Wyniki wyszukiwania - Biblioteka Nauki

1

Free radicals in a conglomerate of peripheral blood with a spin trap investigated by the EPR method before and after angioplasty treatment

100%

Krzyminiewski R. , Kruczynski Z. , Stepien A. , Dobosz B.

Polish Journal of Medical Physics And Engineering

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2008

|

tom 14

|

nr 1

1-12

EN

The Electron Paramagnetic Resonance (EPR) was used to investigate free radicals in the peripheral blood of patients subjected to angioplasty treatment. To detect these free radicals, a nitrosobenzene spin trap was used in this experiment. The EPR spectra of the blood with a spin trap conglomerate was measured at room temperature and at 170 K. To confirm the kind of free radicals in the conglomerate blood-spin trap, simulation and quantum-chemical calculations were made, and the conglomerate spin trap with ascorbic acid was measured. Two different types of radicals, one at room temperature and the other in a frozen sample of blood, were found.

2

Functionalization of polymer surfaces by radiation-induced grafting

100%

Przybytniak G. , Kornacka E. M. , Mirkowski K. , Walo M. , Zimek Z.

Nukleonika

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2008

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tom Vol. 53, No. 3

89-95

EN

The mutual radiation grafting of acrylic acid (AAc) onto polyethylene (PE), polypropylene (PP) and polystyrene (PS) films was performed. At first stage of investigations, the influence of ionizing radiation on the trunk polymers was studied, i.e. the level of radicals stable at room temperature and radiation yield of evolved hydrogen were estimated for each polymer. The measurements were carried out using electron paramagnetic resonance (EPR) spectroscopy and gas chromatography (GC), respectively. Radiation yields of radicals as well as hydrogen emission increased in the following order PS < PP < PE. Under comparable conditions, the same relationship was found for the yield of radiation-induced grafting of AAc. A distinct correlation between content of radicals generated by ionizing radiation in polymeric matrices and grafting degree was confirmed for the studied materials. The effect of monomer and inhibitor concentrations on the efficiency of processes were studied as well.

3

Knockdetection using spectral emission of flames

100%

Piernikarski D.

Journal of KONES

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2009

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tom Vol. 16, No. 2

383-392

EN

Introduction of spectrophotometric methods into engine research considerably expands diagnostic possibilities of the work cycle in the internal combustion engine. Spectral analysis enables to determine concentrations of chemically active compounds - radicals, which are temporary present in the flame and do not constitute finał products of the combustion. The aim of the presented research was to investigate spectral properties of the combustion flame with special regard to the detection and estimation of intensity of knocking combustion. Research was made using modifled single cylinder si test engine equipped with an optical sensor having direct access to the combustion chamber. The sensor enabled on-line transmission of the transient optical signal during the combustion through the bundle of optical wave-guides. Measurements were based on the chemiluminescence phenomena occurring in the combustion flame under the influence of high temperature and pressure. Gathered signal was passed to the monochromator. Spectral recordings were done for wavelengths typical of emission of intermediate products, covering the range from 250 nm to 625 nm, including investigated radicals like C2, CH, CN, OH. Obtained results confirmed, that occurrence of knock can be precisely detected on the basis of signal analysis which was recorded for chemiluminescence traces of different radicals. Comparison with in parallel recorded indicated pressure have shown that characteristics of emitted spectra remain in good conformity and are more sensitive to the changing of engine operating conditions.

4

Free Radical Addition and Cyclization Reactions of [2-(4-(S)-Isopropyl-2-oxazoline)-5-phenyl]dialkyltin Hydrides

100%

Stępień A. , Petrosyan A. , Wilk M. , Cmoch P. , Rupnicki L. , Staliński K.

Polish Journal of Chemistry

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2005

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tom Vol. 79 / nr 6

1015-1024

EN

Radical addition reactions of [2-(4-(S)-isopropyl-2-oxazoline)-5-phenyl]dibutyl and dimethyl hydrides to activated double/triple bonds took place in good yields. Triethylborane in presence of oxygen can serve as a radical initiator. Addition of stannyl radicals to N,N-(2-methoxycarbonyl-allyl)benzyl glycinate results in formation of the corresponding piperidine derivatives. The intramolecular tandem radical addition/ cyclization process can be performed in high yields and good diastereoselectivity.

5

Electron Spin Resonance study of radiation-induced radicals in polycrystalline oligopeptides containing methionine

100%

Strzelczak G. , Bobrowski K. , Kozubek H. , Michalik J.

Nukleonika

|

2000

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tom Vol. 45, nr 1

93-100

EN

The radicals formed on g-radiolysis of oligopeptides containing methionine and glycine residues in the polycrystalline state at 77 K and on subsequent warming over the temperature range of 77-293 K were identified using the electron spin resonance (ESR) technique. In all oligopeptides studied, anion peptide radicals and monomeric sulfur radical cations over the temperature range of 77-95 K and decarboxylation and deamination radicals over the temperature range of 180-250 K were detected. In addition, in oligopeptides containing adjacent methionyl residues, three-electron-bonded dimeric sulfur radical cations (S\S)+ were detected at 110 K. In oligopeptides containing N-terminal methionine residue, H-abstraction radicals in the side chain of methionine residue were observed over the temperature range of 180-250 K. H-abstraction radicals at the a-carbon of the C-terminal amino acid residue were detected at 293 K in most of oligopeptides studied, in contrast to Met-Gly-Met and Met-Gly-Met-Met peptides were H-abstraction radicals at the alfa-carbon of the internal glycine residue were obserwed.

6

Stereoselection at the Steady State within radicals - How far can we go ?

100%

Staliński K.

Polish Journal of Chemistry

|

2004

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tom Vol. 78 / nr 5

611-622

EN

Stereoselection at the steady state is a process, which results from a complex interplay of reaction pathways that diverge and reconverge at various points. Therefore, it can be considered as a manipulation of stereocontrol mainly by reaction topography. The advantages of this process are at least twofold: First, stereoconvergence allows the system to exceed the yield of the initial stereoconvergent event, where stereomeric transition states compete. Second, a successive resolution of the reactive intermediates by chemoselective events allows the system to generate high stereomeric excess, practically without any stereoselective competition. While illustrated with radicals, the process may prove useful in other fields of chemistry.

7

Sterilization of bacteria suspensions and identification of radicals deposited during plasma treatment

88%

Puač N. , Miletić M. , Mojović M. , Popović-Bijelić A. , Vuković D. , Miličić B. , Maletić D. , Lazović S. , Malović G. , Petrović Z. L.

Open Chemistry

|

2015

|

tom 13

|

nr 1

EN

In this paper we will present results for plasma sterilization of planktonic samples of two reference strains of bacteria, Pseudomonas aeruginosa ATCC 27853 and Enterococcus faecalis ATCC 29212. We have used a plasma needle as a source of non-equilibrium atmospheric plasma in all treatments. This device is already well characterized by OES, derivative probes and mass spectrometry. It was shown that power delivered to the plasma is bellow 2 W and that it produces the main radical oxygen and nitrogen species believed to be responsible for the sterilization process. Here we will only present results obtained by electron paramagnetic resonance which was used to detect the OH, H and NO species. Treatment time and power delivered to the plasma were found to have the strongest influence on sterilization. In all cases we have observed a reduction of several orders of magnitude in the concentration of bacteria and for the longest treatment time complete eradication. A more efficient sterilization was achieved in the case of gram negative bacteria.

8

X- and Q-band EPR study on dosimetric biomaterials

88%

Strzelczak G. , Sadło J. , Michalik J.

Nukleonika

|

2009

|

tom Vol. 54, No. 4

247-250

EN

Electron paramagnetic resonance (EPR) spectroscopy (X- and Q-band) was used for identification of stable radicals in: compact bone powder, shell of arcidae mollusc and crystalline alanine. The aim of our investigation was to analyze the complex EPR spectra of these materials and to identify paramagnetic species contributing to it. The most successful results were obtained in the EPR study (X- and Q-band) on deproteinized and irradiated bone powder and arcidae shell at room temperature.

9

Autooxidation of leuco-Methylene Blue – the Role of the Methylene Blue Radicals and Reactive Oxygen Species

88%

Katafias A. , Koter S.

Polish Journal of Chemistry

|

2009

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tom Vol. 83, nr 6

1139-1146

EN

Autooxidation of leuco-Methylene Blue to the dye, Methylene Blue, was studied in the 1.9–7.8 pH range under a large molar excess of dioxygen dissolved in the reaction solution using electronic spectroscopy. The synproportionation of the substrate and the reaction product, yielding Methylene Blue radical, plays a key role in the over all redox process. Numerical simulation of the complicated kinetic curves shows that presence of this radical opens an effective reaction path for the autooxidation process and results in coupling of the reaction steps. Reactive oxygen species (HO2 ź /O2 ź - / and H2O2) formed in the examined system are not effective oxidants and do not affect the autooxidation kinetics under applied conditions.

10

Research on betanidin oxidation by ABTS radicals

88%

Starzak K. , Skopińska A. , Wybraniec S.

Challenges of Modern Technology

|

2012

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tom Vol. 3, no. 4

39--43

EN

Betanidin is a basic betacyanin with 5,6-dihydroxyl moiety which causes its high antioxidant activity. It belongs to betalains, a group of natural, water-soluble plant pigments, which elicit a red-violet coloration of fruits and fl owers. One of the most popular sources of betanidin is red beet root (Beta vulgaris L.). Recent studies have shown importance of betalains oxidation, because of their high natural, antiradical and antioxidant activity and potential benefi ts for human health [1]. An eff ect of oxidation of betanidin using ABTS radicals was investigated in aqueous solutions at pH 3–8 and compared to activity of horseradish peroxidase. Products of the biomimetic betanidin oxidation were monitored by high performance liquid chromatography (HPLC) coupled to optical detection and mass spectrometry (LC-DAD-ESI-MS/MS). The presence of two main oxidation products: 2-decarboxy-2,3-dehydro-betanidin and 2,17-didecarboxy-2,3-dehydro- -betanidin at pH 3 indicates their generation through two possible reaction ways with two diff erent quinonoid intermediates: dopachrome derivative and quinone methide. Both reaction paths lead to the decarboxylative dehydrogenation of betanidin.

11

Hydroxyl radicals as an indicator of knocking combustion in the dual-fuel compression-ignition engine

75%

Lasocki J. , Orliński P. , Wojs M. K. , Owczuk M. , Matuszewska A.

Combustion Engines

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2017

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tom R. 56, nr 1

178--185

EN

The occurrence of knocking combustion is one of the basic problems of dual-fuel compression-ignition engines supplied with diesel oil and gaseous fuel. In order to detect this phenomenon and evaluate its intensity, several methods are commonly used, including the analysis of pressure of working medium in the combustion chamber of the engine or vibrations of certain engine components. This paper discusses the concept of using mass fraction of hydroxyl radicals as the indicator of the occurrence of knocking combustion. Current knowledge on the conditions of hydroxyl radical formation in the engine combustion chamber has been systematized and the results of research on this subject have been presented. Theoretical considerations are illustrated by exemplary results of simulation studies of the combustion process in a dual-fuel compression-ignition engine supplied with diesel oil and methane. The conclusions drawn may be useful for the development of dual-fuel engine control systems.

12

Multifrequency EPR study on radiation induced centers in calcium carbonates labeled with 13C

75%

Sadło J. , Bugaj A. , Strzelczak G. , Sterniczuk M. , Jaegermann Z.

Nukleonika

|

2015

|

tom Vol. 60, No. 3, part 1

429--434

EN

In calcite and aragonite, γ-irradiated at 77 K, several paramagnetic centers were generated and detected by EPR spectroscopy; in calcite, CO3 – (orthorhombic symmetry, bulk and bonded to surface), CO3 3–, NO3 2–, O3 –, and in aragonite CO2 – (isotropic and orthorhombic symmetry) depending on the type of calcium carbonate used. For calcium carbonates enriched with 13C more detailed information about the formed radicals was possible to be obtained. In both natural (white coral) and synthetic aragonite the same radicals were identifi ed with main differences in the properties of CO2 – radicals. An application of Q-band EPR allowed to avoid the signals overlap giving the characteristics of radical anisotropy.

13

Chemical transformations in atmospheric waters

75%

Pasiuk-Bronikowska W.

Archiwum Ochrony Środowiska

|

1999

|

tom Vol. 25, no. 1

9-20

EN

In this overview the importance of agueous-phase reactions for the atmospheric chemistry is discusses with special attention to: transformation involving radicals, solubilization and long-range transport of pollutants as effects of radical scavenging, and the location of reactions within an aqueous phase in multiphase systems. Efforts of international research groups to obtain sound scientific results and implement them in environmental policy via modelling are briefly elucidated. Some links between cloud chemistry and chemical fundamentals of FGD technologies are shown.

PL

W artykule dyskutowane jest znaczenie reakcji w fazie wodnej dla chemii atmosfery ze zwróceniem szczególnej uwagi na przemiany z udziałem rodników, solubilizację i daleki transport zanieczyszczeń w wyniku zmiatania rodników oraz na lokalizację reakcji w obrębie fazy ciekłej układów wielofazowych. Krótko omówiono działania międzynarodowych grup badawczych, zmierzjące do uzyskania dobrze ugruntowanych wyników naukowych i implementacji tych wyników - przez modelowanie - do polityki środowiskowej. Pokazano niektóre związki między chemią chmur i podstawami chemicznymi technologii oczyszczania gazów odlotowych.

14

Metody in-vivo badania właściwości antyoksydacyjnych związków kompleksowych

75%

Malinowski J. , Drzeżdżon J. , Chmurzyński L. , Jacewicz D.

Wiadomości Chemiczne

|

2019

|

tom [Z] 73, 7-8

523--538

EN

This article describes the in-vivo methods of studying the antioxidant properties of complex compounds. The reduced glutathione (GSH) method, which uses the reactivity of the reduced form of GSH with free radicals, is among the described methods. Further the in-vivo methods are based on the use of antioxidant enzymes such as glutathione peroxidase, glutathione S-transferase, superoxide dismutase, catalase. These types of enzymes occur naturally in the human body and they are responsible for the inactivation of free radicals, e. g. superoxide dismutase catalyzes the reaction of disproportionation of superoxide anion radical to water and oxygen. The next in-vivo methods described in this article use y-glutamyl transpeptidase and glutathione reductase, which are components of the antioxidant mechanism occurring in an organism. The last method described in this work relates to the lipid peroxidation, which is determined by the concentration of dimalonic aldehyde.

15

Multifrequency EPR study on radiation induced centers in calcium carbonates labeled with13C

75%

Sadło J. , Bugaj A. , Strzelczak G. , Sterniczuk M. , Jaegermann Z.

Nukleonika

|

2015

|

tom 60

|

nr 3

429-434

EN

In calcite and aragonite, γ-irradiated at 77 K, several paramagnetic centers were generated and detected by EPR spectroscopy; in calcite, CO3− (orthorhombic symmetry, bulk and bonded to surface), CO33−, NO32−, O3−, and in aragonite CO2− (isotropic and orthorhombic symmetry) depending on the type of calcium carbonate used. For calcium carbonates enriched with 13C more detailed information about the formed radicals was possible to be obtained. In both natural (white coral) and synthetic aragonite the same radicals were identified with main differences in the properties of CO2− radicals. An application of Q-band EPR allowed to avoid the signals overlap giving the characteristics of radical anisotropy.

16

The acid-catalyzed interaction of melanin with nitrite ions. An EPR investigation

75%

Matuszak Z. , Chignell C. F. , Reszka K. J.

Nukleonika

|

2015

|

tom 60

|

nr 3

475-481

EN

The interaction of synthetic dihydroxyphenylalanine (DOPA) melanin (DM) with nitrite ions, NO2−, in the pH 3.6–7.0 range, has been investigated using electron paramagnetic resonance (EPR). We found that especially at pH <5.5 (from ca. 5.5 to 3.6) the reaction of DM with nitrite generated large quantities of new melanin radicals, which implies the involvement of nitrous acid, HNO2, in the radical formation process. Measurements carried out at constant pH of 3.6 showed that the melanin signal increased together with nitrite concentration, reaching a plateau level which was more than fourfold larger compared to the initial signal amplitude observed in a nitrite-free buffer of the same pH. The effects of nitrite and DM concentrations on the melanin-free radical content were also investigated. It is proposed that the radicals are generated by one electron oxidation of melanin ortho-hydroquinone groups to ortho-semiquinones by HNO2 or related nitrogen oxides such as NO2• radicals. The possible involvement of nitric oxide (•NO) and peroxynitrite (ONOO−) in DM oxidation was also examined. In air-free solutions, nitric oxide per se did not generate melanin radicals; however, in the presence of oxygen a marked increase in the melanin EPR signal intensity was observed. This result is interpreted in terms of the generation of radicals via the oxidation of DM by peroxynitrite. Our findings suggest that melanin can function as a natural scavenger of nitrous acid and some nitrous acid-derived species. This property may be relevant to physiological functions of melanin pigments in vivo.

17

EPR study of γ-irradiated feather keratin and human fingernails concerning retrospective dose assessment

75%

Strzelczak G. , Sterniczuk M. , Sadło J. , Kowalska M. , Michalik J.

Nukleonika

|

2013

|

tom Vol. 58, No. 4

505--509

EN

In this paper we report the results of comparative EPR studies on free radicals generated in γ-irradiated powder samples of feather keratin powder and human fingernails. In degassed samples of both materials irradiated at 77 K the major component of EPR spectrum represents sulphur-centred radicals in cysteine residues. It quickly decays after air admission at room temperature while a singlet assigned to semiquinone melanin radicals remains the only one seen. The singlet recorded with fingernails decays slowly at room temperature and might be potentially useful for dose assessment by EPR. The advantages and limitations of fingernails EPR dosimetry are discussed.

18

Study of low temperature inactivation of spores using microwave excited air plasma

75%

Nagatsu M. , Singh M. K. , Zhao Y. , Fujioka Y. , Ogino A.

Journal of Automation Mobile Robotics and Intelligent Systems

|

2009

|

tom Vol. 3, No. 4

108-111

EN

In the present study, we investigated the inactivation characteristics and contribution of different inactivating factors generated in a low temperature and low pressure nitrogen, oxygen and air-simulated plasma for the inactivation of Geobacillus stearothermophilus spores. We used three optical filters i.e. thin quartz (lambda>180 nm), lithium fluorine (LiF, lambda>120 nm) and Pyrex glass (lambda>300 nm) plates to identify the most efficient wavelength range. The effect of optical radiations alone was studied through placing a small isolated and evacuated chamber with spore sample inside the plasma chamber.

19

Tautomeric Equilibria and pi-Electron Delocalization for the Substrate (Pyruvate) and Inhibitor (Oxamate) of Lactate Dehydrogenase - DFT Studies

75%

Raczyńska E. D. , Duczmal K. , Hallmann M.

Polish Journal of Chemistry

|

2007

|

tom Vol. 81, nr 9

1655-1666

EN

Keto-enol tautomerism for the substrate (pyruvate) of lactate dehydrogenase (LDH) and amideiminol tautomerism for its inhibitor (oxamate) were studied at the DFT(B3LYP)/6-31++G(d,p) level. Both anions (and also both radicals) prefer the C=O forms, i.e. the keto and amide form, respectively. The OH forms (enolpyruvate and iminoloxamate) have higher Gibbs free energies. Their amounts in the tautomeric mixtures are larger than 0.01% for anions and lower than 0.001% for radicals. pi-Electron delocalization for OCO fragments is greater than that for XCO fragments for both anions and radicals.

20

The acid-catalyzed interaction of melanin with nitrite ions : an EPR investigation

75%

Matuszak Z. , Chignell C. F. , Reszka K. J.

Nukleonika

|

2015

|

tom Vol. 60, No. 3, part 1

475--481

EN

The interaction of synthetic dihydroxyphenylalanine (DOPA) melanin (DM) with nitrite ions, NO2 –, in the pH 3.6–7.0 range, has been investigated using electron paramagnetic resonance (EPR). We found that especially at pH <5.5 (from ca. 5.5 to 3.6) the reaction of DM with nitrite generated large quantities of new melanin radicals, which implies the involvement of nitrous acid, HNO2, in the radical formation process. Measurements carried out at constant pH of 3.6 showed that the melanin signal increased together with nitrite concentration, reaching a plateau level which was more than fourfold larger compared to the initial signal amplitude observed in a nitrite-free buffer of the same pH. The effects of nitrite and DM concentrations on the melanin-free radical content were also investigated. It is proposed that the radicals are generated by one electron oxidation of melanin ortho-hydroquinone groups to ortho-semiquinones by HNO2 or related nitrogen oxides such as NO2 • radicals. The possible involvement of nitric oxide (•NO) and peroxynitrite (ONOO–) in DM oxidation was also examined. In air-free solutions, nitric oxide per se did not generate melanin radicals; however, in the presence of oxygen a marked increase in the melanin EPR signal intensity was observed. This result is interpreted in terms of the generation of radicals via the oxidation of DM by peroxynitrite. Our fi ndings suggest that melanin can function as a natural scavenger of nitrous acid and some nitrous acid-derived species. This property may be relevant to physiological functions of melanin pigments in vivo.