Final answer:
Coomassie brilliant blue G-250 can act as a weak acid and its protonation is dependent on the pH of the solution.
Step-by-step explanation:
The question asks if Coomassie brilliant blue G-250 is acidic and protonated. Coomassie Brilliant Blue (CBB), used in protein staining methods, is a dye that can act as a weak acid. It is typically used in a form that would be protonated under acidic conditions. However, the specific acidity and protonation state can vary depending on the solution's pH. In acidic conditions, the –COOH group can donate a proton and become protonated, while in basic conditions, it exists as a carboxylate ion. The paper by Candiano et al. signifies the sensitivity and use of CBB for proteome analysis but does not explicitly discuss its protonation state.