Abstract
A colorimetric method was developed for determining total proteins in serum using a nickel/biuret reagent. It is based on measurement of a orange-colored complex produced by reactions of peptide bonds with nickel ions in alkali. Eighteen nonprotein compounds were tested, and this proposed method gave color development with glutathione, L-histidine, L-cysteine, and L-leucinamide, the measuring absorbance at 500 nm. The Cu/biuret method, so called the biuret method, however, reacted with all compounds, such as L-threonine, L-serine, D-mannose, D-galactosamine, sialic acid, and others. The correlation between the two methods (x and y) was r=0.996, and the regression, y=1.015x-0.18. The mean value by the present method was about 0.07g/dl less than that by the Cu/biuret method, this difference being statistically significant (p<0.001, t-test). It these appears that this method may be more specific for determining total serum proteins than the Cu/biuret method.
