Immunoblotting and immunodetection.

This unit provides protocols for immunoblotting, which is used to identify specific protein sequences separated by electrophoresis and transferred to an appropriate membrane and recognized by a polyclonal or monoclonal antibody. After the proteins are separated on a gel, they are transferred to a membrane by electroblotting or a semidry transfer system. Proteins on the membrane can be visualized with the reversible stain Ponceau S to assess the completeness of transfer. Then the blot is analyzed with antibodies. The primary antibody is specific for the protein(s) of interest; the secondary antibody (an anti-Ig) is conjugated to horseradish peroxidase or alkaline phosphatase and detected colorimetrically or by chemiluminescence. The membrane can be stripped and reused for other probes.