title: The structure and function of quinones in biological solar energy transduction: a cyclic voltammetry, EPR, and hyperfine sub-level correlation (HYSCORE) spectroscopy study of model naphthoquinones.
abstract: Quinones function as electron transport cofactors in photosynthesis and cellular respiration. The versatility and functional diversity of quinones is primarily due to the diverse midpoint potentials that are tuned by the substituent effects and interactions with surrounding amino acid residues in the binding site in the protein. In the present study, a library of substituted 1,4-naphthoquinones are analyzed by cyclic voltammetry in both protic and aprotic solvents to determine effects of substituent groups and hydrogen bonds on the midpoint potential. We use continuous-wave electron paramagnetic resonance (EPR) spectroscopy to determine the influence of substituent groups on the electronic properties of the 1,4-naphthoquinone models in an aprotic solvent. The results establish a correlation between the presence of substituent group(s) and the modification of electronic properties and a corresponding shift in the midpoint potential of the naphthoquinone models. Further, we use pulsed EPR spectroscopy to determine the effect of substituent groups on the strength and planarity of the hydrogen bonds of naphthoquinone models in a protic solvent. This study provides support for the tuning of the electronic properties of quinone cofactors by the influence of substituent groups and hydrogen bonding interactions.
authors.affiliation: Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Coates
authors.forename: Jessica
authors.initials: J
authors.lastname: Ziegler
authors.forename: Katherine
authors.initials: K
authors.lastname: Manz
authors.forename: Jacob
authors.initials: J
authors.lastname: Good
authors.forename: Bernard
authors.initials: B
authors.lastname: Kang
authors.forename: Sergey
authors.initials: S
authors.lastname: Milikisiyants
authors.forename: Ruchira
authors.initials: R
authors.lastname: Chatterjee
authors.forename: Sijie
authors.initials: S
authors.lastname: Hao
authors.forename: John H
authors.initials: JH
authors.lastname: Golbeck
authors.forename: K V
authors.initials: KV
authors.lastname: Lakshmi
mesh_terms: D055664:Electrochemical Techniques; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009285:Naphthoquinones / Q000737:chemistry*; D011809:Quinones / Q000737:chemistry*; D012993:Solar Energy
chemical_list: D009285:Naphthoquinones; D011809:Quinones