Carrier Protein Conjugation
A standard peptide of 15-20 amino acids in length is too small to elicit an immune response on its own. As a result, it is necessary to conjugate the peptide to a larger carrier protein.
We have found that KLH (Keyhole Limpet Hemocyanin) is an ideal carrier protein for this application. Because it is phylogenetically distinct from mammalian species, and has a high molecular weight, it is highly immunogenic and capable of eliciting a strong immune response when immunized. Also, its structure and amino acid composition allow large quantities of the peptide to be coupled to a single KLH protein.
In terms of conjugating the peptide to the carrier protein, we have found that coupling via a single terminal cysteine residue on the peptide sequence offers an ideal conjugation chemistry and presentation of the peptide to the animal’s immune system. When possible, we try to avoid including a cysteine residue in peptide sequences that we recommend so that a cysteine can be added to the N or C terminal of the peptide sequence.
For peptide sequences that contain an internal cysteine, the peptide can be conjugated to the carrier protein using glutaraldahyde, which couples to the free amines in the peptide sequence.
While antibodies will be generated against the carrier protein in addition to the peptide sequence, affinity purification of the serum against the peptide sequence will allow for isolation of antibodies specific to the peptide sequence.