S K Chamorovsky

Universidad de Colima, Colima, Colima, Mexico

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Publications (28)50.4 Total impact

  • C S Chamorovsky, S K Chamorovsky, P P Knox
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    ABSTRACT: The effect of dehydration and (2)H2O/H2O isotope substitution on electron transport reactions and relaxation of proton-containing groups was studied in chromatophore membranes of Ectothiorhodospira shaposhnikovii. During dehydration (including isotope substitution of hydrate water) of preliminarily dehydrated isolated photosynthetic membranes there was a partial correlation between hydration intervals within which activation of electron transport from high-potential cytochrome c to photoactive bacteriochlorophyll dimer P890 of photosynthetic reaction center and variation of spin-lattice and spin-spin proton relaxation time was observed. Partial correlation between hydration intervals can be considered as evidence of correlation between mobility of non-water proton-containing groups with proton relaxation frequency approximately 10(8) sec(-1) with efficiency of electron transfer at the donor side of the chain.
    Biochemistry (Moscow) 04/2010; 75(4):423-7. · 1.15 Impact Factor
  • I I Pottosin, C S Chamorovsky, S K Chamorovsky
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    ABSTRACT: Cooperative interaction of the high-potential hemes (C(h)) in the cytochrome subunit of the photosynthesizing bacterium Ectothiorhodospira shaposhnikovii was studied by comparing redox titration curves of the hemes under the conditions of pulse photoactivation inducing single turnover of electron-transport chain and steady-state photoactivation, as well as by analysis of the kinetics of laser-induced oxidation of cytochromes by reaction center (RC). A mathematical model of the processes of electron transfer in cytochrome-containing RC was considered. Theoretical analysis revealed that the reduction of one heme C(h) facilitated the reduction of the other heme, which was equivalent to a 60 mV positive shift of the midpoint potential. In addition, reduction of the second heme C(h) caused a three- to four-fold acceleration of the electron transfer from the cytochrome subunit to RC.
    Biochemistry (Moscow) 12/2007; 72(11):1254-60. · 1.15 Impact Factor
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    ABSTRACT: A number of the electrogenic reactions in photosystem I, photosystem II, and bacterial reaction centers (RC) were comparatively analyzed, and the variation of the dielectric permittivity (epsilon) in the vicinity of electron carriers along the membrane normal was calculated. The value of epsilon was minimal at the core of the complexes and gradually increased towards the periphery. We found that the rate of electron transfer (ET) correlated with the value of the dielectric permittivity: the fastest primary ET reactions occur in the low-polarity core of the complexes within the picosecond time range, whereas slower secondary reactions take place at the high-polarity periphery of the complexes within micro- to millisecond time range. The observed correlation was quantitatively interpreted in the framework of the Marcus theory. We calculated the reorganization energy of ET carriers using their van der Waals volumes and experimentally determined epsilon values. The electronic coupling was calculated by the empirical Moser-Dutton rule for the distance-dependent electron tunneling rate in nonadiabatic ET reactions. We concluded that the local dielectric permittivity inferred from the electrometric measurements could be quantitatively used to estimate the rate constant of ET reactions in membrane proteins with resolved atomic structure with the accuracy of less than one order of magnitude.
    Biochimica et Biophysica Acta 07/2007; 1767(6):441-8. · 4.66 Impact Factor
  • Alexey Yu. Semenov, Mahir D. Mamedov, Sergey K. Chamorovsky
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    ABSTRACT: Photoelectric methods to study charge transfer processes in photosynthetic organisms are reviewed along with comparative analyses of photoelectric reactions in Photosystem I, Photosystem II, and the reaction center of purple bacteria. Particular emphasis is placed on a comparison of dielectrically weighted photoelectric signal amplitudes with local structural parameters obtained from the X-ray diffraction data.
    05/2007: pages 319-338;
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    C S Chamorovsky, S K Chamorovsky, A Yu Semenov
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    ABSTRACT: A brief review of studies of dielectric and photoelectric properties of photosynthetic reaction centers of purple bacteria as well as photosystem I and photosystem II of cyanobacteria and higher plants is given. A simple kinetic model of the primary processes of electron transfer in photosynthesis is used to discuss possible mechanisms of correlation between rate constant of charge transfer reaction, free energy of electron transition, and effective dielectric constant in the locus of corresponding carriers.
    Biochemistry (Moscow) 03/2005; 70(2):257-63. · 1.15 Impact Factor
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    ABSTRACT: Organised films containing oriented patches of purple membranes and consisting of 15–75 layers and approximately 1000 layers were fabricated by the Langmuir–Blodgett and electrophoretic sedimentation techniques respectively. ‘Surface pressure vs. molecular area’ isotherms for monolayers of purple membranes suspended in hexane and deposited on the air/water interface were studied. Circular dichroism and absorption spectroscopy were used to investigate the effect of an organic solvent on the chromophore binding site in the purple membranes. Kinetic methods based on flash excitation were employed to determine the influence of the film deposition conditions on the photoelectric response of bacteriorhodopsin and on the M412 intermediate relaxation. Structural characteristics for multilayers prepared from water and hexane purple membrane suspensions were determined by low-angle X-ray scattering. The influence of the layer deposition conditions on the electrical, physical and photoelectrical properties of ordered structures containing bacteriorhodopsin is discussed.
    Advanced Materials for Optics and Electronics 09/2004; 1(3):105 - 115.
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    Alexey Yu Semenov, Mahir D Mamedov, Sergey K Chamorovsky
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    ABSTRACT: The results of studies of charge transfer in cyanobacterial photosystem I (PS I) using the photoelectric method are reviewed. The electrogenicity in the PS I complex and its interaction with natural donors (plastocyanin, cytochrome c(6)), natural acceptors (ferredoxin, flavodoxin), or artificial acceptors and donors (methyl viologen and other redox dyes) were studied. The operating dielectric constant values in the vicinity of the charge transfer carriers in situ were calculated. The profile of distribution of the dielectric constant along the PS I pigment-protein complex (from plastocyanin or cytochrome c(6) through the chlorophyll dimer P700 to the acceptor complex) was estimated, and possible mechanisms of correlation between the local dielectric constant and electron transfer rate constant were discussed.
    FEBS Letters 11/2003; 553(3):223-8. · 3.58 Impact Factor
  • S K Chamorovsky, P M Krasil'nikov, P P Knox
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    ABSTRACT: Isotope substitution of H2O by 2H2O causes an increase in the rate of dark recombination between photooxidized bacteriochlorophyll (P+) and reduced primary quinone acceptor in Rhodobacter sphaeroides reaction centers (RC) at room temperature. The isotopic effect declines upon decreasing the temperature. Dehydration of RC complexes of Ectothiorhodospira shaposhnikovii chromatophores containing multiheme cytochrome c causes a decrease in the efficiency of transfer of a photomobilized electron between the primary and secondary quinone acceptors and from cytochrome to P+. In the case of H2O medium these effects are observed at a lower hydration than in 2H2O-containing medium. In the E. shaposhnikovii chromatophores subjected to dehydration in H2O, the rate of electron transfer from the nearest high-potential cytochrome heme to P+ is virtually independent of hydration within the P/P0 range from 0.1 to 0.5. In samples hydrated in 2H2O this rate is approximately 1.5 times lower than in H2O. However, the isotopic effect of this reaction disappears upon dehydration. The intramolecular electron transfer between two high-potential hemes of cytochrome c in samples with 2H2O is inhibited within this range of P/P0, whereas in RC samples with H2O there is a trend toward gradual inhibition of the interheme electron transfer with dehydration. The experimental results are discussed in terms of the effects of isotope substitution and dehydration on relaxation processes and charge state of RC on implementation of the reactive states of RC providing electron transfer control.
    Biochemistry (Moscow) 12/2002; 67(11):1298-306. · 1.15 Impact Factor
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    M D Mamedov, A A Mamedova, S K Chamorovsky, A Y Semenov
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    ABSTRACT: An electrometric technique was used to investigate electron transfer between spinach plastocyanin (Pc) and photooxidized primary electron donor P700 in photosystem I (PS I) complexes from the cyanobacterium Synechocystis sp. PCC 6803. In the presence of Pc, the fast unresolvable kinetic phase of membrane potential generation related to electron transfer between P700 and the terminal iron-sulfur acceptor F(B) was followed by additional electrogenic phases in the microsecond and millisecond time scales, which contribute approximately 20% to the overall electrogenicity. These phases are attributed to the vectorial electron transfer from Pc to the protein-embedded chlorophyll dimer P700(+) within the PsaA/PsaB heterodimer. The observed rate constant of the millisecond kinetic phase exhibited a saturation profile at increasing Pc concentration, suggesting the formation of a transient complex between Pc and PS I with the dissociation constant K(d) of about 80 microM. A small but detectable fast electrogenic phase was observed at high Pc concentration. The rate constant of this phase was independent of Pc concentration, indicating that it is related to a first-order process.
    FEBS Letters 08/2001; 500(3):172-6. · 3.58 Impact Factor
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    ABSTRACT: The temperature dependence of dark reduction of photooxidized cytochrome c was studied in isolated preparations of Rhodopseudomonas viridis reaction centers. Within the range from room temperature to approximately 260 K this process was found to be mediated by thermal diffusion of exogenous donor molecules, whereas at lower temperatures photooxidized cytochrome is reduced as a result of indirect recombination with photoreduced primary quinone acceptor. Kinetic simulation allowed certain thermodynamic characteristics of this reaction to be calculated. To the first approximation, these characteristics correlate with the estimates obtained from the results of direct redox titration.
    Biochemistry (Moscow) 08/2001; 66(7):769-73. · 1.15 Impact Factor
  • S K Chamorovsky, P P Knox, B V Zubov, I V Chizhov
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    ABSTRACT: Rates of thermoinduced conformational transitions of reaction center (RC) complexes providing effective electron transport were studied in chromatophores and isolated RC preparations of various photosynthesizing purple bacteria using methods of fast freezing and laser-induced temperature jump. Reactions of electron transfer from the primary to secondary quinone acceptors and from the multiheme cytochrome c subunit to photoactive bacteriochlorophyll dimer were used as probes of electron transport efficiency. The thermoinduced transition of the acceptor complex to the conformational state facilitating electron transfer to the secondary quinone acceptor was studied. It was shown that neither the characteristic time of the thermoinduced transition within the temperature range 233-253 K nor the characteristic time of spontaneous decay of this state at 253 K exceeded several tens of milliseconds. In contrast to the quinone complex, the thermoinduced transition of the macromolecular RC complex to the state providing effective electron transport from the multiheme cytochrome c to the photoactive bacteriochlorophyll dimer within the temperature range 220-280 K accounts for tens of seconds. This transition is thought to be mediated by large-scale conformational dynamics of the macromolecular RC complex.
    Biochemistry (Moscow) 06/2001; 66(5):541-7. · 1.15 Impact Factor
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    ABSTRACT: Effects of environmental changes on the reaction pattern of excitation energy trapping and transformation into the "stable" radical pair P+Q(A)-, have been analyzed in isolated reaction centers of the anoxygenic purple bacterium Rhodobacter sphaeroides. The following results were obtained: (a) replacement of exchangeable protons by deuterons significantly retarded the electron transfer steps of primary charge separation, leading to the radical pair P+I- and of the subsequent reoxidation of I- by the quinone acceptor Q(A) but has virtually no effect on the midpoint potential of P/P+ that was found to be 430+/-20 mV; (b) addition of 70% (v/v) glycerol causes a shift of Em by about 30 mV towards higher values whereas the kinetics of the electron transfer reactions remain almost unaffected; (c) in the presence of the cryoprotectant DMSO, a combined effect arises, i.e. a retardation of the electron transfer kinetics comparable to that induced by H/D exchange and simultaneously an upshift of the Em value to 475+/-20 mV, resembling the action of glycerol. These results are discussed within the framework of effects on the midpoint potential due to the dielectric constant of the medium and changes of the charge distribution in the vicinity of the redox groups and the influence of relaxation processes on electron transfer reactions.
    Bioelectrochemistry 04/2001; 53(2):233-41. · 3.95 Impact Factor
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    ABSTRACT: Gel-electrophoretic assay revealed that the photosynthetic reaction center (RC) of Chromatium minutissimum, in contrast to the well-known RC Rhodopseudomonas viridis, consists of five rather than four subunits with molecular masses of 37, 34, 25, 19, and 17 kDa. The 37- and 19-kDa subunits are stained with tetramethylbenzidine for the cytochrome c hemes. Absorption spectra show that the concentration of reduced cytochromes in the C. minutissimum RC poised at redox potential of -150 mV (fully reduced pool of hemes) is about three times more than in the C. minutissimum RC poised at redox potential of +260 mV (only high-potential hemes are reduced). The results of redox titration of absorption changes at the cytochrome c alpha-band are most appropriately approximated by a six-component theoretical curve with the midpoint potentials of Em1 = 390 mV, Em2 = 320 mV, Em3 = 210 mV, Em4 = 100 mV, Em5 = 20 mV, and Em6 = -50 mV. Possible functions of the cytochromes with the midpoint potentials 210 and 100 mV, which have not been found in purple bacteria before, are discussed.
    FEBS Letters 02/1998; 422(2):231-4. · 3.58 Impact Factor
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    ABSTRACT: The conversion of heterocompounds (nitrogen and sulfur) was followed during the conversion of five feedstocks: (a) naphtha from Black Thunder coal, (b) naphtha from Illinois No. 6 coal, (c) the distillate (80%) of the Black Thunder naphtha, (d) the residual (20%) portion of the Black Thunder naphtha and (e) a blend of the residual portion of the Black Thunder and the Illinois No. 6 naphtha. The presence of the heteroatoms contained in the higher molecular weight fraction retards both HDS and HDN. The lower boiling nitrogen compound classes are represented as large, or even larger, fraction of the nitrogen heterocompounds in the hydrotreated product than was present in the feed. This suggests that lower boiling anilines and pyridines are formed as intermediates during the HDN of higher boiling bicyclic nitrogen heterocompounds.
    Fuel 01/1998; 77(11). · 3.36 Impact Factor
  • A B Druzhko, S K Chamorovsky
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    ABSTRACT: Photochemical reactions in a bacteriorhodopsin analog with 4-keto-retinal (4-keto-BR) were studied by using low-temperature and pulsed laser absorption spectroscopy. A photocycle of the photochemical reactions of 4-keto-BR is proposed, which, unlike the photocycle of native BR, includes several spectrally and kinetically distinguishable M-type and O-type intermediates.
    Biosystems 02/1995; 35(2-3):133-6. · 1.58 Impact Factor
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    ABSTRACT: 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.
    Biosystems 02/1995; 35(2-3):129-32. · 1.58 Impact Factor
  • Anna B. Druzhko, Sergey K. Chamorovsky
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    ABSTRACT: Photochemical reactions in a bacteriorhodopsin analog with 4-keto-retinal (4-keto-BR) were studied by using low-temperature and pulsed laser absorption spectroscopy. A photocycle of the photochemical reactions of 4-keto-BR is proposed, which, unlike the photocycle of native BR, includes several spectrally and kinetically distinguishable M-type and O-type intermediates.
    Biosystems. 01/1995;
  • BioSystem, v.35, (1995), pp.129 132. 01/1995; 35:129-132.
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    ABSTRACT: The structure of the Langmuir purple membrane (PM) monolayer was studied by scanning tunneling microscopy (STM). The topography of both the external and cytoplasmic sides of the monolayer was investigated. The thickness of the PM monolayer was determined to be about 4 nm. PM films include specific oval 'crater'-like structures of 50-60 nm in diameter.
    Biosystems 02/1992; 27(4):195-9. · 1.58 Impact Factor
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    ABSTRACT: A temperature dependence of multiheme cytochrome c oxidation induced by a laser pulse was studied in photosynthetic reaction center preparations from Chromatium minutissimum. Absorbance changes and kinetic characteristics of the reaction were measured under redox conditions where one or all of the hemes of the cytochrome subunit are chemically reduced (E h =+300 mV or E h =–20 to -60 mV respectively). In the first case photooxidation is inhibited at temperatures lower than 190–200 K with the rate constant of the photooxidation reaction being practically independent on temperature over the range of 300 to 190 K (k=2.2105 s-1). Under reductive conditions (E h =–20 to -60 mV) lowering the temperature to 190–200 K causes the reaction to slow from k=8.3105 s-1 to 2.1104 s-1. Under further cooling down to the liquid nitrogen temperature, the reaction rate changes negligibly. The absorption amplitude decreases by 30–40% on lowering the temperature. A new physical mechanism of the observed critical effects of temperature on the rate and absorption amplitude of the multiheme cytochrome c oxidation reaction is proposed. The mechanism suggests a close interrelation between conformational mobility of the protein and elementary electron tunneling act. The effect of freezing conformational motion is described in terms of a local diffusion along a random rough potential.
    Photosynthesis Research 11/1989; 22(3):219-231. · 3.15 Impact Factor

Publication Stats

113 Citations
50.40 Total Impact Points

Institutions

  • 2007
    • Universidad de Colima
      Colima, Colima, Mexico
  • 1985–2007
    • Moscow State Textile University
      Moskva, Moscow, Russia
  • 1976–2007
    • Lomonosov Moscow State University
      • • Department of Biophysics at the Faculty of Biology
      • • Department of Biology
      • • A. N. Belozersky Research Institute of Physico-Chemical Biology
      Moskva, Moscow, Russia
  • 1998
    • University of Kentucky
      • Center for Applied Energy Research
      Lexington, KY, United States