Enhancement of Rayleigh light scattering of Acid Chrome Blue K by proteins and protein assay by the scattering technique

Rayleigh light scattering of Acid Chrome Blue K (ACBK) is enhanced greatly by proteins. Based on this, a method for protein assay in aqueous solution was developed. This assay matches the sensitivity of the colorimetric dye-binding method with a linear range of 0.136-10.88 micrograms ml-1. The measurements can be made easily on a common fluorimeter. The reaction between ACBK and proteins is completed in 2 min and the scattered light signal is stable for at lest 3 h. Protein-to-protein variability is encountered in this method as in many other protein assays. There is little or no interference from amino acids, most metal ions and complexing agents (e.g., EDTA). Interferences from salts, urea and detergents can be minimized by dilution.