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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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Elektrochemické vlastnosti tjiolové monovrstvy na povrchu různých elektrod
Josypčuk, Bohdan ; Mareček, Vladimír
Jako podložka pro vytvoření monovrstvy thiolu se tradičně používá rtuť, zlato či stříbro. Největší výhodou rtuti je její ideálně rovný povrch, který zajišťuje získání monovrstvy prakticky neobsahující žádné defekty. Pevné amalgámy různých kovů se dobře smáčí rtutí, a proto lze připravit elektrody pokryté meniskem (m-MeSAE) nebo filmem (MF-MeSAE, kde Me - Ag, Au, Cu, Bi, Cd aj.) nasyceného kapalného amalgámu příslušného kovu. Afinita těžkých kovů tvořících amalgám k síře je velká a za určitých podmínek lze navázat thiol na zvolený kov. Vzhledem k tomu, že vlastnosti monovrstvy jsou ovlivněny vazbou kov-síra, použití amalgámů různého složení vede k vytvoření monovrstvy thiolu, která je stabilní v definovaném rozsahu potenciálů. Elektrochemické studium vlastností thiolových monovrstev na elektrodách o různém složení bylo hlavním cílem této práce.
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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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A study of calixarene self-assembled monolayers on gold metal surfaces
Šustrová, Barbora ; Mareček, Vladimír ; Štulík, Karel
Substituted calix[4]arene molecules were self-assembled on the gold disk electrode surface and the structure of the monolayer formed and the electrochemical behavior of the modified electrode were studied. The formation of the calixarene self-assembled monolayer (SAM) conformed to a Langmuir-type adsorption isotherm, The atomic force microscopy measurement results indicated that the calixarene molecules form a stable monolayer on the Au(111) surface and confirmed the cyclic voltammetry results concerning the SAM structure dependence on the solvent used. Impedance measurements demonstrate that the capacity of the modified electrode varies in the presence of ions, depending on their size and shape.
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