Investigating the Interaction of Fe Nanoparticles with Lysozyme by Biophysical and Molecular Docking Studies

Herein, the interaction of hen egg white lysozyme (HEWL) with iron nanoparticle (Fe NP) was investigated by spectroscopic and docking studies. The zeta potential analysis revealed that addition of Fe NP (6.45 +/- 1.03 mV) to HEWL (8.57 +/- 0.54 mV) can cause to greater charge distribution of nanoparticle-protein system (17.33 +/- 1.84 mV). In addition, dynamic light scattering (DLS) study revealed that addition of Fe NP (92.95 +/- 6.11 nm) to HEWL (2.68 +/- 0.37 nm) increases suspension potential of protein/nanoparticle system (51.17 +/- 3.19 nm). Fluorescence quenching studies reveled that both static and dynamic quenching mechanism occur and hydrogen bond and van der Waals interaction give rise to protein-NP system. Synchronous fluorescence spectroscopy of HEWL in the presence of Fe NP showed that the emission maximum wavelength of tryptophan (Trp) residues undergoes a red-shift. ANS fluorescence data indicated a dramatic exposure of hydrophobic residues to the solvent. The considerable reduction in melting temperature (T(m)) of HEWL after addition of Fe NP determines an unfavorable interaction system. Furthermore circular dichoroism (CD) experiments demonstrated that, the secondary structure of HEWL has not changed with increasing Fe NP concentrations; however, some conformational changes occur in tertiary structure of HEWL. Moreover, protein ligand docking study confirmed that the Fe NP forms hydrogen bond contacts with HEWL.