Fluorescence polarization immunoassays (FPIA) can be used to measure the presenc

Question

Fluorescence polarization immunoassays (FPIA) can be used to measure the presence of a drug in a sample, a process commonly applied to drug tests. In FPIA, a fluorescein-labeled drug and an antibody that binds to this drug are introduced to a sample with an unknown drug concentration. Any drug that was originally present in that sample will compete with the fluorescein-labeled drug to bind with the added antibodies. When polarized light hits the fluorescein-labeled drug, the light is absorbed and emitted at a lower energy. Since this process is occurring in a liquid, the fluorescein-labeled drug is able to move freely. The faster the fluorescein-labeled drug rotates and tumbles, the less polarized the emitted light is. Fluorescein-labeled drugs bound to an antibody are larger molecules and tumble slower, thus yielding a greater amount of polarized light than free fluorescein-labeled drugs. Based on the description above, what sort of response during FPIA indicates that the measured sample contains a significant amount of the drug of concern? A large amount of polarized light is emitted, A large amount of non-polarized light is emitted, No light is emitted.

Explanation / Answer

When the measured sample has significant amount of drug of concern, it will be bound to the antibody and the Fluorescein-lebeled drug which are actually smalla molecules remain un bound.

This Fluorescein-lebeled drug absorbs the polarized light so it will be lost.

So less amount of polarized light is emitted.

Hence answer is large amount of non-polarized light is emitted.

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