Comparative analysis of the interaction mechanism of γ-globulin and hemoglobin with spherical and rod-shaped gold nanoparticles.

The interaction mechanism of spherical gold nanoparticles (AuNPs) and rod-shaped gold nanoparticles (AuNRs) with γ-globulin and hemoglobin was comprehensively and comparatively analyzed. γ-Globulin and hemoglobin have high affinity with AuNPs, and with two different types of binding sites on AuNRs surface. Except hemoglobin interaction with the first binding site of AuNRs, the interaction between γ-globulin/hemoglobin and AuNPs/AuNRs is the spontaneous, endothermic and entropy-driven process, and hydrophobic interaction plays a dominant role. The molecular adsorption mechanism of γ-globulin/hemoglobin on AuNPs and AuNRs surface conforms to Langmuir model and Freundlich model, respectively. The kinetic molecular mechanism between them conforms to the pseudo-second-order model, and chemisorption is the rate-limiting step. AuNPs result in the loosening and unfolding of γ-globulin backbone. AuNRs have no significant effect on γ-globulin backbone. AuNPs/AuNRs result in no significant changes in hemoglobin structure and heme group microenvironment. AuNPs/AuNRs decrease the hydrophobicity of Trp microenvironment of γ-globulin, but there is an intramolecular energy transfer from Trp residue to Tyr residue of hemoglobin. The β-sheet of γ-globulin and the α-helix of hemoglobin reduce by increasing concentrations of AuNPs/AuNRs. Molecular docking is suggesting that the specific amino acid residues of γ-globulin and hemoglobin interaction with AuNPs/AuNRs, and validates the experimental results.