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71.
Electrocatalytic activity towards oxygen reduction of fungal laccase entrapped in poly-o-phenylenediamine (POPDA) matrix on glassy carbon electrodes was studied. Cyclic voltammetry and amperometric responses to dissolved oxygen were investigated in pH range from 2 to 6. POPDA reveals a unique ability to serve as a redox mediator for laccase and immobilizing matrix at the same time. The entrapped enzyme efficiently catalyzes reduction of molecular oxygen without any additional mediators. The electrocatalytic current reaches 0.1 mA/cm−2 per 1 μg of immobilized enzyme on cyclic voltammograms recorded at 1 mV/s in a not stirred electrolyte. Current density values are comparable with those revealed by dissolved laccase (60 μg/ml) mediated by hydroquinone and greatly higher than by the mediator less laccase/glassy carbon system. The potential of oxygen reduction is determined by the polymer redox couple. Consequently, the onset of the oxygen reduction shifts from −0.15 V versus Ag/AgCl in pH 6 to +0.05 V versus Ag/AgCl in pH 2. The laccase-POPDA layers immersed in the deaerated solution show fast amperometric responses to addition of the oxygen containing solution. The observed current values depend linearly on the oxygen concentration. Factors affecting the electrocatalytic activity of the laccase-POPDA system, including the layer thickness and the pH value, are studied. The electrodeposited laccase-POPDA films are characterized by infrared spectra. The results prove that the enzyme secondary structure remains unchanged during the entrapment procedure. POPDA matrix structure consists of the phenazine-type polymer according to infrared spectra. 相似文献
72.
Nafion‐115/aromatic poly(etherimide) with isopropylidene groups/imidazole membranes for polymer fuel cells 下载免费PDF全文
Agnieszka Iwan Marek Malinowski Andrzej Sikora Igor Tazbir Grzegorz Pasciak Eugenia Grabiec 《应用聚合物科学杂志》2015,132(34)
Proton exchange membrane fuel cells (PEMFCs) with Pt/C gas diffusion electrodes and graphite single‐serpentine monopolar plates were constructed based on an aromatic poly(etherimide) with isopropylidene groups (PI)/imidazole (Im) and a popular Nafion‐115 matrix. The electrochemical properties of PEMFCs were tested at 25 and 60°C. The maximum power density of 171 mW/cm2 and the maximum current density of 484 mA/cm2 were detected for Nafion‐115/PI membrane. For both constructed PEMFCs the efficiency at 0.6 V was found about 41%. Immersion of Nafion‐115 in PI or PI/Im increased the thermal stability and mechanical properties of membranes. Thermal, mechanical properties and morphology of membranes were characterized by TGA, and AFM techniques including force spectroscopy. Interactions between the components in composite membranes were established by FT‐IR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42436. 相似文献
73.
Inclusion of flaxseed in turkey diets decreases the n‐6/n‐3 PUFA ratio and increases the proportion of biologically active EPA and DHA without affecting meat quality 下载免费PDF全文
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The Impact of Zeta Potential and Physicochemical Properties of TiO2‐Based Nanocomposites on Their Biological Activity 下载免费PDF全文
Agnieszka Maria Jastrzębska Patrycja Kurtycz Andrzej Olszyna Ewa Karwowska Ewa Miaśkiewicz‐Pęska Monika Załęska‐Radziwiłł Nina Doskocz Dariusz Basiak 《International Journal of Applied Ceramic Technology》2015,12(6):1157-1173
The aim of this research was to observe the relationship between zeta potential, morphology, surface area, porosity, chemical composition, and ecotoxicity of nanocomposite powders such as Au/TiO2, Ag2O/TiO2, PdO/TiO2, Ag/TiO2/SiO2, Ag/N(C)TiO2, and SiO2/TiO2 from which Ag2O/TiO2, Ag/N(C)/TiO2, and Ag/TiO2/SiO2 were exhibiting good antimicrobial properties. It was observed, that nanomaterials characterized by similar morphology and zeta potential revealed the similar toxic behavior. The samples of higher agglomeration and higher zeta potential, especially Ag/TiO2/SiO2 xerogel and TiO2/SiO2 aerogel were generally less ecotoxic to water organisms and plants. They were also not genotoxic in concentrations up to 500 and 250 mg/L, respectively. 相似文献
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Dr. Umberto Maria Battisti Dr. Chunxia Gao Oscar Nilsson Dr. Fady Akladios Dr. Aleksei Lulla Dr. Agnieszka Bogucka Dr. Amalyn Nain-Perez Dr. Liliana Håversen Dr. Woonghee Kim Prof. Jan Boren Prof. Marko Hyvönen Prof. Mathias Uhlen Prof. Adil Mardinoglu Prof. Morten Grøtli 《Chembiochem : a European journal of chemical biology》2023,24(1):e202200339
Enzymes are effective biological catalysts that accelerate almost all metabolic reactions in living organisms. Synthetic modulators of enzymes are useful tools for the study of enzymatic reactions and can provide starting points for the design of new drugs. Here, we report on the discovery of a class of biologically active compounds that covalently modifies lysine residues in human liver pyruvate kinase (PKL), leading to allosteric activation of the enzyme (EC50=0.29 μM). Surprisingly, the allosteric activation control point resides on the lysine residue K282 present in the catalytic site of PKL. These findings were confirmed by structural data, MS/MS experiments, and molecular modelling studies. Altogether, our study provides a molecular basis for the activation mechanism and establishes a framework for further development of human liver pyruvate kinase covalent activators. 相似文献
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Agnieszka?NowakEmail author Danuta?Kusewicz Halina?Kalinowska Marianna?Turkiewicz Piotr?Patelski 《European Food Research and Technology》2004,219(1):84-89
Correlation between H2S productivity (p) and sulfite reductase activity (A) was estimated for seven wine-producing yeasts. It was described by a linear function
p=f(A), the slope of which depended on the yeast strain. The most intensive H2S synthesis by all the examined yeasts was observed within the early logarithmic growth phase, either in nitrogen abundance and SO2 presence, or in nitrogen deficient and SO2-free medium. Sulfite reductase from all the strains was optimally active at pH close to 7.4. The enzyme from cryophilic yeasts displayed maximum activity at approximately 16 °C, and from mesophiles at 22–26 °C. The preparations showed different affinities toward sulfite (Km of 16.7–67.5 M). Values of activation energy in sulfite reduction depended on the yeast, and ranged from 14.07 to 67.04 kJ mol–1. 相似文献
80.
Neural network identification of poets using letter sequences 总被引:1,自引:0,他引:1
Hoorn JF; Frank SL; Kowalczyk W; van der Ham F 《Literary and Linguistic Computing》1999,14(3):311-338