PK _a of ubiquinone, menaquinone, phylloquinone, plastoquinone, and rhodoquinone in aqueous solution.

ABSTRACT: Quinones can accept two electrons and two protons, and are involved in electron transfer and proton transfer reactions in photosynthetic reaction centers. To date, the pK _a of these quinones in aqueous solution have not been reported. We calculated the pK _a of the initial protonation (Q^·- to QH^·) and the second protonation (QH^- to QH₂) of 1,4-quinones using a quantum chemical approach. The calculated energy differences of the protonation reactions Q^·- to QH^· and QH^- to QH₂ in the aqueous phase for nine 1,4-quinones were highly correlated with the experimentally measured pK _a(Q^·-/QH^·) and pK _a(QH^-/QH₂), respectively.

SUBMITTER: Hasegawa R 

PROVIDER: S-EPMC5500672 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature