Peptides and Conjugates
Antigens are also obtained by synthesizing peptides and conjugating these peptides to carrier proteins. Protein sequence analysis to determine immunogenic regions of the protein is completed and peptides corresponding to these immunogenic regions are synthesized.
The following are the key points to consider for preparing peptide antigens:
- Protein sequence: Specificity, hydrophobicity, hydrophility, contents of amino acid residue, potential tertiary structure, and overall immunogenicity are the main aspects to consider.
- Length of peptide: The minimal length for peptide antigen is 6 amino acids. Usually the peptide is designed as 15-18 mer. Longer peptides may have stronger immunogenicity and specificity.
- Residual modification: To match the post-translational modification feature of the target protein, chemically modified residuals can be used as raw material of peptide synthesis. Phospho-peptide is one of the commonly used modified peptides.
- Purity of peptide: For better downstream conjugation and more immunization effectiveness, high peptide purity is needed.
- Cost-effectiveness: It is a factor for large scale, long and complicated peptide synthesis.
- Batch to batch consistency: It is a matter of operational procedure and quality control.
To generate antibodies to a peptide, the peptide must be covalently conjugated to a carrier protein prior to immunization. Molecules smaller than 12 kDa may not elicit an immune response, and so in order to generate an immune response to small molecules, also known as haptens, conjugation to larger carrier proteins is performed. To make immunogens, GenWay conjugates haptens to a carrier protein such as the large protein KLH (Keyhole Limpet Hemocyanin). KLH is useful as a carrier protein as compared to others such as BSA (Bovine Serum Albumin) because there is no reactivity with ELISA or Western Blot blocking reagents.
For other types of antigens, please visit the pages: