AbFlex^® Recombinant Antibodies

AbFlex^® antibodies are recombinant antibodies (rAbs) that have been generated using defined DNA sequences to produce highly specific, reproducible antibodies. The unique advantages of the AbFlex^® antibody are its flexible labeling and purification options. Each AbFlex^® antibody contains a sortase recognition motif (LPXTG) to covalently add fluorophores, enzymatic substrates (HRP, AP...etc), peptides, DNA, drugs or other labels to the antibody in a directed and reproducible manner using our Sortag-IT™ Labeling Kits. Every antibody also contains a 6xHis Tag, which can be used with nickel-based purification systems, and a Biotinylation Tag sequence for enzymatic biotin conjugation using the biotin ligase, BirA.

Figure 1. (A) Schematic of the AbFlex Recombinant Antibody design. (B) Reaction scheme for antibody conjugation with the Sortase A5 enzyme. (C) Labels available for use with the Sortag-IT labeling system.

AbFlex^® antibodies are specifically labeled at the end of the constant region of the heavy chain to avoid interference with antigen recognition and functionality. This is important as it ensures the labeling process maintains the integrity of the antibody so signal is not diminished as a result of non-functional antibodies. In contrast, commonly used chemical labeling methods add labels to the antibody in a random fashion. The randomness of this process has a high potential to block the antigen-binding site and render the antibody ineffective. Chemical labeling can also deposit labels on the Fc region of the antibody which has the potential to obstruct interactions with protein A.

Differences in label distribution between AbFlex^® direct labeling and chemical labeling.

Prior to the development of recombinant antibodies, researchers relied on polyclonal and monoclonal antibodies. Polyclonal antibodies recognize multiple epitopes on the same antigen. This increases antibody affinity, but often has a higher potential for cross-reactivity. Monoclonal antibodies represent a single antibody producing B cell that binds to one unique epitope. However, monoclonal antibodies can be lost or evolve over time.

Unlike monoclonal antibodies, which can experience gene loss, mutations and cell-line drift that alter antibody performance over time and lead to variability across antibody lots, recombinant antibodies are highly consistent because they contain the same immunoglobulin heavy and light chain DNA sequences in every lot. This provides batch-to-batch reproducibility in antibody performance and eliminates the need to re-evaluate or compare different antibody lots, thereby, saving valuable time and effort on assay development.

To ensure optimal performance, each AbFlex^® antibody is carefully screened for specificity and sensitivity. Only heavy and light chain sequences that produce highly specific antibodies, as verified in our bead-based binding assay, are selected. Antibodies that utilize the AbFlex^® direct labeling approach also show greater sensitivity than their parent monoclonal antibodies across a variety of applications.

Another advantage of AbFlex^® recombinant antibodies is the fact that they are produced outside of an animal system. Polyclonal antibodies rely on an animal’s immune response and epitope specificity, both of which are highly variable across animals and immunizations. Polyclonal antibodies are also hindered by having a finite supply, making it difficult to perform long-term antibody projects or reproduce data over time or across labs. With AbFlex^® recombinant antibodies, the full-length IgG is expressed in a mammalian system to ensure a consistent, stable antibody supply. Additionally, any ethical or animal welfare concerns associated with antibody production and maintenance are avoided.

The following list contains Active Motif's AbFlex^® recombinant antibodies (rAbs). For information about site-specific labeling of the AbFlex^® antibodies, please visit our collection of Sortag-IT™ Labeling Kits.