Visualization of serum albumin on electrophoretic gels using the specific ligand bilirubin

Serum albumin, when incubated with bilirubin prior to electrophoresis, was visualized as a yellow-colored band during the electrophoretic run and did not require any staining. Furthermore, free bilirubin served as a tracking dye. A minimum of 20 micrograms of protein was detected very well by this method. The formation of a bilirubin-albumin complex did not affect the electrophoretic mobility as the protein complexed with bilirubin as well as free albumin moved with the same mobility. Only a single protein band was visualized by this method after electrophoresis of human plasma. The method is simple, less time-consuming and may be used in identifying bilirubin-binding proteins in various biological samples.