Microdetermination of proteins by resonance light scattering spectroscopy with tetraiodo phenol sulfonaphthalein

The reaction of tetraiodo phenol sulfonaphthalein (TIPSP) with proteins results in an enhanced resonance light scattering (RLS) at 334 nm. This is the foundation of a new quantitative determination method for proteins in aqueous solution. The assay is characterized by high sensitivity (0.34-12.24 mu g/ml), short reaction time (< 2 min) and simplicity (one-step assay). The protein-to-protein variability of the method was investigated, which had some relationships with the isoelectric points of the proteins. There is little or no interference from amino acids, from most metal ions and from complexing agents (e.g. EDTA). Interference by some metal ions, detergents and salts can be minimized by dilution. Human serum samples were measured by this method and the results were compared with a traditional method.