The preferred binding orientations for the herbicide DCMU within the QB-binding of the D1 protein model from a photosystem II reaction centre have been determined. Calculation of the intermolecular energy between the herbicide and the binding site has been instrumental in obtaining optimum positions reinforced by experimental results from mutation studies and herbicide binding to analogous bact...

Illumination o f thylakoid membranes in the presence o f 3-(3',4'-dichlorophenyl)-1,1-dimethyl urea (D C M U ) causes the reduction o f the primary quinone acceptor QA o f photosys­ tem II (PS II) and the storage o f a positive charge on the donor side o f the photochemical reac­ tion center. These oxidation-reduction reactions are accompanied by characteristic changes o f absorbance in the ult...

The chlorophyll fluorescence of isolated chloroplasts in the presence of phenazine methosulfate (PMS) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) can be quenched in a light-depentdent reaction. This phenomenan has been studied and the following observations were made: 1. Quenching occurs under non-phosphorylating conditions and is stimulated by Mg2+ ions. 2. Under the same conditions, a ...

The liverwort Conocephalum conicum with anion channels blocked by anthracene-9-carboxylic acid (A-9-C) and potassium channels blocked by tetraethylammonium (TEA) generates dose-dependent responses to illumination further called voltage transients (VTs). Unlike the action potentials in untreated Conocephalum thalli, VTs do not propagate and cannot be evoked by electrical stimuli. Except A-9-C, t...

Suinizary. A nunibl)er of pteridfines were examined( for activity in promotinig photop)hosphorylation in broken spinach chlioroplasts anid in stimlulating cvtochrome c photooxidation ill sonicated chloroplasts. Correlation was fouind between activities for the 2 reactions. Photophosphorylation promoted by pteridines was inhibited by DCMU and by anaerobic conditiolns. It is concluded that pterid...

Data are presented that associate three new markers with the uniparental linkage group in Chlamydomonas reinhardii. One of these, mutant 10-6C, is a genetic marker for the structural gene of the large subunit of ribulose bisphosphate carboxylase. These results provide the first direct link between the uniparental gene map and the physical map of chloroplast DNA. The other two markers, Dr2 (DCMU...

Addition of ferredoxin to isolated thylakoid membranes reconstitutes electron transport from water to NADP and to O(2) (the Mehler reaction). This electron flow is coupled to ATP synthesis, and both cyclic and noncyclic electron transport drive photophosphorylation. Under conditions where the NADPH/NADP(+) ratio is varied, the amount of ATP synthesis due to cyclic activity is also varied, as is...