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Reduction and Oxidation of Hydroxyquinolines in Acetonitrile and Dimethylsulfoxide
Sokolová, Romana ; Ramešová, Šárka ; Fiedler, Jan ; Kolivoška, Viliam ; Degano, I. ; Gál, M. ; Szala, M. ; Nycz, J. E.
This study is focused on investigation of oxidation and reduction pathways of selected hydroxyquinoline compounds in nonaqueous solutions. The experimentally obtained reduction potentials are reported to well correlate with calculated values of LUMO energies as well as the obtained oxidation potentials are in a good agreement with theoretical HOMO energies. The cyclic voltammetry, in situ UV/Vis spectroelectrochemistry and in situ IR spectroelectrochemistry confirmed that the oxidation mechanism is complicated. Oxidation unexpectedly proceeds together with protonation of the starting compound. This behaviour was found for all studied compounds, hydroxyquinoline carboxylic acids and also for compounds, where a methyl group is present instead of carboxylic group.
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Comparison of Techniques for Single-Molecule Conductance Measurements of Expanded Pyridinium Molecules
Lachmanová, Štěpánka ; Hromadová, Magdaléna ; Sokolová, Romana ; Kocábová, Jana ; Gasior, Jindřich ; Mészáros, G. ; Lainé, P. P.
This work is focused on the comparison of two techniques of single-molecule conductance measurements: Scanning Tunneling Microscopy Break Junction technique and Mechanically Controlled Break Junction technique. The structure of studied compound 9-(pyridin-4-yl)benzo[c]benzo[1,2]quinolizino[3,4,5,6-ija][1,6]naphthyridin-15-ium allows the formation of the molecular bridge between two gold electrodes, which are connected to a source of the constant voltage in both of the used methods. The differences, advantages and disadvantages of both of the techniques will be discussed. Both techniques provided two values of conductance of studied compound depending on the experimantal conditions.
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Electrochemistry of Flavonolignans and their Interactions with DNA and Proteins
Pyszková, M. ; Zatloukalová, M. ; Biedermann, David ; Křen, Vladimír ; Ulrichová, J. ; Ramešová, Šárka ; Sokolová, Romana ; Vacek, J.
Electrochemical oxidation of flavonolignans silybin, silydianin, silychristin and their 2,3-dehydroderivatives, was studied using ex situ and in situ cyclic and square wave voltammetry at pyrolytic graphite electrode. The pilot results presented here could be used for further investigation of mechanism of oxidation and reactivity of flavonolignans to DNA and proteins.
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Electrochemistry as a Tool for an Enzyme Characterization
Gál, M. ; Krahulec, J. ; Jiríčková, K. ; Sokolová, Romana ; Híveš, J.
Basic biochemical properties such as Michaelis constant (KM) and turnover number (kcat) of enzyme enteropeptidase was measured by electrochemical impedance spectroscopy. Both values determined by impedance measurements are in good agreement with those obtained by traditional spectroscopic techniques. Therefore one can suppose that electrochemical methods might be successful for such measurements also in the case where usual ones (UV-Vis, fluorescence spectroscopy) are not able to determine these enzyme characteristics.
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Electrochemical Study of Rhamnazin
Ramešová, Šárka ; Sokolová, Romana ; Degano, I.
The natural flavonoid compound rhamanzin (3,5,4’-trihydroxy-7,3’-dimethoxyflavone) is important bioactive compound with antioxidative, anti-allergic, and anti-inflammatory properties. The cyclic voltammetry is used for the electrochemistry behavior of rhamnazin. The determination of oxidation pathways is supported by the identification of degradation products using separation technique.
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Adsorption of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine on Au(111) and HOPG
Kocábová, Jana ; Sokolová, Romana
Atomic force microscopy (AFM) was used to study the formation of layers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) on Au(111) and highly oriented pyrolytic graphite (HOPG) in microscopic level. Both substrates were found to support the DPPC layers. The nanoshaving technique was applied to determine the layer thickness. In addition, the influence of deionized water on the DPPC ordering at the substrates was studied by ex-situ and in-situ AFM intermittent contact mode measurements.
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