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E A Akulova

Publications and source records attributed to E A Akulova.

16 recordsLinked to original sources
PubMed1978

[Stimulation mechanism of soluble ATPase from chloroplasts (CF1)].

Effects of various compounds on Mg-dependent ATPase activity of chloroplast coupling factor--CF1--were studied. It was shown that the stimulating effect of compounds is increased with the increase in their hydrophobicity. Under given experimental conditions all compounds under study readily accept and donate protons. The maximal efficiency is reached when pH of the medium is close to the pK value of conjugated acid. It is assumed that the stimulating effects of compounds on Mg-dependent chloroplast ATPase consist in the increase of the rate of the limiting step of enzyme induced proton translocation coupled to the catalytic step of ATP hydrolysis.

2,2'-Dipyridyl↗
PubMed1978

[Effect of phloridzin on photosynthetic electron transport].

Phloridzin (2',4',6',4-tetraoxyhydrochalcon-2'-glucoside) was used to study the localization of synthesis of ATP in the electrontransporting chain of photosynthesis. It was shown that phloridzin inhibits the rate of photoreduction of NADP+ by isolated pea chloroplasts by 40%, electron transport via cytochrome f by 100% and via plastocyanin--by 50%. The "crossover" experiments demonstrated that phloridzin inhibits ADP-induced photoreduction of cytochrome f, having no effect on plastocyanin under identical conditions. It is assumed that the site of ATP synthesis is localized on the reduced site of cytochrome f, while the carrier itself is located in the electron transporting chain coupled to phosphorylation. It is possible that only part of the plastocyanin molecules are located in the phosphorylating pathway of electron transport.

Adenosine Triphosphate↗
PubMed1977

[Cytochrome c immobilized on Sepharose 4B and its participation in photochemical reactions of chloroplasts].

Cytochrome c immobilized on cyanogen bromide-activated Sepharose 4B may be used to study photochemical reactions in chloroplasts. Chloroplast reduction of both immobilized and soluble forms of the cytochrome occurs along the exogenous and endogenous pathways which results in a weaker reduction of the immobilized protein as compared to that of the soluble one. The time of the reduced immobilized cytochrome c oxidation in the dark is two orders of magnitude greater than that of the soluble one. This fact may be interpreted in terms of spatial dissociation of reductase and oxidase centers of chloroplasts with reference to the cytochrome. The optimal ionic strength for cytochrome reduction, i.e. ionic strength causing an in vitro destruction of the ferredoxin-NADP-reductase complex was found to equal to 0.2 M.

Chloroplasts↗
PubMed1977

[Photosynthetic electron transfer at the level of cytochrome f and plastocyanin].

Light-induced redox conversions of cytochrome f and plastocyanin in situ and electron transporst from H2O to NADP+ were studied by a dual-wave differential spectrophotometry under identical conditions and subsequently compared. The analysis in red and far red light, treatment by inhibitors, e. g. diurone and dibromothymoquinone, and the analysis of photoreactions during the greening of etiolated seedlings demonstrated that cytochrome f functions only in the non-cyclic chain of electron transport, whereas plastocyanin--both in the non-cyclic and in the cyclic electron transport chains. The jositions of cytochrome f and plastocyanin in various electron-transport chains are proposed.

Cytochromes↗
PubMed1977

[Immobilization of ferredoxin].

The method of pea ferredoxin (Fd) immobilization has been worked out. Under binding Fd with sepharose 4B activated by cyanogen bromide, a destruction took place in the Fd active center and apoprotein was bound with the matrix. The native immobilized Fd has been obtained when using P-300 biogel as a matrix. The gel was activated by glutaraldehyde and protein was linked with gel through a hexamethylenediamine spacer.

Apoproteins↗
PubMed1976

[Light-induced redox conversions of cytochrome f in pea leaves].

Redox conversions of cytochrome f were studied in intact pea leaves by double wavelength difference spectrophotometry. Using the inhibition of the photosystem II activity by far red light (719 nm) or diurone, it was found that cytochrome f is located between two photosystems on the oxidative side of photosystem I. The inhibitors of phosphorylation, , e.g. antimycin A and phloridzine, as well as the uncoupler, methylamine, strongly decreased electron transport through the carrier. It is concluded that cytochrome f is functioning in the non-cyclic phosphorylation. It is suggested that in vivo cytochrome f is not coupled with cyclic electron transfer.

Chloroplasts↗
PubMed1976

[Two forms of pea leaf ferredoxin].

Some causative factors resulting in the appearance of two components of ferredoxin (Fd) isolated from the pea leaves preparations have been studied by 15% PAG electrophoresis. It has been shown that the composition of the buffer systems (tris-glycine buffer, pH 8,3; veronal buffer, pH 7.0) does not cause Fd separation into two components. Study of the effects of the modifying agents on the active centre and apoprotein of Fd. Showed that the destruction of the active centre does not affect Fd separation and modification of the Fd protein part results in greater amount of the bands on the electrophoregrams. It has been concluded that heterogeneity of Fd is possibly of the genetic nature. The following facts can be regarded as an evidence for existence of both forms of Fd in pea leaves: occurrence of two forms of Fd in chloroplasts isolated in organic media, differing in Fd content during pea ontogenesis and upon varying illumination conditions during their growth.

Chemical Phenomena↗
PubMed1975

Investigation of electron transport in the chloroplasts and their fragments by the ESR method. II. Light-induced interaction of water-soluble nitroxide radical with chloroplasts and chlorophyll containing protein-lipid micelles.

A light-induced reduction of the water-soluble nitroxide radical by chlorophyll in lipid and protein--lipid micelles was demonstrated. In contrast to model systems, in whole chloroplasts the NR is photoreduced by the electrons of the noncyclic electron transport chain. The initiation of cyclic electron transport in light particles, containing only photosystem I, does not lead to photoreduction of NR. When exogenous protein -- human serum albumin -- is added to the light particles, the nitroxide radicals are intensively reduced. The specific role of protein in electron transport from P700 to the exogenous acceptor is discussed.

Binding Sites↗
PubMedDate not supplied

[Light-induced absorption changes at 590 nm in isolated pea chloroplasts and their relation to plastocyanin].

The light-induced decrease in absorption with the minimum at 590-595 nm has been found in chloroplasts of etiolated pea seedlings by the method of dual-wavelength difference spectrophotometry. It has been shown that this effect is caused by photoreduction of the electron carrier with the absorption maximum of its oxidized form at 590 nm. Photoreduction of the carrier has been observed after excitation both by the short-wave (646 nm) and long-wave (709 nm) red light, although the latter is less effective. It has been suggested that the absorption changes at 590 nm are caused by light-induced redox conversions of plastocyanin bound to chloroplast membrane.

Cell Membrane↗
PubMedDate not supplied

[Effect of IAA on the photophosphorylation of pea isolated chloroplasts].

Effect of IAA (10(-10)-10(-3) M) on photophosphorylation, NADP reduction and the oxygen exchange is investigated. It is shown that low concentrations of IAA (10(-10)-10(-7) M) increase the photophosphorylation reaction and the flow of electrones to NADP under the phosphorylation conditions in the chloroplasts, and their effect on the O2 exchange is not the same in different types of photophosphorylation. It is supposed that the effect of IAA on the photophosphorylation is connected with H292 metabolism in chloroplasts and with catalase and peroxidase functions.

Chloroplasts↗
PubMedDate not supplied

[Inhibition of electron transport and photophosphorylation in chloroplasts by quercetin].

The influence of quercetin on electron transport and photophosphorylation of pea isolated chloroplasts with methylviologen and NADP+ has been studied. Quercetin inhibits ATP synthesis and phosphorylating electron transport but does not affect the basal electron transport in the presence of methylviologen. In view of these data and because of the increase of the proton uptake by chloroplasts in the presence of quercetin we consider it as an inhibitor of energy transfer. Under conditions of NADP+ photoreduction quercetin acts also as an inhibitor of electron transfer, interacting with ferredoxin, though a complete inhibition of electron transfer has not been observed. This last phenomenon may be of importance for the understanding of the detailed mechanism of NADP+ reduction by chloroplasts.

Chloroplasts↗