In the present paper we consider application of equation of state for model gases to the description of experimental dependencies of dielectric permeability on pressure and temperature for nonpolar gases. The case of argon is regarded as an example. It is demonstrated that the generalized Van-der-Waals-Berthelot equation describes the dependence of dielectric permeability on pressure and temperature with good accuracy. It is shown that the measurement of dielectric permeability using the isotherms with small temperature increments provides a means to obtain the exact tabulated equation of state. This result can be used in other areas of investigation.

General considerations on the form of the real equation of state make it possible to assume that the ratio of the melting temperature to the critical temperature is constant for each group of elements. This assumption is verified for two groups of elements, the critical temperatures of which are measured. It is shown that, for certain groups of elements, the critical temperatures of which are calculated instead of being measured, this assumption is also valid. The critical temperatures of certain elements are calculated or refined.

The derivation of the Langevin formula is analyzed. It is shown that a basic assumption in it is incorrect. A more correct derivation of a similar formula is proposed.

The equation of state of model gases is considered for describing the experimental pressure dependence of the permittivity of argon. It is shown that the generalized Van der Waals−Berthelot equation describes the pressure dependence of permittivity of argon with a good accuracy.

The possibility of modifying the equation of state of a gas in a closed, thermally insulated capacitor filled with a nonpolar gas and changing the temperature and pressure under the action of an electrostatic field is considered.

A problem on determining effective volumes for atoms and molecules becomes actual due to rapidly developing nanotechnologies. In the present study an exact expression for enthalpy of vaporization is obtained, from which an exact expression is derived for effective volumes of atoms and molecules, and under certain assumptions on the form of an atom (molecule) it is possible to find their linear dimensions. The accuracy is only determined by the accuracy of measurements of thermodynamic parameters at the critical point.

The addition of the channel-forming domain of colicin E1 to liposomes elicited the transmembrane diffusion (flip-flop) of lipids concomitant to the release of the fluorescent dye from liposomes. Good correlation was found between kinetic and concentration dependences of the two processes. Both the liposome leakage and the lipid flip-flop were stimulated upon alkalinization of the buffer solution after colicin binding at acidic pH. These results in combination with the analysis of the data on colicin binding to liposomes provide evidence in favor of the validity of the toroidal (proteolipidic) pore model as the mechanism of colicin channel formation.

The transient receptor potential (TRP) channel TRPC3 is a nonvoltage gated Ca-permeable cation channel that is expressed in skeletal muscle. It is assumed that TRPC3 is important for the cellular Ca homeostasis and that the channel is involved in Ca dependent signal transduction. To study the role of TRPC3 in skeletal muscle we investigated gene expression and cellular localization of the TRPC3 protein. We further tested whether expression and localization of TRPC3 are altered inmurinemuscular dystrophy (mdx), a muscle disease characterized by abnormal cellular Ca regulation. Using RT-PCR and Western blot techniques, we did not find differences in TRPC3 gene expression in limb muscles and diaphragm between mdx and control mice. Immunofluorescent staining of isolated interosseus fibers with an anti-TRPC3 antibody revealed a cross striation pattern near the sarcolemma and a faint cytoplasmic fluorescence. Double labelling experiments showed co-localization of TRPC3with vinculin and dystrophin, but not with the ryanodine receptor or the dihydropyridine receptor. The latter results were confirmed for both genotypes, however, mdx fibers showed a more prominent cytoplasmic TRPC3 staining. The strong cytoplasmic TRPC3 signal diminished, while the sarcolemmal staining increased, after incubation of mdx fibers with Gd (50 mM), nifedipine (50 mM), epidermal growth factor, 2-aminoethoxydiphenly borate (2-APB) or a Ca-free solution. In control fibers, the effects of the ion channel blockers were lesser. Only Gd and nifedipine stimulated the translocation of TRPC3 to the sarcolemma. Our data suggest a costameric localization of TRPC3 in skeletal muscle and a Ca-dependent trafficking of the channel from cytoplasmic pools to the sarcolemma. In dystrophin-deficient mdx fibers TRPC3 seems to be displaced to the cytoplasm, an effect that can be reverted by inhibition of Ca influx. Supported by BMBF (MD-NET, project R14).

The channel-forming activity of gramicidin A derivatives carrying positively charged amino acid sequences at their C-termini was studied on planar bilayer lipid membranes and liposomes. We showed previously (FEBS Lett., 2005, vol. 579, pp. 5247–5252) that, at low concentrations, these peptides form classical cation-selective pores typical of gramicidin A, whereas, at high concentrations, they form large nonselective pores. The ability of the peptides to form nonselective pores, which was determined by the efflux of carboxyfluorescein, an organic dye, from liposomes, decreased substantially as the length of the gramicidin fragment in the series of cationic analogues was truncated. CD spectra showed that large pores are formed by peptides having both β6.3 single-stranded and β5.6 double-stranded helical conformations of the gramicidin fragment, with the C-terminal cationic sequence being extended. The dimerization of the peptides by the oxidation of the terminal cysteine promoted the formation of nonselective pores. It was shown that nonselective pores are not formed in membranes of erythrocytes, which may indicate a dependence of the channel-forming ability on the membrane type. The results may be of interest for the directed synthesis of peptides with antibacterial activity.

Based on the model of a toroidal protein-lipid pore, the effect of calcium ions on colicin E1 channel was predicted. In electrophysiological experiments Ca2+ suppressed the activity of colicin E1 channels in membranes formed of diphytanoylphosphatidylglycerol, whereas no desorption of the protein occurred from the membrane surface. The effect of Ca2+ was not observed on membranes formed of diphytanoylphosphatidylcholine. Single-channel measurements revealed that Ca2+-induced reduction of the colicin-induced current across the negatively charged membrane was due to a decrease in the number of open colicin channels and not changes in their properties. In line with the toroidal model, the effect of Ca2+ on the colicin El channel-forming activity is explained by alteration of the membrane lipid curvature caused by electrostatic interaction of Ca2+ with negatively charged lipid head groups.

Ion‐channel activity of a series of gramicidin A analogues carrying charged amino‐acid sequences on the C‐terminus of the peptide was studied on planar bilayer lipid membranes and liposomes. It was found that the analogue with the positively charged sequence GSGRRRRSQS forms classical cationic pores at low concentrations and large unselective pores at high concentrations. The peptide was predominantly in the right‐handed β6.3‐helical conformation in liposomes as shown by circular dichroism spectroscopy. The single‐channel conductance of the large pore was estimated to be 320 pS in 100 mM choline chloride as judged from the fluctuation analysis of the multi‐channel current. The analogue with the negatively charged sequence GSGEEEESQS exhibited solely classical cationic channel activity. The ability of a peptide to form different type of channels can be used in the search for broad‐spectrum antibiotics.

The channel activity of colicin E1 was studied in planar lipid bilayers and liposomes. Colicin E1 pore‐forming activity was found to depend on the curvature of the lipid bilayer, as judged by the effect on channel activity of curvature‐modulating agents. In particular, the colicin‐induced trans‐membrane current was augmented by lysophosphatidylcholine and reduced by oleic acid, agents promoting positive and negative membrane curvature, respectively. The data obtained imply direct involvement of lipids in the formation of colicin E1‐induced pore walls. It is inferred that the toroidal pore model previously validated for small antimicrobial peptides is applicable to colicin E1, a large protein that contains ten α‐helices in its pore‐forming domain.