Insights into the Mechanism of Nickel-substituted Rubredoxin: A Model Hydrogenase
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Date
2023-05
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The Ohio State University
Abstract
Hydrogen represents a promising carbon-free fuel source but we currently lack
sustainable methods of production. Nickel-substituted rubredoxin (NiRd) is a robust
functional mimic of the NiFe hydrogenase that is active for both the solution-phase and
electrocatalytic reduction of protons to hydrogen gas. This model system offers many
advantages to working with the native system such as being easy to express and
oxygen-tolerant. Several key mechanistic intermediates have been proposed based on
experimental data for the native system, but due to the complexity of the hydrogenase
have been difficult to isolate experimentally. NiRd serves as an excellent model to
provide insight into these key mechanistic intermediates. This work aims to obtain
experimental insights into the mechanism of NiRd.
Intermediates play an important role in understanding how catalysis occurs and
an intimate knowledge of these intermediates enables rational design for NiRd as well
as explaining what makes a catalyst such a NiFe hydrogenase so superior.
Electrochemical simulations are employed to model the catalysis seen experimentally.
These simulations have been integral in identifying and supporting the proposed
mechanism. In addition to mechanistic steps, the simulations are used to bound and
estimate additional kinetic parameters of the system.
There has been extensive past research on how mutations to both the primary
and secondary sphere affect catalysis of NiRd. Even with the wealth of knowledge
available, questions still remain as to why certain mutations affect catalysis in the way
they do. The mechanism and the intermediates of the NiRd system are a potential way
to understand these observations. The electrocatalytic behavior of the wild type NiRd in
various buffer systems will be explored to comprehend the role of buffer in catalysis.
Description
Keywords
peptides and proteins, electrocatalysis, redox reactions, electrodes, reaction mechanisms