Which are precipitation agents for protein turbidimetry?

• A. SSA
• B. TCA
• C. Benzalkonium chloride
• D. SSA, TCA, and Benzalkonium chloride

Answer: (D)

Protein turbidimetry measures how much light is scattered as proteins form a suspended, precipitated phase. The reagents used to create that turbidity are substances that cause proteins to come out of solution and form fine, scattered particles. Sulfosalicylic acid does this by acidifying and disrupting protein solubility, leading to precipitation and a measurable turbidity. Trichloroacetic acid is a strong denaturant that removes the protein’s hydration layer and drives precipitation, again producing turbidity proportional to protein amount. Benzalkonium chloride is a cationic detergent that interacts with proteins to form insoluble complexes and aggregates, resulting in light scattering as well. Because all three can precipitate proteins to generate turbidity, they are all considered precipitation agents for protein turbidimetry.