Colorimetric Micromethod for Protein Determination with Erythrosin B

Reaction of erythrosin B with proteins results in a stable, highly colored chromophore with an absorbance maximum at 545 nm. This is the basis for a new quantitative determination method of proteins in solution. The assay can be performed at room temperature, but is faster and more sensitive at 90-95°C. The erythrosin assay is characterized by (i) stable dye-protein color, (ii) high sensitivity (2-14 μg/ml protein), (iii) short reaction time (1.5-2 min at 90-95°C), (iv) good reproducibility, (v) limited interference by common reagents, and (vi) low protein-to-protein variability. Thus, the erythrosin assay can be useful for routine analytical purposes and may overcome some of the limitations of other currently employed assays.