Search results

1

Experimental study of the structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se by means of NQR and EPR spectroscopy

100%

Bolebrukh O., Sinyavsky N., Korneva I., Dobosz B., Ostafin M., Nogaj B., Krzyminiewski R.

Open Physics

|

2013

|

vol. 11

|

issue 12

1686-1693

EN

The structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se has been studied by means of both NQR (nuclear quadrupole resonance) and EPR (electron paramagnetic resonance) spectroscopy. It is investigated that in the glasses of both systems the value of the electric field gradient at the resonating nuclei grows with increasing concentration of the clusters As2Se3 and Sb2Se3, thereby increasing the NQR resonance frequencies. It appears that for the Ge-As-Se system the structural transition from a two-dimensional to three-dimensional structure occurs at average coordination number $\bar r$ = 2.45. The EPR spectral parameters of glasses depend on the composition, the average coordination number and the temperature, and these are discussed. The effect of ”ageing” for CGS (chalcogenide glassy semiconductors) of As-Sb-Se system due to partial crystallization of the sample is observed from the EPR spectra.

2

Study of As-Sb-Se chalcogenide glasses by NQR and EPR spectroscopy methods

100%

Glotova O., Korneva I., Sinyavsky N., Dobosz B., Krzyminiewski R., Jadzyn M., Ostafin M., Nogaj B.

Open Physics

|

2011

|

vol. 9

|

issue 2

387-391

EN

In this paper experimental results obtained by both 75As NQR and EPR spectroscopy are presented for the three-component system As-Sb-Se. The 75As NQR spectra of glasses of structures (As2Se3)0.78 (Sb2Se3)0.22, (As2Se3)0.75 (Sb2Se3)0.25, (As2Se3)0.5 (Sb2Se3)0.5 have broad lines with two Sb-NQR lines (corresponding to the Sb2Se3 units) and two 75As-NQR lines (corresponding to the As2Se3 units). Differences in the EPR spectra of the different glasses arise because of the different amounts of arsenic and antimony in their structure.

3

In vitro effects of ozone on human erythrocyte membranes: An EPR study

100%

Górnicki A., Gutsze A.

Acta Biochimica Polonica

|

2000

|

vol. 47

|

issue 4

963-971

EN

The effects of ozone at different concentrations (10, 30, 45 g/m3) on fluidity and thermotropic properties of erythrocyte membranes were investigated by EPR using two spin probes: 5-doxylstearic acid (5-DSA) and 16-doxylstearic acid (16-DSA). The effect of ozone on the erythrocyte membrane fluidity was a dose-dependent process. The ozone at concentration of 10 g/m3 caused rigidization of the membrane while at concentration of 45 g/m3 increased fluidity both on the surface and in the deeper hydrocarbon region of the membrane. Temperature transitions close to the polar heads region (monitored by 5-DSA) were not sensitive to an increase in ozone concentration. In the case of 16-DSA, low temperature thermotropic transition (around 20°C) gradually decreased with the increase of ozone concentration. High temperature transition (around 40°C) significantly differed at the ozone concentration of 10 g/m3 and 45 g/m3, being higher and lower, respectively, as compared to untreated cells. For the ozone concentration of 45 g/m3 the disappearance of the low temperature break and the appearance of two breaks at 37°C and 16°C were observed.

4

Mitochondria recycle nitrite back to the bioregulator nitric monoxide.

100%

Nohl H., Staniek K., Sobhian B., Bahrami S., Redl H., Kozlov A. V.

Acta Biochimica Polonica

|

2000

|

vol. 47

|

issue 4

913-921

EN

Nitric monoxide (NO) exerts a great variety of physiological functions. L-Arginine supplies amino groups which are transformed to NO in various NO-synthase-active isoenzyme complexes. NO-synthesis is stimulated under various conditions increasing the tissue of stable NO-metabolites. The major oxidation product found is nitrite. Elevated nitrite levels were reported to exist in a variety of diseases including HIV, reperfusion injury and hypovolemic shock. Denitrifying bacteria such as Paracoccus denitrificans have a membrane bound set of cytochromes (cyt cd1, cyt bc) which were shown to be involved in nitrite reduction activities. Mammalian mitochondria have similar cytochromes which form part of the respiratory chain. Like in bacteria quinols are used as reductants of these types of cytochromes. The observation of one-e- divergence from this redox-couple to external dioxygen made us to study whether this site of the respiratory chain may also recycle nitrite back to its bioactive form NO. Thus, the aim of the present study was therefore to confirm the existence of a reductive pathway which reestablishes the existence of the bioregulator NO from its main metabolite NO2-. Our results show that respiring mitochondria readily reduce added nitrite to NO which was made visible by nitrosylation of deoxyhemoglobin. The adduct gives characteristic triplet-ESR-signals. Using inhibitors of the respiratory chain for chemical sequestration of respiratory segments we were able to identify the site where nitrite is reduced. The results confirm the ubiquinone/cyt bc1 couple as the reductant site where nitrite is recycled. The high affinity of NO to the heme-iron of cytochrome oxidase will result in an impairment of mitochondrial energy-production. "Nitrite tolerance" of angina pectoris patients using NO-donors may be explained in that way.

5

Probing iso-1-cytochrome c structure by site-directed spin labeling and electron paramagnetic resonance techniques

88%

Pyka J., Osyczka A., Turyna B., Blicharski W., Froncisz W.

Acta Biochimica Polonica

|

1999

|

vol. 46

|

issue 4

889-899

EN

A cysteine-specific methanethiosulfonate spin label was introduced into yeast iso-1-cytochrome c at three different positions. The modified forms of cytochrome c included: the wild-type protein labeled at naturally occurring C102, and two mutated proteins, S47C and L85C, labeled at positions 47 and 85, respectively (both S47C and L85C derived from the protein in which C102 had been replaced by threonine). All three spin-labeled protein derivatives were characterized using electron paramagnetic resonance (EPR) techniques. The continuous wave (CW) EPR spectrum of spin label attached to L85C differed from those recorded for spin label attached to C102 or S47C, indicating that spin label at position 85 was more immobilized and exhibited more complex tumbling than spin label at two other positions. The temperature dependence of the CW EPR spectra and CW EPR power saturation revealed further differences of spin-labeled L85C. The results were discussed in terms of application of the site-directed spin labeling technique in probing the local dynamic structure of iso-1-cytochrome c.

6

Magnetic and structural anomalies of NanC60 (n = 2, 3)

88%

Kulbachinskii V., Bulychev B., Kytin V., Krechetov A., Tarasov V., Konstantinova E., Velikodnyi Y., Muravlev Y., Zoteev A.

Open Physics

|

2010

|

vol. 8

|

issue 1

101-112

EN

Sodium fullerides NanC60 (n = 2, 3) have been synthesized by a liquid phase reaction and investigated with X-ray diffraction (XRD), nuclear magnetic resonance (NMR), electron paramagnetic resonance, and differential thermal analysis. XRD data indicate that the crystal structure of Na2C60 at 300 K is face centered cubic (FCC). A phase transition from primitive cubic to FCC crystal structure has been observed in this work in Na2C60 fulleride at 290 K. The transition is accompanied by the step-like change of paramagnetic susceptibility. The crystal structure of Na3C60 is more complicated than, and different from, what has been reported in the literature. A nearly seven-fold increase of paramagnetic susceptibility with increasing temperature has been observed in the Na3C60 fulleride at 240–260 K. In the same temperature range, a new line at about 255 ppm appears in the 23Na NMR spectrum, indicating a significant increase of electron density near the Na nucleus. The observed effect can be explained by a metal-insulator transition caused by a structural transition.

Refine search results

Experimental study of the structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se by means of NQR and EPR spectroscopy

Study of As-Sb-Se chalcogenide glasses by NQR and EPR spectroscopy methods

In vitro effects of ozone on human erythrocyte membranes: An EPR study

Mitochondria recycle nitrite back to the bioregulator nitric monoxide.

Probing iso-1-cytochrome c structure by site-directed spin labeling and electron paramagnetic resonance techniques

Magnetic and structural anomalies of NanC60 (n = 2, 3)