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Magnetic Properties of [FeFe]‐Hydrogenases: A Theoretical Investigation Based on Extended QM and QM/MM Models of the H‐Cluster and Its Surroundings
Author(s) -
Greco Claudio,
Silakov Alexey,
Bruschi Maurizio,
Ryde Ulf,
De Gioia Luca,
Lubitz Wolfgang
Publication year - 2011
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201001058
Subject(s) - chemistry , qm/mm , hydrogenase , cluster (spacecraft) , active site , coupling constant , density functional theory , antiferromagnetism , computational chemistry , electron paramagnetic resonance , crystallography , catalysis , molecular dynamics , condensed matter physics , quantum mechanics , physics , biochemistry , computer science , programming language
In the present contribution, we report a theoretical investigation of the magnetic properties of the dihydrogen‐evolving enzyme [FeFe]‐hydrogenase, based on both DFT models of the active site (the H‐cluster, a Fe 6 S 6 assembly including a binuclear portion directly involved in substrates binding), and QM/MM models of the whole enzyme. Antiferromagnetic coupling within the H‐cluster has been treated using the broken‐symmetry approach, along with the use of different density functionals. Results of g value calculations turned out to vary as a function of the level of theory and of the extension of the model. The choice of the broken‐symmetry coupling scheme also had a significant influence on the calculated g values, for both the active‐ready (H ox ) and the CO‐inhibited (H ox ‐CO) enzyme forms. However, hyperfine coupling‐constant calculations were found to provide more consistent results. This allowed us to show that the experimentally detected delocalization of an unpaired electron at the binuclear subcluster in Desulfovibrio desulfuricans H ox is compatible with a weak interaction between the catalytic centre and a low‐weight exogenous ligand like a water molecule.