Peptides are short chains of amino acids linked by covalent chemical bonds. Covalent bonds are formed by the linkage between the carboxyl group of one amino acid and the amino group of another. Although recent advances in peptide technology have made it possible to synthesize peptides over 150 amino acids long, peptides have typically been distinguished from proteins based on their size. Biological peptides contain approximately up to 50 amino acids.
What are blocking Peptides?
Blocking peptides are peptides that bind specifically to the target antibody and block antibody binding. This is because the peptide resembles the epitope recognized by the antibody. Antibodies bound to the blocking peptide no longer bind to the epitope in the protein. Whatever bands that show up would then be due to non-specific binding. This mechanism is useful when non-specific binding is an issue, for example, in Western blotting (immunoblot) and immunohistochemistry (IHC)
Problem: Non-specific Binding
Non-specific binding is usually more prevalent with polyclonal antibodies, but can also occur with monoclonals. It is not rare to see more than one band when probing a Western blot (immunoblot) with a primary antibody. Comparing conditions in parallel: a lane probed with blocked antibodies and that with the functional antibody would distinguish between non-specific and specific bands. The same principle is applicable in immunohistochemistry (IHC).