Photosystem II uses water as an enzymatic substrate. It has been hypothesized that this water is vectored to the active site for water oxidation via water channels that lead from the surface of the protein complex to the Mn4O5Ca metal cluster. The radiolysis of water by synchrotron radiation produces amino acid residue-modifying OH(•) and is a powerful technique to identify regions of proteins ...

Plants are often exposed to temperatures of around 40 °C. These temperatures can cause serious damage to photosystems, yet plants can survive with minimum damage. Here, we show that plants switch photosystem to protect photosystem II (PSII) at 40 °C. Using wheat and Arabidopsis seedlings, we investigated the mechanisms of heat-derived damage in the dark and avoidance of damage in the light. Hea...

1. CO2-depletion of thylakoid membranes results in a decrease of binding affinity of the Photosystem II (PS II) inhibitor atrazine. The inhibitory efficiency of atrazine, expressed as I50-concentration (50% inhibition) of 2,6-dichlorophenolindophenol reduction, is the same in CO2-depleted as well as in control thylakoids. This shows that CO2-depletion results in a complete inactivation of a par...

An intrinsic 22 kDa polypeptide is associated with the O2-evolving Photosystem II core complex in a variety of green plants, although it does not appear to be required for O2 evolution. Digestion of thylakoid membranes and isolated Photosystem II preparations with trypsin, followed by immunoblotting using spinach anti-22 kDa antibodies, leads to two observations: (1) the domain between the 2nd ...

Thermoluminescence is a simple technique very useful for studying electron transfer reactions on photosystem II (standard thermoluminescence) or the level of lipid peroxidation in membranes (high temperature thermoluminescence) in photosynthetic organisms. Both techniques were used to investigate the effects produced on Chlorella vulgaris cells by six compounds: the chemical intermediates bromo...

The effect o f K-picrate-18-crown-6 (crown) on the photoelectron transport activity o f beet spinach thylakoid membranes was investigated. Addition o f micromolar concentration o f crown to thylakoid preparation inhibited p-benzoquinone, chloride-indophenol, methyl viologen supported Hill activities maximally by 75 per cent in a concentration dependent manner. However, the photosystem I catalyz...

Previously, we reported that rdxB, encoding a likely membrane-bound two [4Fe-4S]-containing center, is involved in the aerobic regulation of photosystem gene expression in Rhodobacter sphaeroides 2.4.1. To further investigate the role of rdxB as well as other genes of the rdxBHIS operon on photosystem gene expression, we constructed a series of nonpolar, in-frame deletion mutations in each of t...

Two sites in the photosynthetic electron transport chain of spinach chloroplasts are sensitive to inhibition by the plastoquinone antagonist dibromothymoquinone (2,5-dibromo3-methyl-&isopropyl-p-benzoquinone). This compound imposes maximal inhibition on reactions involving electron transport from water to a terminal acceptor such as ferricyanide at concentrations of about 1 PM. At concentration...

The pigment and acyl lipid composition ofphotochemically active stroma lamellae and inside-out photosystem II vesicles have been investigated. Mechanical disruption followed by phase partitioning in an aqueous two phase system resulted in a clean separation of the photosystems. A qualitative and quantitative determination of the pigment content was achieved using reversed-phase high performance...

Dramatic increase in the use of nanoparticles (NPs) in a variety of applications greatly increased the likelihood of the release of NPs into the environment. Zinc oxide nanoparticles (ZnO NPs) are among the most commonly used NPs, and it has been shown that ZnO NPs were harmful to several different plants. We report here the effects of ZnO NPs exposure on biomass accumulation and photosynthesis...