Noncovalent Complexes Formed between Metal‐Substituted Polyoxometalates and Hen Egg White Lysozyme

Four Wells–Dawson type metal‐substituted polyoxometalates (MSPs), 1:2 ZrIV‐Wells–Dawson [ZrIV(α2‐P2W17O61)]8– (1), 1:1 CoII‐Wells–Dawson [CoII(α2‐P2W17O61)]10– (2), 1:1 NiII‐Wells–Dawson [NiII(α2‐P2W17O61)]10– (3) and 1:1 CuII‐Wells–Dawson [CuII(α2‐P2W17O61)]10– (4), which differ in the nature of the imbedded metal ion, were examined in co‐crystallization experiments with a protein Hen Egg White Lysozyme (HEWL). Single crystal X‐ray structures of four noncovalent complexes between POMs and HEWL have been determined, and the influence of the type of substituted metal on the mode of POM binding to a protein was investigated. All crystal structures exhibited a high degree of similarity, suggesting that the interaction is largely independent on the nature of substituted metal within the same polyoxometalate (POM) archetype. The main driving force for the formation of the noncovalent complex is electrostatic attraction between POM and HEWL surface regions. Stabilization is further provided by direct and water mediated hydrogen bonding between terminal oxygen atoms of the POM framework and flexible HEWL residues. Single crystal X‐ray structures of four noncovalent complexes between POMs and HEWL were determined, and the influence of the type of substituted metal on the mode of POM binding to a protein was investigated.