Determination of protein concentration by enhancement of the preresonance light-scattering of α,β,γ,δ-tetrakis(5-sulfothienyl)porphine

Abstract

A method of protein determination with the limit of determination at nanogram levels is proposed by using a common spectrofluorometer to detect the intensity of preresonance light-scattering (PRLS). In the pH range 1.81–4.10, the interactions of α,β,γ,δ-tetrakis(5- sulfothienyl)- porphine, T(5-ST)P, with proteins were studied. It was found that the interactions result in a strongly enhanced preresonance light-scattering signal at 472.0 nm. Mechanism studies showed that the enhanced preresonance light-scattering stems from the J-aggregation of T(5-ST)P in the presence of proteins. It was found that the J-aggregation process is speedy and is scarcely affected by temperature, which supplies a precise method for the determination of proteins. Different proteins in the range 0–7 µg ml^–1 can be determined with the limits of determination below 100 ng ml^–1 depending on the concentration of T(5-ST)P. The results of determination for synthetic samples were in agreement with the desired values, and the ones for human serum samples were identical to those obtained according to the Bradford method using CBB G-250.