Antibodies — also referred to as immunoglobulins — represent one of the most powerful tools available for life science researchers. Experimentalists want an antibody that is both specific to their target of interest and sensitive enough for their desired detection method. Balancing these factors is a key consideration during the research and development process for new products.
Synthetic Peptide Sequences for Antibody Production
The Bioss catalog of antibodies includes both polyclonal and monoclonal antibodies. By their nature, polyclonal antibodies are mixtures of serum immunoglobulins, which collectively are likely to bind to multiple epitopes on an antigen. Conversely, monoclonal antibodies constitute a single antibody clone with specific binding to an individual epitope. Bioss employs a proprietary synthesis technique to manufacture small peptides sequences of 10-15 residues, contributing to more monospecific targeting. (Longer peptides can undergo secondary structure alterations that can affect antibody specificity.)
The use of synthetic peptide antigens in antibody production was first described in the late 1970s and has become a standard practice for many laboratories and manufacturers. Small peptides allow for a more specific binding interaction by reducing the number of targets recognized. By themselves, the peptides — referred to as haptens when employed as an antigen — are too small to be immunogenic and therefore must be conjugated to a carrier protein to induce an immune response and produce antibodies. We use keyhole limpet hemocyanin (KLH) as a carrier protein. Because KLH is large and complex, it exhibits high immunogenicity. KLH also provides an ample amount of surface lysine residues, which have reactive amine side chains that are perfect for peptide linkage. KLH is isolated from keyhole limpets (Megathura crenulata) making it evolutionarily distant from vertebrates, where no homologous proteins are found. This means that antibodies produced against the carrier-peptide complex will have little if any cross-reactivity to endogenous proteins in vertebrate samples.
Advantage of Peptide Antigens vs. Native Protein
Peptide antigens provide many advantages over full length or native protein antigens. Firstly, they afford complete control over the immunogen sequence, also known as the epitope — the specific site on an antigen to which an antibody binds. Because of this versatility, we can target specific protein sites of interest, such as unique or highly conserved regions, active sites, extracellular or intracellular domains, and regions of posttranslational modification (e.g., phosphorylation sites). Additionally, this production method allows for the discrimination between alternatively spliced isoforms and the identification of target protein localization on a subcellular scale. Peptide antigens also allow for the production of antibodies against target proteins that are difficult to isolate and purify or that are putative and only defined by a gene sequence.
For an antibody to work in multiple applications, it must be able to interact with the target protein in different conformations. In Western blots, for instance, the target protein is denatured and linearized, so the antibody can recognize internalized and transmembrane regions. However, in flow cytometry, the target is in its natural, folded form, so the antibody must recognize a surface segment. Whenever possible, we elect to design peptides that correspond with surface segments of the native protein, and we test and note the validated applications on each product page.
If researchers require further details about the immunogen sequence or cross-reactivity, they are asked to email firstname.lastname@example.org for more information.