Bromophenol blue protein assay: Improvement in buffer tolerance and adaptation for the measurement of proteolytic activity

A modification of the bromophenol blue dye binding procedure of protein estimation is described. Substritution 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, accompained by approximately 25% loss in the sensitivity of the procedure. The mofified reagent exhibited very marked tolerance to detergents and could be successfuly adapted for the measurement of proteolytic activity in acidic, neutral or alkaline pH ranges.