Dihydrogen (H2) is one of the most promising environmental-friendly alternatives to fossil fuel. Hydrogenases, presenting how Nature produces/cleaves H2, distinguish from the existing inorganic catalysts for being not only with the impressive catalytic performance but also constitute of earth-abundant materials only.&lt;span style="font-size:10.8333px"&gt; &lt;/span&gt;However, the bio-inspired molecular catalysts based on the hydrogenases, which process similar structures with the active site of the hydrogenases, do not show as remarkable catalytic ability.&lt;span style="font-size:10.8333px"&gt; &lt;/span&gt;Our density functional theory (DFT) calculations reveal that the protein-environment effect has significant influence on the Hydrogen Evolution Reaction (HER) in [NiFe] hydrogenases. The two largest thermodynamic impediments to the whole reaction in the amino acids absent model, are the two H+/e– steps (the so-called Ni-SIa to I1, and Ni-C to Ni-R), with Gibbs free energies of 19.48 and 19.72 kcal/mol, respectively; while the free energy demands for the two steps, considering the protein-environment effect, drop dramatically to 11.87 and 12.26 kcal/mol. The hydrogen bonds between the amino acids and the active site are hypothesized to be the main reason for such stability: hydrogen bonds not only work by influencing the charge redistribution, but more importantly, they act by ‘pulling’ the electrons from the active site towards the amino acid. Moreover, the electron ‘pull’ effect is hypothesized to affect the electrons on Ni and therefore change the energy profile.

Protein-environment effect on catalysis performance in H2-producing [NiFe] hydrogenases

253rd National Meeting (2017)

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