Spremembe v pretočnosti plazemske membrane rakavih tkiv

Plasma membrane is a heterogeneous structure with several coexisting domains having different fluidity characteristics. It plays an important role in the control of cell growth, differentiation and transformation. Fluidity of the whole plasma membrane reflects the ordering and dynamics of phospholipid acyl chains in specific membrane domains, as well as the fraction of each domain inthe membrane. Changes in the membrane fluidity affect processes on the membrane such as transport, enzyme activities and expression of the redeptors.In this paper we present results of our recent electron paramagneticresonance (EPR) studies of plasma membrane fluidity characteristics, which take into account heterogeneous nature of the plasma membrane, By the computer simulation of the EPR spectra line-shapes, the number of coexisting domains in the plasma membrane, their relative portion inthe membrane as well as the ordering and dynamics of each domain be determined. Therefore, we could distinguish the contribution of the relative portion of each domain from the contribution of fulidity alterations in the domain to the entire fluidity changes in the membrane. Two examples will be discussed: membrane fluidity characteristics of excised lung tumor tissues andinfluence of microtubule depolymerizing agent vinblastine on membrane fluidity of vinblastine sensitive and resistant HeLa cells

Influence of carboxylic acids on fixation of copper in wood impregnated with copper amine based preservatives

The importance of copper/amine based preservatives is increasing. Leaching of copper from wood preserved with these solutions is still higher than leaching from wood impregnated with copper chromium ones. In order to decrease leaching, different carboxylic acids (octanoic, 2-ethylhexanoic, decanoic) were added to copper/amine/boron aqueous solutions. An experiment of leaching of copper from Norway spruce was performed according to the modified standard procedure (EN 1250). Results confirmed that carboxylic acids significantly improve copper fixation. The best fixation was determined in specimens impregnated with the preservative solutions consisting of copper, ethanolamine, boric acid and octanoic acid. From such wood, only 1.6% of copper was leached

Effect of Growth Medium pH of Aeropyrum pernix on Structural Properties and Fluidity of Archaeosomes

The influence of pH (6.0; 7.0; 8.0) of the growth medium of Aeropyrum pernix K1 on the structural organization and fluidity of archaeosomes prepared from a polar-lipid methanol fraction (PLMF) was investigated using fluorescence anisotropy and electron paramagnetic resonance (EPR) spectroscopy. Fluorescence anisotropy of the lipophilic fluorofore 1,6-diphenyl-1,3,5-hexatriene and empirical correlation time of the spin probe methylester of 5-doxylpalmitate revealed gradual changes with increasing temperature for the pH. A similar effect has been observed by using the trimethylammonium-6-diphenyl-1,3,5-hexatriene, although the temperature changes were much smaller. As the fluorescence steady-state anisotropy and the empirical correlation time obtained directly from the EPR spectra alone did not provide detailed structural information, the EPR spectra were analysed by computer simulation. This analysis showed that the archaeosome membranes are heterogeneous and composed of several regions with different modes of spin-probe motion at temperatures below 70°C. At higher temperatures, these membranes become more homogeneous and can be described by only one spectral component. Both methods indicate that the pH of the growth medium of A. pernix does not significantly influence its average membrane fluidity. These results are in accordance with TLC analysis of isolated lipids, which show no significant differences between PLMF isolated from A. pernix grown in medium with different pH

Influence of cancerostatic perifosine on membrane fluidity of liposomes and different cell lines as measured by electron paramagnetic resonance

AIM: To test whether membrane fluidity and its changes are important for the sensitivity of cells to the action of perifosine (OPP), a new anticancer drug targeting cell membrane and not DNA. METHOD: Influence of OPP on the membrane structure of OPP-resistant MCF7, and OPP-sensitive MT3 breast cancer cell lines, as well as of mouse fibroblasts (L929) cell lines, and model cells (liposomes) was investigated by electron paramagnetic resonance, using spin labeled derivative of OPP (P5) and 5-doxylpalmitoyl methylester (MeFASL(10,3)) as spin probes. RESULTS: OPP increased membrane fluidity of all cell lines at concentrations higher than 50 µM (on the level of P ≤ 0.05, t test). In cells, the differences were observed only by P5 and not by MeFASL(10,3). Average order parameter S(eff) decreased for about 12% in MCF7 and L929 and only for 8% in OPP-sensitive MT3 cells, showing that there was no correlation between membrane fluidity changes and sensitivity of cells to OPP. The only correlation we found was between OPP sensitivity and the cell growth rate. In liposomes, both spin probes were sensitive to the action of OPP. S(eff) decreased with increasing concentration of OPP. For MeFASL(10,3) a significant decrease was observed at 4 mol% OPP, while for P5 it was observed at 8 mol%. CONCLUSION: Influence of OPP on plasma membrane fluidity of breast cancer cells is not the determining factor in the sensitivity of cells to OPP