Herbicides affect fluorescence and electron transfer activity of spinach chloroplasts, thylakoid membranes and isolated Photosystem II

2010 ◽  
Vol 79 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Andrea Ventrella ◽  
Lucia Catucci ◽  
Angela Agostiano
Keyword(s):  
Electron Transfer ◽  
Photosystem Ii ◽  
Thylakoid Membranes ◽  
Transfer Activity ◽  
Spinach Chloroplasts

scholarly journals Bicarbonate Activation of Monomeric Photosystem II-PsbS/Psb27 Complex

2022 ◽  
Author(s):  
A. William Rutherford ◽  
Andrea Fantuzzi ◽  
Dario Piano ◽  
Patrycja Haniewicz ◽  
Domenica Farci ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Photosystem Ii ◽  
Water Splitting ◽  
Thylakoid Membranes ◽  
Protective Mechanism ◽  
Slow Electron ◽  
Enhanced Fluorescence ◽  
Transfer Rates ◽  
Redox Tuning ◽  
In Transit

In thylakoid membranes, Photosystem II monomers from the stromal lamellae contain the subunits PsbS and Psb27 (PSIIm-S/27), while Photosystem II monomers from granal regions (PSIIm) lack these subunits. Here, we have isolated and characterised these two types of Photosystem II complexes. The PSIIm-S/27 showed enhanced fluorescence, the near-absence of oxygen evolution, as well as limited and slow electron transfer from QA to QB compared to the near-normal activities in the granal PSIIm. However, when bicarbonate was added to the PSIIm-S/27, water splitting and QA to QB electron transfer rates were comparable to those in granal PSIIm. The findings suggest that the binding of PsbS and/or Psb27 inhibits forward electron transfer and lowers the binding affinity for the bicarbonate. This can be rationalized in terms of the recently discovered photoprotection role played by bicarbonate binding via the redox tuning of the QA/QA?- couple, which controls the charge recombination route, and this limits chlorophyll triplet mediated 1O2 formation (Brinkert K et al. (2016) Proc Natl Acad Sci U S A. 113(43):12144-12149). These findings suggest that PSIIm-S/27 is an intermediate in the assembly of PSII in which PsbS and/or Psb27 restrict PSII activity while in transit, by using a bicarbonate-mediated switch and protective mechanism.

Effect of α- and β-cyclodextrins on the photochemical activity of thylakoid membranes and photosystem II particles from barley (Hordeum vulgare): oxygen evolution and whole chain electron transport

2005 ◽  
Vol 83 (3) ◽  
pp. 320-328 ◽  
Author(s):  
S Dudekula ◽  
G Sridharan ◽  
M Fragata
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Hordeum Vulgare ◽  
Photosystem Ii ◽  
Oxygen Evolution ◽  
Thylakoid Membranes ◽  
Photochemical Activity ◽  
Nonlinear Dependence ◽  
Hordeum Vulgare L ◽  
Sigmoidal Curve

The effect of α- and β-cyclodextrin (CD) concentration (0–16 mM) on oxygen evolution in photosystem II (PSII) and whole chain electron transport (H2O to photosystem I (PSI)) was studied in isolated thylakoid membranes and PSII particles from barley (Hordeum vulgare L.). The CDs are cyclic oligosaccharides containing, for example, six (α-CD) or seven (β-CD) α-D-glucose residues linked by α-1,4 glycosidic bonds. These compounds alter the lipid composition of the thylakoids and most likely also the structure of their membrane proteins. We show for the first time that in the thylakoid membranes, but not in the isolated PSII particles, the relationship between oxygen evolution in PSII and the CD concentration is represented by a S-shaped (sigmoidal) curve displaying a sharp inflexion point or transition. We found, in addition, that the CDs inhibit the whole chain electron transport from H2O to methyl viologen, that is, PSI, measured as oxygen uptake, according to a nonlinear dependence that is also sigmoidal. Moreover, another interesting observation is that in the thylakoid membranes the electron transport from H2O to PSI is quite well inhibited at low CD concentrations (<4–6 mM), whereas the oxygen evolution in PSII is only substantially enhanced at CD concentrations greater than 8–10 mM. To explain this, we suggest that the mechanisms underlying the inhibition of electron transfer from H2O to PSI become operative before those giving origin to the enhancement of oxygen evolution in PSII.Key words: cyclodextrins, electron transfer, nonlinearity, oxygen evolution, photosystem, thylakoid membrane.

Photosystem II Inhibition by Pyran-enamine Derivatives

1993 ◽  
Vol 48 (3-4) ◽  
pp. 163-167
Author(s):  
Koichi Yoneyama ◽  
Yoshihiro Nakajima ◽  
Masaru Ogasawara ◽  
Hitoshi Kuramochi ◽  
Makoto Konnai ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Thylakoid Membranes ◽  
Major Determinant ◽  
Ps Ii ◽  
Structure Activity Relationships ◽  
Structure Activity

Abstract Through the studies on structure-activity relationships of 5-acyl-3-(1-aminoalkylidene)-4-hydroxy-2 H-pyran-2,6(3 H)-dione derivatives in photosystem II (PS II) inhibition, overall lipophilicity of the molecule was found to be a major determinant for the activity. In the substituted N -benzyl derivatives, not only the lipophilicity but also the electronic and steric characters of the substituents greatly affected the activity. Their mode of PS II inhibition seemed to be similar to that of DCMU , whereas pyran-enamine derivatives needed to be highly lipophilic to block the electron transport in thylakoid membranes, which in turn diminished the permeability through biomembranes.

scholarly journals Singlet oxygen damages the function of Photosystem II in isolated thylakoids and in the green alga Chlorella sorokiniana

2021 ◽  
Author(s):  
Faiza Bashir ◽  
Ateeq Ur Rehman ◽  
Milán Szabó ◽  
Imre Vass
Keyword(s):  
Photosystem Ii ◽  
Singlet Oxygen ◽  
Screening Method ◽  
Physiological Role ◽  
Thylakoid Membranes ◽  
Chlorella Sorokiniana ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Intact Cells ◽  
Green Alga Chlorella

AbstractSinglet oxygen (1O2) is an important damaging agent, which is produced during illumination by the interaction of the triplet excited state pigment molecules with molecular oxygen. In cells of photosynthetic organisms 1O2 is formed primarily in chlorophyll containing complexes, and damages pigments, lipids, proteins and other cellular constituents in their environment. A useful approach to study the physiological role of 1O2 is the utilization of external photosensitizers. In the present study, we employed a multiwell plate-based screening method in combination with chlorophyll fluorescence imaging to characterize the effect of externally produced 1O2 on the photosynthetic activity of isolated thylakoid membranes and intact Chlorella sorokiniana cells. The results show that the external 1O2 produced by the photosensitization reactions of Rose Bengal damages Photosystem II both in isolated thylakoid membranes and in intact cells in a concentration dependent manner indicating that 1O2 plays a significant role in photodamage of Photosystem II.

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