Determination of protein concentrations with Varioskan® using BCA protein assay

Laura Turunen, M.Sc. & Matti Höyhtyä, Ph.D., VTT Technical Research Center of Finland, Espoo, Finland

Abstract

Photometric assays are commonly used in many laboratories for protein detection as they are well established, reliable and inexpensive to run. BCA protein assay in one of the most popular methods for colorimetric detection and quantification of total protein (Smith et al. 1985). The assay is based on the reduction of Cu²⁺ to Cu¹⁺ by protein in an alkaline medium with the highly sensitive and selective photometric detection of cuprous cation (Cu¹⁺) by bicinchoninic acid. The purple-colored reaction product is formed as a result of the molecules of BCA with one Cu¹⁺ ion.