What does the Bradford assay measure?

The Bradford assay is a widely used colorimetric method for determining the concentration of proteins in a solution. It is based on the binding of the Coomassie Brilliant Blue dye to proteins. When the dye binds to protein, it undergoes a color change that can be measured spectrophotometrically. The intensity of the color that develops is directly proportional to the concentration of protein present. This makes it an effective and simple tool for quantifying protein levels in various samples.

Options addressing the size or charge of proteins do not pertain to what the Bradford assay specifically measures, as the assay does not provide information about these attributes. Additionally, while the assay does involve protein-dye interactions, it is focused on quantifying the concentration rather than exploring those binding interactions in depth. Therefore, the most accurate choice regarding what the Bradford assay measures is the concentration of protein in a solution.