For most immunoassays, like immunolocalization, ELISA or Western blot, blocking is a crucial step. This procedure blocks spaces that are not occupied by immobilized proteins, and thus prevents non-specific binding of the antibodies used in the assay. If blocking is not performed, false signals or high background will occur.

If normal serum is used as a blocker, it is recommended to use serum derived from the same host species as the detection antibody, conjugated with a reporter enzyme, like HRP (Horseradish peroxidase) and ALP (Alkaline phosphatase), or a fluorochrome, like DyLight®, FITC or others. 

Example: 
Primary antibody: Rabbit anti-target protein

Blocking serum: Normal Chicken Serum (usually used at 5% v/v in PBS with Tween®20 detergent)

Secondary antibody: Chicken anti-Rabbit IgG-HRP conjugated

Note: Rabbit serum cannot be used for blocking in such a combination.
 
  Agrisera blocking serum
Agrisera blocking serum from various species, is provided in three purity grades: non-purified, purified on Protein G and ultrapure, available as in research and bulk quantities.

Not certain which blocker to use? Ask Agrisera.

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