Search

Start Over Creator Koblížek, M.

2. Integrity and activity of photosystem 2 complexes isolated from the thermophilic cyanobacterium Synechococcus elongatus using various detergents

Creator:
Šetlíková, E., Sofrová, D., Prášil, O., Budáč, P., Koblížek, M., and Šetlík, I.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
fluorescence induction, low temperature fluorescence spectra, oxygen evolution, PQ pool, QA- reoxidation, QB pocket, and thermoluminescence
Language:
Multiple languages
Description:
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. and E. Šetlíková ... [et al.].
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