Which substances stain dark blue with Alcian blue 2.5?

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Multiple Choice

Which substances stain dark blue with Alcian blue 2.5?

Explanation:
Alcian blue 2.5 highlights acidic mucins because the dye is a cationic stain that binds to negatively charged groups on mucin glycoproteins. At pH 2.5, sulfated and carboxylated mucins—such as those found in sulfated mucins, hyaluronic acid, and sialomucins—carry negative charges that attract the dye, producing a dark blue color. Neutral mucins lack these acidic groups, so they do not bind Alcian blue 2.5 and remain unstained or faint. The same logic explains why substances like keratin, glycogen, fats, and nucleic acids (DNA/RNA) are not stained blue under this stain: they do not present the acidic mucin features Alcian blue targets.

Alcian blue 2.5 highlights acidic mucins because the dye is a cationic stain that binds to negatively charged groups on mucin glycoproteins. At pH 2.5, sulfated and carboxylated mucins—such as those found in sulfated mucins, hyaluronic acid, and sialomucins—carry negative charges that attract the dye, producing a dark blue color. Neutral mucins lack these acidic groups, so they do not bind Alcian blue 2.5 and remain unstained or faint. The same logic explains why substances like keratin, glycogen, fats, and nucleic acids (DNA/RNA) are not stained blue under this stain: they do not present the acidic mucin features Alcian blue targets.

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