Probing the Effect of Ag2S Quantum Dots on Human Serum Albumin Using Spectral Techniques

Abstract

The understanding of the interaction between protein and quantum dots (QDs) has significant implications for biological applications of QDs. Herein, we studied the effect of Ag2S QDs on human serum albumin (HSA) using UV-Vis absorption spectra and fluorescence spectroscopy and found that the fluorescence intensity of HSA was gradually decreased with increasing Ag2S QDs concentrations. By using the Stern-Volmer equation for the fluorescence quenching constant (KSV) of the response of Ag2S QDs to HSA as well as thermodynamic equations, the values of thermodynamic enthalpy change (ΔHθ), entropy change (ΔSθ), and free energy change (ΔGθ) were calculated to be −10.79 KJ·mol−1, 37.80 J·mol−1·K−1, and −22.27 KJ·mol−1, respectively. The results indicate that Ag2S QDs exert an obvious static fluorescence quenching effect on HSA and electrostatic interaction plays a key role in the binding process. Furthermore, Raman spectral analysis reveals that Ag2S QDs alter the external environment of tyrosine and tryptophan or the C-H bending of HSA but not the α-helical content.