Modelling Low‐Potential [Fe₄S₄] Clusters in Proteins

Developments in the Biomimetic Chemistry of Cubane-Type and Higher Nuclearity Iron–Sulfur Clusters

“…In the [Fe 4 S 4 ] 2+ state, these clusters manifest multi-featured circular dichroism spectra and diastereotopic splittings of cysteinate β-CH 2 protons in 1 H NMR spectra. In contrast, synthetic clusters with chiral ligands are nearly unknown, the few examples involving cysteinyl peptides 11,13,49 and [Fe 4 S 4 (SCH 2 CH(OH)Me) 4 ] 2− synthesized from the racemic thiol. 50 If ligands with chiral centers are employed in synthesis, diastereomeric or enantiomeric clusters will result depending upon whether the ligand is racemic or optically pure.…”

De novo design of functional proteins: Toward artificial hydrogenases

“…Despite containing isostructural [4Fe4S] clusters, iron‐sulfur proteins exhibit redox potentials ranging from −700 to +450 mV, and have been shown to use three different redox states: [4Fe4S] 3+/2+/1+ . It is believed that the electrostatic environment of amino acids surrounding the cluster, the hydrogen bonding interactions of bridging S‐atoms, and the accessibility of the cluster to the solvent influence the potential observed for a particular cluster in a given context .…”

In Vivo Biogenesis of a De Novo Designed Iron–Sulfur Protein

“…The as-purified holo-CCIS (without sodium dithionite) sample had no detectable EPR signal, as would be expected in the oxidized [4Fe-4S] 2+ state. Upon dithionite reduction, a weak rhombic EPR spectrum was observed, characteristic of the reduced [4Fe-4S] + cluster with a rhombic g -factor (2.042, 1.920, 1.905) (Figure B). Previous spectra of rec-CCIS had distinctly different g -values (2.053, 1.970, 1.975) .…”