Non‐Covalent and Covalent Binding of New Mixed‐Valence Cage‐like Polyoxidovanadate Clusters to Lysozyme
Gabriella Tito, Giarita Ferraro, Federico Pisanu, Eugenio Garribba, Antonello Merlino
Abstract
Abstract The high‐resolution X‐ray structures of the model protein lysozyme in the presence of the potential drug [V IV O(acetylacetonato) 2 ] from crystals grown in 1.1 M NaCl, 0.1 M sodium acetate at pH 4.0 reveal the binding to the protein of different and unexpected mixed‐valence cage‐like polyoxidovanadates (POVs): [V 15 O 36 (OH 2 )] 5− , which non‐covalently interacts with the lysozyme surface, [V 15 O 33 (OH 2 )] + and [V 20 O 51 (OH 2 )] n− (this latter based on an unusual {V 18 O 43 } cage) which covalently bind the protein. EPR spectroscopy confirms the partial oxidation of V IV to V V and the formation of mixed‐valence species. The results indicate that the interaction with proteins can stabilize the structure of unexpected – both for dimension and architecture – POVs, not observed in aqueous solution.