Increased uniformity in the response of the coomassie blue G protein assay to different proteins.

Coomassie blue G dye-based protein assays are exceptionally convenient because of their simplicity, sensitivity, speed, and resistance to interfering chemicals, notably reducing agents and most buffers. A major problem with the assay is the variation in response to different proteins. The addition of NaOH to the protein assay reagent reduced the variation in the response of this assay to different proteins. In addition, the sensitivity of the assay is increased. The NaOH can be added either in a separate step to solubilize cells or membranes or directly to the reagent. Linear standard curves were obtained when the log of the absorbance was plotted against the log of the protein quantity.