Photodynamic inactivation of gramicidin channels: a flash-photolysis study

AbstractPhotosensitized inactivation of ionic channels formed by gramicidin in the planar bilayer lipid membrane (BLM) has been studied upon exposure of the BLM to single flashes of visible light in the presence of tetrasulphonated aluminium phthalocyanine. The gramicidin photoinactivation is inhibited by the addition of unsaturated phospholipids to the membrane-forming solution as well as by the addition of azide to the bathing solution, consistent with involvement of singlet oxygen. The characteristic time of the photoinactivation (T) does not change markedly under these conditions. Moreover, T remains nearly constant upon alteration of the flash energy and the photosensitizer concentration. The value of T appears to be sensitive to the gramicidin concentration and to the factors affecting the open time of the gramicidin channels, namely the temperature and the solvent used in the membrane-forming solution. The photoinactivation is not observed with covalent gramicidin dimers. The equations derived from the model of Bamberg and Laeuger (J. Membrane Biol. (1973) 11, 177–194), describing the relaxation of the gramicidin-induced conductance after a sudden distortion of the dimer-monomer equilibrium, are shown to explain consistently the time course of the photoinactivation provided that the damage of the gramicidin molecules leads to deviation from the equilibrium

Hydrothermal synthesis of zeolites from coal fly ash

The fly ash, from the combustion of coal to produce energy and heat, is an industrial waste, in which large accumulations represent a serious environmental threat. To reduce the environmental burden and improve the economic benefits of energy production, the science and industry focus on the transformation of coal combustion byproducts into new functional materials. The fly ash was studied by modern analytical methods. As a result of the hydrothermal reaction, several types of zeolites were synthesised from the fly ash: analcime, faujasite (zeolite X) and gismondine (zeolite P). It was shown that the experimental conditions (temperature, reaction time and alkali concentration) have a significant influence on the type of zeolite and its content in the reaction products. The series of experiments resulted in building approximate crystallisation field of zeolites and other phases as the first stage of the formation of ceramic membrane and other materials

Verifying the chronology of Ukrainian Neolithic

This paper addresses the earliest Neolithic phases in Ukraine: aspects relating to the chronology, methods and time of Neolithisation. In general, the earliest Neolithisation relates to the times of the Linear Pottery culture. Nevertheless, Ukraine has numerous eco-zones so the process could have been different in other zones. The authors emphasize that the key to getting closer to solving this problem is the chronology-re-dating and validation program. Hitherto dates of one culture or period of culture have been treated against each other. This article presents a small series of AMS from well-defined contexts of four sites, previously dated by the Kyiv radiocarbon facility. The results are compared with existing dates in order to establish the validity of existing chronologies for the Neolithic of Ukraine. Obtained results allowed the authors to conclude that the Kyiv dates should not be obligatorily treated as wrong. Furthermore, the authors reopened the discussion to establish what was the role of LBK and Azov-Dnieper culture communities in spreading farming and herding in Ukraine during the second half of the VIth millennium BC

The interaction of phthalocyanine with planar lipid bilayers Photodynamic inactivation of gramicidin channels

AbstractThe effect of phthalocyanines, the potent photodynamic sensitizers, on the electric properties of the bilayer lipid membrane (BLM) is studied. It is shown, that tetrasulfonated, as well as trisulfonated, aluminium phthalocyanine do not alter the conductance of BLM, but elicit certain changes in the boundary potential difference, which points in favor of dye adsorption on BLM. Under the conditions of intense visible light irradiation, the phthalocyanines cause an increase in the conductance, resulting in the irreversible breakdown of BLM, formed from soy bean phosphati-dylcholine, but fail to change the conductance of BLM, formed from diphytanoilphosphatidylcholine. The phthalocyanine-sensitized inactivation of gramicidin channels incorporated into BLM is observed under the conditions of weak visible light irradiation using an He-Ne laser. The photodynamic blockage of model ionic channels is considerably suppressed after oxygen depletion. The phenomenon consists of a marked reduction of a number of open channels, probably due to photomodification of tryptophan residues, essential for gramicidin functioning. The mechanism of the channel inactivation, involving the photosensitized reaction of the II type, and the relevance to the interaction of sensitizers with biomembranes, is discussed

Tandem Gramicidin Channels Cross-linked by Streptavidin

The interaction of biotin-binding proteins with biotinylated gramicidin (gA5XB) was studied by monitoring single-channel activity and sensitized photoinactivation kinetics. It was discovered that the addition of streptavidin or avidin to the bathing solutions of a bilayer lipid membrane (BLM) with incorporated gA5XB induced the opening of a channel characterized by approximately doubled single-channel conductance and extremely long open-state duration. We believe that the deceleration of the photoinactivation kinetics observed here with streptavidin and previously (Rokitskaya, T.I., Y.N. Antonenko, E.A. Kotova, A. Anastasiadis, and F. Separovic. 2000. Biochemistry. 39:13053–13058) with avidin reflects the formation of long-lived channels of this type. Both opening and closing of the double-conductance channels occurred via a transient sub-state of the conductance coinciding with that of the usual single-channel transition. The appearance of the double-conductance channels after the addition of streptavidin was preceded by bursts of fast fluctuations of the current with the open state duration of the individual events of 60 ms. The streptavidin-induced double-conductance channels appeared to be inherent only to the gramicidin analogue with a biotin group linked to the COOH terminus through a long linker arm. Including biotinylated phosphatidylethanolamine into the BLM prevented the formation of the double-conductance channels even with the excess streptavidin. In view of the results obtained here, it is suggested that the double-conductance channel represents a tandem of two neighboring gA5XB channels with their COOH termini being cross-linked by the bound streptavidin at both sides of the BLM. The finding that streptavidin induces the formation of the tandem gramicidin channel comprising two channels functioning in concert is considered to be relevant to the physiologically important phenomenon of ligand-induced receptor oligomerization

Investment development of Russian regions backed up by natural monopolies

The article considers the issues of the relationship between business investment activities and the economic and social development of the regions. Based on the statistical data analysis it is shown that the decrease in investment activities negatively affects all key indicators of regional development after a short period of time. The article shows that a peculiarity defining Russian economy is that its significant part is actually controlled by natural monopolies. At the same time, they are strongly sensitive to all the problems of socioeconomic development of the country's territories and, therefore, are parties concerned in ensuring sustainable and qualitative growth of regional economies. Today many of the natural monopolies implement large-scale investment programs with allocated substantial resources. The analysis of these investment programs showed that they all contain components that contribute to the development of the region where the manufacturing facilities or transportation capacities of these companies are located. It is concluded that a systemic state investment policy aimed at stimulating real investments, rather than "portfolio" ones, is required to address the problem of sustainable economic growth.peer-reviewe

Semantic context of professional identity crisis experience by teachers

The topicality of the problem under research is predetermined by the need of psychology and pedagogy for the study of the phenomenology of professional identity crisis, the process of its experience by school teachers as well as for the development of the system of psychological and pedagogical support of teachers' professional development in the situation of permanent changes in the education system. The objective of the study is to reveal the content of the professional identity crisis, to describe its main features and analyze the semantic context of its experience by teachers. The principal methods of study of this problem are the phenomenological method, tests to identify the semantic context of the process of the professional identity crisis experience by teachers. The results of the study broaden the understanding of the phenomenon of professional identity crisis and its experience, the content of professional crisis and the phenomenology of professional development of teachers. The materials of the article may be useful for psychologists when designing programs of psychological support of teachers´ professional development. © 2017, Slovenska Vzdelavacia Obstaravacia. All rights reserved.Russian Humanitarian Foundation: No.16-36-01031The research is performed thanks to the support of the Russian Humanitarian Scientific Foundation within the framework of scientific and research project "Psychological mechanisms of professional identity crisis experience by teachers", project No.16-36-01031

Phase Filters for 3D Localization of Point Light Sources

The work relates to the engineering and research of phase filters for three-dimensional localization of point light emitters. These phase filters form a light field having two clearly visible maxima in their intensity distribution (i.e. two-lobe fields). By means of numerical simulation, the influence of the amplitude and phase distortions of the wave front of the illuminating beam on the two-lobe field formation has been studied in the work. Keywords: spiral light beams, amplitude distortions, phase distortions, threedimensional localization, two-lobe field