Ellman Assay Protocol

Ellman assay makes it possible to monitor inhibition of the blood cholinesterase, a molecule that initiates the breakdown of hormones like acetylcholine. Consequently, it permits identification of a person's exposure to certain pesticides.

Advantages

• When used in combination with the measurement of urinary metabolite excretions, Ellman's reagent method provides laboratories with a fast and easy way to prove that a selected subject has or has not been exposed to organophorous pesticides.

  A single drop of blood is all that is needed. Performance of the Ellman assay does not require the availability of a large ether centrifuge. Conducting this assay requires only an instrument that has the ability to detect light waves.

Method

• Coat the well of a microtiter plate with the assay's all important mixture, one that contains acetylthiocholine (AChE). After each well has been coated, then a micro amount of one subject's blood can be placed in each well. When this has been completed, then you add a substance that identifies the protein of interest and attaches to that protein.

  The reagent that is added just prior to measurement of the emitted light waves is one that should give off light waves that have a length of 405 nm. The machine used in the laboratory measures the amount of light absorbed at that wavelength.

Precautions

• The chromogenic (colorizing) reagent used during performance of this test has been shown to alter the length of the emitted light waves when it is exposed to higher temperatures. Therefore, keep that reagent refrigerated.