[L.A. Blumenfeld and study of photosynthesis by spectroscopy methods at Chair of Biophysics, Faculty of Physics, Moscow State University].

Nowadays spectroscopy methods are widely employed to study photosynthesis. For instance, fluorescence methods are often in use to study virtually all steps of photosynthesis process. Theoretical models of phenomena under study are of importance for interpretation of experimental data. A decisive role of L.A. Blumenfeld, the former head of the Chair of Biophysics, Faculty of Physics, Moscow State University, in the study of photosynthesis process is shown in this work.

[Theoretical study of fluorescence of photosynthetic pigments at complex dependence of intensity of exciting light on time].

Now the methods using the radiance with complex dependence of light intensity on time are applied to research of photosynthesis by means of fluorescence, exciting photosynthetic pigments. One of these methods is applied in PAM-fluorometers--the commercial devices currently widely used to investigate a state of photosynthesizing systems. However, if excitation is performed in this way, the question, what components of fluorescence are registered at an output of such devices, remains to be open-ended. In this work an attempt to analyse this task has been made.

[A theoretical discussion on oscillations of concentrations of P700+ and the intermediates of the Calvin-Benson cycle].

A theoretically obtained oscillatory mode caused by long-wave illumination is discussed. Repetitive variations in the performance of photosystem I, the electron transport chain, and the Calvin-Benson cycle take place in this mode. The corresponding alterations of photosystem II performance are not repetitive. Damped oscillations of P700+ concentration and CO2 assimilation rate are observed on the theoretical curves. The oscillations of the photosystem I variables of the model look similar to the P700+ concentration dependences derived earlier during experiments on registration of photosystem I EPR signal at different temperatures.

[Proton transfer via the external proton channel of bacteriorhodopsin].

The process of proton transfer across the membrane via the external proton channel in bacteriorhodopsin is considered. A possible amino acid composition of the channel is suggested and the step-by-step mechanism of proton transfer is proposed which agrees with the experimental data. The rate of proton transfer between fixed centers at several chains of the channel was estimated for which the spectroscopic data are available.

[A mathematical model of delayed luminescence oscillations of higher plants and analysis of the reaction rates calculated by the model].

The oscillatory regime of delayed millisecond luminescence was obtained by the model developed earlier. We compared the rates of changes in the concentrations of some of the metabolites calculated by the model with the rates calculated by other known models. The results of calculations for the changes in metabolite concentrations after switching off the light were compared with experimental data.

[A new approach to the problem of oxygen formation in photosynthesis].

A detailed quantum-mechanical analysis of the model of water oxidizing complex, based on recent X-ray data on the structure of PSII, was made. A mechanism of water oxidation was suggested and explained for the first time. The role of three manganese atoms that are not involved directly in water oxidation, the role of the cubic structure of the complex, and the necessity of the presence of calcium and chlorine atoms during water oxidation are discussed. Theoretical computations of the energies of the complex in each S-state were made.

[The submolecular mechanism of the initial stage of the electron coupling in the water oxidizing center of higher plants]. / Submolekuliarnyi mekhanizm nachal'nogo étapa sopriazheniia élektronnogo transporta v komplekse razlozheniia vody vysshikh rastenii.

The results of quantum chemistry calculations of the total energy and proton position in tyrosine-histidine system in a water-oxidizing complex are presented. On the basis of these calculations, the submolecular mechanism of the initial stage of the electron coupling was proposed.

Study of temperature influence on electron transport in higher plants via delayed luminescence method: experiment, theory.

The temperature dependence of steady-state millisecond delayed luminescence (DL) is studied within the temperature range from -23 to 45 degrees C in leaf segments of chinese rose (Hibiscus rosa-sinensis L.) and bean (Ficia faba). To describe the experimental dependence of DL steady-state intensity on temperature theoretically, we suggest the temperature dependences of rate constants in earlier proposed model of photosynthesis. Under these conditions, the temperature dependence of DL steady-state value has the same form as experimental curve.

A theoretical model for electron and proton coupling at quinone-binding site of photosystem II of higher plants.

In this work we consider the coupling of electron and proton transfer near Q(B) in the reaction center (RC) of photosystem II (PS2). We have carried out the calculations of the energy levels and proton density in the system Q(B)(-) Histidine L190. It is shown that the proton of the histidine forms the H-bond with twice-reduced Q(B)(2-). Based on these calculations, we propose a new explanation of the coupling between the electron and proton transfer.

[Initial stage of coupling electron and proton transport in the vicinity of the secondary quinone in photosynthesis of bacteria and plants]. / Nachal'nyi étap sopriazheniia élektronnogo i protonnogo transporta okolo vtorichnogo khinona v bakterial'nom i rastitel'nom fotosinteze.

The coupling of electron and proton transport in the vicinity of the secondary quinone QB in the reaction center of bacteria and photosystem II of higher plants was investigated. The energy levels and wave functions of the proton in the system QB--histidine L 190 were calculated. It was shown that the proton of histidine forms a hydrogen bond with the doubly reduced quinone QB2-. A new scheme of proton transport through histidine L 190 and its coupling with electron transport was proposed.

[L.A. Bliumenfeld and quantum conceptions in biophysics]. / L.A. Bliumenfel'd i kvantovye predstavleniia v biofizike.

The development of quantum conceptions in biophysics and the role of experimental and theoretical works of L.A. Blumenfeld in this process were considered. The influence of his investigations on the researches of other scientists in the field of quantum biophysics was shown.

[Experimental and theoretical study of temperature dependence of steady-state parameters of delayed luminescence induction in leaves of higher plants]. / Eksperimental'noe i teoreticheskoe issledovanie temperaturnoi zavisimosti statsionarnogo znacheniia induktsii zamedlennoi liuminestsentsii list'ev vysshikh rastenii.

The temperature dependence of delayed luminescence of Hibiscus rosa sinensis leaves was studied in the temperature range from -25 degrees C to degrees C. Temperature dependence of the steady-state delayed luminescence intensity has two maxima, at -10 and at +35 degrees C. For the theoretical modeling, the mathematical model of plant photosynthesis developed earlier was used. The temperature dependence of the delayed fluorescence induction was obtained by introducing into the model the temperature dependences for 12 rate constants derived from the data on the effect of temperature on different stages of photosynthesis. The theoretical temperature dependence of the steady-state delayed luminescence was shown to have the same shape as the experimental one.

[Influence of the sucrose outflow from leaves of higher plants on delayed luminescence induction in photosynthesis]. / Vliianie ottoka sakharozy iz list'ev vysshikh rastenii na induktsiiu zamedlennoi liuminestsentsii pri fotosinteze.

The effect of the transport of sucrose from leaves of higher plants on the width of the spectra of induction of delayed luminescence was studied. It was shown that the duration of the induction period decreases when the sucrose outflow from the leaves is limited by cooling the leaf petiole for two hours under light. It was concluded that the accumulation of sucrose in the conducting tissues of the leaf stimulates the increase in the CO2 fixation rate on rellumination after dark adaptation.

Backward electron transport in photosystem 2 reaction center and temperature dependence of delayed luminescence characteristics.

The temperature dependence of parameters of light-induced changes in millisecond delayed luminescence (half-width of the maximum, maximal and steady-state luminescence intensity) is studied within the temperature range from -23 to 45 degrees C in leaf segments of Chinese rose (Hibiscus rosa sinensis). Delayed luminescence (DL) is induced and registered by a homemade setup based on a Lewis-Kasha-type phosphoroscope. The temperature dependence of steady-state luminescence intensity is shown to have two maxima, at -10 and 35 degrees C. At room temperatures, the steady-state value of luminescence intensity is minimal, and its value correlates with the temperature tolerance of the plant. Depending on cooling and heating regimes, the DL steady-state value vs. temperature curves is found to be different. We suppose this effect to be caused by temperature-induced destructive changes in the structure of photosystem 2 reaction centre and probably by salting out.

[Effect of light of various spectral composition on kinetics of changes in a green leaf resistivity]. / Kinetika izmenenii soprotivleniia zelenogo lista pod deistviem sveta razlichnogo spektral'nogo sostava.

The kinetics of changes in the resistance of a green leaf by the action of exciting light was studied. It was shown that the illumination-induced changes in leaf conductance are mainly due to an elevation of temperature caused by the absorption of light energy. Based on the experimental results, the fraction of absorbed light energy converted into heat calculated under assumption that heating of the leaf across the thickness is uniform. It was found that the fraction of absorbed energy converted into heat does not depend on the intensity of radiation in the IR range and increases with decreasing intensity of photosynthetically active radiation. An explanation of the phenomenon is proposed, which is based on that in reality the heating of the leaf across the thickness is nonhomogeneous and this inhomogeneity of heating becomes more pronounced upon photoinduced changes in absorption resulting from a decrease in photosynthetically active radiation. It was shown that nonphotochemical fluorescence quenching does not substantially affect the leaf conductance at intensities of photosynthetically active radiation not higher than 200 Wt/m2.

[Theoretical study of the pulse method for the quenching analysis of photosystem II fluorescence]. / Teoreticheskoe issledovanie impul'snogo metoda analiza tusheniia fluorestsentsii fotosistemy II.

The kinetics of photochemical (qQ) and nonphotochemical (qE) fluorescence quenching during induction was studied in terms of the earlier developed theoretical model of photosynthesis. Photochemical and nonphotochemical quenching was calculated from the parameters of fluorescence induction upon simultaneous excitation with continuous light and by high-intensity light pulses by the method used in a PAM fluorometer. It is shown that the fraction of closed reaction centers during the pulse can change in the course of induction. In consequence, even when none of supposed mechanisms of photochemical quenching is taken into account, the value of qE during induction varies and is not equal to zero.

[Electron structure of plastoquinone and coupling of electron and proton transport in thylakoids of the higher plants]. / Elektronnaia struktura plastokhinona i sopriazhenie élektronnogo i protonnogo transporta v tilakoidakh vysshikh rastenii.

The energy dependence on hydrogen position for a system, consisting of plastoquinone (in different redox states) and histidine molecules was studied. The distance between the atoms forming the hydrogen bond, an oxygen of the quinone molecule and a nitrogen of histidine, was supposed to be fixed. It was shown that for neutral quinone the total energy is minimal when the hydrogen is bound to histidine; for reduced quinone, the probability of hydrogen binding to quinone and histidine is approximately equal (so that a hydrogen bond is formed) and on secondary reduction of plastoquinone, the hydrogen binds to it.

[Induction of delayed luminescence of pea photosystem II with genetically changed level of starch in the seeds]. / Induktsiia zamedlennoi liuminestsentsii fotosistemy II rastenii gorokha s geneticheski izmenennym urovnem soderzhaniia krakhmala v semenakh.

We studied the curves of delayed luminescence induction in leaves of pea plants with mutations affecting the starch branching enzyme (r locus) and ADPG pyrophosphorylase (rb locus). In mutated pants, a 75% reduction of starch content in seeds was observed. The half-decay time of delayed luminescence intensity during induction for double mutants was shown to be longer than for wild type plants.

[Comparative experimental and theoretical study of the dependence of parameters of curved induction of fluorescence and millisecond delayed luminescence on dark adaptation time]. / Sravnitel'noe éksperimental'noe i teoretichesoe issledovanie zavisimosti parametrov krivykh induktsii fluorestsentsii i millisekundnoi zamedlennoi liuminestsentsii ot vremeni temnovoi adaptatsii.

The dependences of G = (Fm - Fs)/Fm parameter for slow fluorescence induction and delayed luminescence induction curves on adaptation time t(ad) were obtained both in experiment, for the leaves of Hibiscus rosa chinensis in vivo, and in a theoretical study with the help of the theoretical model developed earlier. In both cases, the G(t(ad)) dependences have the form of curves with saturation, which are well described by G = A(1 - exp(-(t(ad)/T0)). Both in experiment and in theoretical calculations, G values for delayed luminescence were larger than for fluorescence. The ratio of saturation times for G(t(ad)) for fluorescence and delayed luminescence was 1.40 for experiment and 1.46 for theoretical calculations. These results suggest that delayed luminescence induction is more sensitive to changes in the state of plant than the slow fluorescence induction.

[Possible states of the photosystem II reaction centerand thermoluminescence of higher plants. II. Application of the theory to experimental data analysis. Relation of thermoluminescence peaks to initial states of reaction center and excitation conditions]. / Vozmozhnye sostoianiia reaktsionnogo tsentra fotosistemy II i termoliuminestsentsiia vysshikh rastenii. II.Primenenie teorii termovysvechivaniia k analizu éksperimental'nykh dannykh. Sviaz' pikovtermoliuminestsentsii s nachal'nymi sostoianiiami reaktsionnogo tsentrai usloviiami vozbuzhdeniia.

Initial conditions for the thermoluminescence theory described in the first part of the present work were determined. The initial populations of possible states of the photosystem II reaction center and thermoluminescence of higher plants for different excitation conditions were estimated. The estimation enables one to explain the known experimental conditions favoring the appearance of certain thermoluminescence peaks. The possibility of applying the theory to the deconvolution of experimental curves into components was shown.