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Antigen Peptide
Peptide Coupling and Conjugation with KLH, BSA, OVA

Selleck provides antigen peptides with KLH, BSA, OVA conjugation used for antibody production against peptides. The use of peptides is often insufficient to elicit an immune response, however, carrier proteins containing epitopes can help to stimulate T-helper cells, which help induce B-cell response.

It is important to remember that the immune system reacts to the peptide-protein conjugate as a whole. As a result, there will always be a portion of antibodies bound to the peptide, linker, and carrier protein. Some of the most common carrier proteins include:

KLH (Keyhole Limpet Hemocyanin) is a copper containing, non-heme protein found in arthropods and molluscas. It is isolated from Megathura crenulata and has a MW of 4.5 x 105 ~ 1.3 x 107 Da. KLH is a commonly selected carrier due to its high immunogenicity compared to that of BSA.

BSA (Bovine Serum Albumin) is a plasma protein in cattle, belonging to the most stable and soluble albumins. It has a MW of 67 x 103 Da – containing 59 lysines. About 30-35 of these primary amines are accessible for linker conjugation, which makes BSA a popular carrier protein for weak antigenic compounds.

Often BSA is used in many experiments as a blocking buffer reagent. However, if the antisera against the peptide-BSA conjugates are used in such assays, false positives can occur since these sera can also contain antibodies to BSA.

OVA (Ovalbumin) is a protein isolated from the egg whites of hens and a MW of 45 x 103 Da. The use of OVA is a great choice as a second carrier protein to verify if antibodies are specific for the peptide alone and not for the carrier protein (e.g. BSA).

Thiol group modifications (via Cys side chain) are used for KLH, BSA or OVA conjugation.

All modifications carrying thiol-reactive functional groups can be employed and the most commonly used modifications include:
1. Iodoacetamides
2. Maleimides
3. Alkyl halides