Computer-assisted determination of protein concentrations from dye-binding and bicinchoninic acid protein assays performed in microtiter plates.

The bicinchoninic acid protein assay was scaled down to operate in the wells of microtiter plates. The total volume of the assay was reduced to 210 microliters and required only 10 microliters of sample per assay. The assay can be rapidly performed and then read with a plate reader. The analysis of the data was performed with a microcomputer interfaced with the reader. A computer program was developed to analyze the data from the bicinchoninic acid assay as well as the dye-binding assay at either the high or low protein concentration ranges. Based upon the absorbance values of the standards, the program computed a linear regression formula which was then used to calculate the concentrations of the sample proteins. A series of assays performed using bovine serum albumin, alpha-chymotrypsin and gamma globulin demonstrated that the scaled down bicinchoninic acid assay produced linear absorption versus concentration data with average correlation coefficients between 0.9967 and 0.9940 at the high and low concentration ranges respectively. The protein-to-protein variation and proper selection of either protein assay based upon the presence of interfering materials was considered.