Wyniki wyszukiwania - Biblioteka Nauki

1

Mechanism of peroxynitrite interaction with cytochrome c.

100%

Gębicka L. , Didik J.

Acta Biochimica Polonica

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2003

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tom 50

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nr 3

815-823

EN

Kinetics of the reaction of peroxynitrite with ferric cytochrome c in the absence and presence of bicarbonate was studied. It was found that the heme iron in ferric cytochrome c does not react directly with peroxynitrite. The rates of the absorbance changes in the Soret region of cytochrome c spectrum caused by peroxynitrite or peroxynitrite/bicarbonate were the same as the rate of spontaneous isomerization of peroxynitrite or as the rate of the reaction of peroxynitrite with bicarbonate, respectively. This means that intermediate products of peroxynitrite decomposition, ·OH/·NO2 or, in the presence of bicarbonate, CO3-·/·NO2, are the species responsible for the absorbance changes in the Soret band of cytochrome c. Modifications of the heme center of cytochrome c by radiolytically produced radicals, ·OH, ·NO2 or CO3-·, were also studied. The absorbance changes in the Soret band caused by radiolytically produced ·OH or CO3-· were much more significant that those observed after peroxynitrite treatment, compared under similar concentrations of radicals. ·NO2 produced radiolytically did not interact with the heme center of cytochrome c. Cytochrome c exhibited an increased peroxidase-like activity after reaction with peroxynitrite as well as with radiolytically produced ·OH, ·NO2 or CO3-· radicals. This means that modification of protein structure: oxidation of amino acids and/or tyrosine nitration, facilitates reaction of H2O2 with the heme iron of cytochrome c, followed by reaction with the second substrate.

2

Radiation-induced oxidation of thiaproline derivatives in frozen acidic aqueous solutions: theoretical and Electron Spin Resonance study

100%

Pogocki D. , Sadło J.

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2000

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tom Vol. 45, nr 1

101-108

EN

Radicals formed by gamma-radiolysis of thiaproline (thiazolidine-4-carboxylic acid) amino acid and its derivatives in a frozen acidic aqueous solution at 77 K and by subsequent warming from 95 to 200 K have been studied by electron spin resonance (ESR). The experimental parameters of radical spectra were compared with those obtained by quantum-mechanical calculations on AM1 and PM3 semiempirical levels.

3

Physico chemical properties of irradiated i-SANEX diluents

75%

Mossini E. , Macerata E. , Giola M. , Brambilla L. , Castiglioni C. , Mariani M.

Nukleonika

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2015

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tom 60

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nr 4

893-898

EN

The development of effective processes to recover minor actinides from spent nuclear fuel cannot leave out of consideration the evaluation of the impact of ionizing radiations on safety, fluid dynamics and extraction efficiency. It is common knowledge from the literature that radiation damage mainly affects the diluents and, indirectly, the extractants [1], but a lack of knowledge remains regarding the radiolytic behavior of innovative selective actinide extraction (i-SANEX) diluents [2, 3]. As natural prosecution of the work already performed on diluted nitric acid solutions [4], 0.44 M nitric acid solutions were irradiated in contact with a mixture of kerosene + 5 vol.% 1-octanol by a Co-60 source at 2.5 kGy/h dose rate and up to 100 kGy absorbed dose, conditions of interest for the future industrial facility. Density, viscosity, acidity, nitrate anion concentration and phase transfers were systematically measured before and after γ-irradiation. This was performed because radiation-induced modifications of these parameters may induce alterations of both the fluid dynamics and the separation performances of the extracting system. The results suggest that the fluid-dynamics of the system should be unaltered. In fact, only slight alterations of the organic phase viscosity and of the aqueous phase acidity were measured after irradiation, suggesting the occurrence of limited phase transfers and of diluent by-products formation.

4

Radiacyjna obróbka żywności. Stan prawny i dawki promieniowania

75%

Dzwolak W.

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2009

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tom T. 63, nr 4

32-35

PL

W artykule zaprezentowano aktualne informacje z zakresu zastosowania promieniowania jonizującego w produkcji żywności. Scharakteryzowano międzynarodowe (Komisji Kodeksu Żywnościowego i Unii Europejskiej) oraz polskie przepisy prawa żywnościowego w zakresie napromieniania środków spożywczych. Ponadto przedstawiono aktualne dopuszczalne dawki promieniowania jonizującego.

EN

In the article some current information on application of ionizing irradiation in food manufacturing are presented. International (CAC and EU) and Polish food law acts on food irradiation are characterized. Moreover, levels of irradiation dose are discussed.

5

Radiacyjna obróbka żywności

63%

Dzwolak W.

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2010

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tom T. 64, nr 4

24-25

PL

W artykule omówiono wpływ promieniowania jonizującego na składniki żywności, łącznie z powstawaniem 2-alkilocyklobutanonów w napromienianej żywności, oraz możliwości zastosowania promieniowania jonizującego do redukcji kancerogennych związków chemicznych (N-nitrozoamin i amin irradiabiogennych) obecnych w niektórych środkach spożywczych. Podano również podstawowe zasady znakowania żywności napromienionej. Artykuł jest rozszerzeniem publikacji zamieszczonej w nr 4/2009 "Przemysłu Spożywczego" pod tytułem "Radiacyjna obróbka żywności. Stan prawny i dawki promieniowania".

EN

The influence of ionizing irradiation on food compounds is discussed in the article. Formation af 2-alkylcyklobutanone in irradiated foods is also presented. Some possibilities of reduction in some foods cancerous compounds (N-nitrosamines and biogenic amines) by ionizing tion are shown. There are also presented some general information on labeling of irradiated food. The article is an extension of a paper published in issue No. 4/2009 of "Przemysł Spożywczy" does under the tile "Irradiation of Food. Legal Status and Irradiation".

6

ESR studies of silver clusters in the isostructural A and ZK-4 molecular sieves

63%

Michalik J. , Yu J.-S. , Sadło J.

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2000

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tom Vol. 48, No. 4

293-301

EN

Cationic silver clusters formed in l-irradiated Ag+-exchanged Linde 4A zeolite and isostructural synthetic ZK-4 zeolite with Si/ Al ratio of 1.2 and 2.4 have been studied by electron spin resonance (ESR) spectroscopy. Whereas dehydrated AgNa-A zeolite shows rem.arkable ability for stabilization of Ag(6)n+ clusters in AgNa-ZK-4 zeolites hexameric silver clusters are not formed at all. .In ZK-4 samples exposed to water or methanol tetrameric silver clusters Ag(3)(4)+ are efficiently produced. Although geometri-cal size constraints play a crucial role with respect to cluster nuclearity and stability, in this paper we show that other factors like total cation capacity and/ or the presence of molecular adsorbates can affect the silver agglomeration process to a great extent.

7

Mechanizm ochrony przed radiolizą polipropylenu

51%

Zagórski Z. P.

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2001

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tom Vol. 50, nr 23

93-96

PL

Osiągnięcie planowanych skutków obróbki radiacyjnej polimerów, np. w celu sterylizacji radiacyjnej wyrobów medycznych, wymaga zastosowania dodatków ochronnych, zwłaszcza gdy stosowany polimer należy do tych, w których degradacja dominuje nad sieciowaniem, jak w przypadku polipropylenu. Referat omawia podstawy oddziaływań radiacyjnych w polimerach, decydujących o rozkładzie energii i produktów radiolizy. Dotychczas dobór dodatków ochronnychpolegał na stosowaniu typowych dodatków umożliwiających przetwórstwo i które metodą prób i błędów wykazywały jednocześnie korzystną ochronę przed radiolizą. Dziś coraz więcej wiadomo o mechanizmach radiolizy polimerów, a więc dobór składu może być łatwiejszy i bardziej skuteczny. Znajomość mechanizmów radiolizy jest też pożądana przy planowaniu składu dla osiągnięcia innych niż sterylizacja celów obróbki radiacyjnej. Najlepszym mechanizmem ochronnym jest przenoszenie energii jonizacji do związku aromatycznego, który jest w stanie rozproszyć energię pochłoniętą z minimalnym efektem chemicznym.

EN

The aim of radiation processing of polymers, e. g. sterilization of medical devices made from polymers can be reached only in the presence of proper additives, especially in the case of polymers which degrade and do not crosslink when irradiated, as polypropylene. The paper presents the background of radiation interactions, which decide on the distribution of energy and of product of radiolysis in the polymer blend. The choice of additives was determined several years ago by the application of usual preparations available commercially, which make processing of polymers possible at all. It has been found by try and error approach, that some conventional additives are protecting polypropylene from radiolysis better than others. Another approach consisted in application of polymers in mixtures of aliphatic and aromatic polymers in which the presence of aromatic moiety reduces the extend of radilysis. Deeper knowledge of mechanisms of protection and energy transfer permits improvement of radiation processing towards other applications, not only medical. They are directed towards the positive aspects of radiolysis (e.g. crosslinking) and not negative ones dominating in radiation sterilization. Differences in the protection effects from light and from ionizing radiation are explained in terms of photochemistry and radiation chemistry of polymers. Special attention is paid to the role of single-ionization spurs which can change their final location to specific places and multi-ionization spurs which cause irreparable scission of the chain, which cannot lead in the case of polypropylene to formation of crosslinks, as in the case of polyethylene (c.f. reference 1 in print).