A study of protein–drug interaction based on solvent-induced protein aggregation by fluorescence correlation spectroscopy

The identification of molecular targets for achieving beneficial effects from small-molecule drugs is a crucial and currently unsolved challenge, which leads to high costs and long development cycles. Therefore, it is urgent to develop methods for easily and quickly acquiring information about protein-drug interaction at a molecular level. In this study, we propose a novel method for the study of protein-drug interaction by fluorescence correlation spectroscopy (FCS) based on organic solvent-induced protein aggregation. We used β-secretase (BACE-1) and dihydrofolate reductase (DHFR) as model proteins. Fluorescence-labelled proteins aggregated in aqueous solutions containing organic solvents. In the presence of drugs, the aggregation of proteins was inhibited greatly, and FCS was used to characterize protein aggregates. The decrease in the characteristic diffusion time (τD) of protein aggregates demonstrated a strong interaction between proteins and drug molecules. We presented a new parameter IC50 to assess the inhibitory effects of drugs on the basis of the changes in the τD of fluorescence-labelled proteins under different concentrations of the drugs in the presence of organic solvents. We acquired a remarkable difference in the IC50 values for different drugs and in terms of the trend, our results were consistent with those reported by other methods. Compared with current methods, our approach is simple, low-cost, and time-saving, and has the potential to become a promising and universal tool for drug screening at the molecular level.