scholarly journals Electron paramagnetic resonance (EPR) study of DOPA–melanin complexes with kanamycin and copper(II) ions

2011 ◽  
Vol 25 (3-4) ◽  
pp. 197-205 ◽  
Author(s):  
Lidia Najder-Kozdrowska ◽  
Barbara Pilawa ◽  
Ewa Buszman ◽  
Dorota Wrzesniok ◽  
Andrzej B. Więckowski
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Epr Spectroscopy ◽  
Paramagnetic Centers ◽  
High Concentration ◽  
Paramagnetic Resonance ◽  
Fitting Method ◽  
Epr Parameters ◽  
Dopa Melanin ◽  
Electron Paramagnetic ◽  
Paramagnetic Centres

This work comprises the study of DOPA–melanin complexes with kanamycin and copper(II) ions made by electron paramagnetic resonance EPR spectroscopy. The high concentration of paramagnetic centers in melanin makes the use of EPR spectroscopy possible. The unpaired electron localized on the oxygen atom in indol-5,6-quinone groups is the paramagnetic centers in this polymer. The aim of this work was the analysis of EPR parameters of recorded spectra. For researches were prepared melanin complexes which differed in complexing order of drug and Cu(II) ions, and in concentration of CuCl2solutions used during synthesis. The introduction of drugs and metal ions into melanin causes changes in EPR parameters of recorded spectra. Kanamycin causes the increase and copper(II) ions the decrease of concentrations of paramagnetic centres in melanin. Shape of EPR signal of DOPA–melanin was analyzed by fitting method. Results indicate that EPR line of DOPA–melanin is superposition of Gaussian and Lorentzian function.

Investigation of Antioxidant Activity of Pomegranate Juices by Means of Electron Paramagnetic Resonance and UV-Vis Spectroscopy

2015 ◽  
Vol 98 (4) ◽  
pp. 866-870 ◽  
Author(s):  
Violetta Kozik ◽  
Krystyna Jarzembek ◽  
Agnieszka Jędrzejowska ◽  
Andrzej Bąk ◽  
Justyna Polak ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radical ◽  
Epr Spectroscopy ◽  
Antioxidant Properties ◽  
Free Radical Scavenger ◽  
Pomegranate Juice ◽  
Radical Scavenger ◽  
Paramagnetic Resonance ◽  
Vis Spectroscopy ◽  
Electron Paramagnetic

Abstract Pomegranate fruit (Punica granatum L.) is a source of numerous phenolic compounds, and it contains flavonoids such as anthocyanins, anthocyanidins, cyanidins, catechins and other complexes of flavonoids, ellagitannins, and hydrolyzed tannins. Pomegranate juice shows antioxidant, antiproliferative, and anti-atherosclerotic properties. The antioxidant capacity (TEAC) of the pomegranate juices was measured using electron paramagnetic resonance (EPR) spectroscopy and 1,1-diphenyl-2-picrylhydrazyl (DPPH•) as a source of free radicals, and the total phenolic (TP) content was measured using UV-Vis spectroscopy. All the examined pomegranate juices exhibited relatively high antioxidant properties. The TEAC values determined by means of EPR spectroscopy using Trolox (TE) as a free radical scavenger were in the range of 463.12 to 1911.91 μmol TE/100 mL juice. The TP content measured by the Folin-Ciocalteu method, using gallic acid (GA) as a free radical scavenger, widely varied in the investigated pomegranate juice samples and ranged from 1673.62 to 5263.87 mg GA/1 L juice. The strongest antioxidant properties were observed with the fresh pomegranate juices obtained from the fruits originating from Israel, Lebanon, and Azerbaijan. Correlation analysis of numerical data obtained by means of EPR spectroscopy (TEAC) and UV-Vis spectroscopy (TP) gave correlation coefficient (r) = 0.90 and determination coefficient (r2) = 0.81 (P <0.05).

INVESTIGATIONS OF ELECTRON-PARAMAGNETIC-RESONANCE PARAMETERS OF OCTAHEDRAL (CrO6)9- and (MnO6)8- CLUSTER IN MgTiO3:Cr3+, SrTiO3:Cr3+ AND SrTiO3:Mn4+ CRYSTALS

2011 ◽  
Vol 25 (21) ◽  
pp. 1779-1785
Author(s):  
MINJIE WANG ◽  
LIANXUAN ZHU ◽  
JIANLIANG DANG
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Crystal Field ◽  
Valence State ◽  
Spin Orbit ◽  
Contribution Rate ◽  
Paramagnetic Resonance ◽  
Epr Parameters ◽  
Experimental Values ◽  
Electron Paramagnetic ◽  
G Factors

The complete high-order perturbation formulas are established by both crystal-field (CF) and charge-transfer (CT) mechanisms. The EPR g factors of MgTiO 3: Cr 3+, SrTiO 3: Cr 3+ and SrTiO 3: Mn 4+ crystals are calculated from the formulas. The calculations of the EPR g factors are in agreement with the experimental values. The contribution rate of the CT mechanism (|ΔgT/ΔgF|) to EPR parameters, increases with the growth of the valence state for the 3dn ions in the crystals. For the higher valence state 3d3 ion Mn 4+ in crystals, the explanation of the EPR parameters reasonably involves both CF and CT mechanisms. The g values are also given from one-spin-orbit-parameter model and crystal-field (CF) mechanism for comparison.

scholarly journals Chain initiation

2019 ◽  
Vol 89 (2) ◽  
pp. 179-186
Author(s):  
V. V. Ptushenko
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Epr Spectroscopy ◽  
Paramagnetic Resonance ◽  
Chain Initiation ◽  
Radio Spectroscopy ◽  
Scientific Instrumentation ◽  
History Of ◽  
Scientists And Engineers ◽  
Electron Paramagnetic

This article describes the formation of the chemical electron paramagnetic resonance (EPR) spectroscopy institute established by Academician Vladislav V. Voevodsky (1917–1967) along with the history of the development of the instrumentation basis for this field of science in the Union of Soviet Socialist Republics (USSR). The design of the first EPR spectrometers for the chemical radio spectroscopy initiated the emergence of a new scientific instrumentation field in this country. Based on recollections shared by scientists and engineers and an examination of archive materials, the author reconstructs relevant events and identifies major participants in this process.

Paramagnetische Elektronenresonanz (EPR) des Europiums in Cadmiumfluorid (CdF2: Eu 2+ ), weitere Untersuchungen / Electron Paramagnetic Resonance (EPR) of Europium in Cadmium - Fluoride (CdF2 : Eu2+), Further Details

1971 ◽  
Vol 26 (10) ◽  
pp. 1589-1603
Author(s):  
D. Geist ◽  
E. Gerstenhauer ◽  
G. Rsckebrandt
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Eigenvalue Problem ◽  
Numerical Solution ◽  
Paramagnetic Resonance ◽  
Cadmium Fluoride ◽  
Crystalline Field ◽  
Superhyperfine Structure ◽  
Forbidden Transitions ◽  
Epr Parameters ◽  
Electron Paramagnetic

Abstract This paper describes EPR measurements within the system CdF2 : Eu 2+ between 77 K and 300 K at 9 GHz and 35 GHz for B || [001]. The measurements enable a test of the formerly determined EPR parameters by the strict numerical solution of the eigenvalue problem including the hyper-fine terms. In particular “forbidden” transitions (ΔM = 2) also occur in a strict cubic crystalline field. An interpretation of the superhyperfine structure at 9 GHz and 35 GHz is compatible with the constants T|| = 6.26 MHz and T| = - 6.04 MHz of the interaction with the F ions of the 1 st shell.

On The EPR Parameters of Divalent Cobalt in ZnX (X = S, Se, Te) And CdTe

2004 ◽  
Vol 59 (12) ◽  
pp. 938-942 ◽  
Author(s):  
Shao-Yi Wu ◽  
Hui-Ning Dong
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Charge Transfer ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Paramagnetic Resonance ◽  
A Value ◽  
Epr Parameters ◽  
Divalent Cobalt ◽  
Structure Constants ◽  
Electron Paramagnetic

The electron paramagnetic resonance (EPR) parameters g and the hyperfine structure constants A of Co2+ in ZnX (X = S, Se, Te) and CdTe are studied, using the perturbation formulas of the EPR parameters for a 3d7 ion in tetrahedra based on two mechanism models. In these formulas, both the contributions from the conventional crystal-field (CF) mechanism and those from the charge-transfer (CT) mechanism are taken into account. According to the investigations, the sign of the g-shift ΔgCT from the CT mechanism is the same as ΔgCF from the CF mechanism, whereas the contributions to the A value from the CF and CT mechanisms have opposite signs. Particularly, the contributions to the EPR parameters from the CT mechanism increase rapidly with increase of the spin-orbit coupling coefficient of the ligand and the covalency effect of the systems, i. e. S2− < Se2− < Te2−.

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