An epitope is a fragment of a larger molecule, usually a protein, that is recognized by the immune system. The recognition involves the binding of a protein (or peptide) from an antigen to a specific binding site on an antibody molecule. Epitopes on a protein can be linear or conformational and can be found anywhere within a protein.
Epitopes are often referred to as “antigenic determinants” since they are the specific parts of a protein or peptide that can be recognized by an immune response. These epitopes are important for the generation of antibodies, and can be found in any part of a protein.
In general, epitope recognition is a major factor in the success of a vaccine or therapeutic agent. This is because of the ability of an epitope to specifically bind to and activate an immune response. For example, small peptide sequences within a protein can be recognized by the immune system and targeted for destruction, or to trigger an immune response against the rest of the protein.
In addition, epitopes can be used to distinguish one form of a protein from another. This is possible because certain regions of the protein can be recognized by the immune system and distinguish the two forms, thus allowing the antibody to target the correct form.
In conclusion, the best definition of epitope would be a fragment of a larger molecule, usually a protein, that is recognized by the immune system. It is responsible for antibody generation as well as being important for distinguishing one form of a protein from another.