Noncovalent Association Thermodynamics of Turn‐On Fluorescent Probes with Human Serum Albumin: Dual‐Concentration Ratio Method

Abstract

AbstractEfficient quantification of the affinity of a drug and the targeted protein is critical for strategic drug design. Among the various molecules, turn‐on fluorescent probes are the most promising signal transducers to reveal the binding strength and site‐specificity of designed drugs. However, the conventional method of measuring the binding ability of turn‐on fluorescent probes by using the fractional occupancy under the law of mass action is time‐consuming and a massive sample is required. Here, we report a new method, called dual‐concentration ratio method, for quantifying the binding affinity of fluorescent probes and human serum albumin (HSA). Temperature‐dependent fluorescence intensity ratios of a one‐to‐one complex (L ⋅ HSA) for a turn‐on fluorescent probe (L), e. g., ThT (thioflavin T) or DG (dansylglycine), with HSA at two different values of [L]0/[HSA]0 under the constraint [HSA]0>[L]0 were collected. The van't Hoff analysis on these association constants further resulted in the thermodynamic properties. Since only two samples at different [L]0/[HSA]0 are required without the need of [L]0/[HSA]0 at a wide range, the dual‐concentration ratio method is an easy way to greatly reduce the amounts of fluorescent probes and proteins, as well as the acquisition time.