Fluorescent dye method for determination of the bilirubin-binding capacity of serum albumin.

A simple, rapid microfluorometric method utilizing a fluorescent dye, Direct Yellow 7, for quantitative measurement of serum albumin-binding capacity for bilirubin has been developed. The dye binds exclusively to serum albumin with enhancement of fluorescence. The dye shares bilirubin-binding sites on albumin with up to 2 mols of bilirubin per mol of albumin with differing affinities to the first and second sites. Lowered pH reduces albumin-binding capacity and exposure to light increases binding capacity of icteric sera. The binding capacity of adult human sera is greater than that of human cord sera or purified human serum albumin compared on albumin molar basis.