 cm −1, From ESR signal kinetics it follows that for chlorophyll-b, population and depopulation mainly involve the spin level y⪢, describing a spin moving in a plane perpendicular to the molecular plane: P y ⪢ P x ⪢ P z ; k x = 240 ± 40 s −1; k y = 600 ± 120 s −1; k z ⩽ 75 s −1, where P i and k i denote populating and decay rates. Thus, the kinetic scheme for the chlorophyll triplet is different from that of porphyrins with heavier metal ions, but very similar to that of the porphin free base. The spin-lattice relaxation time is found to be anisotropic and shorter than the decay rates of individual spin levels. Nevertheless, spin polarization can be observed, essentially because the ESR signal amplitude depends on population differences.

Variation of ESR signal amplitude with duration of tumor growth

Variation of ESR signal amplitude with duration of tumor growth

ESR Study of the Mercury-photosensitized H2+O2 Reaction

Abstract The ESR technique has been applied to a study of the mercury-photosensitized reaction of H2+O2 mixtures in the PO2=10–200 μHg and PH2=0.2–4 mmHg regions. For the determination of this reaction, the concentration (ESR signal amplitude) of H atoms was followed with time throughout the reaction. The concentration of H atoms varied with time; its maximum was determined. The time (Tm) at which the H atom concentration reached a maximum depended on oxygen and hydrogen pressures. From the variations in Tm and some kinetic considerations, it was concluded that oxygen played an important role in this reaction in increasing the stationary concentrations of H atoms in the system. In this experiment, I0=2.4×1015 molecules/sec, the rate of the production of H atoms in Reaction (1), was determined from the variations in Tm with the initial oxygen pressure: (Remark: Graphics omitted.) The pressure of oxygen at the maximum concentration of H atoms was found to be little dependent on the PH2 used in this experiment; 5 μHg was found to be this pressure.