Bromophenol blue protein assay: improvement in buffer tolerance and adaptation for the measurement of proteolytic...

A modification of the bromophenol blue dye binding procedure of protein estimation is described. Substitution of glycine/phosphoric acid, pH 2.6, for dilute acetic acid in the colour reagent extended the applicability of the procedure to protein solutions containing buffers of various pH values. This was, however, accompanied by approximately 25% loss in the sensitivity of the procedure. The modified reagent exhibited very marked tolerance to detergents and could be successfully adapted for the measurement of proteolytic activity in acidic, neutral or alkaline pH ranges.