Which Alcian Blue staining condition demonstrates sulfated mucopolysaccharides at both pH 1.0 and pH 2.5?

• A. pH 1.0 only
• B. pH 2.5 only
• C. pH 1.0 and 2.5
• D. None

Answer: (C)

Alcian Blue binds to acidic mucopolysaccharides based on charge. At very acidic pH (pH 1.0), carboxyl groups are not negatively charged, so only sulfated mucosubstances bind the dye. At pH 2.5, both sulfated and carboxylated mucosubstances carry negative charges and bind the dye. Therefore, sulfated mucopolysaccharides will be stained under both conditions, while carboxylated ones appear only at pH 2.5. The condition that demonstrates sulfated mucopolysaccharides at both pH levels is staining at both pH 1.0 and pH 2.5.