Interaction between silver nanoparticle and bovine hemoglobin at different temperatures

The binding of silver nanoparticles to bovine hemoglobin (BHb) was studied by fluorescence, UV-Visible, and circular dichroism (CD) spectroscopic techniques at different temperatures of 20, 37, and 42 A degrees C. The absorption spectrum of soret band, in the presence of silver nanoparticle, showed a significant spectral change, which indicated the heme groups of BHb were directly attacked and degraded by silver nanoparticle. The fluorescence data explained that the nanoparticle binding to BHb occurred at a single binding site, which demonstrated a dynamic quenching procedure. Nanoparticles could reduce the fluorescence of tryptophanyl residues of BHb to a lesser extent. Circular dichroism studies demonstrated a conformational change of BHb in the presence of silver nanoparticles. The helicity of BHb was reduced by increasing silver nanoparticle concentration at different temperatures. Thermodynamic analysis of the protein interaction by silver nanoparticles suggested that the binding process is only entropy driven.