A resonance light-scattering determination of proteins with fast green FCF.

The interaction of Fast Green FCF (FCF) with proteins (including bovine serum albumin (BSA), human serum albumin (HSA), pepsin (Pep) and alpha-chymotrypsin (Chy), and lysozyme (Lys)) was characterized by enhanced resonance light-scattering (RLS) measurements using a common spectrofluorometer. The enhanced RLS signals of FCF by proteins at 279.0 nm were obtained, and the mechanism of the RLS enhancement was considered in terms of the effects of the pH and ionic strength on the interaction. It was found that the enhanced RLS intensities were in proportion to the concentrations of proteins in the range of nanogram levels, displaying that the present assay is much more sensitive than the reported RLS methods, with the limits of determination being 4.54, 0.6, 22.8, 4.32 and 1.75 ng/ml for BSA, HSA, Pep, Chy, and Lys. respectively.