Better BCA Protein Assay Kit: The Better BCA Assay Kit can be used for quantitation of total protein in samples while minimizing interference from disulfide reducing agents. The BCA assay is based on the well-known reduction of Cu2+ to Cu+ by protein in an alkaline medium and the highly sensitive and selective colorimetric detection of the cuprous cation using bicinchoninic acid (BCA). Disulfide reducing agents, particularly dithiothreitol, 2-mercaptoethanol and TCEP are also capable of reducing Cu2+ to Cu+.To minimize the affect of these copper reducers, a compatibility reagent that modifies disulfide reducing agents is added to the sample before adding the BCA reagents. This assay is also compatible with most ionic and non-ionic detergents in the presence of a disulfide reducing agent. Purification of membrane proteins presents unusual challenges to protein quantitation, as these proteins often require the presence of detergents and a disulfide reducing agent to maintain solubility and stability. The dual compatibility of this kit enables researchers to more accurately determine protein concentration for such samples. The kit is compatible with protein samples containing up to 5 mM DTT, 10 mM 2- mercaptoethanol or 10 mM TCEP.