Biuret assays are biochemical tests utilized to measure protein concentration in biological samples. This method relies on the formation of a blue-colored complex, known as the biuret complex, when proteins react with copper(II) ions in an alkaline solution. The intensity of the blue color is directly proportional to the protein concentration in the sample, allowing for quantitative measurement using spectrophotometry or colorimetry.
In practice, a protein sample is mixed with an alkaline copper(II) sulfate solution, incubated to allow the biuret reaction to occur, and then the absorbance of the resulting blue solution is measured. By comparing the absorbance to a standard curve generated from known concentrations of a protein standard, the protein concentration in the sample can be determined. Biuret assays widespread use in various fields such as biochemistry, molecular biology, and diagnostics, providing a simple and cost-effective method for quantifying total protein content in diverse biological samples.