Question

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

Answer 1

Coomassie blue dye interacts with protein through binding with it through Van Der Waals Interaction and Ionic Bonds.

• The ionic bond occur between protein's amino group and sulphonic acid group.
• The amino group of protein is positively charged and basic. (histidine, arginineand lysine)
• The dye is negatuvely charged or anionic.
• When the dye binds with protein, it forms a complex.
• The complex is called as the "Protein-Dye Complex"
• This complex stabilizes the anionic form of the dye.
• All this happens in acidic conditions of the dye.
• The number of positive charges on the protein binds with the same number of coomassie dye ligands. So both are directly proportional to each other.
• Protein-binding causes the dye to change from reddish-brown to blue.
• Hence there is a shift of the wavelength from 470 to 595 nm because the absorption maximum equals to 595 nm.

This is how the resulting complex influences the wavelength of light absorbed.