ELASTIC LIGHT-SCATTERING OF PROTEIN-CHROM E AZUROL-S COMPLEX AND ITS PRELIMINARY ANALYTICAL APPLICATION

In the medium of citric acid-NaOH buffer (pH 3.5),proteins may combine with chrome azurol S (CAS) by intermolecular forces (mainly by electr ostatic force) to form macromolecular ion-association complexes, causi ng an elastic light-scattering signal with a maximum wavelength of abo ut 370 nm. Based upon this, a new method for the determination of seru m albumin with a detection limit of 0.02 mu g.mL(-1) was proposed. Its calibration curve is linear over the range of 0-1.0 mu g.mL(-1). The sensitivity of this method is fifty-fold higher than that of the Cooma ssie brilliant blue protein assay. The scattering spectra of this syst em were measured using an ordinary spectrofluorophotometer. Influence of experimental conditions, such as pH, ionic strength, and concentrat ion of CAS, on the intensity of light-scattering was studied. Effects of surfactants (cationic, anionic, and nonionic), amino acids, and met al ions on the combination of CAS with protein were also investigated. This method has been used for the determination of urinary protein wi th good results.