Selective Hydrolysis of Ovalbumin by Zr-Based Lacunary Polyoxotungstate in Surfactant Solutions

This study aims to design an artificial metalloprotease based on a Zr-containing polyoxometalate Na8[Zr­(W5O18)2] [Zr­(W5)2] for the hydrolysis of ovalbumin (OVA) in the presence of different surfactants, which can be used in many areas of the biological and medical sciences, particularly for targeted proteolytic drug design. For this reason, parameters, including the free energy of binding, the chemical nature of amino acid residues, secondary structures, and electrostatic potentials, of Zr­(W5)2-OVA and Zr­(W5)2-OVA-surfactant were analyzed by molecular docking simulations. The investigations showed that the presence of surfactants decreases the binding affinity of Zr­(W5)2 for OVA amino acids, and hydrogen bonds and van der Waals interactions are formed between Zr­(W5)2 and OVA amino acids. Additionally, GROMACS further illustrated the significance of SDS and CTAB surfactants in influencing the conformational changes of the OVA that lead to selective protein hydrolysis. In agreement with molecular dynamics simulation results, the experimental analysis showed more protein hydrolysis for the Zr­(W5)2-OVA-surfactant systems. For instance, circular dichroism spectroscopy indicated that Zr­(W5)2-OVA-CTAB and Zr­(W5)2-OVA-TX-100 were more hydrolytically efficient due to the increased level of β-structures rather than α-chains, which showed that surfactants can facilitate the accessibility of Zr­(W5)2 to the cleavage sites by inducing partial unfolding of the OVA structure.