Determination of the concentration of protein by dry weight--a comparison with spectrophotometric methods

A protocol for dry weight determination of the concentration of protein, using 0.2-1.0 mg of protein per sample, has been presented and applied to nine proteins: bovine serum albumin, ovalbumin, bovine carbonic anhydrase B, galactoside binding protein (rabbit), lens calinaris lectin B, green pea lectin, soy bean agglutinin-m, wheat germ agglutinin, and antithrombin III. Dry weights, combined with spectrophotometry, have been used to calculate A1% 1 cm values at 280 nm for these proteins in dilute salt solutions and are compared with published values. From absorptivities at 288 and 280 nm in 6 M guanidine hydrochloride, the number of tryptophan residues per molecule has also been calculated and compared with literature values. These results demonstrate the utility of the present method of dry weight determination.