The BCA protein assay is used for quantitation of total protein in a sample. The principle of this method is that proteins can reduce Cu+2 to Cu+1 in an alkaline solution (the biuret reaction) and result in a purple color formation by bicinchoninic acid. The reduction of copper is mainly caused by four amino acid residues including cysteine or cystine, tyrosine, and tryptophan that are present in protein molecules. However, unlike the Coomassie dye-binding methods, the universal peptide backbone also contributes to color formation, helping to minimize variability caused by protein compositional differences. Compared to the Bradford assay, the BCA assay is more objective since the universal peptide backbone also contributes to color formation. One disadvantage of the BCA assay compared to the Bradford assay is that it is susceptible to interference by some chemicals present in protein samples, including reducing agents (i.e., DTT and beta—mercaptoethanol), copper chelators (i.e., EDTA, EGTA) and buffers with high concentration, which can be avoided by generating diluted samples., BCA蛋白测定用于定量样品中的总蛋白。该方法的原理是蛋白质可以在碱性溶液(缩二脲反应)中将Cu 2+还原为Cu 2+ +1并且导致通过二喹啉酸形成紫色。铜的还原主要由存在于蛋白质分子中的四个氨基酸残基(包括半胱氨酸或胱氨酸,酪氨酸和色氨酸)引起。然而,与考马斯染料结合方法不同,通用肽骨架也有助于颜色形成,有助于使由蛋白质组成差异引起的可变性最小化。与Bradford测定相比,BCA测定更客观,因为通用肽骨架也有助于颜色形成。与Bradford测定相比,BCA测定的一个缺点是其易受蛋白质样品中存在的一些化学物质的干扰,包括还原剂(例如DTT和β-巯基乙醇),铜螯合剂>即EDTA,EGTA)和具有高浓度的缓冲液,通过产生稀释的样品可以避免。