Biomedical subjects
Publications and source records attributed to A B Rubin.
The temperature dependence of laser-induced (694.3 nm, 30 ns, 10 mJ.cm-2) high-potential cytochrome c (Em=+290 mV) oxidation kinetics was studied in Ectothiorhodospira shaposhnikovii chromatophores. It was shown that the rate constant of this reaction is independent of temperature in the range of 300 K to 120 K.
The development of Polyporus brumalis basidomycete cultures, both in the dark and in the light, was studied in the 17 day experiment on the orbital station Salyut 5 and in the 20 day experiment on the orbital station Salyut 6. In the first experiment the test tube cultures were exposed to weightlessness beginning from the stage of the fruiting body primordium. In the second experiment the culture was exposed in large containers at the stage of mycelium growth. In the first experiment fruiting bodies that had formed in light had stems and caps approximating the appearance and anatomical structure of the control culture. The fruiting bodies and caps were oriented towards the light. Some structural changes in the hymenophore were observed. Fruiting bodies developed in the dark had twisted stems and no caps. In the second experiment no fruiting bodies were formed in the dark. Light-optical and electron-microscopic studies of Polyporus brumalis growth under weightlessness were carried out.
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.
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.
In dry films of bacteriorhodopsin-containing purple membranes from Halobacterium halobium the external electric field (10(4) -- 10(5) V . cm-1) induces the appearance of a product spectrally close to the initial intermediate of bacteriorhodopsin (BR) photochromic cycle (bathoform, K). This result and also preliminary data of the electret-thermal analysis of the preparations suggest that the dielectric polarization in chromophore-protein-lipid complexes might be an essential step of the primary stabilization of light energy in photo-bioenergetic processes.
Using optical differential spectroscopy and EPR, a parallel study of light-induced electron transfer between the primary (X1) and secondary (X2) quinone-like acceptors in the preparations of reaction centers (RC) isolated from bacterial chromatophore membranes with sodium dodecyl sulfate was carried out. The data from direct measurements of the rate constant temperature dependence for the interaction between light-reduced X1 and X2 (KX1X2) are in good agreement with the data calculated from the kinetic analysis of dark reduction of photooxidized bacteriochlorophyll RC on the acceptors X1 and X2 (KX1X2 = 2.10(-1)S at 20 degrees; Ea = 11,8 kcal.mol-1 within the temperature range of 20 degrees-- -20 degrees). This evidence proves the efficiency of the previously used approach /1, 2/ for the evaluation of the X1-X2 interaction. The method proposed was used for a kinetic analysis of a low-temperature electron transfer from X1 to X2 in RC isolated with lauryldimethylaminoxide (KX1X2 = 2,3.10(2) S-1 at 20 degrees; Ea = 5,5 kcal.mol-1 within the temperature range of 10 degrees-- --70 degrees).
The uncoupler, m-chlorocarbonyl cyanide phenylhydrazone (CCCP) added to anerobic, dark-adapted whole cells of Chromatium vinosum is found to speed the reduction of cytochrome after oxidation by laser or by steady illumination and, subject to unknown factors, to slow the laser-induced oxidation. There is considerable evidence, including spectra and loss of low-temperature oxidizability that this results from a switch of the identity of the cytochrome oxidized from the low-potential cytochrome c-552 to the high-potential cytochrome c555. Redox control and/or control by conformational movements of the cytochromes, either being coupled to energy transduction in the cyclic system, are suggested as mechanisms for the switching. If the switching hypothesis is not accepted, the increased rate of reduction could alternatively be explained by postulating a phosphorylation site in the reduction pathway.
Many laboratories in different countries are involved in the study of the mechanism of conversion of light energy into chemical energy, namely photosynthesis. As is evident from the literature, the initial phases of photosynthesis, which determine the character of this process, proceed at time intervals of 10(-8) and 10(-13) s. They are associated with absorption of light quanta and energy transfer from the molecules of light-harvesting antenna (LHA) chlorophyll and accesory pigments to the reaction centers (RC), where the key reaction of photosynthesis occurs: photo-induced charge separation. Evidently it is of importance to study experimentally the process that occurs within the 10(-8) -10(-13)s time domain.
Electric fields of 10(5) V/cm cause the polarization of chromatophore and reaction center films prepared from photosynthesizing purple bacteria. Photosynthetic pigments, and in particular carotenoids, the absorption spectra of which are changed in response to electric fields (electrochromism), may serve as intrinsic indicators of the development of a polarized state. Polarization occurs due to changes in the orientation and the spatial position of different charged groups and particles. The field-induced polarized state can be fixed by exposure to low temperature (-120 degrees C). On being heated, the system relaxes to the initial state and this can be seen as a thermodepolarization current in an electric circuit. The effects of hydration, chemical modification or heat treatment on thermodepolarization current indicate the involvement of macromolecular components in the formation of a polarized state. In light-adapted samples the polarization effect is markedly greater, indicating that conformational changes occur during the primary photoact. It is assumed that the polarization of the reaction centers during electron transfer might be involved in the stabilization of separated charges and in the storage of energy.
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The effect of flight factors on the growth and development of the fruit bodies of the higher fungus Polyporus brumalis is investigated under the conditions of an experiment on the earth satellite Cosmos 690. Fungi were grown on the earth under conditions of simulated flight and transit; fungi were also grown in the laboratory at a temperature similar to that in flight, at various orientations and under various illuminations. Polyporus brumalis grows well on wort; it forms fruit bodies on long pedicles (up to 25 cm) and possesses a strongly marked negative geotropism. Investigations have shown that the formation of hymenium and pileus is induced by definite time exposures to light. In darkness the formation of fruit bodies takes place, but without formation of hymenium and pileus, and the rate of growth is greater than in light. The strong negative geotropism remains in fruit bodies when developed in darkness and with test-tubes in a vertical position. When the test-tube orientation is changed the pedicles change direction in darkness as well as in light. In maintaining their negative geotropism the fruit bodies bend with changes of space orientation. In the absence of gravity a disorientation of fruit bodies takes place, and the pedicles are strongly twisted into a spiral or into a ball. A flattened type of fruit body can also occur. Such a picture of growth and formation was not observed in control samples. Thus, there is a strong dependence of the formation of the fruit body of Polyporus brumalis on space orientation, gravity and light.
The purpose of the experiment was to study general and local effects of space flight factors on the rhythm of cellular activity and on the morphological and genetic properties of biological objects. The Pushchino strain, Actinomyces levoris Kras 17-225A-IBFM, isolated at the Institute of Biological Physics, Moscow, was chosen as the main biological object. Under appropriate conditions it gives distinct and continuous rings of spore formation reflecting its intrinsic high degree of synchronism in changing its reproduction forms seen with the unaided eye as transparent rings (vegetative growth) alternate with convex white rings (spore-formation growth). As an additional test object, a film culture of bacteriophage T4Br+ developed at the institute was used. The strains were placed together in one bioblock together with plastic detectors for detecting nuclear particles. The film culture of bacteriophage enabled us to amplify the area of registration of local radiation effects by studying the genetic effects of these: frequency of mutations, induced radiation, their spectrum, subsequent revertability under the action of chemical mutagens with known mechanisms of action on DNA molecules.
A method for calculating the rate constant (KA1A2) for the oxidation of the primary electron acceptor (A1) by the secondary one (A2) in the photosynthetic electron transport chain of purple bacteria is proposed. The method is based on the analysis of the dark recovery kinetics of reaction centre bacteriochlorophyll (P) following its oxidation by a short single laser pulse at a high oxidation-reduction potential of the medium. It is shown that in Ectothiorhodospira shaposhnikovii there is little difference in the value of KA1A2 obtained by this method from that measured by the method of Parson ((1969) Biochim, Biophys. Acta 189, 384-396), namely: (4.5 +/- 1.4)-10(3) s-1 and (6.9 +/- 1.2)-10(3) s-1, respectively. The proposed method has also been used for the estimation of the KA1A2 value in chromatophores of Rhodospirillum rubrum deprived of constitutive electron donors which are capable of reducing P+ at a rate exceeding this for the transfer of electron from A1 to A2. The method of Parson cannot be used in this case. The value of KA1A2 has been found to be (2.7 +/- 0.8)-10(3) s-1. The activation energies for the A1 to A2 electron transfer have also been determined. They are 12.4 kcal/mol and 9.9 kcal/mol for E. shaposhnikovii and R. rubrum, respectively.
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Picosecond fluorescence kinetics of pea chloroplasts have been investigated at room temperature using a pulse fluorometer with a resolution time of 10-11 s. Fluorescence has been excited by both a ruby and neodymium-glass mode-locked laser and has been reocrded within the 650 to 800 nm spectral region. We have found three-component kinetics of fluorescence from pea chloroplasts with lifetimes of 80, 300 and 4500 ps, respectively. The observed time dependency of the fluorescence of different components on the functional state of the photosynthetic mechanism as well as their spectra enabled us to conclude that Photosystem I fluoresces with a lifetime of 80 ps (tauI) and Photosystem II fluoresces with a lifetime of 300 ps (tauII). Fluorescence with a lifetime of 4500 ps (tauIII) may be interpreted as originating from chlorophill monomeric forms which are not involved in photosynthesis. It was determined that the rise time of Photosystem I and Photosystem II fluorescence after 530 nm photoexcitation is 200 ps, which corrsponds to the time of energy migration to them from carotenoids.