ubiquinone-q2 and quinone

We synthesized novel vitamin K derivatives by converting the naphthoquinone group to benzene derivatives and benzoquinone. We evaluated their neuronal differentiation activities to investigate the effect of the quinone moiety on this process. We observed that the 1,4-quinone as well as the side chain part play important roles in neuronal differentiation. We also performed QSAR analysis to predict the compounds which would have higher differentiation activity.

Topics: Animals; Benzene Derivatives; Benzoquinones; Cell Differentiation; Dose-Response Relationship, Drug; Mice; Molecular Structure; Naphthoquinones; Neurons; Quantitative Structure-Activity Relationship; Vitamin K

When the superoxide radical O(2)(•-) is generated on reaction of KO(2) with water in dimethyl sulfoxide, the decay of the radical is dramatically accelerated by inclusion of quinones in the reaction mix. For quinones with no or short hydrophobic tails, the radical product is a semiquinone at much lower yield, likely indicating reduction of quinone by superoxide and loss of most of the semiquinone product by disproportionation. In the presence of ubiquinone-10, a different species (I) is generated, which has the EPR spectrum of superoxide radical. However, pulsed EPR shows spin interaction with protons in fully deuterated solvent, indicating close proximity to the ubinquinone-10. We discuss the nature of species I, and possible roles in the physiological reactions through which ubisemiquinone generates superoxide by reduction of O(2) through bypass reactions in electron transfer chains.

Topics: Benzoquinones; Chemistry, Physical; Dimethyl Sulfoxide; Electron Spin Resonance Spectroscopy; Electron Transport; Oxidation-Reduction; Oxygen; Protons; Solutions; Superoxides; Ubiquinone

A series of arylthiolated 2,3-dimethoxy-1,4-benzoquinones was synthesized and tested for the effect on the respiratory system and the lipid peroxidation in bovine heart mitochondria (BHM). These quinones showed intense inhibitory activities on the respiratory system in BHM. Their inhibitory activity in the succinate oxidase system was greater than that in the NADH oxidase system. No difference between the difference spectra, with and without these quinones, of the reduced minus oxidized forms of cytochromes (cyt.) suggested that these quinones inhibit at the site after cyt. a+a3 in the respiratory chain. Moreover, these quinones were as efficient as exogenous ubiquinone-10 (UQ-10) for the inhibition of lipid peroxidation. 5- And 5,6-di-arylthio groups on the quinone ring were found to be favorable for inhibition of the respiratory system and lipid peroxidation. Our results suggest that arylthiolated 2,3-dimethoxy-1,4-benzoquinones act as antioxidants by increasing the amount of endogenous reduced UQ-10 in BHM.

Topics: Animals; Benzoquinones; Cattle; Electron Transport; Lipid Peroxidation; Mitochondria, Heart; Multienzyme Complexes; NADH, NADPH Oxidoreductases; Oxidoreductases; Ubiquinone

Quinones caused quenching of Chl a fluorescence in native and model systems. Menadione quenched twofold the fluorescence of Chl a and BChl a in pea chloroplasts, chromatophores of purple bacteria, and liposomes at concentrations of 50-80 microM. To obtain twofold quenching in Triton X-100 micelles and in ethanol, the addition of 1.3 mM and 11 mM menadione was required, respectively. A proportional decrease in the lifetime and yield of Chl a fluorescence in chloroplasts, observed as the menadione concentration increased, is indicative of the efficient excitation energy transfer from bulk Chl to menadione. The decrease in the lifetime and yield of fluorescence was close to proportional in liposomes, but not in detergent micelles. The insensitivity of the menadione quenching effect to DCMU in chloroplasts, and similarity of its action in chloroplasts and liposomes indicate that menadione in chloroplasts interacts with antenna Chl, i.e., nonphotochemical quenching of fluorescence occurs.

Topics: Bacterial Chromatophores; Bacteriochlorophylls; Benzoquinones; Chlorophyll; Chlorophyll A; Chloroplasts; Diuron; Fluorescence; Liposomes; Micelles; Pisum sativum; Quinones; Rhodobacter sphaeroides; Rhodospirillum rubrum; Spectrometry, Fluorescence; Ubiquinone; Vitamin K

The rate of NADH oxidation by inverted membrane vesicles prepared from the halotolerant bacterium Ba1 of the Dead Sea is increased specifically by sodium ions, as observed earlier in whole cells. The site of this sodium effect is identified as the NADH: quinone oxidoreductase, similarly to the other such system known, Vibrio alginolyticus (H. Tokuda and T. Unemoto (1984) J. Biol. Chem. 259, 7785-7790). Sodium accelerates quinone reduction severalfold, but oxidation of the quinol, with oxygen as terminal electron acceptor, is unaffected. The sodium-dependent pathway of quinone reduction exhibits higher apparent affinity to extraneous quinone (Q-2) than the sodium-insensitive pathway, and is specifically inhibited by 2-heptyl-4-hydroxyquinoline N-oxide. ESR spectra of the membranes contain a feature at g = 1.98 which is tentatively identified as one originating from semiquinone. This feature is increased by NADH and decreased by addition of Na+, suggesting that, as proposed from different kinds of evidence for the V. alginolyticus system, sodium affects the semiquinone reduction step. As in the other system, the site of sodium stimulation in Ba1 probably corresponds to the site of sodium translocation, which was shown earlier (S. Ken-Dror, R. Shnaiderman, and Y. Avi-Dor (1984) Arch. Biochem. Biophys. 229, 640-649) to be linked directly to a redox reaction in the respiratory chain.

Topics: Bacteria; Benzoquinones; Cytochrome b Group; Electron Transport; Hydrogen-Ion Concentration; Hydroxyquinolines; NAD; Oxidation-Reduction; Quinone Reductases; Quinones; Sodium; Succinates; Succinic Acid; Ubiquinone; Vibrio