Question

Which form of the Coomassie reagent binds to proteins and how?

a) Coomassie Brilliant Blue G-250, binding via electrostatic interactions
b) Coomassie Brilliant Blue R-250, binding via covalent linkage
c) Coomassie Brilliant Green G-250, binding via hydrogen bonding
d) Coomassie Brilliant Red R-250, binding via van der Waals forces

Answer 1

Coomassie Brilliant Blue G-250 binds to proteins predominantly through electrostatic interactions after SDS-PAGE, which uniformly negatively charges the proteins.

Step-by-step explanation:

The form of the Coomassie reagent that binds to proteins is Coomassie Brilliant Blue G-250. It binds to proteins primarily through electrostatic interactions. The extended aromatic regions of the dye interact with proteins, mainly through non-covalent means, such as van der Waals forces and hydrogen bonding, but the predominant form of binding is thought to be electrostatic, due to the attraction between the anionic dye and the cationic sites on the proteins. This is particularly effective because the process of SDS-PAGE, which the proteins usually undergo before staining, involves a detergent, SDS, that denatures the proteins and masks their native charges, making them uniformly negatively charged and thus able to strongly interact with the positively charged Coomassie dye.