Maximum binding capacity of serum albumin for bilirubin is one, as revealed by circular dichroism

Abstract

A reinvestigation of the binding capacity of bovine serum albumin (BSA) and human serum albumin (HSA), respectively, for bilirubin (BR) at pH 7.4 is presented using circular dichroism (CD), UV–VIS spectroscopy and light scattering measurements. Evidence is provided that mixtures of either SAs with BR do not form true solutions in aqueous buffer if the excess of BR over SA exceeds ca. 1.4 equivalents. The study throws doubt on multiple BR binding onto SA at pathophysiological conditions and on the significance of this process for lowering the concentration in unbound BR.