Which assay technique can quantify apolipoproteins?

Which assay technique can quantify apolipoproteins?

• A. Spectrophotometric endpoint
• B. Ion-selective electrode
• C. Immunonephelometric assay
• D. Refractometry

Answer: (C)

Quantifying apolipoproteins requires a method that specifically detects a particular protein in a complex mixture. An immunonephelometric assay uses antibodies directed against the target apolipoprotein; when the antibody binds the apolipoprotein, immune complexes form and scatter light. The amount of light scattered is proportional to the concentration of the apolipoprotein in the sample, allowing precise, specific measurement even in serum with many other proteins. This makes immunonephelemetric assays well suited for determining levels of apolipoproteins such as apoB or apoA-I, which are clinically informative for lipid disorders and cardiovascular risk. Other methods aren’t as suited for this specific task. A spectrophotometric endpoint relies on color change or absorbance, which is useful for many assays but not inherently specific to apolipoproteins unless a dedicated colorimetric test is used. An ion-selective electrode targets particular ions rather than proteins. Refractometry gauges overall solute concentration via refractive index and isn’t able to distinguish apolipoproteins from other serum proteins.

Quantifying apolipoproteins requires a method that specifically detects a particular protein in a complex mixture. An immunonephelometric assay uses antibodies directed against the target apolipoprotein; when the antibody binds the apolipoprotein, immune complexes form and scatter light. The amount of light scattered is proportional to the concentration of the apolipoprotein in the sample, allowing precise, specific measurement even in serum with many other proteins. This makes immunonephelemetric assays well suited for determining levels of apolipoproteins such as apoB or apoA-I, which are clinically informative for lipid disorders and cardiovascular risk.

Other methods aren’t as suited for this specific task. A spectrophotometric endpoint relies on color change or absorbance, which is useful for many assays but not inherently specific to apolipoproteins unless a dedicated colorimetric test is used. An ion-selective electrode targets particular ions rather than proteins. Refractometry gauges overall solute concentration via refractive index and isn’t able to distinguish apolipoproteins from other serum proteins.