The assay bases on the bichinchoninic acid method (1). Proteins reduce alkaline Cu(II) to Cu(I). Bichinchoninic acid forms a purple complex with Cu(I) with an absorbance maximum at 562 nm. The absorbance is directly proportional to protein concentration.

• Fast and sensitive assay: linear detection range from 0.5 – 20 µg protein/ml

• Easy to use: contains ready-to-use reagents and protein standard

• Compatible with many detergents

• Less binding variation between different proteins than Bradford assay

1. Smith, P.K., et al. (1985) Anal. Biochem. 150, 76 - 85