The blocking peptide is the antigen we use for immunization during antibody generation so that we can create an antigen-specific antibody. You can use this blocking peptide as a negative control alongside other controls in an immunoassay to give some insight into antibody specificity, but not selectivity.

It’s important to note that the blocking peptide is not an effective control for use with live cells. If you need a control for flow cytometry, we recommend an isotype antibody control instead.

For more details, see our guide to blocking peptides.

Affinity-purified rabbit polyclonal antibodies are mainly IgGs.

To make sure you get optimal blocking of the primary antibody, incubate the antibody, in parallel, with and without the antigen (the antibody/antigen ratio is available in the certificate of analysis delivered with the antibody) in a small volume (500 µl of 1% BSA in PBS) for 1 hour at room temperature with rotation. After the incubation, dilute each vial to the appropriate working concentration in the desired buffer and apply the contents of each vial to each membrane for parallel experiments.

• We recommend that you use the blocking peptide at the ratio specified in the datasheet, or 1 µg of peptide per µg of antibody.
• If you’re using a fusion protein to block the antibody, be aware that fusion proteins are sometimes more delicate to handle than peptides. If the fusion protein was correctly reconstituted (by adding 100 µl of PBS) and handled (avoidance of repeat freezing and thawing), a more diluted antibody together with an increased amount of fusion protein may be necessary for complete blocking of the antibody. We normally recommend adding 3 µg of fusion protein for each µg of antibody, but sometimes you need a larger ratio depending on the sample.