Photoemission studies and electronic structure of U(2)T(2)In (T = Ni, Rh, Pt) compounds.

The electronic structure of the tetragonal U(2)T(2)In (T = Ni, Rh, Pt) compounds in the paramagnetic phase were studied by x-ray photoelectron spectroscopy (XPS). Both valence band and core level spectra were analysed. The experimental data are compared with the calculations of the density of states using the tight-binding linear muffin-tin orbital method (TB-LMTO) and full-potential local-orbital full-relativistic method (FPLO). The calculated data reveal a dominant U 5f electron character for the states near the Fermi level E(F) with a small contribution from U 5d, Ni 3d, Rh 4d, Pt 5d and In 5p states. The XPS valence bands of these compounds are characterized by a sharp peak of the U 5f states near the Fermi level (E(F)) and broad peaks of the Ni 3d, Rh 4d and Pt 5d states at about 2.6, 3.2 and 4.0 eV below E(F), respectively. The small change in the position of the U 5f peak with respect to E(F) is -0.35 eV for T = Ni and -0.15 eV for T = Rh and Pt. A satellite between the Ni 2p(1/2) and Ni 2p(3/2) peaks is visible, suggesting that the Ni 3d band is not completely filled, and the existence of a small induced magnetic moment on the Ni atoms cannot be ruled out.

ESR and monolayer study of the localization of coenzyme Q10 in artificial membranes.

The data obtained from the ESR experiments show a complex, depth dependent effect of CoQ10 on the lipid molecules mobility in the bilayer. These effects depend both on its concentration and the temperature. CoQ10 disturbs not only the hydrophobic core of the membrane but also the region close to the hydrophilic headgroups of phospholipids. Both these effects could be explained by the fact that the high hydrophobicity of CoQ10 causes the molecules to position itself in the interior of the bilayer, but at the same time its water seeking headgroup is located close to the region of the polar headgrops of membrane lipids. The presence of CoQ10 in the hydrophobic core has further implications on the properties of membrane intrinsic domain. Results of monolayer experiments indicate that CoQ10 may form aggregates when mixed with PC molecules in the lipid hydrocarbon chain-length dependent manner. CoQ10 is not fully miscible with DMPC or DPPC but it is well miscible with the long-chain DSPC molecules. Our suggestion is that CoQ10 when present in long-chain phospholipid bilayer, interacts with saturated fatty acyl-chains and adapt the structure which allows such interactions: either parallel to the saturated acyl chains or "pseudo-ring" conformation resembling sterol structure.

Molecular mechanism of hydrogen peroxide conversion and activation by Cu(II)-amikacin complexes.

The interactions between Cu(II)-amikacin complexes [Cu(II)-Ami] and hydrogen peroxide were studied by spectroscopy (EPR, UV-vis, CD, XAS) and cyclic voltammetry. A monomer-dimer equilibrium was detected at complex concentrations above 5 mM (log K(dim) = 1.84 +/- 0.03). The dimeric complex undergoes easy, although irreversible oxidation (ca. 0.5-0.6 V) to a Cu(III) species on platinum electrode. However, the monomeric complexes are able to catalyze hydrogen peroxide disproportionation reaction at pH 7.4 in a multistep process, mediated by hydroxyl radicals and involving both Cu(I)/Cu(II) and Cu(II)/Cu(III) redox pairs.

Copper(II)-lincomycin: complexation pattern and oxidative activity.

Coordination of Cu(II) to lincomycin was studied by potentiometry, UV-Vis, circular dichroism (CD), EPR, NMR, cyclic voltammetry (CV) and ESI-MS. Only mononuclear complexes of stoichiometries ranging from CuL to CuH(-3)L were found. In the main species present at neutral pH, CuH(-2)L, lincomycin bonds Cu(II) through both of its nitrogen donors, and a deprotonated oxygen donor at C4 of the sugar moiety. High pressure liquid chromatography (HPLC) of products of 2'-deoxyguanosine (dG) oxidation and agarose gel electrophoresis of plasmid DNA confirmed that lincomycin complexes effectively facilitate dG oxidation by H2O2, but are not able to cleave double-stranded plasmid DNA.

[Results of treatment of vesicovaginal fistulas]. / Wyniki leczenia przetok pecherzowo-pochwowych.

OBJECTIVES: The results of treatment of 74 patients with vesicovaginal fistulas are presented. MATERIALS AND METHODS: The clinical analysis have been performed in 74 women aged from 24 to 70 years (on average 53.4), who had to be treated for vesicovaginal fistulas in the Department of Urology of Lublin University School of Medicine between 1966-1999. RESULTS: The most common cause of vesicovaginal fistulas was gynaecological surgery. Patients who-underwent the operation 96, 9% were cured (after 1st operation 84, 8%). 8 cases were cured by using conservative therapy.

Electron paramagnetic resonance (EPR) studies on stable and transient radicals in humic acids from compost, soil, peat and brown coal.

Quantitative EPR method was applied to characterise four types of humic acids (HA) derived from composts, soil, peat and soft brown coal. For each sample of HA the level of native (indigenous) radicals was estimated. Interactions of the HA with various gaseous agents and organic solvents were investigated. Strong effects of gaseous ammonia and aliphatic amines on spin concentration enhancement were observed; additionally, higher values of g-value were found to be associated with the formed 'transient' radicals. Correlation of copper(II) ions uptake by different HA with effect diminishing primary spin concentration was established. It was recognised that the radical centres, which are enhanced by 'ammonia effect' are quenched in the formed HA-Cu(II) complexes. The both opposite effects are competitive from each other, where 'copper(II) quenching effect' prevails. Reaction of nitrogen dioxide with the humic acids was also examined. The presence of diketones and/or other compounds with active methylene group results in formation of the iminoxy radicals; these radicals are immobilized in the solid (macromolecular) matrix of the humic acids.

Interaction of membrane skeletal proteins with membrane lipid domain.

The object of this paper is to review briefly the studies on the interaction of red blood cell membrane skeletal proteins and their non-erythroid analogues with lipids in model systems as well as in natural membranes. An important question to be addressed is the physiological significance and possible regulatory molecular mechanisms in which these interactions are engaged.

Decrease in 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) EPR signal in ozone-treated erythrocyte membranes.

In ozone-treated erythrocyte membrane suspension a slow decrease occurs in the EPR signal of 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO). Because of the absence of such a phenomenon in control membranes and ozonized buffer, this effect must be caused by reaction of nitroxide radicals with products of ozone reactions with membrane components. To find out which components are responsible for the decrease in EPR signal we studied this effect in simple model systems. The same phenomenon was observed both in lipid and protein systems treated by ozone. For unsaturated fatty acids, the correlation between the rate of decrease in EPR signal and the number of double bonds in the lipid molecule was very strong. This suggests that the observed decrease in the nitroxide radical TEMPO EPR signal in ozone-treated erythrocyte membranes is a complex process, but probably the most important reaction is recombination of nitroxide radicals with organic free radicals produced both in the process of lipid peroxidation and ozonolysis of double bonds.

Electron paramagnetic resonance studies of proteins in ozone-treated erythrocyte membranes.

The sulfhydryl group specific spin labels have been used to study the membrane proteins in the bovine and human erythrocyte membranes treated with ozone. The ratio hw/hs, determined from the respective peak amplitudes of the resulting EPR spectra of 3-maleimido-1-oxyl-2,2,5,5-tetramethylpyrrolidine bound to the ozone treated membranes, was shown to be elevated following an increased ozone concentration. The ratio of the central to high-field peak amplitude h0/h-1, a measure of the rotational correlation time, determined from EPR spectra of ozonized membranes covalently labeled with 4-(iodoacetamido)-1-oxyl-2,2,5, 5-tetramethylpyrrolidine was shown to be diminished. The changes in the erythrocyte membranes treated with ozone, observed for both spin labels, indicate a dose dependent increase in the mobility of membrane proteins.

Interaction of caldesmon with endoplasmic reticulum membrane: effects on the mobility of phospholipids in the membrane and on the phosphatidylserine base-exchange reaction.

We have previously demonstrated by tryptophan fluorescence the interaction of caldesmon with anionic phospholipid vesicles [Czurylo, Zborowski and Dabrowska (1993) Biochem. J. 291, 403-408]. In the present work we investigated the interaction of caldesmon with natural-membrane (rat liver endoplasmic reticulum) phospholipids by co-sedimentation assay. The results indicate that 1 mol of caldesmon binds approx. 170 mol of membrane phospholipids with a binding affinity constant of 7.3 x 10(6) M-1. The caldesmon-membrane phospholipid complex dissociates with increasing salt concentration and in the presence of Ca2+/calmodulin. As indicated by EPR measurements of membrane lipids labelled with 5-doxyl stearate and TEMPO-phosphatidylethanolamine, binding of caldesmon results in an increase in mobility of the acyl chains (in the region of carbon 5) and a decrease in polar headgroup mobility of phospholipids. Interaction of caldesmon with phospholipids is accompanied by inhibition of phosphatidylethanolamine synthesis via a phospholipid base-exchange reaction, with phosphatidylserine as substrate. This shows that, of the endoplasmic reticulum membrane phospholipids, the main target of caldesmon is phosphatidylserine.