Exploring changes in the structural integrity of lysozymes in the presence of ZnONP: a thermodynamic-based approach

Abstract

Proteins maintain a dynamic 3D structure essential for homeostasis, which is largely governed by non-covalent interactions that are sensitive to physicochemical changes. Metal nanoparticles, used for biological applications because of their unique properties in the biological milieu, adsorb proteins to form protein coronas, disrupting the intramolecular interactions governing the protein's native structure and functions. Understanding these changes is crucial for sustainable nanoparticle-based biological applications. Along this line, herein, lysozyme-zinc oxide nanoparticle (ZnONP) interactions at pH 7.4 and 9 and their effects on protein conformations are explored. Lysozymes with different molecular interacting interfaces interacted differently with the same ZnONP interface at these pH values. The native conformation of lysozyme, characterized by a melting temperature of 345.2 K, upon entropically driven interaction with the NP surface, adapted a partially unfolded conformation with a melting temperature of 343.9 K and reduced protein-mediated antibacterial activity. The partially unfolded lysozyme at pH 9 upon enthalpically driven interaction with the NP surface adapted a native-like rigid conformation and exhibited a melting temperature of 345 K, which is comparable to that of the native protein.