A study on the interaction of proteins with some heteropoly compounds and their analytical application by resonance Rayleigh scattering method

In the dilute sulfuric acid medium, the reactions of proteins with some heteropoly compounds (HPC) including some heteropoly acids (HPA) and their reducing products would result in the enhancement of resonance Rayleigh scattering (RRS) intensity and the appearance of the corresponding RRS spectra. Their maximum scattering peaks were all at 470 nm, and there were four smaller peaks at 400, 510, 800 and 940 nm, respectively. In a certain range, the concentrations of proteins were directly proportional to the enhanced intensities of RRS. The methods have high sensitivities, and the detection limits (DL) were in the range of 11.6–54.0 ng ml−1 depending on different heteropoly compounds. Among these methods, the phosphato-antimo-molybdate heteropoly acid (PSbMoA) system was the most sensitive, and its detection limits (3σ) were 11.6 ng ml−1 for bovine serum albumin (BSA), 12.5 ng ml−1 for human serum albumin (HSA), and 16.0 ng ml−1 for α-chymotrypsin (α-Chy), separately. Taking the PSbMoA and its reducing product systems for example, the suitable reaction conditions, affecting factors as well as the influence of coexisting substance have been investigated. The method has fairly good selectivity, and could be applied to the determination of protein in synthetic samples and practical samples with satisfactory results. A new method for the determination of trace amounts of protein based on RRS technique has been developed.