Protein analysis with bicinchoninic acid.

Some of the variables and the interferences which affect the reaction kinetics of proteins with bicinchoninic acid (BCA) (4,4'-dicarboxy-2,2'-biquinoline) have been studied. Interferences attributed to glucose, ascorbic acid, and uric acid in this reaction were significantly reduced by performing a two-point assay and by including borate ions in the buffer. The method was shown to be suitable for automation and can be applied for the analysis of protein in physiological fluids, such as cerebrospinal fluid and cells grown in tissue cultures. The method compared well with other established methods for protein assays, such as the Coomassie blue and the turbidimetric method, and it is more sensitive to globulins than albumins.