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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of psbO and psbH deletion mutants of Synechocystis PCC 6803 indicates that degradation of D1 protein is regulated by the QB site and dependent on protein synthesis (1995)
    s.l. : American Chemical Society
    Biochemistry 34 (1995), S. 9625-9631 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00029a040
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  • 2
    Electronic Resource
    Electronic Resource
    Involvement of protein phosphorylation in the sensitivity of photosystem II to strong illumination (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 92 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Four types of differently phosphorylated hylakoids isolated from field grown spinach (Spinacia oleracea L.) were tested for the sensitivity of photosystem II (PSII) to photoinactivation. Phosphorylation of light-harvesting II complexes (LHCII) protected PSII electron transfer from photoinhibitory damage, while the phosphorylation of the PSII core polypeptides slightly accelerated the decline of electron transfer during high irradiance treatment. Dephosphorylation of the CP43 apoprotein and PsbH protein by an alkaline phosphatase resulted in an extreme sensitivity of the thylakoids to strong illumination. The PSII photoinactivation of thylakoids with the impaired oxygen-evolving complex was found to be independent of phosphorylation.The thylakoids of the thermophilic cyanobacterium Synechococcus elongates were used in order to compare the plants with an organism where LHCII complexes are missing and the PSII core proteins are not phosphorylated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb06669.x
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  • 3
    Electronic Resource
    Electronic Resource
    Strategies of ultraviolet-B protection in microscopic algae (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Different species of microalgae show a wide range of susceptibility to ultraviolet-B (UV-B) radiation. To identify factors responsible for the UV-B tolerance of some of the algae, we compared 8 species that are highly tolerant to UV-B to 8 species that are highly susceptible. The tolerant species contained substantial amounts of an acetolysis-resistant residue. The residue consists of sporopollenin, a biopolymer of variable chemical composition that occurs in the algal cell walls and absorbs UV-B radiation. The susceptible species contained little or no sporopollenin. We propose that sporopollenin provides protection to the tolerant species by screening the incident UV-B radiation. Previous studies showed that the mycosporine-like amino acids (MAA) also act as effective UV-B screens. Our data indicate that sporopollenin provides a constant protection while MAA are induced by radiation stress and occur with some delay. The tolerant species also differ from the susceptible species in their capacity to repair the reaction centers damaged by UV-B. The tolerant algae became vulnerable to UV-B when protein synthesis needed for repair was blocked by streptomycin. In the susceptible species, streptomycin had no effect during the UV-B stress. The repair deficiency in the susceptible species can be explained either by relatively less effective protein synthesis or by an inhibition of the protein synthesis by UV-B. In the tolerant species, the structures needed for protein synthesis are protected by UV-B screening of sporopollenin and MAA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb04796.x
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  • 4
    Electronic Resource
    Electronic Resource
    Photoadaptation of two members of the Chlorophyta (Scenedesmus and Chlorella) in laboratory and outdoor cultures: changes in chlorophyll fluorescence quenching and the xanthophyll cycle (1999)
    Springer
    Planta 209 (1999), S. 126-135 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Chlorella ; Electron transport rate ; Non-photochemical quenching ; Photosynthesis ; Scenedesmus ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The role of the xanthophyll cycle in the adaptation of two chlorococcal algae Scenedesmus quadricauda and Chlorella sorokiniana to high irradiance was studied under laboratory and outdoor conditions. We wished to elucidate whether the xanthophyll cycle plays a key role in dissipating the excesses of absorbed light, as in higher plants, and to characterise the relationship between chlorophyll fluorescence parameters and the content of xanthophyll-cycle pigments. The xanthophyll cycle was found to be operative in both species; however, its contribution to overall non-photochemical quenching (NPQ) could only be distinguished in Scenedesmus (15–20% of total NPQ). The Scenedesmus cultures showed a larger pool of xanthophyll-cycle pigments than Chlorella, and lower sensitivity to photoinhibition as judged from the reduction of maximum quantum yield of photosystem II. In general, both algae had a larger xanthophyll-cycle pool when grown outdoors than in laboratory cultures. Comparing the two species, Scenedesmus exhibited a higher capacity to adapt to high irradiance, due to an effective quenching mechanism and high photosynthetic capacity; in contrast, Chlorella represents a species with a larger antennae system, less-efficient quenching and lower photosynthetic performance. Non-photochemical quenching (NPQ) induced through the xanthophyll cycle can, to a limited extent, represent a regulatory factor in diluted algal cultures grown in outdoor solar photobioreactors, as well as in natural algal phytoplankton populations exposed transiently to high irradiance. However, it does not play an appreciable role in dense, well-mixed microalgal suspensions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050614
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  • 5
    Electronic Resource
    Electronic Resource
    Characterization of processes responsible for the distinct effect of herbicides DCMU and BNT on Photosystem II photoinactivation in cells of the cyanobacterium Synechococcus sp. PCC 7942 (2000)
    Springer
    Photosynthesis research 63 (2000), S. 135-144 
    Details
    ISSN: 1573-5079
    Keywords: D1 protein ; photoinhibition ; PS II inhibitors ; Synechococcus PCC 7942
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-induced modification of Photosystem II (PS II) complex was characterized in the cyanobacterium Synechococcus sp. PCC 7942 treated with either DCMU (a phenylurea PS II inhibitor) or BNT (a phenolic PS II inhibitor). The irradiance response of photoinactivation of PS II oxygen evolution indicated a BNT-specific photoinhibition that saturated at relatively low intensity of light. This BNT-specific process was slowed down under anaerobiosis, was accompanied by the oxygen-dependent formation of a 39 kDa D1 protein adduct, and was not related to stable QA reduction or the ADRY effect. In the BNT-treated cells, the light-induced, oxygen-independent initial drop of PS II electron flow was not affected by formate, an anion modifying properties of the PS II non-heme iron. For DCMU-treated cells, anaerobiosis did not significantly affect PS II photoinactivation, the D1 adduct was not observed and addition of formate induced similar initial decrease of PS II electron flow as in the BNT-treated cells. Our results indicate that reactive oxygen species (most likely singlet oxygen) and modification of the PS II acceptor side are responsible for the fast BNT-induced photoinactivation of PS II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006307417977
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  • 6
    Electronic Resource
    Electronic Resource
    Degradation of the Photosystem II D1 and D2 proteins in different strains of the cyanobacterium Synechocystis PCC 6803 varying with respect to the type and level of psbA transcript (2000)
    Springer
    Plant molecular biology 42 (2000), S. 635-645 
    Details
    ISSN: 1573-5028
    Keywords: cyanobacteria ; D1 ; D2 ; Photosystem II ; psbA ; Synechocystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The turnover of the D1 and D2 proteins of Photosystem II (PSII) has been investigated by pulse-chase radiolabeling in several strains of the cyanobacterium Synechocystis PCC 6803 containing different types and levels of the psbA transcript. Strains lacking psbA1 and psbA3 gene and containing high levels of the psbA2 transcript showed the selective synthesis of D1 whose degradation could be slowed down by the protein synthesis inhibitor lincomycin. In contrast, in strains containing just the psbA3 gene, the intensity of the D1 protein labeling was lower and labeling of the D2 and CP43 proteins was stimulated in comparison to the psbA2-containing strains. In addition, the rate and selectivity of the D1 degradation and its dependence on the presence of lincomycin was proportional to the level of the psbA3 transcript in the particular strain. Consequently, there was parallel, lincomycin-independent and slowed-down breakdown of the D1 and D2 proteins in strains with the lowest level of psbA3 transcript. These results are discussed in terms of a model in which the rate of D1 and D2 degradation in cyanobacteria is affected not only by the rate of PSII photodamage, but also by the availability of newly synthesized D1 protein. Moreover, the comparison of the non-oxygen-evolving D1 mutants D170A** and Y161F*** differing by the presence of tyrosine Z has indicated a minor role of the oxidized form of this secondary PSII electron donor in the donor side mechanism of D1 and D2 protein breakdown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006305308196
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  • 7
    Electronic Resource
    Electronic Resource
    Three types of Photosystem II photoinactivation (1990)
    Springer
    Photosynthesis research 24 (1990), S. 89-97 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll a fluorescence ; D1 protein ; oxygen evolving Photosystem II particles ; pheophytin ; photoinactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oxygen evolving Photosystem II particles were exposed for up to 10 h to 100 W m-2 white light at 20°C under aerobic, low oxygen, strictly anaerobic and strongly reducing conditions. The fast and slow photoinactivation processes described earlier (Šetlík et al. 1989) were observed during the first 120 min. The third and by far the slowest process impaired the primary charge separation P680+−Pheo−. Its half-time was about 2.5 h under aerobic and strongly reducing conditions and about 4 h under anaerobic and low oxygen conditions. In these time intervals there were no changes in the chlorophyll-protein and polypeptide composition of the particles irradiated under anaerobic, low oxygen or strongly reducing conditions while a dramatic degradation of chlorophyll-proteins and polypeptides occurred under aerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00032648
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  • 8
    Electronic Resource
    Electronic Resource
    Purification of a Photosystem II reaction center from a thermophilic cyanobacterium using immobilized metal affinity chromatography (1995)
    Springer
    Photosynthesis research 43 (1995), S. 201-211 
    Details
    ISSN: 1573-5079
    Keywords: Photosystem II ; reaction centers ; Synechococcus ; IMAC ; Cu2+ loaded Sepharose ; QA binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oxygen-evolving PS II particles from the thermophilic cyanobacterium Synechococcus elongatus are partially purified by centrifugation on a sucrose gradient and are bound to a Chelating Sepharose column loaded with Cu2+ ions. Bound particles are then transformed into PS II RC complexes by two washing steps. First, washing with a phosphate buffer (pH=6.5) containing 0.02% of SB 12 removes the rest of phycobilins and leaves pure PS II core particles on the column. Second, washing with a phosphate buffer (pH=6.2) containing 0.2 M LiClO4 and 0.05% of DM removes CP 47 and CP 43 and leaves bare PS II RC complexes on the column. These are then eluted with a phosphate buffer containing 1% of dodecylmaltoside (DM). The molar ratio of pigments in the eluate changes with the progress of elution but around the middle of the elution period a nearly stable ratio is maintained of Chl a: Pheo a: Car: Cyt b 559 equal to 2.9: 1: 0.9: 0.8. In these fractions the photochemical separation of charges could be demonstrated by accumulation of reduced pheophytin (ΔA of 430–440 nm) and by the flash induced formation of P680+ (ΔA at 820 nm). The relatively slow relaxation kinetics of the latter signal (t1/2 ≈ 1 ms) may suggest that in a substantial fraction of the RCs QA remains bound to the complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029933
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of Photosystem II inhibitors DCMU and BNT on the high-light induced D1 turnover in two cyanobacterial strains Synechocystis PCC 6803 and Synechococcus PCC 7942 (1998)
    Springer
    Photosynthesis research 57 (1998), S. 193-202 
    Details
    ISSN: 1573-5079
    Keywords: herbicides ; photoinhibition ; photosynthesis ; protein degradation and synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of the Photosystem II (PSII) inhibitors dichlorophenyldimethylurea (DCMU) and bromonitrothymol (BNT) on the rate of the high-light induced D1 protein turnover was studied in whole cells of two cyanobacterial strains Synechocystis PCC 6803 and Synechococcus PCC 7942. In Synechocystis the D1 degradation was slowed down to a similar extent in the presence of either inhibitor compared with control cells. This slower degradation corresponded with the retardation of Photosystem II photoinactivation (PSIIPI) measured as a decline of PS II activity in the illuminated cells treated with chloramphenicol (CAP). The ongoing D1 synthesis in the presence of both PS II inhibitors was confirmed by unchanging PS II activity and the steady-state level of D1 during illumination in the absence of CAP. In Synechococcus cells both DCMU and BNT blocked the turnover of the 'low-light' D1 form (D1:1) but did not prevent the exchange of the 'high-light' form D1:2 for the D1:1 form. The similar effect of both herbicides on the D1 exchange was in contrast with their influence on the rate of PSIIPI. While DCMU had a pronounced protective effect, BNT significantly increased the rate of PS II photodamage. The fast BNT-induced decline of PS II activity was also observed in Synechocystis cells treated with azide, an inhibitor of reactive oxygen species scavenging enzymes. Therefore, we assume that the distinct sensitivity of the two cyanobacterial strains to BNT can be caused by different content and/or activity of these enzymes in each strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006015214868
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  • 10
    Electronic Resource
    Electronic Resource
    A sensitive photosystem II-based biosensor for detection of a class of herbicides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 664-669 
    Details
    ISSN: 0006-3592
    Keywords: herbicides ; photosystem II ; thermophilic cyanobacteria ; biosensor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have developed a biosensor for the detection of residual triazine-, urea- and phenolic-type herbicides, using isolated photosystem II (PSII) particles from the thermophilic cyanobacterium, Synechococcus elongatus, as biosensing elements. The herbicide detection was based on the fact that, in the presence of artificial electron acceptors, the light-induced electron transfer through isolated PSII particles is accompanied by the release of oxygen, which is inhibited by the herbicide in a concentration-dependent manner. The PSII particles were immobilized between dialysis membrane and the Teflon membrane of the Clark oxygen electrode mounted in a flow cell that was illuminated. Inclusion of the antibiotic chloramphenicol in the reaction mixtures prolonged, by 50%, the lifetime of the biosensor. The use of highly active PSII particles in combination with the flow system resulted in a reusable herbicide biosensor with good stability (50% of initial activity was still remaining after 35-h use at 25°C) and high sensitivity (detection limit for diuron was 5 × 10-10 M). © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 664-669, 1998.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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