Fig. 4.

UV–vis absorbance spectra of [BSA–indigotin complex]−[indigotin] (A) and [HSA–indigotin complex]−[indigotin] (B); the concentrations of BSA and HSA were kept at 5.0 μM (a); the indigotin concentrations for two systems were maintained at 2.00 μM (b), 4.00 μM (c), 6.00 μM (d), 8.00 μM (e) and 10.00 μM (f); a concentration of 2.00 μM (g) was used for indigotin only.