Based on the analysis of the molecular organization and properties of an isolated oxygen-evolving complex of photosystem II of plant chloroplasts, a mechanism of water oxidation and oxygen release during photosynthesis was proposed. It is suggested that the photolysis of water occurs in a dimeric oxygen-evolving complex consisting of two core complexes. In the region of contact of these complexes, a hydrophobic "boiler" is formed where the conditions for screening and stabilization of Z-linanded manganese cations accumulating positive charges for the oxidation of water molecules are created. A prerequisite to the photolysis of water is the formation of a binuclear [Mn(3+)-OH ... HO-Mn3+] hydroxyl-manganese associate, which appears in the dimeric oxygen-evolving complex after the first two light flashes as a result of photohydrolysis of photochemically oxidized Z-liganded manganese cations. The process is accompanied by the release of the first water protons to the medium. The photosynthetic oxidation of water hydroxyls occurs at the next stage and is considered as synchronous detachment of four electrons from two bound OH-groups of the associate upon photooxidation of Mn3+ cations to Mn4+ cations after two subsequent light flashes. This process is accompanied by the disproportionation of electron density and the formation of a bond between oxygen atoms of hydroxyls followed by the evolution of molecular oxygen and protons, and regeneration of two starting Mn2+ cations and the primary state of the system.

Proteoliposomes containing oxygen-evolving particles of Photosystem II and associated with a planar phospholipid membrane generate a transmembrane electric potential difference (DeltaPsi) induced by a laser flash. With direct electrometrical technique, it was shown that the direction of the electrical field ("minus" inside the proteoliposome) corresponds to acceptor side of the Photosystem II complex facing inside and donor side facing outside of the liposomes. In addition to the fast phase (tau < 0.1 microsec) of the DeltaPsi generation due to electron transfer between YZ of the water-oxidizing complex and the primary plastoquinone QA, a phase with tau approximately 120 microsec and maximum amplitude approximately 30% of the amplitude of the fast phase was observed under the first flash in proteoliposomes containing potassium ferricyanide, which is known as an oxidant of the non-heme iron (Fenh) on the acceptor side of Photosystem II. This additional phase was absent under the second laser flash but was completely restored after 5 min dark adaptation. The phase of the photoelectric response with tau approximately 120 microsec is probably due to electron transfer from QA to Fenh(III) and likely includes a component related to H+ transfer.

A method is suggested for estimating unfavorable environmental impacts on plants. The method is based on the measurement of the luminescence ratio (Xp) Of the autotrophic and heterotrophic energy storage systems of plant cells, This method was implemented as a luminescence microspectral analysis of sections of native leaves and as a luminescence analysis of organic extracts of leaf tissues. Comparative assessment of the two modifications showed that the method proposed can be used for the early diagnosis of plant dysfunction. The luminescence analysis of leaf extracts provides a higher accuracy of determination of X-p and improves the diagnostic performance of the method in ecological monitoring systems.

The conditions of the initiation of regular arrays of intramembranous particles on the exoplasmic fracture face (EF,) of thylakoid membranes during prolonged storage at 4-7 degrees C have been studied. The regulatory of particles takes place on the 5th-7th days of storage and correlated with the dedradation of membrane lipids and oxygenevolving activity of chloroplasts. Using thin-layer chromatography we found, that the intensity of MGDG and phospolipis bands reduced significantly, whereas the intensity of DGDG band reduced slightly. New lipid bands appear, that probably represent the products of the polar membrane lipid hydrolisis. As can be seen in thin sections of chloroplasts, large lipid osmiophylic drops, often of irregular shape, are formed on the thylakoid edges under the storage conditions. The fraction of these drops was isolated that consisted mainly of hydrolisis products. It has been suggested, that the drops are formed by the coalescing lipids from thylakoid membrane during storage. The drops are composed of the aggregates of cylindrical inverted micelles, that can be seen at fracture faces. The regularity of the particles disappears under nonstable storage conditions (mixing), and the particles are reduced in sizes, as compared to freshly isolated chloroplasts or chloroplasts stored under stable conditions. It is supposed, that the regularity of the intramembranous particles, that are structural manifestation of the chlorophyll-protein complexes results from the considerable loss of lipids from thylakoid membranes and, therefore, alterations in the electrostatical surface potencial.

The rates of thermal inactivation of the oxygen evolution in three subchloroplast preparations has been compared The preparations are the isolated oxygen-evolving pigment-protein-lipid complex (OEC) which is the functional core of Photosystem H (PS-II), PS-II subchloroplast particles, and the initial granal thylakoids of spinach chloroplasts. Substantial increase in thermal lability of these preparations was found in the series. PS-II subchloroplast particles < granal thylakoids < OEC. The temperatures for half-inactivation of oxygen evolution are 45, 40, and 34-degrees-C, respectively. The thermally induced inhibition is irreversible and is accompanied by sudden release of endogenous Mn2+ which occurs in the range of the half-inactivation temperatures. The thermal lability series correlates with the exposure of hydrophilic groups of the functional core to the aqueous phase in the corresponding preparations. This exposure was estimated from the ratio between the rates of oxygen evolution in the presence of hydrophilic and hydrophobic electron acceptors. An increase in hydrophilicity of the surface of the PS-II core occurs on isolation of OEC from membranes using detergent. This effect is clearly related to the interaction of the OEC with the light-harvesting complex. Three thermally induced structural transitions in the functional core of PS-II have been observed by differential scanning microcalorimetry. The low-temperature or A-transition correlates strictly with the corresponding half-inactivation temperature of oxygen evolution in the studied preparations. The A-transition occurs below the melting temperatures of proteins in the OEC. From physicochemical analysis of this data, it is proposed that the water-oxidizing system is located in a region of hydrophobic contacts between two PS-II reaction centers. The native state of the OEC has also been suggested to be a dimer of two core complexes. We assume that the water-oxidizing system cannot be isolated in the form of a single enzyme complex. The hydrophobic locus forming the contact region of the two reaction centers may play a key role in the structure of water-oxidizing system and in stabilization of the highly reactive oxidized intermediates that are produced during its function. The low thermal stability of the water-oxidizing system may be due to thermally induced dissociation of the dimer complex.

The effect of specific inhibitors of translation in chloroplasts (chloramphenicol) and in cytoplasm (cycloheximide) on the formation of pigment-protein-lipid complexes of photosynthetic membranes, on the chlorophyll state in chloroplasts and isolated membrane complexes had been studied. It is proved that the inhibition of translation blocks chlorophyll incorporation only into the complexes of reaction centres of photosystems without any change of the light-harvesting complex. The action of inhibitors leads to the disappearance of long-wave native forms of pigment in the complexes of reaction centres, which are characteristic for them. But the action of inhibitors does not effect the formation of non-specific short-wave forms which are present in all types of membrane complexes. Chloramphenicol proved to be more active in such processes than cycloheximide. On the basis of the data on localization of biosynthesis of polypeptide components of plastid membranes we suppose that during biogenesis of the photosynthetic apparatus the conditions for self-assembly of non-specific native forms of chlorophyll in light-harvesting complexes are made as the result of polymerazation of the main membrane polypeptides which are synthesized in the cytoplasms. Minor polypeptides of plastid (photosystems 1 and 2) and cytoplasmic (photosystem 1) orgin are necessary for self-assembly of the dense units of pigment in reaction centre complexes.