Dimer of calcein used as fluorescence probe in the determination of proteins

Abstract

In the presence of appropriate amounts of the cationic surfactant cetyl trimethyl ammonium bromide (CTMAB), the anionic dye calcein dimerizes. The weak fluorescence intensity of the dimer is enhanced by adding proteins at pH 6–8. The interaction between calcein-CTMAB and proteins was studied on the basis of this behavior and a new method was developed for determining proteins. Under optimal conditions, the enhanced fluorescence intensity is proportional to the concentration of proteins in the range 0.4–8 µg mL−1 for human serum albumin (HSA) and 0.8–10 µg mL−1 for bovine serum albumin (BSA), with detection limits of 0.034 µg mL−1 and 0.032 µg mL−1, respectively. Three samples were determined by using this method satisfactorily with relative standard deviations (RSD) of 1.1–3.1%.