Multiscale Modeling of the Active Site of [Fe] Hydrogenase: The H 2 Binding Site in Open and Closed Protein Conformations

A series of QM/MM optimizations of the full protein of [Fe] hydrogenase were performed. The FeGP cofactor has been optimized in the water‐bound resting state ( 1 ), with a side‐on bound dihydrogen ( 2 ), or as a hydride intermediate ( 3 ). For inclusion of H 4  MPT in the closed structure, advanced multiscale modeling appears to be necessary, especially to obtain reliable distances between CH‐H 4 MPT + and the dihydrogen (H 2 ) or hydride (H − ) ligand in the FeGP cofactor. Inclusion of the full protein is further important for the relative energies of the two intermediates 2 and 3 . We finally find that hydride transfer from 3 has a significantly higher barrier than found in previous studies neglecting the full protein environment.