Determination of proteins at nanogram levels based on their resonance light scattering decrease effect on the dibromo-o-nitrophenylfluorone-sodium lauroyl glutamate system

A novel method for the determination of proteins at nanogram levels was proposed based on the decrease of resonance light scattering (RLS) signal resulting from the interaction of dibromo-o-nitrophenylfluorone (DBONPF)-sodium lauroyl glutamate (SLG) with proteins. At pH 2.97, the decrease RLS intensity was proportional to the concentration of proteins in the range of nanogram levels with 3 sigma detection limits being 3.4 ng mL(-1) for bovine serum albumin (BSA), 1.7 ng mL(-1) for human serum albumin (HSA), 4.1 ng mL(-1) for gamma-globulin (gamma-IgG), 4.4 ng mL(-1) for egg albumin, 6.2 ng mL(-1) for pepsin (Pep) and 3.7 ng mL(-1) for alpha-chymotrypsin (Chy). The method is no protein-to-protein variability, simple, rapid, practical and relatively free from interference from coexisting substance, as well as much more sensitive than most of the reported methods. The proposed method was successfully applied to determine total protein in human serum samples.