Dithiothreitol, which completely inhibits the de-epoxidation of violaxanthin to zeaxanthin, was used to obtain evidence for a causal relationship between zeaxanthin and the dissipation of excess excitation energy in the photochemical apparatus in Spinicia oleracea L. In both leaves and chloroplasts, inhibition of zeaxanthin formation by dithiothreitol was accompanied by inhibition of a componen...

The molecular weight of a DPN-linked isocitrate dehydrogenase preparation, exhibiting a single major band on polyacrylamide disc gel electrophoresis, has been examined by molecular sieve chromatography. Comparison of the elution volume (V,) of the enzyme with reference proteins of known molecular weight on columns of Sephadex G-ZOO and Sepharose 6B permitted calculation of a molecular weight in...

Two isozymes of 3-deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthase, denoted DS-Mn and DS-Co, were identified following DEAE-cellulose chromatography of crude extracts prepared from suspension-cultured cells of Nicotiana silvestris. The strikingly different properties of the isozymes allowed the development of assays for the selective detection of either isozyme in samples containing a ...

Changes in the topography of the sea urchin egg after fertilization were studied by scanning and transmission electron microscopy. Strongylocentrotus purpuratus eggs were treated with dithiothreitol to modify the vitelline layer and to prevent formation of a fertilization membrane. Dithiothreitol treatment caused the microvilli to become more irregular in shape, length, and diameter than those ...

Two novel phosphoenolpyruvate carboxylase (PEPC) isoforms have been biochemically characterized from endosperm of developing castor oil seeds (COS). The association of a 107 kDa PEPC subunit (p107) with an immunologically unrelated bacterial PEPC-type 64 kDa polypeptide leads to marked physical and kinetic differences between the PEPC1 p107 homotetramer and PEPC2 p107/p64 heterooctamer. COS p10...

The dithiol reagents phenylarsine oxide (PAO) and dibromobimane (DBrB) have opposite effects on the F 1 O -ATPase activity. PAO 20% increases ATP hydrolysis at 50 μM when enzyme activity is activated by natural cofactor Mg 2+ 150 it Ca . PAO-driven activation reverted to basal dithiothreitol (DTE). Conversely, 300 DBrB decreases 25% 50% In both cases, inhibition insensitive DTE. mitochondrial p...