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 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 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.

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