The Interaction between ZnONP and Lysozymes induces structural heterogeneity: A thermodynamic-based approach

Protein is an important biomolecule that needs to maintain 3D (three-dimensional) dynamic structure in respective physiological conditions in order for homeostasis to be maintained in an organism. This 3D structure is majorly governed by non-covalent interactions. These interactions are highly subjected to changes in the local physicochemical environments of proteins. Any changes in the environment perturb the protein 3D conformation, leading to partial unfolding, consequently rendering the protein non-functional. In recent years, various domains of biological sciences have increasingly embraced nanoparticles, primarily driven by its diverse array of physicochemical properties and applications. Protein adsorption onto nanoparticle surfaces affects the interaction that governs a 3D structure, resulting in conformational rearrangement and altered functional efficacy. The induced changes are very important to explaining the proper functioning of proteins in the presence of nanoparticles, regardless of whether if it is being used as a platform for various biological applications. In this line, lysozyme, a well-studied globular protein model, interacts with the ZnONP interface and its effect on the protein conformational rearrangement in different pH conditions using various biophysical techniques is explored. Lysozymes exhibit different conformations at varying pH levels, affecting their interaction with ZnONP. This protein conformation significantly influences the nature of interactions and ultimately impacts its thermodynamic attributes with ZnONP. Once the lysozyme interacts with the ZnONP interface, it sequesters the protein monomeric population into predominantly two populations, where the stable bulk monomeric population remains in equilibrium with relatively less thermodynamically stable monomeric lysozymes present in corona of the protein--ZnONP complex. However, changes in the conformation do not affect the secondary structure or the functional efficacy of the protein, thereby leaving the protein functional and adequately preserving its efficacy.