Oxygen inhibition of photosynthesis was studied with intact spinach (Spinacia oleracea L.) chloroplasts which exhibited very high rates of photosynthetic CO(2) reduction and were insensitive to additions of photosynthetic intermediates when CO(2) was available at saturating concentrations. Photosynthetic rates were measured polarographically as O(2) evolution, and the extent of the reduction of...

Highly purified intact chloroplasts were isolated from spinach (Spinacia oleracea L.) leaves by free flow electrophoresis. Morphological and biochemical studies showed that the fraction enriched in intact chloroplasts has a higher protein to chlorophyll ratio and a higher linolenic acid content than the broken organelles of the other fraction. The intact chloroplasts prepared by electrophoresis...

A technique for the isolation of intact plastids from spinach (Spinacia oleracea) and pea (Pisum sativum) leaves, pea roots and castor bean (Ricinus communis) endosperm is described. This technique involves brief centrifugation of whole homogenates on density gradients. Intact plastids were located in the gradient by assaying for triose phosphate isomerase activity. Contamination of the plastic...

Studies of isolated intact spinach (Spinacia oleracea L.) chloroplasts reveal that most of the available sulfhydryl groups are associated with stromal protein as opposed to a thylakoid membrane fraction under non-denaturing conditions. Increases in sulfhydryl content of approximately 50% occurred with illumination and could be correlated kinetically with a reductive activation of fructose-1,6-b...

The subcellular compartmentation of nucleoside diphosphate kinase (EC 2.7.4.6) and the uridine nucleotides has been studied in leaves. Membrane filtration of barley (Hordeum vulgare L.) leaf mesophyll protoplasts and differential centrifugation of spinach (Spinacia oleracea L.) leaf extracts showed that about half the nucleoside diphosphate kinase is present in the cytosol. The activity is adeq...

Stearyl-acyl carrier protein desaturase (EC 1.14.99.6), present in the stroma fraction of spinach (Spinacia oleracea) chloroplasts, rapidly desaturated enzymatically prepared stearyl-acyl carrier protein to oleic acid. No other substrates were desaturated. In addition to stearyl-acyl carrier protein, reduced ferredoxin was an essential component of the system. The electron donor systems were ei...

Factors affecting CO(2) fixation in the spinach (Spinacia oleracea) chloroplast were investigated. Free magnesium ions are shown to be highly inhibitory for photosynthetic CO(2) fixation in isolated intact spinach chloroplasts. The pH optimum for CO(2) fixation is about 8.5 but is dependent upon the reaction medium. Conditions are defined under which chloroplasts illuminated in the absence of C...

Infrared and Raman spectroscopy were applied to identify restraints for the structure determination of the 20 amino acid loop between two beta-sheets of the N-terminal region of the PsbQ protein of the oxygen evolving complex of photosystem II from Spinacia oleracea by restraint-based homology modeling. One of the initial models has shown a stable fold of the loop in a 20 ns molecular dynamics ...

Yeast cationic ferricytochrome c was able to bind to the spinach (Spinacia oleracea) chloroplast envelope with a low affinity (Kd = 1.1 mum). The total amount of low affinity binding sites was of the order of 50 nmol cytochrome c mg(-1) protein. We gave the evidence that binding of ferricytochrome c to the envelope was electrostatic and that the envelope membranes were strongly negatively charg...

Comparison of several lipid reconstitution methods showed that they were not equally efficient at transferring the predominant thylakoid lipid, monogalactosyldiglyceride (MG), to the aqueous phase. We report a reverse phase evaporation method that employs Freon 11 as a lipid solvent and is capable of successfully hydrating MG in spinach (Spinacia oleracea L.) at room temperature within minutes....