Electrochemical Study on the Interaction of Protein with Bromothymol Blue and Its Analytical Application

The interaction of bromothymol blue(BB) with human serum albumin(HSA) was studied by electrochemical techniques and a sensitive method for proteins assay was developed. When BB interacted with HSA, the voltammetric peak current value of BB decreased linearly with the concentration of HSA in a range of 1.0—40.0 mg/L, and the peak potential shifted negatively. Based on the results, a sensitive assay method for proteins, such as HSA, bovine serum albumin(BSA), and egg albumin etc. was established. This method was further applied to determining the HSA in healthy human blood samples, and the results are not significantly different from those obtained by the classic Coomassie Brilliant Blue G-250 spectrophotometic method. The detecting conditions of this method were optimized and the interaction mechanism was discussed. The results show that the electrochemical parameters(formal potential E⁰, standard rate constant of the electrode reaction k_s, parameter of kinetic nα) of BB have no obvious changes before and after the interaction, which indicate that BB can interact with HSA, forming an electrochemical non-active complex. The equilibrium constant(β_s) and the binding ratio(m) for this complex were calculated. The m is 4 and β_s is 1.41×10¹⁹. This method is fast, simple, highly sensitive, and has good selectivity, which can be used in clinical measurements.