Spectroscopic studies on pH- and thermally induced conformational changes of Bovine Serum Albumin adsorbed onto gold nanoparticles

In this work we used gold nanoparticles (GNPs) as probes to evaluate the pH- and temperature-induced conformational changes of Bovine Serum Albumin (BSA) adsorbed on their surface. UV–vis and fluorescence spectroscopy were employed to monitor the adsorption and binding modes of BSA on GNPs. The results suggest that GNPs quenched the fluorescence emission of tryptophan residues of BSA mainly through a static mechanism, the binding constant (Kb) being sensitive to the pH values. The Stern–Volmer quenching constant (KSV) and the corresponding thermodynamic parameters (ΔH, ΔS and ΔG) were also determined. In addition, the results concerning the thermally induced conformation changes of BSA, before and after interfacing with GNPs, demonstrate the dependence of the protein conformational transition temperature on pH. Moreover, the linking between BSA and GNPs was monitored by surface-enhanced Raman scattering (SERS), assessing the influence of pH on this specific nano–bio interface.