Question

Describe how Coomassie Blue dye interacts with protein and how the resulting complex influences the wavelength of light absorbed.

Answer 1

The Coomassie Brilliant Blue dye which is commonly used in SDS-PAGE was first described by the German scientist Volker Neuhoff. The dye gets its name from the African city Kumasi, formerly Coomassie, a city in central Ghana. Currently, there are two kinds of the Coomassie dyes: R-250 and G-250. Coomassie R-250 is the more commonly used and sensitive of the two. Though less sensitive, Coomassie G-250 has particular properties that enable it to be used to create a rapid and convenient staining procedure. In the staining reaction, the Coomassie dye binds to proteins through ionic interactions between sulfonic acid groups and positive protein amine groups through Van der Waals attractions. DNR developed unique Bio-Imaging systems that can easily detect the Coomassie Brilliant Blue dye in a quick, accurate and reproducible manner. Our superior GelCapture software and camera allow the user to detect both the highest and lowest band intensity.

DETECTION

• There is a shift in the peak absorbance of the dye when it binds to a protein. Unbound Coomassie Blue absorbs light maximally at a wavelength of 465 nm, while the absorption maximum is at 595 nm when the dye is bound to protein.