Steady-state kinetic analyses of the Photosystem II activity elicited by quinones and quinonediimines in KCN/Hg-inhibited chloroplasts reveal that: 1. Quinones generate a single reaction in which one quinone competes with another for photoreduction by Photosystem II. 2. Quinonediimines also compete with one another for photoreduction, but the electron transport activity elicited by quinonediimi...

NQO1 catalyzes obligate two electron reduction of a wide variety of substrates. The most efficient substrates are quinones but the enzyme will also reduce quinoneimines, nitro and azo compounds. The enzyme functions via a hydride transfer mechanism and requires a pyridine nucleotide cofactor. Reduction proceeds with equal facility with both NADH and NADPH. NQO1 can generate antioxidant forms of...

The long-lived mutant of Caenorhabditis elegans, clk-1, is unable to synthesize ubiquinone, CoQ(9). Instead, the mutant accumulates demethoxyubiquinone(9) and small amounts of rhodoquinone(9) as well as dietary CoQ(8). We found a profound defect in oxidative phosphorylation, a test of integrated mitochondrial function, in clk-1 mitochondria fueled by NADH-linked electron donors, i.e. complex I-...

A semiquantitative analytical method has been developed for the determination of the total quinonoid content (o-benzoquinones and p-benzoquinones) of soluble lignins. The method is based on detailed measurements and observations made with model oand p-quinones, which in dry organic solvents were shown to form adducts with trimethyl phosphite in quantitative yield. These adducts gave 31P NMR sig...

Reaction of dithienophospholes with quinones provides hypervalent phosphorus species square-pyramidal geometry and promising reactivity.

The virucidal and antiviral photoactivities of three compounds, hypericin, tetrabromohypericin and gymnochrome B, were evaluated against dengue viruses. All the three products were active, and both the virucidal and antiviral activities were enhanced by light. Gymnochrome B was more potent than hypericin and tetrabromohypericin. The presence of the side chains on the hypericin core of gymnochro...

4. CRANE, F. L., LESTER, R. L., WIDMER, C. and HATEFI, Y. Studies on the electron transport system XVIII. Isolation of coenzyme Q from beef heart and beef heart mitochondria. Biochim. Biophys. Acta 32: 73-79. 1959. 5. CRANE, F. L., WIDMER, C., LESTER, R. L. and HATEFI, Y. Studies on the electron transport system XV. Coenzyme Q (Q275) and the succinoxidase activity of the electron transport part...

Before any of the eleven possible quinones of azulene were known, predictions were made about their proper— ties on the basis of Hickel, MINDO/3, PPP and ab initio SCF (STO—3G) calculations (3). Four unsubstituted quinones of azulene have now been prepared, and the experimental results obtained so far provide information regarding their stability, reduction potentials, cycloadditions with cyclo...

1. A comparison is made of several procedures for the extraction of tocopherols and isoprenoid quinones from plant tissues. 2. Gradient-elution column chromatography on acid-washed alumina efficiently separates the isoprenoid quinones and tocopherols into groups that can then be assayed spectrophotometrically or, with the tocopherols, separated into their individual components and determined by...