Question

To form electrostatic interactions with proteins at pH 2.5, what must the sign of the charge on Coomassie Blue be at pH 2.5? (0.5 marks)

Select one:

a. zero

b. positive

c. negative

Answer 1

Answer. (1)

Coomassie Brilliant Blue (CBB) is a commonly used dye for staining in biochemistry. It exists in 2 forms - CBB-R250 and CBB-G250. The latter has 2 extra methyl groups.
CBB-R250 is very commonly used in SDS PAGE. It stains the protein bands blue.

CBB-G250 can give different colours based on its pH. It is green in colour at a pH around 1. Blue colour is in neutral pH while in alkaline pH it exists in pink colour. These different colours are due to the different ionization states of the dye in different pH.

The dye binds non-covalently to the amino and carboxyl groups of proteins to form a coloured dye-protein comples.

CBB-R250 is generally used in SDS-PAGE. Although G250 can also be used, its not preferred because it takes a lot f time to prepare it. CBB-R250 can be made almost instantenously.

CBB-G250 is generally used in Bradford reagent.