Number of found documents: 455
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Chronopotentiometry of Papain Modified by Ruthenium Complexes
Nováková Lachmanová, Štěpánka; Pospíšil, Lubomír; Talbi, B.; Salmain, M.; Hromadová, Magdaléna
2019 - English
Catalytic hydrogen evolution reaction is one of known effects observed during the electrochemical studies of proteins. Constant current chronopotentiometric stripping technique is suitable tool for the study of catalytic hydrogen evolution reaction due to the formation of peak H. This contribution compares the catalytic behaviour of nonmodified papain and its artificial derivatives prepared by the interaction of organometallic complexes of ruthenium with free sulfhydryl group of protein. The comparison of the chronopotentiometric behaviour of papain and its derivatives would help to better understand the catalytic hydrogen evolution reaction in these derivatives. Keywords: papain; ruthenium organometallic complexes; artificial metalloproteins; catalytic hydrogen evolution reaction Available on request at various institutes of the ASCR
Chronopotentiometry of Papain Modified by Ruthenium Complexes

Catalytic hydrogen evolution reaction is one of known effects observed during the electrochemical studies of proteins. Constant current chronopotentiometric stripping technique is suitable tool for ...

Nováková Lachmanová, Štěpánka; Pospíšil, Lubomír; Talbi, B.; Salmain, M.; Hromadová, Magdaléna
Ústav fyzikální chemie J. Heyrovského, 2019

Charge Transport in Single Oligophenylene Molecular Wires with Different Anchoring Groups
Hromadová, Magdaléna; Kolivoška, Viliam; Šebera, Jakub; Sebechlebská, Táňa; Gasior, Jindřich; Nováková Lachmanová, Štěpánka; Mészáros, G.; Lindner, M.; Mayor, M.; Valášek, M.
2019 - English
This work compares single molecule conductance measurements of selected organic systems containing identical oligophenylene molecular wires and different tripodal anchoring groups. Single molecule conductance G was obtained by a scanning tunneling microscopy break junction technique complemented by theoretical calculations based on the density functional theory and non-equilibrium Green’s function formalism. Two molecules were compared where the same oligophenylene wire is connected to one of the electrodes via a tripod substituted on each leg by a thiol group either in the meta or para position. By combined experimental and theoretical analysis it was possible to confirm that single molecule conductance in the metal-molecule-metal junction of both molecules corresponds to a fully extended molecular wire, which is attached to one of the electrodes by all three thiolate bonds of the tripod. Experimental results confirmed that G value of meta-connected molecules is lower than that of para, whereas junction formation probability was higher for meta functionalization. Keywords: STM break junction; Tetraphenylmethane Tripodal anchor; Single molecule conductance Available at various institutes of the ASCR
Charge Transport in Single Oligophenylene Molecular Wires with Different Anchoring Groups

This work compares single molecule conductance measurements of selected organic systems containing identical oligophenylene molecular wires and different tripodal anchoring groups. Single molecule ...

Hromadová, Magdaléna; Kolivoška, Viliam; Šebera, Jakub; Sebechlebská, Táňa; Gasior, Jindřich; Nováková Lachmanová, Štěpánka; Mészáros, G.; Lindner, M.; Mayor, M.; Valášek, M.
Ústav fyzikální chemie J. Heyrovského, 2019

Electrochemical Investigation of Polylactic Acid/Carbon Black Composite Filament for the Manufacture of 3D Printed Electrodes
Sebechlebská, Táňa; Vaněčková, Eva; Shestivska, Violetta; Kolivoška, Viliam
2019 - English
Fused deposition modeling 3D printing has recently attracted increasing attention as an inexpensive, fast, reliable, adaptable and environmentally friendly tool to fabricate electrodes and electrochemical cells from composites of thermoplastics and carbon nanostructures. In this work, we use electric conductance measurements and cyclic voltammetry employing Ru(acac)30/1- as an electroactive probe to demonstrate that commercial polylactic acid(PLA)/carbon black composite filaments may be readily used as functional working electrodes in aqueous electrolytes. We further devise a procedure that leads to an improvement of their electrochemical performance. Characteristics of composite filaments treated by the optimized procedure approach those of classical metallic electrodes. Keywords: 3D printed electrodes; Fused deposition modeling; Polylactic acid; Carbon black Available on request at various institutes of the ASCR
Electrochemical Investigation of Polylactic Acid/Carbon Black Composite Filament for the Manufacture of 3D Printed Electrodes

Fused deposition modeling 3D printing has recently attracted increasing attention as an inexpensive, fast, reliable, adaptable and environmentally friendly tool to fabricate electrodes and ...

Sebechlebská, Táňa; Vaněčková, Eva; Shestivska, Violetta; Kolivoška, Viliam
Ústav fyzikální chemie J. Heyrovského, 2019

Mechanism of the Water Clusters Formation in the Organic Phase in the Presence of Hydrated Ions
Holub, Karel; Samec, Zdeněk; Mareček, Vladimír
2019 - English
A two-electrode cell comprising a liquid/liquid interface is used to study the water clusters formation in the organic solvent phase following the extraction of tetraalkylammonium chloride (TAACl) from the aqueous phase. The change in the concentration of the common TAA+ ion on the aqueous side of the interface is monitored by the open circuit potential measurements. It is shown that the amount of TAACl extracted into the organic phase exceeds considerably the limit determined by the concentration of Cl- in the organic phase at a given interfacial potential difference and the electroneutrality condition. A mechanism is proposed including an accumulation of the excess TAACl in the water clusters formed from the hydration shell of the Cl- ions, water already dissolved in the organic phase, and additional water extracted from the aqueous phase. At higher concentration of TAACl in the aqueous phase this process leads to the formation of emulsion in the organic phase. Keywords: liquid/liquid interface; water co-extraction dynemics; emulsification Available on request at various institutes of the ASCR
Mechanism of the Water Clusters Formation in the Organic Phase in the Presence of Hydrated Ions

A two-electrode cell comprising a liquid/liquid interface is used to study the water clusters formation in the organic solvent phase following the extraction of tetraalkylammonium chloride (TAACl) ...

Holub, Karel; Samec, Zdeněk; Mareček, Vladimír
Ústav fyzikální chemie J. Heyrovského, 2019

Construction and Application of Flow Amperometric Biosensor Based on Enzymatic Reactor for Determination of Choline
Tvorynska, Sofiia; Barek, J.; Josypčuk, Bohdan
2019 - English
In this contribution, a novel fast, simple and stable biosensor with the enzymatic reactor based on choline oxidase (ChOx) was developed and applied for the determination of choline using flow injection analysis with amperometric detection. The preparation of the reactor is based on the covalent immobilization of ChOx with glutaraldehyde to mesoporous silica powder (SBA-15) previously covered by NH2-groups. The experimental parameters affecting the sensitivity and stability of the biosensor were optimized. The proposed biosensor with the newly developed ChOx-based reactor possesses good repeatability, reproducibility, long-term stability, and reusability. It was successfully applied for the determination of choline in commercial pharmaceuticals. Keywords: choline; choline oxidase; Flow analysis; enzymatic reactor Available on request at various institutes of the ASCR
Construction and Application of Flow Amperometric Biosensor Based on Enzymatic Reactor for Determination of Choline

In this contribution, a novel fast, simple and stable biosensor with the enzymatic reactor based on choline oxidase (ChOx) was developed and applied for the determination of choline using flow ...

Tvorynska, Sofiia; Barek, J.; Josypčuk, Bohdan
Ústav fyzikální chemie J. Heyrovského, 2019

Electrochemical Measurements in Flow Systems on Silver Amalgam Tubular Detector Combined with Auxiliary Electrode
Josypčuk, Bohdan; Barek, J.; Josypčuk, Oksana
2018 - English
A new type of tubular detector (TD+AuxE) was proposed, fabricated, tested and compared\nwith a typical silver amalgam tubular detector developed earlier. Non-stop-flow differential\npulse voltammetric anodic stripping method (AS-DPV) and amperometric method in a\nglucose oxidase biosensor arrangement were tested. Both detectors were applied for AS-DPV\nmeasurements in flow systems for the first time. The proposed combination of tubular\ndetector with auxiliary electrode provides a much greater current response than the classic\narrangement with three individual electrodes. All relevant parameters (potentials of\naccumulation or detection, flow rate, analyte concentrations, shielding sleeve length, etc.)\nwere optimized for the developed TD+AuxE. Keywords: Flow analysis; Amperometry; Voltammetry Available on request at various institutes of the ASCR
Electrochemical Measurements in Flow Systems on Silver Amalgam Tubular Detector Combined with Auxiliary Electrode

A new type of tubular detector (TD+AuxE) was proposed, fabricated, tested and compared\nwith a typical silver amalgam tubular detector developed earlier. Non-stop-flow differential\npulse voltammetric ...

Josypčuk, Bohdan; Barek, J.; Josypčuk, Oksana
Ústav fyzikální chemie J. Heyrovského, 2018

Aplikace mikro-objemové voltametrické cely pro stanovení doxorubicinu hydrochloridu
Skalová, Štěpánka; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
2018 - Czech
Byla úspěšně otestována aplikace mikro-objemové voltametrické cely na příkladu stanovení protinádorového léčiva doxorubicinu hydrochloridu. Objem analyzovaného vzorku činil 50 mikroL s LOD 0,39 micromol L-1 a LDR 0,4-10 mikromol L-1. Tato mikro-objemová cela byla také úspěšně použita k analýze tohoto analytu v modelových vzorcích pitné vody a lidské moči. Doxorubicin is an anticancer drug, which is used for treatment of various cancer types. It contains a quinone structure, similarly as some other drugs belonging to the same category (e.g., daunorubicin and epirubicin). Its monitoring can lead to optimization of individual patient dosages and increase chances for recovery of patients. A micro-volume voltammetric cell and differential pulse cathodic stripping voltammetry have been used for determination of doxorubicin hydrochloride. A volume of used sample was 50 microL. Limit of detection was 0.39 micromol L-1. An applicability of this method was verified on samples of drinking water and of human urine. Keywords: Doxorubicine hydrochloride; Voltametry; Micro-volume Available on request at various institutes of the ASCR
Aplikace mikro-objemové voltametrické cely pro stanovení doxorubicinu hydrochloridu

Byla úspěšně otestována aplikace mikro-objemové voltametrické cely na příkladu stanovení protinádorového léčiva doxorubicinu hydrochloridu. Objem analyzovaného vzorku činil 50 mikroL s LOD 0,39 ...

Skalová, Štěpánka; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
Ústav fyzikální chemie J. Heyrovského, 2018

Chování metalothieneinů a fytochelatinů na rtuťových a amalgámových elektrodách
Šestáková, Ivana; Navrátil, Tomáš; Josypčuk, Bohdan
2018 - Czech
Při použití elektrod AgSAE či CuSAE pro elektrochemická měření s metalothioneiny či fytochelatiny vznikají příslušné Ag-MT, Cu-MT, Ag-PC či Cu-PC komplexy. V čistých elektrolytech a pro nízké koncentrace analytů jsou odezvy lineárně závislé na jejich koncentraci, odezvu je možné zvýšit akumulací při vhodném potenciálu. Pro reálné vzorky je podstatný negativní vliv matrice, který může vést až k nutnosti přípravy nového povrchu a jeho aktivace pro každý jednotlivý záznam. The presence of cysteine residues in molecules of metallothioneins or phytochelatins is crucial for their electrochemical behavior. At mercury electrodes, the reduction of\ntetracoordinated Cd and Zn in molecule of mamamalian MT is observed in solution of pH 8- 8.5, whereas with lowering pH or at presence of excessive ions, signals of differently coordinated or free metal ions appear. Such changes were confirmed on model complexes with phytochelatin PC2 .Using amalgam electrodes CuSAE or AgSAE for voltammetry of metallothioneins or phytochelatins, their Cu or Ag complexes are formed on the electrode surface, which could be with limitations - employed for the analytical purposes. Keywords: metallothioneins; amalgam electrode; voltammetry Available on request at various institutes of the ASCR
Chování metalothieneinů a fytochelatinů na rtuťových a amalgámových elektrodách

Při použití elektrod AgSAE či CuSAE pro elektrochemická měření s metalothioneiny či fytochelatiny vznikají příslušné Ag-MT, Cu-MT, Ag-PC či Cu-PC komplexy. V čistých elektrolytech a pro nízké ...

Šestáková, Ivana; Navrátil, Tomáš; Josypčuk, Bohdan
Ústav fyzikální chemie J. Heyrovského, 2018

Determination of Roughness Factor and Fractal Dimension of Zirconium in its Native and Surface Modified State using Atomic Force Microscopy. Effect of the Hydrogen Evolution Reaction on the Surface Structure
Novák, M.; Kocábová, Jana; Kolivoška, Viliam; Pospíšil, Lubomír; Macák, J.; Cichoň, Stanislav; Cháb, Vladimír; Hromadová, Magdaléna
2018 - English
Atomic force microscopy (AFM) was used to characterize surface morphology of pristine zirconium, Si modified and FeSi modified zirconium electrodes prior and after hydrogen evolution at potentials negative of the open circuit potential value. Two main characteristic parameters were obtained from the ex situ AFM height images, namely, the roughness factor and fractal dimension of the studied surface. The effect of hydrogen evolution reaction on the electrode surface morphology was discussed. Fractal dimension values were used successfully to explain the non ideality of the interfacial capacitance. Keywords: zirconium electrode; atomic force microscopy; fractal dimension Available on request at various institutes of the ASCR
Determination of Roughness Factor and Fractal Dimension of Zirconium in its Native and Surface Modified State using Atomic Force Microscopy. Effect of the Hydrogen Evolution Reaction on the Surface Structure

Atomic force microscopy (AFM) was used to characterize surface morphology of pristine zirconium, Si modified and FeSi modified zirconium electrodes prior and after hydrogen evolution at potentials ...

Novák, M.; Kocábová, Jana; Kolivoška, Viliam; Pospíšil, Lubomír; Macák, J.; Cichoň, Stanislav; Cháb, Vladimír; Hromadová, Magdaléna
Ústav fyzikální chemie J. Heyrovského, 2018

Differences in Oxidation Mechanism of Selected Bioflavonoids, UV-Vis and IR Spectroelectrochemical Study
Sokolová, Romana; Fiedler, Jan; Ramešová, Šárka; Kocábová, Jana; Degano, I.; Quinto, A.; Křen, Vladimír
2018 - English
The oxidation of selected bioflavonoids (quercetin, rhamnazin, fisetin, rhamnetin, taxifolin, luteolin, silybin and 2,3-dehydrosilybin) was studied by electrochemical and spectroscopic methods. The oxidation mechanism and formation of oxidation products depends on the chemical structure. Only small differences in the chemical structure of compounds with flavone, flavanone and flavonol motif result in extremely variable oxidation pathways and products. Products of oxidation and further decomposition were determined by HPLC-ESIMS/MS and HPLC-DAD. Keywords: oxidation; flavonoids; decomposition Available on request at various institutes of the ASCR
Differences in Oxidation Mechanism of Selected Bioflavonoids, UV-Vis and IR Spectroelectrochemical Study

The oxidation of selected bioflavonoids (quercetin, rhamnazin, fisetin, rhamnetin, taxifolin, luteolin, silybin and 2,3-dehydrosilybin) was studied by electrochemical and spectroscopic methods. The ...

Sokolová, Romana; Fiedler, Jan; Ramešová, Šárka; Kocábová, Jana; Degano, I.; Quinto, A.; Křen, Vladimír
Ústav fyzikální chemie J. Heyrovského, 2018

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