TY - JOUR
T1 - Parent anion radical formation in coenzyme Q0
T2 - Breaking ubiquinone family rules
AU - Ameixa, J.
AU - Arthur-Baidoo, E.
AU - Pereira-da-Silva, J.
AU - Ončák, M.
AU - Ruivo, J. C.
AU - Varella, M. T.do N.
AU - Ferreira da Silva, F.
AU - Denifl, S.
N1 - Funding Information:
S.D. acknowledges support by the FWF, Vienna (P30332). JA, JPS and FFS acknowledge the Portuguese National Funding Agency FCT-MCTES through the research grant UID/FIS/00068/2020 (CEFITEC).
M.T.N.V. acknowledges support from National Council for Scientific and Technological Development ( CNPq , grant no. 304571/2018-0 ) and São Paulo Research Foundation ( FAPESP , grant no. 2020/16155-7 ).
The calculations used HPC resources from STI (University of São Paulo) and the HPC infrastructure LEO of the University of Innsbruck.
Publisher Copyright:
© 2022 The Authors
PY - 2023/1
Y1 - 2023/1
N2 - We report electron attachment (EA) measurements for the parent anion radical formation from coenzyme Q0 (CoQ0) at low electron energies (<2 eV) along with quantum chemical calculations. CoQ0 may be considered a prototype for the electron withdrawing properties of the larger CoQn molecules, in particular ubiquinone (CoQ10), an electron carrier in aerobic cell respiration. Herein, we show that the mechanisms for the parent anion radical formation of CoQ0 and CoQn (n = 1,2,4) are remarkably distinct. Reported EA data for CoQ1, CoQ2, CoQ4 and para-benzoquinone indicated stabilization of the parent anion radicals around 1.2–1.4 eV. In contrast, we observe for the yield of the parent anion radical of CoQ0 a sharp peak at ∼ 0 eV, a shoulder at 0.07 eV and a peak around 0.49 eV. Although the mechanisms for the latter feature remain unclear, our calculations suggest that a dipole bound state (DBS) would account for the lower energy signals. Additionally, the isoprenoid side chains in CoQn (n = 1,2,4) molecules seem to influence the DBS formation for these compounds. In contrast, the side chains enhance the parent anion radical stabilization around 1.4 eV. The absence of parent anion radical formation around 1.4 eV for CoQ0 can be attributed to the short auto-ionization lifetimes. The present results shed light on the underappreciated role played by the side chains in the stabilization of the parent anion radical. The isoprenoid tails should be viewed as co-responsible for the electron-accepting properties of ubiquinone, not mere spectators of electron transfer reactions.
AB - We report electron attachment (EA) measurements for the parent anion radical formation from coenzyme Q0 (CoQ0) at low electron energies (<2 eV) along with quantum chemical calculations. CoQ0 may be considered a prototype for the electron withdrawing properties of the larger CoQn molecules, in particular ubiquinone (CoQ10), an electron carrier in aerobic cell respiration. Herein, we show that the mechanisms for the parent anion radical formation of CoQ0 and CoQn (n = 1,2,4) are remarkably distinct. Reported EA data for CoQ1, CoQ2, CoQ4 and para-benzoquinone indicated stabilization of the parent anion radicals around 1.2–1.4 eV. In contrast, we observe for the yield of the parent anion radical of CoQ0 a sharp peak at ∼ 0 eV, a shoulder at 0.07 eV and a peak around 0.49 eV. Although the mechanisms for the latter feature remain unclear, our calculations suggest that a dipole bound state (DBS) would account for the lower energy signals. Additionally, the isoprenoid side chains in CoQn (n = 1,2,4) molecules seem to influence the DBS formation for these compounds. In contrast, the side chains enhance the parent anion radical stabilization around 1.4 eV. The absence of parent anion radical formation around 1.4 eV for CoQ0 can be attributed to the short auto-ionization lifetimes. The present results shed light on the underappreciated role played by the side chains in the stabilization of the parent anion radical. The isoprenoid tails should be viewed as co-responsible for the electron-accepting properties of ubiquinone, not mere spectators of electron transfer reactions.
KW - Dipole-bound anion radical
KW - Electron attachment
KW - Electron transfer
KW - Para-benzoquinone
KW - Resonance
KW - Ubiquinone
UR - http://www.scopus.com/inward/record.url?scp=85144373163&partnerID=8YFLogxK
U2 - 10.1016/j.csbj.2022.12.011
DO - 10.1016/j.csbj.2022.12.011
M3 - Article
AN - SCOPUS:85144373163
SN - 2001-0370
VL - 21
SP - 346
EP - 353
JO - Computational and Structural Biotechnology Journal
JF - Computational and Structural Biotechnology Journal
ER -