Electronic states of the O 2 -tolerant [NiFe] hydrogenase proximal cluster

Abstract

Recently, Pandelia et al. (1) used density functional theory (DFT) calculations to interpret their Mossbauer experiments on the superoxidized state of the O2-tolerant hydrogenase [4Fe3S] proximal cluster. Experimentally (table 2 in ref. 1), the subspectrum (S) exhibits the largest quadrupole splitting (ΔEQ = 2.45 mm/s) and a positive hyperfine value A , indicating that the corresponding iron ion belongs to the minority spin sites (i.e., the projection coefficient K of its local spin onto the cluster spin is negative). Among the possible DFT broken symmetry (BS) states Oxn\_ij computed to identify this (S) signal [ij: mixed-valence pair; n = 1: nearby protonated glutamate, n = 2: deprotonated Glu], the authors have retained Ox2\_14 and Ox2_24, as we did previously [BS13 and BS34, respectively (2), considering local iron spin alignments only]. Note that changing Fe1→1, Fe2→4 (unique … [↵][1]1To whom correspondence may be addressed. E-mail: jean-marie.mouesca{at}cea.fr or juan.fontecilla{at}ibs.fr. [1]: #xref-corresp-1-1