PubMed Health⌕ Search

Biomedical subjects

A A Kononenko

Publications and source records attributed to A A Kononenko.

At least 19 recordsLinked to original sources
PubMed1997

Mixed lipid-protein films of bacterial photosynthetic reaction centres. II. Mixed multilayers on solid supports.

Mixed lipid-protein multilayers composed of the reaction centre (RC) proteins from the Chloroflexus aurantiacus and Rhodobacter sphaeroides (wild type) photosynthetic bacteria and synthetic lipids were investigated. The optimal conditions for forming thin films on solid plates (approximately 100% transfer) were 30 mN/m surface pressure and transfer of the interfacial monolayers from the buffer/air interface onto the plates by the Langmuir-Schaefer method. The films transferred onto quartz and optical transparent current-conducting plates retained their optical and photoelectric properties. The preferential orientation of the protein of the interfacial surface depended on the type of lipid used. In RC-acryloylphosphatidylethanolamine films, the H subunit of the RC from Rhodobacter sphaeroides was oriented toward the water phase, in contrast to RC-diacetylenic acid films, in which the H-subunit was oriented toward the air phase. It is shown that RC can change their orientation in a monolayer, even to the opposite one, depending on the type of lipid matrix.

Bacterial Proteins↗
PubMed1997

Effect of hydration on the structure, dynamics and function of photosynthetic membranes of purple bacteria.

NMR spectra and relaxation times T1 and T2 for 31P in membranes of Rhodobacter sphaeroides were investigated at different relative humidity levels. The results are compared to the hydration curves, fatty acid composition and the structure-dynamic and functional characteristics of the membranes of photosynthetic bacteria Rb. sphaeroides, Rhodospirillum rubrum and Ectothiorhodospira shaposhnikovii. The differences in the state of lipid phase of these membranes are revealed under low humidity, and this is conducive to variability of their structural dynamic and functional characteristics during the hydration process. Based on the results obtained and the data on model systems, four stages of hydration process are distinguished with different effects on the structure and dynamics of membrane components. These stages are: hydration of a portion of polar groups, involvement of water molecules in the hydrogen bonds within macromolecules and the lipid phase, hydration of all polar groups with the appearance of water with high dielectric constant thus making possible the lateral diffusion within the membrane and realization, through water participation, of conditions within organelles and cells required for the process regulation at these levels. The mechanism of water action on various membrane components and their dynamics at each stage are discussed, as well as the effect of different types of motion on the efficiency and regulation of electron transport in the photosynthetic chain of the membranes studied.

Cell Membrane↗
PubMed1996

Polymer ultrathin films with immobilized photosynthetic reaction center proteins.

Mixed monolayers of lipids with photosynthetic reaction center proteins (RCs) from Rb. sphaeroides and C. aurantiacus were studied and the optimum conditions for stable films fabrication were determined. The following synthetic: ACPE, TDA, PDA, DODL and natural lipids: PE, PC were used. The rate of polymerization of the mixed ACPE-RC and TDA-RC monolayers is lower than those for pure lipid-like monomers on the air/water interface but high enough for the fast preparation of the polymer films. The optical and photoelectrical measurements provide evidence for an orientation of RCs (from Rb. sphaeroides) on interface. Hydrophilic H-subunit in the mixed ACPE-RCs and DODL-RCs monolayers is preferentially oriented towards water as in the pure RC monolayers. Opposite orientation was found with TDA-RCs and PDA-RCs films. No preferential orientation was found for lipid-RCs (C. aurantiacus) monolayers probably because of the low asymmetry of hydrophobic subunits (M and L) of these RCs.

Chlorobi↗
PubMed1995

4-Keto-bacteriorhodopsin films as a promising photochromic and electrochromic biological material.

Photochromic and electrochromic spectral properties of 4-keto-bacteriorhodopsin (4-keto-BR) embedded in a polymer matrix were studied. The light-induced spectral changes were found to be similar to those for 4-keto-BR in suspension, but the duration of the photocycle is substantially longer (up to ten of h). Application of a constant electric field induces a bathochromic shift of the main absorption band, the amplitude of the field-induced spectral changes, showing a quadratic dependence on the field strength. Polymer films containing bacteriorhodopsin analogs show promise as new spectrally-selective photochromic and electrochromic materials.

Bacteriorhodopsins↗
PubMed1990

Effect of replacing the primary quinone by different species on the ultrafast photosynthetic electron transfer in bacterial reaction centres.

Using picosecond absorption spectroscopy it has been shown that in Rhodobacter sphaeroides reaction centres the substitution of the primary quinone acceptor (QA), ubiquinone-10, by other quinone species (with redox potentials higher or lower than that of ubiquinone-10) has essentially no modifying effect on the reaction centre protein. The molecular relaxation processes that accompany the localization and stabilization of a photo-excited electron on the intermediate acceptor, bacteriopheophytin (I), are not affected, although the subsequent transfer of the electron from I to QA is slowed down. Consequently, this leads to a lower quantum efficiency of high rate of direct I-----QA reaction is normally due to the specificity of the primary quinone species and its binding site in the reaction centre protein which provide optimum steric and chemical conditions for an effective interaction between I and QA.

Bacterial Proteins↗
PubMed1981

Fast stages of photoelectric processes in biological membranes. III. Bacterial photosynthetic redox system.

Chromatophores of photosynthetic bacteria Rhodospirillum rubrum, Rhodopseudomonas sphaeroides and Chromatium minutissimum were associated with a collodion film impregnated with a decane solution of asolectin. A very short light flash inducing a single turnover of the chromatophore photosynthetic redox system was found to induce the formation of an electrical potential difference amounting to 60 mV, directed across the film as measured with an orthodox electrometer technique. The main phase of the photoelectric response had a tau value of less than 200 ns. Addition of menadione and some other redox mediators increases the main phase amplitude and induces a slower phase (tau = 200 microseconds). In Ch. minutissimum chromatophores that retained their endogenous cytochrome c pool, one more electrogenic phase was revealed (tau = 20 microseconds). Redox titrations of the electric response and bacteriochlorophyll absorption at 430 nm as well as measurements of the kinetics of cytochrome c oxidation have indicated that the fastest electrogenic phase is due to electron transfer from bacteriochlorophyll to Fe-ubiquinone, the 20-microseconds phase to cytochrome c2+ - bacteriochlorophyll+ oxidoreduction, and the 200-microseconds phase to Fe-ubiquinone- oxidation by a secondary quinone. In the decay of the photoelectric response, a 30-ms phase was identified which was explained by a reverse electron transfer from reduced Fe-ubiquinone to oxidated bacteriochlorophyll. The difference in the fast kinetics of photoelectric generation by the bacteriochlorophyll system from those by bacterial and animal rhodopsins has been discussed.

Ascorbic Acid↗
PubMed1981

[Photooxidation and light-induced transport of phenazine methosulfate in chromatophores of purple bacteria].

The light-induced interaction of phenazine methosulfate (PMS) with chromatophores of the purple bacteria Rhodospirillum rubrum and Rhodopseudomonas sphaeroides was studied, using an ion-specific electrode. Illumination caused an initial rapid increase in the concentration of methylphenazinium cation (MP+) and a subsequent slow (1-3 min) decrease of the MP+ concentration to a low steady level. The rapid phase of the light-induced MP+ concentration change is specifically enhanced by ascorbate. The slow phase (uptake of MP+ from the medium) is stimulated on addition of valinomycin, which is known to collapse the membrane potential of energized chromatophores, and is partly inhibited by NH4Cl, which enhances the membrane potential in chromatophores. The light-induced uptake of MP+ is sharply stimulated by dibromothymoquinone. It is concluded that the initial rapid increase of the MP+ concentration in the outer medium results from the oxidation of the reduced PMS by photooxidized reaction centers. The slow decrease of the external MP+ concentration is due to active transport of MP+ into the internal space of the chromatophores via a mechanism of a chemiosmotic type. The accumulation of MP+ is directly mediated by the redox reactions of PMS at the outer and inner surfaces of the photosynthetic membrane, which are involved in cyclic electron transport.

Biological Transport↗
PubMed1981

[Structural-functional characteristics of photosynthetic reaction centers extracted by treatment with lauryldimethylamine oxide from Rhodopseudomonas sphaeroides (wild type)].

A method for isolation of photoactive reaction centers from Rps. sphaeroides (wild type) chromatophores, using lauryldimethylamine oxide (LDAO) as detergent, is described. The preparation obtained is free of a light-harvesting pigment-protein complex and cytochromes. A high degree of purity can be demonstrated from the adsorption indexes of the preparation equal to A280 : A800 = 1.2--1.3; A760 : A800 : A870 = 1 : 2 : 0.9. Data from polyacrylamide gel electrophoresis suggest that the integral protein component of the preparation is made up of three polypeptides with molecular weights of 30 000, 24 000 and 20 000. Under continuous illumination the preparation exhibits an effective electron transfer from the bacteriochlorophyll dimer (BChl)2 to a system of quinone acceptors (X1, X2). The ambient potential Em of (BChl)2 half-recovery was estimated as + 475 mV and pH 7.2. The rate constant for direct electron transfer from X1- to X2 is about 0.5 . 10(3) s-1 at 300 degrees K (0.01 M phosphate buffer; 0.05% LDAO, pH 7.2). The activity of this transfer is exponentially reduced with a decrease in temperature within the range of 300 to 230 degrees K, with an activation energy, Ea, of approximately equal to 8 kcal. The recombination rate constant of light-induced ion-radicals, (BChl)2+ and X1-, was found to be 5 . 10(-2) s-1 at 180 degrees K. The preparations thus obtained can be used for studying mechanisms of primary events in photosynthesis and electron-exchange conformations in the reaction center.

Bacterial Proteins↗
PubMed1981

[Isolation and properties of the pigment-protein complex (protochlorophyllide - holochrome) from etiolated leaves of corn sprouts].

A pigment -- protein complex was isolated from etiolated leaves of corn sprouts using treatment by the detergent Triton X-100, ultracentrifugation and gel-filtration. The complex has a molecular weight of 50000 and upon illumination can convert protochlorophyllide (Pchld) into chlorophyllide (Chld). The low temperature fluorescence spectra of dark preparations reveal maxima of Pchld 632 (photo-inactive form) and Pchld 653 (photo-active form). Upon illumination Pchld 653 is converted into Chld 685. The kinetics of the precursor photoconversion into Chld are coincident with those for photoconversion in native etiolated corn leaves. The complex is completely inactivated at a decrease of pH down to 6.5 or during incubation at high temperature (30 degrees).

Bacterial Proteins↗
PubMed1980

Electric field promotion of the bacteriorhodopsin BR570 to BR412 photoconversion in films of Halobacterium halobium purple membranes.

The combined action of electric field (105-107 V x m-1) and light (380-580 nm, 80 W x m-2) activating the photoenergetic reaction of bacteriorhodopsin (BR) in dry films of purple membranes from Halobacterium halobium was studied. A new stimulating effect of the field on the BR412 intermediate accumulation in the normal photochromic cycle of BR570 has been observed. The formation of the product BR412 is supposed to be accompanied by specific rearrangements of certain charged, polar and polarizable groups in the BR pigment-protein matrix. Such an intrinsic polarization could be promoted by an external electric field, the displacement vector of those groups being oriented in the direction of the filed. The dielectric polarization properties of the purple membranes have been demonstrated by electret-thermal analysis.

Bacteriorhodopsins↗
PubMed1980

Photo-induced electron transport and water state in Rhodospirillum rubrum chromatophores.

It is shown that in bacterial chromatophores the pronounced changes in the free water content with a proton spin-spin relaxation time (T2) of 10(-3)--10(-2) s does not influence the efficiency of electron transfer from the photosynthetic reaction centre to the membrane pool of secondary acceptors. An abrupt inhibition of this process occurs only after the loss of the water with faster proton spin-spin relaxation time (T2 of 10(-4) s). The process is reversible. The water fraction in question is obviously bound to the chromatophore proteins and forms the primary hydration layer.

Bacterial Chromatophores↗
PubMed1980

Electron tunneling process and the segment mobility of macromolecules.

New experimental data [Berg, A. I., Noks, P. P., Kononenko, A. A., Frolov, E. N., Khrymova, I. N., Rubin A. B., Likhtenstein, G. I., Goldanskii, V. I., Parak, F., Bukl, M. & Mössbauer, R. (1979) Mol. Biol. (USSR) 13, 81-89; Berg, A. I., Noks, P. P., Kononenko, A. A., Frolov, E. N., Uspenskaya, N. Y., Khrymova, I. N., Rubin, A. B., Likhtenstein, G. I. & Hideg, K. (1979) Mol. Biol (USSR) 13, 469-477] provide evidence that the electron tunneling process is connected to a special type of conformational transition (segmental transition) protein macromolecules in photosynthetic membranes. This problem is investigated with a simple mechanical model. It is shown that the segmental degree of freedom can play the role of the strongly interacting accepting mode for the electron tunneling process. The temperature dependences of the electron tunneling rate and the recoilless gamma-ray absorption of membrane-bound 57Fe, as an indicator of the intramolecular mobility, are calculated. The problem of energy storage in proteins is also discussed.

Biophysical Phenomena↗
PubMed1980

[Effect of cobalt and copper o-phenanthroline complexes on electron transport and energy coupling activity in reaction centers and chromatophores of purple bacteria].

The effects of cobalt and copper o-phenanthroline complexes on electron transfer and energy coupling activity in the reaction center and chromatophore preparations of purple bacteria were studied. In terms of their effects on the systems under study these complexes fall into two groups, i.e. cobalt complexes with a high electron transfer activity, which stimulate membrane energization, and copper complexes which contribute to the chromatophore membrane deenergization. Among a variety of complexes studied the perchlorate tris-o-phenanthroline complex Co(II) and the chloride 4,7-diphenyl-o-phenanthroline complex Cu(II) were found to have the highest activity. Both cobalt and copper o-phenanthroline complexes may be a promising tool for regulating bioenergetic processes.

Bacterial Chromatophores↗
PubMed1980

[Components of cyclic electron transport in stromal subchloroplast particles enriched with photosystem I].

The effects of specific electron transport inhibitors (e. g. Hg2+, dibromothymoquinone, antimycin A) on photo-induced oxidation-reduction of P700, electrochromic pigment changes and ATP yields in the photophosphorylation reactions of PS I-enriched subchloroplast particles, were studied. The results obtained suggest that in the absence of exogenous cofactors the cyclic electron transport proceeds through plastoquinone and plastocyanine molecules, partly maintained in the preparations. The low ATP production is correlated with the low rates of an electron transfer. The cyclic transfer increases to some extent after addition of exogenous plastocyanine; in addition to the above-mentioned carriers it includes also cytochrome b6; however, the electron flow in this case is not coupled with phosphorylation. None of these components are involved in cyclic electron transport in the presence of reduced DCIP, which ensures the ATP synthesis via an artificial loop for proton translocation.

2,6-Dichloroindophenol↗