A novel method for the study of molecular interaction by using microscale thermophoresis

The fundamental studies for the binding events of protein and its partner are crucial in drug development. In this study, a novel technology named microscale thermophoresis (MST) was applied in the investigation of molecular interaction between an organic dye fluorescein isothiocyanate (FITC) and bovine serum albumin (BSA), and the results were compared with those obtained from conventional fluorescence spectroscopy. The MST data demonstrated that with a short interaction time, FITC showed a high binding affinity for BSA by weak interaction instead of labeling the protein. By using competitive strategies in which warfarin and ibuprofen acted as the site markers of BSA, FITC was proven to mainly bind to the hydrophobic pocket of site II of BSA compared to site I of BSA. Except for the binding affinity, MST also provided additional information with respect to the aggregation of BSA and the binding of FITC to BSA aggregates, which is unobtainable by fluorescence spectroscopy. This work proves that MST as a new approach is powerful and reliable for investigation of protein-small molecule interaction.