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Transport of divalent cations across the gel supported phospholipid membranes
Navrátil, Tomáš ; Šestáková, Ivana ; Mareček, Vladimír
This contribution deals with elucidation of principles of transporting processes of heavy metals (mainly lead, cadmium) across the biological membranes. The real membranes were for purposes of described experiments, replaced by model membranes, which were composed of phospholipid bilayers. Two different phorpholipids (1,2-dipalmitoyl-sn-glycero-3-phosphocholine and the mixture of phospholipids obtained from soybeans (under commercial name Asolectin)) were used as the building elements for the formation of these membranes on the surface of the constructed gel electrode. The registered transporting processes have been characterized using voltammetry, and electrochemical impendance spectrometry (EIS). The impact of some parameters on these systems and processes was investigated.
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Polycrystalline gold electrode modified by thiols
Šustrová, Barbora ; Mareček, Vladimír ; Štulík, K.
The article reports on our continued investigation of modification of the gold electrode surface by thiolated compounds aimed at construction of an ion-selective sensor. Our previous work was focused on utilization of calix[4]arene molecules as a cavity sized ligand molecule. In this paper, calixarene and linear undecanethiol molecules were used as modifiers. We compared two ways of deposition thiol molecules, namely the spontaneous self-assembly process and the electrochemical deposition, in which the potential was applied on the electrode immersed into an adsorption solution. The concentration, time and potential conditions were optimized from the point of view of the SAM homogeneity. The modifying layers of calixarene and undecanthiol molecules were visualized by atomic force microscopy.
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Monolayers at electrodes as basis for models of natural membranes
Josypčuk, Bohdan ; Mareček, Vladimír
Properties of thiol (HS(CH2)10COOH) monolayers were investigated at stationary electrodes based on silver, copper, bismuth and cadmium solid amalgams covered by a mercury meniscus or by a mercury film. For comparison, parallel experiments were performed at a classical hanging mercury drop electrode. Dependences of monolayer parameters on time of electrochemical deposition of thiol and on scan rate were performed. Statistical evaluation of all obtained results has confirmed that solid amalgam electrodes are a convenient tool for research of thiol layers.
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Electrochemical properties of thiol monolayers at surfaces of different electrodes
Josypčuk, Bohdan ; Mareček, Vladimír
Solid amalgam electrodes covered by a mercury meniscus or by mercury film (m-AgSAE, MF-AgSAE, m-CuSAE, m-BiAgSAE and m-CdSAE) are convenient for obtaining thiol films which are bound to different metals. By choosing an appropriate metal for the amalgam preparation, a thiol monolayer can be created which is stable in the given potential range. After a short accumulation time (1-2 min), the area of the reduction peak (charge) practically does not change it the monolayer is created from 1 nM thiol solution. Statistical results based on many times repeated formation and desorption of thiol monolayers (RSD = 2-3 %) attest that the stationary SAEs are convenient tools for study of electrochemical properties of thiol films.
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Transport of cadmium ions across model supported phospholipid membranes
Navrátil, Tomáš ; Šestáková, Ivana ; Mareček, Vladimír ; Štulík, Karel
These results report on experiments focussed on the formation of supported model phospholipid membranes, formed from phosphatidyl choline in the micrometric pores of hydrophilic polycarbonate supports, their chatacterization using voltammetry and electrochemical impendance spectrometry (EIS). Attention was paid transport of heavy metal ions (ions of cadmium, etc.) across these membranes in the presence or absence of ionophores (valinomysing and calciomycin) or in the presence of oxalic acid. The impact of some parameters on these systems and processes was investigated.
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Proton transfer across a liquid/liquid interface facilitated by phospholipid interfacial films
Holub, Karel ; Jänchenová, Hana ; Štulík, Karel ; Mareček, Vladimír
The five-step mechanism proposed earlier for the formation of phospholipid films at aqueous/organic interfaces and for their behavior involving transfer of protons from the aqueous to the organic phase was further studied by cyclic voltammetry. A theoretical model was created for this mechanism and compared with the experimental results. Both the experimental and theoretical results support the proposed mechanism and evaluate the importance of the individual steps. It seems that the decisive step is the regenration of the zwitterionic form of the phospholipid at the interface, ensuring stability of the film in time and its continuous functioning.
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