Miroslav Karabaliev

Interaction of solid supported thin lipid films with saponin

Abstract The interaction of solid supported liquid films of lipids with saponin is investigated in the present work by impedimetric analysis. It is shown that the specific reaction of saponin with the cholesterol molecules present in the modified films can readily be distinguished by the impedance data. In this respect, possibilities for the realization of sensor devices based on solid supported lipid films are briefly discussed.

Voltammetric study of levomepromazine induced ionic permeability in a model lipid membrane system

The interaction of solid supported liquid films of lipids with levomepromazine is investigated in the present work by voltammetry. It is shown that the levomepromazine penetrates into the films, which results in a readily detectable change of the film permeability to electroactive species. In this respect, possibilities for the employment of supported lipid films as model systems in the research of biomembrane active compounds are briefly discussed.

Probing the “interfacial” and “bulk” characteristics of solid-supported thin liquid films

Abstract The conversion of relatively “thick” (on the order of 100 A) solid-supported liquid films of lipids to mono- or bilayer molecular structures by the aid of electrostriction is considered in the present work. Technique based on the concept of impedance is used for the investigation of the parameters of these different types of films. It is shown that the “thick” films could structurally be regarded as composed of “bulk” and “interfacial” parts with readily distinguished characteristics. Some possibilities of using this information for the realization of sensor devices based on solid-supported thin liquid films of lipids are discussed.

Preparation of extremely thin solid supported films of lipids by the method of electrostriction

Preparation of stable ultra thin lipid layers onto polished glassy carbon (GC) surface is reported in this work. The method of formation relies on additional thinning of wetting films by electrostriction. The possible final structure of the films, as well as, their relevance for sensor development are discussed.

Mn2+ as a mediator for the electron transfer across thin wetting films of lecithin

Abstract The employment of manganese (Mn 2+ ) as a mediator for the electron transfer across glassy carbon-supported thin lecithin films in contact with electrolyte is described in the present work. The results suggest, that the ascorbate oxidation, which is normally hampered by the film, can proceed through the incorporated manganese. In this respect, the potential of Mn for modification of lipid wetting films in construction of sensitive interfaces is briefly outlined.

Impedance dispersion analysis of drug-membrane interactions

Thin lipid films modified glassy carbon electrodes (GCE) were used in this work as model system for studying the interactions between two antipsychotic phenothiazine drugs, chlorpromazine and thioridazine, and the lipid fraction of the biomembranes. The lipid films on the electrode surface were obtained through the thinning of film-forming lipid solution deposited between an electrolyte phase and the working GC electrode. The effects of the drugs on the lipid film structure were investigated by electrochemical impedance spectroscopy (EIS). To characterize the electric properties of the lipid film the impedance of the working GCE is modeled with an equivalent circuit consisting of parallel capacitance Cp and resistance Rp. These capacitance and resistance are not frequency independent but could be calculated as equivalent Cp and Rp for each measured frequency of the impedance spectrum and presented as functions of the frequency f, Cp = Cp(f) and Rp= Rp(f). For the lipid films used in this work, it is demon...

Thermal dielectroscopy - A new method for studying the membrane skeleton of human erythrocytes

The structure and mechanical properties of erythrocyte plasma membrane are strongly affected by both the dephosphorylation and thermal denaturation (49.5°C) of erythrocyte under-membrane spectrin skeleton. Here, the dielectric loss (DL) of suspensions, containing native erythrocytes or erythrocyte ghost membranes (EGMs), was determined applying a mathematical method to remove the conductive loss from the imaginary capacitance, Cim, of the suspensions. The DL frequency profile of spectrin skeleton was obtained subtracting the DL data collected prior to, and after the denaturation of spectrin at 49.5°C. Spectrin skeleton exhibited narrow bell-shaped DL frequency curve, centered at 1.5 MHz, presumably reflecting the segmental mobility of spectrin. The area of this curve was reduced by 30 % after mild dephosphorylation (starvation of erythrocytes at 37°C for 5 h) and reduced to zero at EGMs resealed with alkaline phosphatase (full dephosphorylation). These results, combined with others, indicate the relevance...