Determination of Total Protein Using the LAMBDA UV/Vis Spectrophotometer: Lowry Method

The Lowry and Biuret methods are standard methods for protein quantification. Though the latter is more sensitive and is used for investigative work, it is limited by (1) poor stability of the combined reagent, (2) non-reproducibility of color, especially at low protein concentrations, and (3) a non-linear chromogenic response with protein concentration. Ohnishi and Barr modified and simplified the Biuret combined reagent for the Lowry procedure and at the same time improved its stability. This application note describes the modified Lowry procedure for protein analysis.