Wyniki wyszukiwania - Biblioteka Nauki

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Wykorzystanie metod spektroskopowych w badaniach procesów i produktów polimeryzacji rodnikowej

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Pabin-Szafko B. , Wiśniewska E.

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tom Vol. 65, nr 7

637-642

PL

Zastosowanie metod spektroskopowych w chemii polimerów pozwala na uzyskanie niezbędnych informacji przy identyfikowaniu struktury chemicznej związków i tym samym na badanie różnych procesów, począwszy od syntezy inicjatorów, ich zachowania się w różnych warunkach (np. w reakcji rozpadu), poprzez badanie pozostałych substratów oraz produktów polimeryzacji, a także badanie innych procesów - modyfikacji czy destrukcji polimerów.

EN

The utilization of spectroscopic methods in polymer chemistry allows obtaining the necessary information to identify the chemical structure of compounds and moreover different processes studies, starting from initiator synthesis, their behaviour at various conditions (e.g. during thermal decomposition), through the other polymerization substrates and products study, and also other processes - polymers modification or destruction investigations.

2

Optimization of extraction of pyrrolizidine alkaloids from plant material

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Mroczek T. , Widelski J. , Głowniak K.

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tom Vol. 51, No. 4

567-580

EN

Various techniques of extraction of pyrrol izidine alkaloids (PAs) from comfrey have been developed and compared. Different extraction media: methanol, ethanol, 1% methanolic solution of tartaric acid, 2.5% HC1 solution, 5% CH.COOH solution, alkaline chloro form- -methanol mixture at various temperatures (room temperature, 50-60°C, solvent's boiling point) have been used in various extraction techniques (percolation, electric basket, ultrasonic water bath) and various extraction times. Total concentration of pyrrolizidine alkaloids (PAs) was estimated from UV-VIS spectrophotometric studies according to Dann- -Mattocks procedure. For the most promising extraction techniques one determined recoveries of monocrotaline added to crude pre-extracts. Extraction and co-extraction processes were investigated using UV-VIS spectra of the adducts of 3,4-dehydro-PAs and Ehrlich's reagent. The best result of PAs extraction from comfrey was obtained using 1% methanolic solution of tartaric acid and electric basket technique at the temperature 100 š 5°C for 2 h. Possible applications of the method have been discussed.

PL

W prezentowanej pracy podjęto badania optymalizacji ekstrakcji alkaloidów pirolizydy-nowych (PAs) z materiału roślinnego (źywokostu lekarskiego). Zastosowane metody obejmowały ekstrakcję metanolem, etanolem, l % roztworem kwasu winowego w metanolu, 2.5% roztworem kwasu solnego, 5% roztworem kwasu octowego, alkaliczną fazą organiczną (chloroform-metanol). Badano również wpływ temperatury ekstrakcji (pokojowa, 50-60°C, wrzący rozpuszczalnik) wykorzystując różne techniki ekstrakcyjne (perkolacja, ekstrakcja w płaszczach grzewczych, ekstrakcja wspomagana ultradźwiękami) oraz wpływ czasu ekstrakcji na odzysk PAs z surowca roślinnego. Caikowitą zawartość PAs oznaczono w oparciu o spektrofotometrię UV-VIS wg metody Danna i Mattocksa. W przypadku najbardziej obiecujących metod ekstrakcji oznaczono odzysk wzorca monokrotaliny dodawanego do pre-ekstraktu tuż przed rozpoczęciem właściwej ekstrakcji. Analizując widma U V—VIS adduktów 3,4-dehydro-PAs z odczynnikiem Ehrlicha możliwa była analiza stopnia ekstrakcji PAs z surowcajak i współekstrakcji substancji balastowych. Najlepszą wydajnością oraz najmniejszym stopniem współekstrakcji balastów charakteryzowała się 2-godzinna ekstrakcja wrzącym (temp. 100 š 5°C) 1% roztworem kwasu winowego w metanolu w płaszczach grzewczych. Przedyskutowano także potencjalne wykorzystanie opracowanej metody.

3

Influence of LCVD technological parameters on properties of polyazomethine thin films

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Hajduk B. , Weszka J. , Jurusik J.

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tom Vol. 36, nr 1

41-48

EN

Purpose: The aim of this paper is to show influence of technological parameters (temperature and gas stream intensity) of low-temperature chemical vapour deposition (LCVD) on optical properties and morphology of polyazomethine thin films. Design/methodology/approach: Thin layers of poly (1,4-phenylene-methylenenitrilo-1,4-phenylenenitrilo-methylene) (PPI) were prepared by low temperature LCVD method with use of argon as a transport agent. The UV-Vis spectroscopy and AFM microscopy measurements on PPI thin films were performed. Findings: The LCVD parameters, like temperature and argon stream intensity, influence growth rate, morphology and optical properties of polyazomethine thin films. Optimalization of technical parameters allows for thin films with desired properties to be prepared. Research limitations/implications: Optimalization of technical LCVD parameters leads to preparing PPI thin films having desired morphology and optical properties suitable for optoelectronic applications. Practical implications: PPI polyazomethine is good material for potential applications as the active layer in optoelectronic or photonic structure (diods or photovoltaic cells). Originality/value: LCVD with use of argon is relatively new method for preparing of thin polymer films. Recognizing of optimal technical parameters will make possible getting of thin films with required properties.

4

Tri-tert-butoksysilanotiolanowe kompleksy cynku(II), kadmu(II) i kobaltu(II) jako modele koordynacji jonu cynku w miejscu aktywnym dehydrogenazy alkoholowej i niektórych innych enzymów

80%

Dołęga A.

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2010

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tom [Z] 64, 5-6

389-411

EN

Zinc is ubiquitous in living organisms and second only to iron among the transition metals. Catalytic zinc sites have been found in all six classes of enzymes. Liver alcohol dehydrogenase (EC 1.1.1.1, LADH, Fig. 1) is a zinc enzyme, which catalyzes reversible oxidation of alcohols to aldehydes utilizing as a co-substrate NAD+. The mechanism of an action of the enzyme is summarized by an equation: R1R2CHOH + NAD+ = R1R2CO + NADH + H+ The coordination of zinc in LADH is usually described as pseudotetrahedral but there were several findings supporting penta-coordination of zinc during the catalytic cycle (Fig. 1 and 2) [1–7]. Studies on synthetic analogues of functional sites of the enzymes are used to elucidate the substrate – metal interactions [8]. Tri-tert-butoxysilanethiol which was used as a ligand to model cysteinate – metal ion centers has several advantageous features. It secures formation of mononuclear transition-metal complexes, exhibits resistance towards hydrolysis, and additionally its pKa value is close to that of cysteine mercapto group [9–11]. Over 20 tri-tertbutoxysilanethiolate complexes with MS2NO2 (M = transition metal) cores were synthesized to model the enzymatic centre of alcohol dehydrogenase, including complexes with water, methanol and ethanol (Fig. 5). Crystal structures of zinc(II), cobalt(II), cadmium(II), and manganese(II) complexes were determined and compared to the structures of LADH [12–17]. Structural features of zinc(II) and cadmium(II) complexes were analyzed (Fig. 9, Tab. 2) [15]. 113Cd CP/MAS NMR spectra of tri-tert-butoxysilanethiolate cadmium(II) complexes were determined and compared with the 113Cd NMR spectra of the cadmium-substituted alcohol dehydrogenase. Solid state 113Cd NMR shifts of five-coordinate cadmium(II) complexes with the CdNO2S2 coordination core were found to be identical to that of cadmium-substituted alcohol dehydrogenase in complex with NAD+ [15,18]. The equilibrium character of the reactions between bis(bis(tri-tert-butoxysilanethiolate) cadmium(II) and nitrogen ligands, with a low equilibrium constant of heteroleptic complex formation, were proved by 113Cd NMR studies in solution [18, 19]. The electronic absorption spectra of heteroleptic cobalt(II) complexes with tri-tert-butoxysilanethiolate and imidazole ligands were measured in methanol and solid state. The equilibrium reactions in the methanolic solutions of cobalt complexes were described on the basis of the analysis of charge transfer bands S→dCo LMCT and the molecular structures of the obtained complexes [17]. EPR spectra revealed the high-spin configuration of the studied cobalt(II) compounds [17]. Quantum mechanical calculations performed on the model zinc complex indicate ca10–20% decrease in enthalpy of ethanol deprotonation due to complexation with Zn2+ [15].

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Badania spektroskopowe dowodów odbarwiania olejów napędowych i lekkich olejów opałowych przeznaczanych na cele energetyczne

80%

Grabowski I. , Zaleszczyk G. , Sznajder M.

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tom R. 15, nr 6

28-32