Quantitative estimation of proteins in the presence of phenolic compounds: viability of the dye-binding assay.
Ananthanarayanan T. V., Chacko E. K.
Author Affiliation: Indian Institute of Horticultural Research, Bangalore 560?080, India.
: 470-472
Abstract : Protein contents were determined (using bovine serum albumin and cytochrome C as standards) in the presence of phenolics (protocatechuic acid, caffeic acid or ferulic acid) by the methods of Lowry et al. (Journal of Biological Chemistry (1951) 195, 265-275) using the Folin-Cioncalteau reagent, and of Bradford (Analytical Biochemistry (1976) 72, 248-254) using dye-binding with Coomassie Brilliant Blue G-250. The phenolics at a concentration of 10-5 M interfered with protein determination when Lowry's method was used, but not when Bradford's method was used, even at phenolic concentrations of 10-1 M. When used for the analysis of protein in the crude 10% homogenate of Alphonso mango leaves in 0.1 M phosphate buffer (pH 7.4), Lowry's method gave 14.0 mg/g, approximately double the value obtained by Bradford's method (6.8 mg/g). When the protein was purified by precipitation with 10% trichloroacetic acid and dissolved in 0.1 M NaOH, both methods gave the same value (6.9 mg/g).