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2. Low temperature optical spectroscopy of photosystem 2 particles: an influence of photosynthetic activity

Creator:
Vácha, M., Pšenčík, J., Adamec, F., Ambrož, M., Dian, J., Komenda, J., and Hála, J.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
Low temperature phosphorescence, fluorescence and transient hole buming spectra of the photosystem 2 particles isolated from the cyanobacterium Synechococcus elongatus were measured. The role of photosynthetic activity was estimated by comparison of these spectroscopic methods. A model explaining chlorophyll fluorescence changes and both phosphorescence quantum efficiency increase and transient hole bimiing efficiency decrease connected with Chemical or heat photosynthetic deactivation is presented.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Photoadaptation in the green alga Spongiochloris sp. A three-fluorometer study

Creator:
Koblížek, M., Ciscato, M., Komenda, J., Kopecký, J., Šiffel, P., and Masojídek, J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence, photochemical yield, non-photochemical quenching, connectivity, and electron transport rate
Language:
Multiple languages
Description:
The dark-adapted cells of the green alga Spongiochloris sp. were exposed to "white light" of 1000 µmol(photon) m-2 s-1 for 2 h and then dark adapted for 1.5 h. Changes of photochemical activities during photoadaptation were followed by measurement of chlorophyll (Chl) fluorescence kinetics, 77 K emission spectra, photosynthetic oxygen evolution, and pigment composition. We observed a build-up of slowly-relaxing non-photochemical quenching which led to a decrease of the Fv/Fm parameter and the connectivity. In contrast to the depression of Fv/Fm (35 %) and the rise of non-photochemical quenching (∼ 1.6), we observed an increase in effective absorption cross-section (20 %), Hill reaction (30 %), photosynthetic oxygen evolution (80 %), and electron transport rate estimated from the Chl fluorescence analysis (80 %). We showed an inconsistency in the presently used interpretation schemes, and ascribe the discrepancy between the increase of effective absorption cross-section and the photosynthetic activities on one side and the effective non-photochemical quenching on the other side to the build-up of a quenching mechanism which dissipates energy in closed reaction centres. Such a type of quenching changes the ratio between thermal dissipation and fluorescence without any effect on photochemical yield. In this case the Fv/Fm ratio cannot be used as a measure of the maximum photochemical yield of PS2. and M. Koblížek ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4. Photoinactivation of isolated D1/D2/cytochrome b559 complex under aerobic and anaerobic conditions

Creator:
Allakhverdiev, S. I., Komenda, J., Feiziev, Y. M., Nedbal, L., and Klimov, V. V.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
The preparation of Dl/D2/cytochrome 6559 complex isolated from pea (Pisum sativum h.) was photoinactivated by "white light" (140 W m‘2) at 20 and 4 "C in both the presence and absence of oxygen. The inactivation was followed by measuring the decline of the photoinduced absorbance change A/4683 (the photoaccumulation of reduced pheophytin), by measuring absorption spectra and fluorescence emission, and by polypeptide analysis. In the presence of oxygen, the ability of the DUDUcyi 6559 complex to acciunulate reduced pheophytin was lost with the halftime im of about 3 min and fluorescence quantum yield declined with ti/2 of about 30 min at both 20 and 4 ^C. The D\ and Dl polypeptides were rapidly modified at 20 °C as reflected by the presence of their large aggregates at the start of the electrophoretic gel and by a decrease of the mobility of remaining Dl and Dl monomers. This modification was substantially limited at 4 “C. Subímits of cytochrome 6559 were not modified at any temperature. When oxygen was removed, the halftime of the A/1683 decline increased by about one order of magnitude, fluorescence emission did not decline, but slightly increased, and the polypeptide pattem was only slightly affected during irradiation.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. Photosystem 2 photoinactivation and repair in the Scenedesmus cells treated with herbicides DCMU and BNT and exposed to high irradiance

Creator:
Komenda, J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
algae, 2-bromo-3-methyl-6-isopropyl-4-nitrophenol, chloramphenicol, chlorophyll fluorescence induction, and 3-(3,4-dichlorophenyl)-1,1-dimethylurea
Language:
Multiple languages
Description:
Changes in fluorescence parameters observed during irradiation of the Scenedesmus cells showed that photosystem 2 (PS2) photoinactivation in cells treated with phenolic PS2 inhibitor 2-bromo-3-methyl-6-isopropyl-4-nitrophenol (BNT) was significantly accelerated in comparison with control and DCMU-treated cells. Moreover, a negligible difference in the rate of PS2 photoinactivation in the absence and presence of chloramphenicol indicated that both DCMU and BNT blocked the PS2 repair process.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6. The PsbH protein of photosystem 2

Creator:
Komenda, J., Štys, D., and Lupínková, L.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chloroplast, cyanobacterium, D1 protein, phosphorylation, and photosynthesis
Language:
Multiple languages
Description:
The PsbH protein belongs to a group of small protein subunits of the photosystem 2 (PS2) complex and genes encoding PsbH homologues have been so far found in all studied oxygenic phototrophs. This single helix membrane protein is important for the proper function of the PS2 acceptor side and for stable assembly of PS2. Its hypothetical function as an analogue of the H subunit of the bacterial reaction centre as well as a putative role of its phosphorylation is evaluated. and J. Komenda, D. Štys, L. Lupínková.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

7. Two mechanisins of photosystem 2 photoinactivation: do they exist in vivo?

Creator:
Komenda, J., Masojídek, J., Prášil, O., and Boček, J.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
High (HI, 200 W m'^) and low (LI, 30 W m"^) irradiance treatments on the cells of cyanobactenum Synechococcus elongatus Nfig., var. thermalis Geitl. strain KOVROV 1972/8 were perfonned in the presence of chloramphenicol (CAP), and with addition of DCMU and hydroxylamine (HA), respectively, at growth (56 °C) and low (20 °C) temperatures, to distínguish allegedly different mechanisms of PS 2 photoinactivation (PS 2 PI). At both temperatures HI caused a decline of Fy and Hill reaction activity (HRA) followed by degradation of Dl and to a lesser extent also D2 protein. Fq increased slowly during irradiance at 56 while at 20 ®C it quickly rose to constant level. Degradation of proteins was slowed at a lower temperature. The presence of DCMU during photoinhibition significantly blocked the Fq rise and also prevented PS 2 protein degradation at both temperatures. The course of PS 2 PI under LI resembled tlmt, observed at HI, but changes were much slower. During irradiation of the cells, in which oxygen evolving complex (OEC) was impaired by HA, we observed: (/) at least a ten-fold faster decline of PS 2 electron transport activity than in the cells vňth fimctional OEC under the same conditions; (2) an extensive degradation not only of Dl and D2, but also of the apoprotein of chlorophyll-protein CP43 {ACP43y, (3) almost complete inhibition of PS 2 protein degradation in the presence of DCMU. Thus under all conditions tested in vivo which do not affect the fimction of OEC, the fimction of OEC, PS 2 PI proceeds via the acceptor side and a fimctional impairment of OEC is necessary for induction of the donor side mechanism. When OEC is impaired (e.g. by HA) this mechanism can come in action.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public