Critical evaluation of two neutron structures of Mn superoxide dismutase with quantum refinement

In 2021, neutron structures of oxidised and reduced human manganese superoxide dismutase were published, suggesting several unexpected features, including deprotonated glutamate, tyrosine and histidine residues and a reduced Mn ion with two hydroxide ligands. We have used quantum refinement to evaluate whether alternative interpretations of the structures are possible, comparing many structural models with different possible protonation states or other structural interpretations. Quantum refinem