Western blotting WB (immunoblotting) is a widely practiced analytical technique to detect target proteins within samples using antigen-specific antibodies. WB involves two major processes: Separation of soluble proteins into discrete bands and transfer of those proteins onto a solid matrix for subsequent analysis by immunological probes. Under standard denaturing conditions, SDS-polyacrylamide gel electrophoresis (SDS-PAGE) is used to separate sample proteins based on polypeptide length. The separated proteins are transferred (blotted) onto a membrane matrix of nitrocellulose or PVDF where they are stained with antibody probes specific to target protein antigens. Typically, blots are incubated with antibodies against the antigen of interest followed by a secondary antibody and detection. Analysis of protein migration and the intensity of chromogenic, chemiluminescent, or fluorescent signals offer protein expression details from cells or tissue homogenates. When coupled with high-resolution gel electrophoresis, antibodies of strong avidity and specificity to target antigens, and robust signal reporting, Western blotting can detect picogram quantities of protein.