Determination of Albumin and Globulin at Nanogram Levels by a Resonance Light-Scattering Technique with α,β, γ, δ-Tetrakis(4-sulfophenyl)porphine

A method for determination of bovine serum albumin (BSA) and γ-globulin (γ-IgG) at nanogram levels is proposed by using a common spectrofluorometer to detect the intensity of resonance light-scattering. In the presence of BSA or γ-IgG at pH 1.86 and ionic strength 0.04, the aggregation of α,β,γ,δ-tetrakis(4-sulfophenyl)porphine (TPPS4) was observed. It was found to result in strong enhanced resonance light-scattering (RLS) signal with a scattering peak at 490.0 nm. But at pH 1.86 and ionic strength 0.11, only BSA can induce the aggregation of TPPS4 resulting in the strong enhanced RLS. Determination for synthetic samples by making use of the effect of ionic strength showed that if the ratio of γ-IgG in the mixture of γ-IgG and BSA is lower than 0.20, the results for the simultaneous determination of BSA and γ-IgG fractions without separation are satisfactory, but if the content of γ-IgG in the mixture is too high, the determination error is significant. However, the total content of BSA and γ-IgG in human serum can be determined with results identical to those obtained according to the Bradford method using CBB G-250.