Alcian blue staining at pH 0 is particularly used to demonstrate which group of substances?

• A. Sulfated acid mucopolysaccharides
• B. Neutral mucopolysaccharides
• C. Glycogen
• D. Lipid-rich substances

Answer: (A)

Alcian blue is a cationic dye that binds to negatively charged groups in mucopolysaccharides. When staining at an extremely low pH, the carboxyl groups on acidic mucopolysaccharides become protonated and lose their negative charge, while the sulfate groups remain negatively charged. This means the dye will bind specifically to sulfated glycosaminoglycans, highlighting sulfated acid mucopolysaccharides such as sulfated GAGs, and not neutral or non-sulfated mucopolysaccharides. Therefore, the group demonstrated is sulfated acid mucopolysaccharides.