NEW SPECTROPHOTOMETRIC ASSAY FOR PROTEIN IN CELL-EXTRACTS

Protein concentrations in cell-free extracts can be determined quickly and accurately using the measured absorbances at 230 and 260 nm. The choice of these 2 wavelengths, rather than those (280 and 260 nm) used by Warburg and Christian, decreases interference by nucleic acids and results in sensitivity equivalent to that of the method of Lowry et al. The 230/260 method is less dependent on changes in the amino acid composition of the protein(s) being measured than is the 280/260 method. Using buffered solutions of crystalline bovine serum albumin and yeast RNA as standards, the following equation was derived: Protein concentration (.mu.g/ml) = 183 A230 - 75.8 A260, where A230 and A260 are the absorbances at 230 and 260 nm.