[Photochemical reaction of chlorophyll a and pheophytin a with low concentrations of hydroquinone]. / O fotokhimicheskom vzaimodeistvii khlorofilla a i feofitina a s malymi kontsentratsiiami gidrokhinona.

It has been shown that when illuminating chlorophyll a solution (approximately 10(-5) M) in ethanol containing small concentrations of hydroquinone at pH higher than 7, a markable negative photopotential (-PhP) is initiated. Similar picture is also observed both in the presence of 2 . 10(-5) M parabenzoquinone and when using pheophytin a instead of chlorophyll. The data obtained are in favour of the idea that when illuminating the solutions of these pigments in ethanol containing pure p-benzoquinone at pH higher than the definite value, PhP initiation is conditioned by photochemical reaction of pigments with equilibrium amounts of hydroquinones or semiquinone always present in quinone solutions.

[Study of the kinetics of chlorophyll photosensitized dye reduction by photopolarography]. / Izuchenie kinetiki fotosensibilizirovannogo khlorofillom vosstanovleniia krasitelei metodom fotopoliarografii.

It has been shown by photopolarographic method that under stationary illumination chlorophyll-photosensitized reduction of dyes with ascorbic acid proceeds according to the first kinetic order. Rate constants of photoreduction of vitamin K3, methelene red, safranin-T and methylviologen were found in the course of sensitization which proceeded by oxidative and reduction mechanisms. Similarity of kinetics at both sensitization mechanisms was shown. Results obtained by polarographic and spectroscopic methods were compared.

[Resolution of the structure of the absorption spectrum of blue-green algae by a method of measuring the 2d derivative at -196 degrees C]. / Razreshenie struktury spektra pogloshcheniia sine-zelenykh vodoroslei metodom izmereniia 2-i proizvodnoi pri -196 gradusov C.

By measuring the 2nd derivative at -196 degrees C the thin structure of the absorption spectrum of intact cells, isolated in phycobilisomes and pure pigments of blue-green algae Anabaena variabilis and Aphanizomanon flos-aquae is shown. 8 absorption bands in the region 669--710 nm pertaining to chlorophyll a in different aggregation region were found. Almost the same number of bands were found in the region 550--660 nm. The latter were conditioned by the absorption of allophycocyanin, phycocyanin, and probably by phycoerythrin present in the form of different associates.

Phycobilisomes from the blue-green algae Aphanizomenon flos-aquae and Anabaena variabilis.

Phycobilisomes (PBS) were isolated from Aphanizomenon flos-aquae and Anabaena variabilis. The absorption spectra and second derivative of the absorption spectra of isolated PBS indicate the presence of phycoerythrocyanin, and allophycocyanin. The fluorescence spectra of PBS were measured at room temperature and -196 degrees C. Undamaged PBS have the principal fluorescence maximum in the region of 660 nm at room temperature and in the region of 685-690 nm at -196 degrees. When the PBS were heated from ) to 60 degrees the fluorescence at 685-690 nm disappeared and it increased in the region of 650-660 nm. This is apparently due to disruption of the structure of PBS, which results in a disturbance in the migration of energy along the chain phycoerythrocyanin leads to phycocyanin leads to allophycocyanin.

[Role of singlet-excited and triplet states in chlorophyll photooxidation]. / O roli singletno-vozbuzhdennogo i tripletnogo sostoianii pri fotookislenii khlorofilla.

Effect of p-benzoquinone concentration [Q] on the yield of ion-radicals during photooxidation of chlorophyll a with p-benzoquinone was studied by the method of impulse photoconductivity. It has been shown that in the studied range [Q] = 10(-6)--10(-1) M the relationship delta n ([Q]) has a bell-like shape with the maximum at [Q] approximately 10(-3) M. From the relationship obtained the ratio beta = delta ns/delta nt of the contributions of singlet--excited (Chl) and triplet (Chl) states of the pigment into the total yield of ion-radicals is evaluated: for [Q] less than or equal to 10(-1) M beta less than or approximately 10(-3). Primary contribution of the triplet state to the formation of ion-radical is explained, first, by a larger, as compared to the singlet-excited state, life time of the state Chl in solution and second, by the fact that the ion-radical pair 3(Chl+Q-) in the triplet state regenerates less effectively to Chl+Q, than the pair (Chl+Q-).

[Relationship between the electron structure of phosphates and the problem of ATP synthesis and utilization]. / Elektronnoe stroenie fosfatov v sviazi s problemoi sinteza i ispol'zovaniia ATF.

The nature of macroergic bonds and some problems of ATP formation and utilization are considered in terms of electron structure of phosphates. The main acting compound in the ATP synthesis and in the reactions of transfer and utilization of the energy of macroergic bonds as well, is ATP terminal phosphate or phosphoryl group which in the free state is a monomeric methaphosphate-ion. High reactive ability of monomeric methaphosphate-ion, its affinity of lown electrom pairs is conditioned by the presence of a vacant sp3-orbitals in phosphor atom of methaphosphate-ion. Therefore in the reactions with ATP participation the phosphoryl group plays the role of electrophilic agent. Formation of intermediate methaphosphate-ion preceding the synthesis of ATP from ADP during substrate phosphorylation results from the breakage of O--P bond, during which both electrons which form the bond stay in the oxygen atom. Another possible pathway of methaphosphate-ion formation is the ejaction of the electron from ortophosphate dianion with the help of suitable acceptor of the electrons, by light-stimulated pigment system of chloroplasts or chromatophores or singlet oxygen liberated during the decomposition of hydrogen peroxide with catalase. Due to the redistribution of electron density in the phosphate radical the latter turns into the monomeric methaphosphate-ion bound to ADP with the formation of ATP.

[Impulse photoconductance of solutions of chlorophyll and its analogs. IV. Absolute quantum yield of ion radical formation during photooxidation of chlorophyll a by n-benzoquinone]. / Impul'snaia fotoprovodimost' rastvorov khlorofilla i ego analogov. IV. Ob absoliutnom kvantovom vykhode obrazovaniia ion-radikalov pri fotookislenii khlorofilla a n-benzokhinonom.

The values of absolute quantum yield phi of the formation of free ion-radicals during the illumination of alkohol solutions of chlorophyll alpha (Chl) and rho-benzoquinone (Q) at room temperature were obtained by the method of impulse photoconductance. With an increase of the dielectric constant epsilon of the solvent from approximately 6 to approximately 25 phi increases by two orders ( approximately 10(-3)--approximately 10(-1). That obtained relationship phi (epsilon) is explained by epsilon effect on the efficiency of dissociation of "solvent-shared" ion-radical pair Chls+. Os-. The comparison of experimental data and theoretically expected ones allowed the estimation of some parameters to be obtained which characterize the ion-radical pair: interionic distance (10 A), the dissociation velocity constant ( approximately 10(5)--10(8) s-1), the velocity constant of reverse electron transfer (10(8) s-1), the life time approximately 10(-8) s).

The photosensitizing action of phycobiliproteins in the adsorbed state.

In connection with the elucidation of the possibility of photochemical participation of phycobiliproteins in the primary processes of photosynthesis, the ability of a mixture of phycocyanin + allophycocyanin (PC + APC) for photosensitization of redox reactions in the adsorbed state was investigated. It was shown that adsorbates of PC + APC on Sephadexes G-200 and G-25, diethylaminoethylcellulose, carboxyethylcellulose, Bacto-agar, Lifogel, polyethylene glycol, Dowex 50Wx2, and aluminum oxide are capable of sensitizing the photoreduction of methyl red by ascorbid acid. In this case the effectiveness of the sensitizing action depends on the concentration of the adsorbate, the pigment concentration on the carrier, the pH of the medium, and the nature of the solvent. It was shown that in the case of binding to a carrier, the sensitizing ability of PC + APC increases in comparison with that for pigments in the dissolved state. It is suggested that this is promoted by an increase in the concentration and a mutual approach of the reagents after adsorption, and the possible formation of complexes of some or all the participants of the reaction on the surface of the adsorbent.

[Mechanism of activation of the photosensitizing effect of water-soluble analogs of chlorophyll when bound to a polymer]. / O mekhanizme aktivirovaniia fotosensibiliziruiushchego deistviia vodorastvorimykh analogov khlorofilla pri sviazyvaniia ikh polimerom.

It has been shown that the order of mixture of photoreduction components of methylene red with ascorbic acid sensitized with clorine e in an aqueous solution of polyvinilpyrrolidone markedly affects the rate and depth of the reaction. The data obtained support the hypothesis that the intensificiation of the sensitized reaction in the presence of polymer is conditioned by joint polymer binding of the reaction components. This binding facilitates the interaction between the electron donor or acceptor with the light-excited pigment.

[Comparative study of the photopotential and EPR signal arising after photooxidation of metal substituted pheophytins]. / Sravnitel'noe izuchenie fotopotentsiala i signala EPR, voznikaiushchikh pri fotookislenii metallzameshchennykh feotitinov.

Ethanolic solutions of Zn-, Cd-Phe a and b and Chl a and b with p-benzoquinone as electron acceptor have been studied at pH 4. In all systems positive photopotentials and singlet ESR lines of the pigment cation radicals are observed. A conclusion is made that the photopotential is only partly attributable to an electrode reaction of the cation radicals, to a greater extent arising due to unknown, non-radical particles.

[Photochemical and photoelectronic properties of components of the photosynthetic apparatus. III. Heat-stimulated conductivity in the lamellar system chlorophyll a--n-chloranil]. / Fotokhimicheskie i fotoélektronnye svoistva komponentov fotosinteticheskogo apparata. III. Termostimulirovannaia provodimost v lamelliarnoi sisteme khlorofill a--n-khloranil.

Traps with the bedding depth of 0.1 ev in the layers of chlorophyll alpha treated with the electron acceptor n-chloranil were discovered by the method of thermostimulating conductivity. It is suggested that the traps catch mobile vacancies, which occur due to the decomposition of the excited states of the pigment on electron-acceptor centres of the dissociation.

[Spectral-kinetic characteristics of the cation-radical of pheophytin a]. / Spektral'no-kineticheskie kharakteristiki kation-radikala feofitina a.

The photochemical generation of pheophytin a cation-radical in acidulated ethanol and aceto nitril has been studied by the method of flash-photolysis. The bands with maxima at 450, 580 and 800 nm correspond to pheophytin a cation-radical in the differential absorption spectra. The efficient rate constants of pheophytin a triplet state desactivation in ethanol, acetonitril, aceton have the following values: 1.5.10(4), 9.10(3), 8.7.10(3) sec(-1) correspondingly. The rate constant of electron transfer from pheophytin a to p-benzoqui-none in ethanol solutions is 7.8.10(9) l/m.sec. The recombination constants of pheophytin a cation-radical with Q-in acetonitril, and with quinone neutral (QH) in acidulated ethanol have the following values: 5.10(9) and 2.10(9) l/m.sec correspondingly.

[Photophosphorylation, sensitized by chlorophills a and b, pheophytin and beta-carotene in a modelled system]. / Fotofosforilirovanie, sensibilizirovannoe khlorofillami a i b, feofitinom i beta-karotinom v model'noi sisteme.

In aqueous solutions in air atmosphere chlorophylls a and b, pheophytin and beta-carotene adsorbed on aluminium oxide powder are capable of sensibilizing electron transfer from phosphate ions coupled with the formation of high energy bonds of adenosine phosphates. The highest activity of chlorophylls a and b and pheophytin is observed within the pH range of 7.5-7.8; that of beta-carotene--at pH 7.3-7.5.

[Photochenical and photoelectronic properties of components of the photosynthetic apparatus. II. Stationary photoconductivity in chlorophyll-acceptor and chlorophyll+protein-acceptor lamellar systems]. / Fotokhimicheskie i fotoélektronnye svoistva komponentov fotosinteticheskogo apparata. II. Statsionarnaia fotoprovodimost' v lamelliarnykh sistemakh khlorofill-aktseptor i khlorofill+belok-aktseptor.

It has been shown that the treatment of chlorophyll a amorphous layer surface with the electron acceptor n-chloranyl leads to an increase of photocurrent by 10(1)--10(3) times. The photoinduced polarization in the lamellar system chlorophyll a--n-chloranyll is studied. It has been shown that under the effect of the red light the n-chloranyl layer is negatively charged in relation to the pigment layer. Photoconductivity was discovered in the rigid layers of chlorophyll a+human serum albumin. When a thin film of n-chloranyl is sprayed on the surface of the chlorophyll-protein layer, the photocurrent increases approximately 6--7 times. The experimental results are discussed within the scheme according to which the formation of free radical carriers in chlorophyll layers is carried out by the destruction of excited states, possibly excitons on the electron-acceptor centres of dissociation.

[Role of phycobilin pigments in photosynthesis]. / O roli fikobilinovykh pigmentov v fotosinteze.

Experimental data on possible role of phicobilliprotein (PhBP) in photosynthesis are analysed. It is concluded that the widely spread notion about PhBP only as the light-gathering pigments which transfer the energy to chlorophyll, turned to be insufficiently substantiated experimentally until recently. At the same time the discovered ability of PhBP for reversible redox transformations together with the new data on the nature of fluorescence of blue-green algae and PhBP localization in the cell allowed a suggestion that PhBP can independently of chlorophyll or together with it directly participate in photochemical reactions of photosynthesis. A suggestion is advanced concerning possible existence of the reaction centres of PhBP in phicobillisomes.

[Yield of pigment cation-radicals in the reaction of quinone photooxidation of chlorophyll]. / Issledovanis vykhoda kation-radikalov pigments v reaktsii fotookisleniia khlorofilla khinonami

Photoinduced transfer of electrons in alkohol solutions of chlorophyll and its deuterated analog, deuterochlorophyll containing the quinoses: p-benzoquinone, chloranyl, duroquinone, 1,4-naftoquinone and ubiquinone (coenzyme Q6) is studied. It is shown that pigment cation-radical and quinone anion-radical are the primary products of photoreaction. A relationship between stationary concentrations of deuterochlorophyll and p-benzoquinone radicals and quinone concentration in solution is obtained. The reaction mechanism and causes of other authors' (G. Tollin et al.) failure in finding pigment cation-radicals which are formed in the reaction of the latter with quinoses are discussed. It is shown that optimal conditions for accumulating photoinduced cation-radicals of the pigment in pigment solutions of chlorophyll with quinones are lowered temperature, high viscosity of the solvent, low pH of the solution, careful purification of the quinone from hydroquinone admixture.

[Oxidation-reduction potentials of chlorophyll pigments in photosynthesizing organisms on different levels of evolutionary development]. / Okislitel'no-vosstanovitel'nye potentsialy khlorofillovykh pigmentov fotosinteziruiushchikh organizmov, stoiashchikh na raznykh urovniakh évoliutsionnogo razvitiia

According to polarographically measured EOred of bacteriochlorophyll "a", chlorobium chlorophyll "660", "b" and "a" chlorophylls (-0.67 V, -0.73 V, -0.79 V, -0.86 V-n.h.e.) and literature data about Eoox of these pigments (+/-0.62 V, + 0.62 V, + 0.78 V, +0.77 V correspondingly) it has been shown that chemical energy stored in the singular photochemical set is increased in the evolution of the photosynthetic apparatus. It has apparently resulted in the possibility of evolutionary approach to utilization of more inert and more accessible (water) electron donors and favoured further development of photosynthesizing organisms.

[The photoelectrochemical effect in solid films of flucoxanthine].

A negative photopotential was shown to appear upon illumination on a fucoxanthin solid film-covered platinum electrode, immersed into an electrolyte solution. The effects of electrolyte pH and the reducing and oxidyzing agents on the photopotential value and its kinetic behaviour upon illumination and in the dark were studied. The data obtained are indicative of the ability of fucoxanthin to perform photochemical reactions at the level of electron transfers, which accounts for its photosensitizing activity.