Photosystem (PS) II particles retaining a high rate of O2 evolution were isolated from the mesophilic filamentous cyanobacterium, Spirulina platensis. To achieve high production of PSII complexes in the cells, irradiance from halogen incandescent lamps was used. Disruption of cells by vibration of glass beads proved to be the most suitable procedure for isolation of thylakoid membranes. The selectivity of detergents for PSII particle preparation rose in the order of Triton X-100 < decyl-β-D-glucopyranoside < dodecyldimethyl-aminooxide < n-heptyl-β-D-thioglucoside < N-dodecyl-N,N-dimethylammonio-3-propane sulphonate < n-octyl-β-thioglycoside < octylglucoside < n-dodecyl-β-D-maltoside. The last four detergents yielded extracts, from which pure PSII particles not contaminated by PSI complexes could be obtained by sucrose-gradient centrifugation (20–45%) at the 43% sucrose level. We assumed both the acceptor and donor sides of the isolated n-dodecyl-β-D-maltoside (DM) particles to be intact due to high oxygen production by DM particles [1,500 meq(e−) mol−1 (Chl) s−1] achieved in the presence of all artificial acceptors tested. The PSII particle fraction from the sucrose gradient was used with immobilized metal (Cu2+) affinity chromatography (IMAC) for the preparation of the PSII core complex. By washing the column with a MES buffer containing MgCl2 and CaCl2, the phycobiliproteins were stripped off. The PSII core complex was eluted in a buffer containing 1% DM, mannitol, MgCl2, NaCl, CaCl2, and ɛ-aminocaproic acid. SDS-PAGE of the core complex provided pure bands of D1 and D2 proteins and PsbO protein from thylakoid membrane, which were used to raise polyclonal antibodies in rabbits. These antibodies recognized D1 and D2 not only as monomers of 31 and 32 kDa proteins, but also as heterodimers of D1, D2 corresponding to the band of 66 kDa on SDS-PAGE. This was in contrast to antibodies of synthetic determinants, which reacted only with the monomers of D1 and D2 proteins. These negative reactions against heterodimers of D1, D2 supported the hypothesis that dimeric forms of PSII reaction centre proteins have a C-terminal sequence sterically protected against a reaction with specific antibodies.

A review is presented on some aspects of metabolism and supramolecular structures typical of oxygenic photoautotrophs, in particular the higher plants: (i) The problem of photosystem 2 (PS2) heterogeneity, namely the PS2 core-protein phosphorylation and PS2 oligomeric state, are discussed. There are at least four proteins reversibly phosphorylated in the PS2 core. The phosphorylation is light-dependent and its exact function is unclear. The PS2 dimer, usually considered the native state, may not be the only form occurring in vivo. (ii) The reaction of plants to various stress factors is described. Heat shock, reactive oxygen species and toxic metal exposition have been chosen as stressor examples, since the response of plants to them is specific and different from animals. A review with 182 references.

Thylakoid membranes (TM) of the cyanobacterium Synechococcus elongatus were exposed for 30 min to the influence of 0, 10, 100, and 1 000 mM CdCl 2 (= Cd 0 , Cd 10 , Cd 100 , and Cd 1000 ).Cd 10 and Cd 100 caused some increase in activity of photosystem 2, PS2 (H 2 O → DCPIP), while distinct inhibition was observed with Cd 1000 .We also observed a similar effect when measuring oxygen evolution (H 2 O → PBQ + FeCy).Chloroplasts of spinach (Spinacia oleracea L.) were incubated for 30 min with 0, 15, 30, and 60 mM CdCl 2 (= Cd 0 , Cd 15 , Cd 30 , and Cd 60 ).All concentrations studied inhibited the PS2 activity, the effect being stronger with increasing concentration of Cd 2+ .The photosynthetic oxygen evolution activity was also influenced most distinctly by the highest concentration employed, i.e.Cd 60 .Electrophoretic analysis of the protein composition of cyanobacterium TM showed chief changes in the molecular mass regions of M r 29 000 and 116 000, while with spinach chloroplasts the most distinct differences were observed in the regions of M r 15 000 and 50 000.Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity in cyanobacterial spheroplasts still remained on the 40 % level in the case of Cd 1000 , but it decreased down to approx.2.5 % in the Cd 60 sample of spinach chloroplasts.

Intact cells of Synechococcus elongatus were treated with different concentrations (0.1 and 1.0 mM = Cd0.1, Cd1.0) of CdCl2 for 24 h. Cd0.1 treatment stimulated growth of the cell culture and chlorophyll (Chl) a concentration in the culture. Cd1.0 inhibited both the above mentioned parameters. The oxygen evolving activity of intact cells (H2O → BQ) as well as of isolated thylakoid membranes, TM (H2O → DCPIP; H2O → PBQ + FeCy) decreased after 24 h of Cd1.0 cultivation to 7 %. Photosystem 1 (PS1) activity was less sensitive to the effect of Cd2+ than PS2 activity. CdCl2 concentration in cultivation media after 24 h of cultivation proved that the cyanobacterium cells take up these ions to a large extent from the cultivation medium. After 24 h of the Cd1.0 treatment only 12 % of the amount of Cd2+ originally added to the cultivation medium was found. The ratio of external-antenna pigments, phycocyanin, and allophycocyanin to Chl increased approximately twofold with growing Cd2+ concentration in the cultivation medium. This ratio was found in both TM and dodecylmaltoside extracts.

Pigment-protein complexes enriched in photosystem 1 (PS1) and, for comparison, enriched in photosystem 2 (PS2) were isolated from the cyanobacterium Synechococcus elongatus Nag. f. thermalis Geitl. They were immobilized and oriented in the polyvinyl alcohol (PVA) films, and studied by linear dichroism (LD), fluorescence polarization (FP), photoacoustic spectroscopy (PAS), and polarized photoacoustic spectroscopy (PAS‖ and PAS⊥). The LD signal of β-carotene in the region with maximum at 500 nm was positive in the PS1 complex. The maximum value of fluorescence polarization (FP) in the measured photosynthetic pigment region was 1.25 and was similar to higher plant values. Carotenoids exhibited different efficiencies of thermal deactivation (max. at 500 nm) in PS1 and PS2. The thermal deactivation efficiency of carotenoids in comparison with that of chlorophyll (Chl) a at its red absorbance maximum was much higher in PS1 than in PS2 complexes. Cyanobacterial complexes did not contain Chl b, interpretation of the LD, PAS, and FP results is thus easier and can be compared with PS1 and PS2 values of higher plants, especially with Chl b-less mutant values.

Photochemical activity of isolated mesophyll chloroplasts was measured as Hill reaction activity (HRA) and photosystem 1 (PS1) activity in three diallel crosses of maize (Zea mays L.) inbred lines and F-1 hybrids. Statistically significant differences between genotypes together with positive heterotic effect in F-1 generation were found for both traits studied. These differences were more pronounced when HRA or PS1 activity was expressed per leaf area unit or dry matter unit compared to the expression per chlorophyll content unit. Analysis of variance showed that both the genetic and non-genetic components of variation in the photochemical activity of isolated mesophyll chloroplasts are present in all three diallel crosses examined. The positive heterosis in F-1 hybrids probably arises from non-additive genetic effects of a positive dominance type. Additive genetic effects were also statistically highly significant. We found no differences between reciprocal crosses.

The efficiency in selective extraction of photosystem (PS) 2 oxygen evolving complexes was compared among seven detergents. These were applied to thylakoid membranes of the thermophilic cyanobacterium Synechococcus elongatus. Used were five non-ionic detergents with one ionic and one zwitterionic for comparison. To compare the suitability and efficiency of the detergents the following properties of the extracts were examined: maximum rate of oxygen evolution with various electron acceptors, the relative variable fluorescence (FV/FM), the contamination of the extract with photosystem (PS) 1, and the status of the electron acceptor side of PS2 reaction centre. None of the detergents yielded a highly selective extraction of the PS2 complexes (negligible contamination with PS1) which would simultaneously display a high photochemical activity and high structural intactness. Heptylthioglucoside and dodecylmaltoside yielded the nearest approximation to the optimum result. Kinetic fluorometry was applied here for the first time to characterize the functional and structural properties of PS2 particles from cyanobacteria.

While attention was given chiefly to the effect of stabilizers on photochemical activity of cyanobacterial thylakoid membranes in the preceding period (1), the purpose of the present paper is the study of isolation and stabilization of cyanobacterial PS 2 particles evolving oxygen.

The introduction of zwitterionic [1] and nonionic [2 to 5] detergents marked a big leap forward in the isolation of PS2 particles with high activity. They were used for investigation of functional [2, 3] and structural [4, 5] properties of PS2. For both purposes the integrity of the PS2 complexes is equally essential as their purity. It is, however, difficult to achieve top parameters in both directions simultaneously, since the effects of the detergents used for solubilization are often antagonistic. In various laboratories various detergents have been used under different conditions. Consequently a basis for comparing their relative efficiency is missing. In this contribution we try to provide this comparative characterization with respect to purity, activity and integrity of the isolated complexes.

Pigment-protein complexes of photosystem 1 (CP1), and of photosystem 2 (CPa1 and CPa2) from the cyanobacterium Synechococcus elongatus (Nageli) were studied. After solubilisation of the thylakoid membranes with the detergent Sulfobetaine SB 12, followed by preparative electrophoresis and high performance liquid chromatography, the following pigments were found: chlorophyll a and a', myxoxanthophyll, nostoxanthin, caloxanthin, zeaxanthin, cryptoxanthin and beta-carotene. The complexes of photosystem (PS) 2 contained higher concentrations of chlorophyll and of all identified carotenoids compared to PS 1. A clear difference was also found between CPa1 and CPa2, implying a different carotenoid composition between the proximal antennae of PS 2 (49 and 43 kDa, respectively).

Persistent spectral holes were burned into fluorescence spectra of peripheral and core antenna complexes of Synechococcus elongatus cells and thylakoid membranes at 4.2 K. The observed hole structure with antihole and phonon side-band hole is typical for non-photochemical mechanism. The zero-phonon holes are suggested to be broadened by fast energy transfer. The comparison of peripheral and core antenna hole burned spectra is discussed together with the effect of the polyacrylamide gel isolation procedure of the core complex. The results obtained on the antenna complexes are compared with an in vitro reference system lacking energy transfer.

The isolated pigment-protein complex PS1 of cyanobacteria occurs in 5 multiple forms after electrophoretic separation on polyacrylamide gel. Mutual conversion and the relative representation of individual forms is influenced by the presence of the anionic detergent SDS, its concentration and the relative SDS/chlorophyll ratio, the decisive factor being the final detergent concentration, while the SDS-chlorophyll ratio has no particular effect on complex stability. The decomposition rate in the sequential reactions is distinctly dependent on SDS incubation time and temperature.

When isolating Photosystem 1 from the thylakoid membranes of cyanobacteria, a multiplicity of photosystem complexes can be encountered, which has not yet been observed in any other phototrophic organisms: After solubilisation of thylakoid membranes with detergents, trimeric, dimeric and monomeric forms of Photosystem 1 can be separated. The question must now be answered, which of the stable Photosystem 1 forms is the functional form in vivo-monomeric or trimeric? The two possibilities are discussed, though we mainly present arguments for the existence of the trimeric form of Photosystem 1 in cyanobacterial thylakoid membranes.