Deciphering the Underlying Mechanism for Au/ZnO Nanocomposites-Induced Modulation of Structural Features and Thermodynamic Stability of Horse Myoglobin.

The research focuses on how Au/ZnO nanocomposites (NCs) influence the structural features and thermodynamic stability of horse myoglobin. The researchers found that these nanocomposites disrupt the protein’s structure and reduce its thermodynamic stability, with these effects being more pronounced in a denaturant media than in an aqueous solution.

Synthesis and Analysis of Nanocomposites

• The Au/ZnO nanocomposites (NCs) were synthesized and set up for examination using different analytical techniques.
• Through these techniques, the researchers were able to scrutinize the effects of Au/ZnO NCs on the spectra (CD, fluorescence, absorbance, and H NMR) of horse myoglobin under different conditions.

Effects on Protein Structures

• The findings revealed that the Au/ZnO NCs weaken the interactions between the heme and globin components of the protein, a critical aspect that maintains the protein’s structure and function.
• Moreover, these nanocomposites disrupt the secondary and tertiary structure of myoglobin, manipulating its overall conformation and stability.
• More significant impacts on weakening heme-globin interactions and destabilizing protein structures by the nanocomposites were observed when the protein was in a denaturant environment compared to a water-based solution.

Influence on Thermodynamic Stability

• The research also investigated the changes in thermodynamic parameters of horse myoglobin caused by the Au/ZnO NCs, observing a decrease in the protein’s thermodynamic stability.
• These nanocomposites were found to reinforce the effect of urea, a known denaturant, to further decrease the protein’s stability.

Changes to Unfolding Free Energy and Enthalpic Interactions

• The examination of the urea concentration-dependent unfolding free energy of myoglobin in presence of Au/ZnO NCs showed that these nanocomposites enhance the impact of urea on reducing the protein’s stability.
• The research estimates that the local (heme-globin interactions) and structural thermodynamic stability of myoglobin are decreased due to the enthalpic interactions of the protein with Au/ZnO NCs.

Binding Interactions Between Protein and Nanocomposites

• Time-resolved fluorescence studies and isothermal titration calorimetry (ITC) suggested that Au/ZnO NCs form binding interactions with the horse myoglobin. These interactions could be responsible for the observed changes in protein structure and thermodynamic stability.