Which dye is used to stain lipoproteins?

• A. Oil Red O
• B. Coomassie Brilliant Blue
• C. Ponceau S
• D. Silver nitrate

Answer: (A)

Staining lipids requires a dye that dissolves in and partitions into lipid-rich regions rather than binding to proteins. Oil Red O is that type of fat-soluble dye; it specifically stains neutral lipids such as triglycerides and cholesterol esters, giving lipid-rich areas a red-orange color. It’s commonly used on frozen tissue sections because routine paraffin processing removes lipids, so freezing preserves them for accurate staining of lipids and lipoproteins.

Lipoproteins have a lipid core, so they appear stained by Oil Red O due to their lipid content. The other dyes target proteins rather than lipids: Coomassie Brilliant Blue binds to amino groups on proteins, staining protein-rich areas; Ponceau S also stains proteins on membranes; Silver nitrate staining is used for proteins or other structures in specialized protocols, not for lipids. Hence Oil Red O is the best choice for staining lipoproteins.