The manganese site of the photosynthetic oxygen-evolving complex probed by EPR spectroscopy of oriented photosystem II membranes: the g = 4 and g = 2 multiline signals

Biochemistry ◽  
1992 ◽  
Vol 31 (2) ◽  
pp. 541-547 ◽  
Author(s):  
Dennis H. Kim ◽  
R. David Britt ◽  
Melvin P. Klein ◽  
Kenneth Sauer
Keyword(s):  
Photosystem Ii ◽  
Epr Spectroscopy ◽  
Oxygen Evolving Complex ◽  
Photosynthetic Oxygen ◽  
Oxygen Evolving

Different sensitivities of photosystem II in green algae and cyanobacteria to phenylurea and phenol-type herbicides: effect on electron donor side

2017 ◽  
Vol 72 (7-8) ◽  
pp. 315-324 ◽  
Author(s):  
Ekaterina K. Yotsova ◽  
Martin A. Stefanov ◽  
Anelia G. Dobrikova ◽  
Emilia L. Apostolova
Keyword(s):  
Photosystem Ii ◽  
Kinetic Parameters ◽  
Oxygen Evolution ◽  
Oxygen Evolving Complex ◽  
Photosynthetic Oxygen Evolution ◽  
Donor Side ◽  
Short Term Treatment ◽  
Psii Photochemistry ◽  
Photosynthetic Oxygen ◽  
Oxygen Evolving

AbstractThe effects of short-term treatment with phenylurea (DCMU, isoproturon) and phenol-type (ioxynil) herbicides on the green algaChlorella kessleriand the cyanobacteriumSynechocystis salinawith different organizations of photosystem II (PSII) were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence and photosynthetic oxygen evolution measured by polarographic oxygen electrodes (Clark-type and Joliot-type). The photosynthetic oxygen evolution showed stronger inhibition than the PSII photochemistry. The effects of the studied herbicides on both algal and cyanobacterial cells decreased in the following order: DCMU>isoproturon>ioxynil. Furthermore, we observed that the number of blocked PSII centers increased significantly after DCMU treatment (204–250 times) and slightly after ioxynil treatment (19–35 times) in comparison with the control cells. This study suggests that the herbicides affect not only the acceptor side but also the donor side of PSII by modifications of the Mn cluster of the oxygen-evolving complex. We propose that one of the reasons for the different PSII inhibitions caused by herbicides is their influence, in different extents, on the kinetic parameters of the oxygen-evolving reactions (the initial S0−S1state distribution, the number of blocked centers SB, the turnover time of Sistates, misses and double hits). The relationship between the herbicide-induced inhibition and the changes in the kinetic parameters is discussed.

EPR Spectroscopy and the Electronic Structure of the Oxygen-Evolving Complex of Photosystem II

2013 ◽  
Vol 44 (6) ◽  
pp. 691-720 ◽  
Author(s):  
Thomas Lohmiller ◽  
William Ames ◽  
Wolfgang Lubitz ◽  
Nicholas Cox ◽  
Sushil K. Misra
Keyword(s):  
Electronic Structure ◽  
Photosystem Ii ◽  
Epr Spectroscopy ◽  
Oxygen Evolving Complex ◽  
Oxygen Evolving

The Effects of 3-(3,4-Dichlorophenyl)-1,1-dimethylurea on the Photosynthetic Oxygen Complex

1984 ◽  
Vol 39 (5) ◽  
pp. 347-350 ◽  
Author(s):  
Marie-José Delrieu
Keyword(s):  
Photosystem Ii ◽  
Kinetic Properties ◽  
Oxygen Evolving Complex ◽  
Separation Systems ◽  
Acceptor Side ◽  
Oxygen Complex ◽  
Inhibitory Site ◽  
Donor Acceptor ◽  
Photosynthetic Oxygen ◽  
Oxygen Evolving

In the presence of trypsin and ferricyanide as external electron acceptor, lettuce chloroplasts are resistant to DCMU, showing that the inhibitory site of DCMU is only situated on the acceptor side of photosystem II. However, kinetic properties of the oxygen evolving complex are modified at non-saturating concentrations of DCMU. These changes are interpreted in terms of a model with two distinct charges separation systems on the same center: the auxiliary donor- acceptor system DQL implicated in the transitions S1 → S2 and S2 → S3 would be much less affected by DCMU than the main donor-acceptor system YQH after the first flash.

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