In the title compound, C18H18ClNO4, the imide group with its two alkyl substituents is approximately perpendicular to the plane of the naphtho-quinone ring system [dihedral angle = 78.5 (1)°]. Further, the imide carbonyl groups are oriented in an anti sense. In the crystal, the substituted naphtho-quinone rings form π-π stacks in the a-axis direction [perpendicular centroid-centroid distance = ...

Melanins are stable and non-toxic biomaterials with a great potential as chemopreventive agents for diseases connected oxidative stress, but the mechanism of their antioxidant action is unclear. Herein, we show that polydopamine (PDA), well-known synthetic melanin, becomes an excellent trap alkylperoxyl radicals (ROO., typically formed during autoxidation lipid substrates) in presence hydropero...

Ubiquinone-2 (UQ-2) selectively labeled with (13)C (I =(1)/(2)) at either the position 1- or the 4-carbonyl carbon is incorporated into the ubiquinol oxidase bo(3) from Escherichia coli in which the native quinone (UQ-8) has been previously removed. The resulting stabilized anion radical in the high-affinity quinone-binding site (Q(H)(*)(-)) is investigated using multifrequency (9, 34, and 94 G...

A deodorizing substance in black cumin (Nigella sativa L.), a spice for curry and vegetable foods in Southwest Asia, was examined. The essential oil prepared from the seeds of this plant exhibited strong deodorizing activity against methyl mercaptan, which is a main factor in oral malodor. After purification with silica gel column chromatography, the active substance in black cumin seed oil was...

In the bacterium R. sphaeroides, the polypeptide PufX is indispensable for photosynthetic growth. Its deletion is known to have important consequences on the organization of the photosynthetic apparatus. In the wild-type strain, complexes between the reaction center (RC) and the antenna (light-harvesting complex 1 (LH1)) are associated in dimers, and LH1 does not fully encircle the RC. In the a...

Mitochondrial respiration, an important bioenergetic process, relies on operation of four membranous enzymatic complexes linked functionally by mobile, freely diffusible elements: quinone molecules in the membrane and water-soluble cytochromes c in the intermembrane space. One of the mitochondrial complexes, complex III (cytochrome bc1 or ubiquinol:cytochrome c oxidoreductase), provides an elec...

Benzo(a)pyrene 1,6-, 3,6-, and 6,1 2-quinones were found to be noncompetitive inhibitors of mixed-function oxidation of benzo(a)pyrene (BP) and frans-7,8-dihydro-7,8-dihydroxybenzo(a)pyrene (BP 7,8-dihydrodiol). BP 6,1 2-quinone was the most potent inhibitor of both BP and BP-7,8-dihydrodiol oxi dation followed by BP 1,6-quinone and BP 3,6-quinone. The K, for inhibition of BP mixed-function oxi...

The kinetic model of Ragan & Cottingham [(1985) Biochim. Biophys. Acta 811, 13-31] for electron transport through a mobile pool of quinone predicts that, under certain conditions, the normal linear dependence of electron flow on the degree of reduction (or oxidation) of the quinone should no longer be found. These conditions can be met by reconstituted NADH: cytochrome c reductase (Complex I-II...