scholarly journals Theoretical analysis of the inverted region in photoinduced proton-coupled electron transfer

2019 ◽  
Vol 216 ◽  
pp. 363-378 ◽  
Author(s):  
Zachary K. Goldsmith ◽  
Alexander V. Soudackov ◽  
Sharon Hammes-Schiffer
Keyword(s):  
Electron Transfer ◽  
Theoretical Analysis ◽  
Energy Conversion ◽  
Rate Constant ◽  
Inverted Region ◽  
Significant Challenge ◽  
Proton Coupled Electron Transfer ◽  
Wide Range ◽  
Design Systems

Photoinduced proton-coupled electron transfer (PCET) plays a key role in a wide range of energy conversion processes, and understanding how to design systems to control the PCET rate constant is a significant challenge.

scholarly journals Proton-coupled electron transfer reactions: analytical rate constants and case study of kinetic isotope effects in lipoxygenase

2016 ◽  
Vol 195 ◽  
pp. 171-189 ◽  
Author(s):  
Alexander V. Soudackov ◽  
Sharon Hammes-Schiffer
Keyword(s):  
Electron Transfer ◽  
Rate Constant ◽  
Isotope Effects ◽  
Thermal Fluctuations ◽  
Proton Donor ◽  
Nonadiabatic Transitions ◽  
Proton Coupled Electron Transfer ◽  
Wide Range ◽  
Donor Acceptor ◽  
Vibronic States

A general theory has been developed for proton-coupled electron transfer (PCET), which is vital to a wide range of chemical and biological processes. This theory describes PCET reactions in terms of nonadiabatic transitions between reactant and product electron–proton vibronic states and includes the effects of thermal fluctuations of the solvent or protein environment, as well as the proton donor–acceptor motion. Within the framework of this general PCET theory, a series of analytical rate constant expressions has been derived for PCET reactions in well-defined regimes. Herein, the application of this theory to PCET in the enzyme soybean lipoxygenase illustrates the regimes of validity for the various rate constant expressions and elucidates the fundamental physical principles dictating PCET reactions. Such theoretical studies provide significant physical insights that guide the interpretation of experimental data and lead to experimentally testable predictions. A combination of theoretical treatments with atomic-level simulations is essential to understanding PCET.

scholarly journals Concerted proton-electron transfer reactions in the Marcus inverted region

Science ◽  
2019 ◽  
Vol 364 (6439) ◽  
pp. 471-475 ◽  
Author(s):  
Giovanny A. Parada ◽  
Zachary K. Goldsmith ◽  
Scott Kolmar ◽  
Belinda Pettersson Rimgard ◽  
Brandon Q. Mercado ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Charge Recombination ◽  
Transfer Reactions ◽  
Inverted Region ◽  
Electron Transfer Reactions ◽  
Proton Coupled Electron Transfer ◽  
Marcus Inverted Region ◽  
A Charge ◽  
Theory Yield

Electron transfer reactions slow down when they become very thermodynamically favorable, a counterintuitive interplay of kinetics and thermodynamics termed the inverted region in Marcus theory. Here we report inverted region behavior for proton-coupled electron transfer (PCET). Photochemical studies of anthracene-phenol-pyridine triads give rate constants for PCET charge recombination that are slower for the more thermodynamically favorable reactions. Photoexcitation forms an anthracene excited state that undergoes PCET to create a charge-separated state. The rate constants for return charge recombination show an inverted dependence on the driving force upon changing pyridine substituents and the solvent. Calculations using vibronically nonadiabatic PCET theory yield rate constants for simultaneous tunneling of the electron and proton that account for the results.

scholarly journals Driving Force Dependence of Rates for Nonadiabatic Proton and Proton-Coupled Electron Transfer: Conditions for Inverted Region Behavior

2009 ◽  
Vol 113 (44) ◽  
pp. 14545-14548 ◽  
Author(s):  
Sarah J. Edwards ◽  
Alexander V. Soudackov ◽  
Sharon Hammes-Schiffer
Keyword(s):  
Electron Transfer ◽  
Driving Force ◽  
Inverted Region ◽  
Proton Coupled Electron Transfer

Electrochemical Proton-Coupled Electron Transfer of an Osmium Aquo Complex: Theoretical Analysis of Asymmetric Tafel Plots and Transfer Coefficients

2010 ◽  
Vol 132 (4) ◽  
pp. 1234-1235 ◽  
Author(s):  
Michelle K. Ludlow ◽  
Alexander V. Soudackov ◽  
Sharon Hammes-Schiffer
Keyword(s):  
Electron Transfer ◽  
Theoretical Analysis ◽  
Transfer Coefficients ◽  
Proton Coupled Electron Transfer ◽  
Aquo Complex

scholarly journals Electric field modulated redox-driven protonation and hydration energetics in energy converting enzymes

2019 ◽  
Vol 55 (43) ◽  
pp. 6078-6081 ◽  
Author(s):  
Patricia Saura ◽  
Daniel M. Frey ◽  
Ana P. Gamiz-Hernandez ◽  
Ville R. I. Kaila
Keyword(s):  
Electron Transfer ◽  
Electric Field ◽  
Energy Conversion ◽  
Chemical Basis ◽  
Proton Coupled Electron Transfer ◽  
Photosynthetic Enzymes ◽  
Energy Converting

Biological energy conversion is catalysed by proton-coupled electron transfer (PCET) reactions that form the chemical basis of respiratory and photosynthetic enzymes.

The Kinetics of Reactions in and Near the Cytochrome b/f Complex of Chloroplasts. II. Cytochrome b-563 Reduction

1989 ◽  
Vol 16 (4) ◽  
pp. 353 ◽  
Author(s):  
AB Hope ◽  
J Liggins ◽  
DB Matthews
Keyword(s):  
Electron Transfer ◽  
Cytochrome B ◽  
Rate Constant ◽  
Apparent Rate Constant ◽  
Rate Limiting Step ◽  
Q Cycle ◽  
Proton Transfers ◽  
Wide Range ◽  
Dimethyl Urea ◽  
Rate Limiting

The reduction of cytochrome b-563 was measured following flash-induced electron transfer from duroquinol to methyl viologen, in the presence of 3,(3,4-dichlorophenyl)-1,1-dimethyl urea and 1 �M nonactin or 1 �M valinomycin (plus 10 mM K+). The apparent rate constant of this reduction (nonactin present) increased from about 100 s-1 to 460 s-1 as the external concentration of duroquinol was varied from 0.01 to 0.5 mM. The corresponding maximum extent of reduction of cytochrome b-563 varied from 0.13 to 0.27 molecules per b/f complex. Rate constants in the presence of valinomycin were lower at all concentrations of duroquinol by a factor of about 1.5. The mean enthalpy of activation calculated from Arrhenius plots of apparent rate constant for cytochrome b-563 reduction was 60 kJ mol-1, for temperature variation between 23 and 4°C. The above, and further data in oxidising conditions, and with added 2-n-nonyl-4-hydroxyquinoline N-oxide, together with data on proton deposition, were compared with the predictions of a kinetic model. In this model, flash-generated oxidised plastocyanin oxidised Rieske centres during random diffusion, and plastoquinol reduced the Rieske centres and cytochrome b-563 sequentially; subsequent electron and proton transfers followed those in a Q-cycle. Many observations were predicted by the model, in which the rate-limiting step was the first electron transfer from plastoquinol to the Rieske centre, subsequent steps being much faster. The rate and extent of reduction of cytochrome b-563 were fully consistent with a reaction between it and a radical form of plastoquinone formed after oxidation of the latter by Rieske centres (referred to as 'oxidant-induced reduction'), under a wide range of conditions.

Sign in / Sign up

Export Citation Format

Share Document