4 years ago

Redox potentials of ubiquinone, menaquinone, phylloquinone, and plastoquinone in aqueous solution

Keisuke Saito, Shinnosuke Kishi, Hiroshi Ishikita, Yuki Kato


Quinones serve as redox active cofactors in bacterial photosynthetic reaction centers: photosystem I, photosystem II, cytochrome bc 1, and cytochrome b 6 f. In particular, ubiquinone is ubiquitous in animals and most bacteria and plays a key role in several cellular processes, e.g., mitochondrial electron transport. Their experimentally measured redox potential values for one-electron reduction E m(Q/Q·−) were already reported in dimethylformamide (DMF) versus saturated calomel electrode but not in water versus normal hydrogen electrode (NHE). We calculated E m(Q/Q·−) of 1,4-quinones using a quantum chemical approach. The calculated energy differences of reduction of Q to Q·− in DMF and water for 1,4-quinone derivatives correlated highly with the experimentally measured E m(Q/Q·−) in DMF and water, respectively. E m(Q/Q·−) were calculated to be −163 mV for ubiquinone, −260 mV for menaquinone and phylloquinone, and −154 mV for plastoquinone in water versus NHE.

Publisher URL: https://link.springer.com/article/10.1007/s11120-017-0433-4

DOI: 10.1007/s11120-017-0433-4

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