Cayman's Protein Determination is a microplate-based, colorimetric method for rapid total protein quantification. Based on the well-known Bradford method, it takes advantage of the color change of Coomassie? Dye when it binds to proteins in acidic medium. When the dye binds, there is an immediate shift of the absorption maximum from 465 to 595 nm with a simultaneous change in color from brown to blue.