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A A Kononenko

Publications and source records attributed to A A Kononenko.

70 records · Page 4Linked to original sources
PubMedDate not supplied

[Electron-conformation transitions in the complex of bacterial photosynthetic reaction centers with cytochromes].

A theoretical model of conformation--regulated electron transfer from multihaem cytochrome c to bacteriochlorophyll of the reaction centre (RC) is considered. The theoretical data are compared with the experimental ones on the basis of temperature dependence of laser-induced electron transfer from high-potential cytochrome Ch bacheriochlorophyll of RC in Ectothiohodospira shaposhnikovii chromatophores. From this comparison there were calculated the thermodynamic characteristics of cytochrome Ch transfer from the configuration without electron transfer to RC bacteriochlorophyll into the coordinated configuration with an effective transfer. The values obtained are: H = 7,1 kJ/M; S = --(30,2--36,9) J/grad. M. Possible regulatory role of such conformation transitions is discussed.

Bacterial Proteins↗
PubMedDate not supplied

[Effect of dehydration on the primary picosecond stages of charge separation in Rhodospirillum rubrum].

Effects of dehydration on the quantum yield of charge separation in the reaction centres, fluorescence and nanosecond recombination luminescence in R. rubrum chromatophores have been investigated. It has been shown that dehydration results in more than a 10 times decrease in the quantum efficiency of photosynthesis. Besides, photoinduced fluorescence changes practically disappear in dehydrated samples and the parameters of nanosecond luminescence substantially change. These observations indicate that strong dehydration causes a deterioration of the primary charge separation process at the early picosecond stages of excitation energy transduction into energy of separated charges. This is, probably, due to either changes in the dynamic characteristics of the reaction centre pigment-protein complex or alteration in the structure state (spacings and mutual orientations) of the primary reactants involved in the primary charge separation.

Bacterial Chromatophores↗
PubMedDate not supplied

[Protein fluorescence of photosynthetic reaction centers from Rhodopseudomonas sphaeroides].

Luminescence emitted by tryptophan residues of reaction center (RC) preparations was studied. The RG preparations were isolated from the photosynthetic bacterium Rhodopseudomonas sphaeroides by treatment with lauryl dimethyl amine oxide (LDAO). After excitation at lambda 280 nm the quantum yield of luminescence is 0,02. It is shown that 60% of tryptophanyls are located inside the protein globule in the surrounding of relaxating polar groups and the rest approximately 40% on the outer surface of the globule--predominantly in the positively charged region of the LDAO-RC protein--in the surrounding of protein-bound water molecules. There is a correlation between the pH dependencies of the position of the peak of luminescence from tryptophanyls and effectivity of electron transfer from the primary (quinone) to secondary acceptor. The two parameters are invariant at pH from 7 to 9 and vary at pH less than 7 and pH greater than 9. The phenomena responsible for the observed correlation are discussed on the basis of pH-dependent changes in the RC protein which govern electron transport activity at the reaction center.

Bacterial Chromatophores↗
PubMedDate not supplied

[Thermoluminescence and electric polarization in chloroplasts].

Exposure of pea chloroplasts to electric field causes the appearance of a new thermoluminescence (TL) band at--(40-50) degrees C and a reduction of the intensity of its main bands. Extents of intensity drop are different for different components of TL and depend on the temperature of illumination. The charge traps responsible for the individual TL components seem to be localized in microsurroundings having different field susceptibility. The electric field effects observable at different temperatures are in correlation with the thermodepolarization currents which reflect the mobility and number of charged groups undergoing a field-induced displacement in chloroplast membranes. Dehydration. of chloroplast film preparations causes a reduction in the intensities of the TL peaks and thermodepolarization currents and a shift of the peaks positions toward higher temperatures. It is assumed that the traps of the recombining charges have two different conformations, each with its own frequency factor for the recombination reaction. Changes in the thermoluminescence behavior in applied electric field are due to the polarization of the traps, which increases the existence probability of a conformation with a high frequency factor.

Chloroplasts↗
PubMedDate not supplied

[Mössbauer spectroscopy of intramolecular mobility in chromatophores from Rhodopseudomonas spheroides].

Mobility of the Mössbauer label attached to the membrane proteins and the Mössbauer probe embedded into the lipid matrix of the bacterial chromatophores were studied. Positive correlation was established between the dynamic properties of hydrophobic compartments in the chromatophores and functional electron--transport activity at the level of quinone cofactors associated with the photosynthetic reaction centres.

Bacterial Chromatophores↗
PubMedDate not supplied

[Kinetics of the generation of a photo-induced electric potential in chromatophores of photosynthetizing bacteria].

Flash-induced formation of an electric potential difference (delta psi) was monitored by a direct method in chromatophores associated with the collodion phospholipid membrane. In Rhodospirillum rubrum and Rhodopseudomonas sphaeriodes chromatophores, the kinetics of delta psi generation exhibit fast (tau less than or equal to 0.3 microseconds) and slow (tau congruent to 200 microseconds) phases, the latter observed in the presence of exogenous quinones. Comparison of the kinetic and potentiometric characteristics of the process with those of electron transport reactions suggests that the fast phase of delta psi rise is due to charge separation between the primary electron donor, P870, and primary electron acceptor QIFe; the slow phase, which is inhibited by o-phenanthroline, is due to electron donation from QIFe to the secondary acceptor, quinone QII. The kinetics of delta psi decay include components arising form the recombination of primary separated charges (tau congruent to 30 ms) and from the passive discharge of the membrane (tau congruent to 400 ms; tau congruent to 1400 ms). From a redox titration of the photo-induced electric signal and the photo-induced absorption changes of P870 at different pH meanings, the value of pK for the primary acceptor FeQI was found to be 7.4 in Rps. sphaeroides chromatophores. In Chromatium minutissimum, a phase ( tau congruent to 20 microseconds) was observed in addition to those seen in Rps. sphaeroids and R. rubrum which was explained by the reduction of P890+ from the high potential cytochrome c555. Possible distribution of the electron transport components in the chromatophore membrane are discussed.

Bacterial Chromatophores↗
PubMedDate not supplied

[Effect of deuteration on the kinetics of photoinduced electron transport in the reaction centers of purple bacteria].

Substitution of H2O for D2O in the preparations of reaction centres from chromatophore membranes of photosynthesizing bacteria Rhodopseudomonas sphaeroides, 1760-1 results in a decrease of the efficiency of direct electron transfer from photoreduced primary quinone X1- to the secondary ones and in rising possibilities for reversible reaction X1- with photooxidized bacteriochlorophyll. The value of isotope effect which does not usually exceed 1.2 depends on temperature; it is not found in the temperature range below -60 degrees divided by -80 degrees C.

Bacterial Chromatophores↗
PubMedDate not supplied

[Effect of pH on photoinduced electron transport in reaction center preparations from Rhodopseudomonas sphaeroides].

The effect of ph on kinetics of photo-induced electron transport process was studied on reaction centre preparations extracted by LDAO treatment of R. sphaeroides chromatophores (strain 1760-1). Reaction centre activity was found to be optimal at pH 7--9. Within this range of pH, the rate constant, KX1X2, for electron transfer from the primary FeQ acceptor complex (X1) to the secondary quinone acceptor X2 appeared to be invariant. On pH lowering from 7 to 5 the value of KX1X2 increases by several times. It abruptly drops, when pH is increased from 9 to 9.5. The nature of these phenomena including influence of pH on KX1X2 value is discussed.

Binding Sites↗
PubMedDate not supplied

[Study of ferredoxins in membranes of Rhodopseudomonas spheroides by means of Mossbauer spectroscopy].

Mössbauer spectra were investigated in membranes (chromatophores) of Rhodopseudomonas sphaeroides, enriched in 57Fe, over a temperature range from 4.2 to 300 K. The spectrum of isolated chromatophores is a symmetric doublet characterized by an isomeric shift delta=0.60+/-0.03 mm/s, quadrupole splitting delta=0.54+/-0.03 mm/s and a width gamma delta of 1.42+/-0.04 mm/3 at half maximum. These parameters, which are in fact characteristic of the Mössbauer spectra of bacterial ferredoxins, appeared practically invariable over a wide range of temperatures. The spectrum of dithionite-treated chromatophores, measured immediately after dithionite treatment, exhibits, in addition, a doublet having parameters characteristic of high-spin bivalent iron. The doublet linewidth of the Fe2+ (S=2) iron is equal, at room temperature, to the emission spectrum linewidth. At 4K, some broadening of the spectrum is observed, which is of magnetic origin. The intensity of the Fe2+(S=2) doublet from a dithionite-treated sample shows a pronounced drop after several days of storage, with the intensity of the initial doublet rising. The overall area under the spectra, the linewidth and shape are not changed. Based on experimental data obtained, possible models of the active center composed of most frequently encountered membrane-bound ferredoxins of the photosynthetic bacterium Rhodopseudomonas sphaeroides are discussed.

Cell Membrane↗
PubMedDate not supplied

[Light-induced changes in pH and buffer capacity in reaction center preparations of Rhodopseudomonas spheroides].

In experiments with reaction centers (RC) preparations of Rps. sphaeroides, strain 1760-1, pH of the suspension medium was found to change under continuous light excitation. The concentration of hydrogen ions starts to decrease fastly (t1/2 = 2--4 s) after the light is on, whereupon it increases slowly, to a steady-state level, within t1/2 = 5--7 min. During the fast phase 0.3 microM H+/1 microM of RC are absorbed and 7--8 microM H+/1 microM of RC are released under the slow phase. The fast phase is suppressed by ortho-phenantroline (10 mM)--an inhibitor of electron transfer from the primary (Fe-quinone complex) to the secondary (quinone) electron acceptors. Glutaraldehyde which is known to modify a protein structure of the RC inhibits the slow phase. The obtained data suggest that fast light-induced pH changes are due to a H+ uptake by the secondary quinoid anion-radical products; slow pH changes are ascribed to structural changes within the RC complex, which lead to a pK shift and/or changes in the amount of dissociating groups on the protein interfacial surface. The conclusion was supported by an observation of light-induced changes in buffer capacity of an RC suspension and by a light-induced increase in the amount of SH-groups titrated by 5.5-dithio-bis(2 nitro)-benzoic acid. The role of conformational dynamics of photoactive pigment--protein complexes in the functions of the RC is discussed.

Bacterial Proteins↗
PubMedDate not supplied

[Effect of temperature and humidity on the electroinduced bathochromic shift in the absorption band of bacteriorhodopsin (Br 570)].

In dried films of purple membranes from Halobacterium Halobium, R1, the bathochromic shift of the absorption band of bR 570 in the external electric field is inhibited to a great extent on low temperatures (over the range +20 divided by -20 degrees C) and on decreasing the hydration of preparation (P/Ps from 50% to 12%). Role of polarization processes in the formation of batho-bR is discussed.

Bacteriorhodopsins↗
PubMedDate not supplied

[Conformational kinetic model of the functioning of the photosynthetic reaction center].

A model for stabilization of separated charges in the pigment-protein complex of the photosynthetic reaction center (RC) in purple bacteria is proposed. Alongside with ordinary electron transfers, the model involves conformational transitions in the pigment-protein complex. Based on the proposed model, an estimation of basic parameters of conformational mobility of RC protein complexes is made.

Bacteria↗
PubMedDate not supplied

[Theoretical study of the kinetics of dark reduction of photochemically oxidized bacteriochlorophyll in the reaction center of Rhodospirillum rubrum chromatophores].

It is shown from the results of theoretical study that the scheme involving two successive interacting components of the pool of secondary acceptors shows the biexponential character of the kinetics of dark reduction of the pigment of P870 observed in the experiment. The velocity constants of the electron transport reactions considered are evaluated.

Bacteriochlorophylls↗
PubMedDate not supplied

[The effect of millimeter-band radiation of nonthermal intensity on sensitivity of Staphylococcus to various antibiotics].

The affect of preliminary irradiation of staphylococcus culture by electromagnetic radiation of extremely high frequency (42, 54, 66 + 78 GHz) of nonthermal intensity on the bacteria growth on the media containing various antibiotics is studied. The reliable change in bacteria sensitivity toward 5 antibiotics, mainly having membranotropic properties is observed in the experiments using 14 antibiotics with various mechanisms of action. It has been established that in the presence of subbactericide concentrations of active antibiotics the irradiation could result in both further suppression of bacteria growth and its stimulation. As shown, the development of these effects takes place even in a matter of minutes of preliminary irradiation, and weak changes are observed at further increase of this period up to 60 min.

Drug Resistance, Microbial↗