scholarly journals Hydrogen bonding between hydroxylic donors and MLCT-excited Ru(bpy)2(bpz)2+ complex: implications for photoinduced electron–proton transfer

2019 ◽  
Vol 55 (42) ◽  
pp. 5870-5873 ◽  
Author(s):  
Sergei V. Lymar ◽  
Gerald F. Manbeck ◽  
Dmitry E. Polyansky
Keyword(s):  
Free Energy ◽  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Energy Correlation ◽  
Electron Proton Transfer

Rates of electron–proton transfer within the H-bonded exciplexes are evaluated using the free energy correlation with donor's H-bonding acidity.

scholarly journals Visualizing the protons in a metalloenzyme electron proton transfer pathway

2020 ◽  
Vol 117 (12) ◽  
pp. 6484-6490 ◽  
Author(s):  
Hanna Kwon ◽  
Jaswir Basran ◽  
Juliette M. Devos ◽  
Reynier Suardíaz ◽  
Marc W. van der Kamp ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Transfer ◽  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Proton Donor ◽  
Biological Processes ◽  
Proton Coupled Electron Transfer ◽  
Neutron Structure ◽  
Bona Fide ◽  
Electron Proton Transfer

In redox metalloenzymes, the process of electron transfer often involves the concerted movement of a proton. These processes are referred to as proton-coupled electron transfer, and they underpin a wide variety of biological processes, including respiration, energy conversion, photosynthesis, and metalloenzyme catalysis. The mechanisms of proton delivery are incompletely understood, in part due to an absence of information on exact proton locations and hydrogen bonding structures in a bona fide metalloenzyme proton pathway. Here, we present a 2.1-Å neutron crystal structure of the complex formed between a redox metalloenzyme (ascorbate peroxidase) and its reducing substrate (ascorbate). In the neutron structure of the complex, the protonation states of the electron/proton donor (ascorbate) and all of the residues involved in the electron/proton transfer pathway are directly observed. This information sheds light on possible proton movements during heme-catalyzed oxygen activation, as well as on ascorbate oxidation.

scholarly journals Role of Hydrogen Bonding in Photoinduced Electron–Proton Transfer from Phenols to a Polypyridine Ru Complex with a Proton-Accepting Ligand

2017 ◽  
Vol 8 (17) ◽  
pp. 4043-4048 ◽  
Author(s):  
Sergei V. Lymar ◽  
Mehmed Z. Ertem ◽  
Anna Lewandowska-Andralojc ◽  
Dmitry E. Polyansky
Keyword(s):  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Ru Complex ◽  
Electron Proton Transfer

The Role of Free Energy Change in Coupled Electron−Proton Transfer

2007 ◽  
Vol 129 (49) ◽  
pp. 15098-15099 ◽  
Author(s):  
Christine J. Fecenko ◽  
H. Holden Thorp ◽  
Thomas J. Meyer
Keyword(s):  
Free Energy ◽  
Proton Transfer ◽  
Free Energy Change ◽  
Energy Change ◽  
Electron Proton Transfer

scholarly journals Base-enhanced catalytic water oxidation by a carboxylate–bipyridine Ru(II) complex

2015 ◽  
Vol 112 (16) ◽  
pp. 4935-4940 ◽  
Author(s):  
Na Song ◽  
Javier J. Concepcion ◽  
Robert A. Binstead ◽  
Jennifer A. Rudd ◽  
Aaron K. Vannucci ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Proton Transfer ◽  
Water Oxidation ◽  
Proton Acceptor ◽  
Half Time ◽  
X Ray ◽  
X Ray Crystallography ◽  
Buffer Base ◽  
Electron Proton Transfer ◽  
C Nmr

In aqueous solution above pH 2.4 with 4% (vol/vol) CH3CN, the complex [RuII(bda)(isoq)2] (bda is 2,2′-bipyridine-6,6′-dicarboxylate; isoq is isoquinoline) exists as the open-arm chelate, [RuII(CO2-bpy-CO2−)(isoq)2(NCCH3)], as shown by 1H and 13C-NMR, X-ray crystallography, and pH titrations. Rates of water oxidation with the open-arm chelate are remarkably enhanced by added proton acceptor bases, as measured by cyclic voltammetry (CV). In 1.0 M PO43–, the calculated half-time for water oxidation is ∼7 μs. The key to the rate accelerations with added bases is direct involvement of the buffer base in either atom–proton transfer (APT) or concerted electron–proton transfer (EPT) pathways.

scholarly journals Cavity hydration dynamics in cytochrome c oxidase and functional implications

2017 ◽  
Vol 114 (42) ◽  
pp. E8830-E8836 ◽  
Author(s):  
Chang Yun Son ◽  
Arun Yethiraj ◽  
Qiang Cui
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Proton Transfer ◽  
Molecular Dynamics Simulations ◽  
Transmembrane Protein ◽  
Wetting Transition ◽  
Protonation State ◽  
Hydration Level ◽  
Level Change ◽  
Dynamics Simulations

Cytochrome c oxidase (CcO) is a transmembrane protein that uses the free energy of O2 reduction to generate the proton concentration gradient across the membrane. The regulation of competitive proton transfer pathways has been established to be essential to the vectorial transport efficiency of CcO, yet the underlying mechanism at the molecular level remains lacking. Recent studies have highlighted the potential importance of hydration-level change in an internal cavity that connects the proton entrance channel, the site of O2 reduction, and the putative proton exit route. In this work, we use atomistic molecular dynamics simulations to investigate the energetics and timescales associated with the volume fluctuation and hydration-level change in this central cavity. Extensive unrestrained molecular dynamics simulations (accumulatively ∼4 μs) and free energy computations for different chemical states of CcO support a model in which the volume and hydration level of the cavity are regulated by the protonation state of a propionate group of heme a3 and, to a lesser degree, the redox state of heme a and protonation state of Glu286. Markov-state model analysis of ∼2-μs trajectories suggests that hydration-level change occurs on the timescale of 100–200 ns before the proton-loading site is protonated. The computed energetic and kinetic features for the cavity wetting transition suggest that reversible hydration-level change of the cavity can indeed be a key factor that regulates the branching of proton transfer events and therefore contributes to the vectorial efficiency of proton transport.

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