A comparison of the Bradford and Lowry methods for the analysis of protein in chlorophyllous tissue

Abstract

A comparison of the dye-binding method of Bradford (1976) with the Folin phenol method of Lowry et al. (1951) for the assay of protein in chlorophyllous tissue is described. Additions of chlorophyll to protein standards precluded reliable determinations with either method. Absorbance readings were increased by nearly 20% with the Bradford assay and by over 400% using the Lowry procedure. Trichloroacetic acid precipitation of the proteins effectively eliminated any significant interference by chlorophyll; however, the practice of washing the protein precipitate with 80% acetone to remove residual chlorophyll resulted in large protein losses. Eluting leaf tissue with acetone prior to extraction of protein increased protein yield significantly. Both assay procedures provide satisfactory measurement of leaf proteins once chlorophyll is removed. The dye-binding method is fast, simple, and more sensitive, but the Lowry procedure gives better linearity at high protein concentrations and better stability once color has developed.