Epitope tagging is a technique that employs genetic engineering to fuse a known epitope, called an affinity tag, to either the C or N terminus of a recombinant protein to facilitate affinity purification and detection. This approach enables high selective capture and circumvents the multistep purification processes that limit throughput during R&D.

The ideal affinity tag should be small in size and as inert as possible to limit any potential interaction with the recombinant protein or proteins that might be present in culture media.

CaptureSelect C-tagXL affinity tag system

CaptureSelect C-tagXL is a novel affinity tag system offering unique selectivity for a small four amino acid peptide tag: E-P-E-A (glutamic acid–proline–glutamic acid–alanine), which enables simple purification of C-tagged proteins.

C-tag benefits

  • Smallest affinity tag available comprised of four residues: E-P-E-A
  • Limited effect on protein functionality unlike larger tags (GST, HIS6)
  • High selectivity and binding affinity for recombinant protein purification
  • Enabling high target yield and purity from complex mixtures (compared to HIS6-tag)

CaptureSelect C-tagXL resin

  • High binding affinity when E-P-E-A tag displayed at C-terminus of protein
  • Binding under both physiological and denaturing conditions (up to 8 M urea)
  • Crude feed stock can be applied
  • Mild elution, protecting the protein of interest
  • Robust and reusable affinity matrix
CaptureSelect C-tagXL Affinity MatrixUnique selectivity for a small four amino acid peptide tag (E-P-E-A). Purifies C-terminal tagged proteins with high affinity and selectivity from complex mixtures like cell culture harvests and periplasmatic fractions in a one-step process.
CaptureSelect C-tagXL Affinity Matrix (pre-packed)
1 mL and 5 mL columns pre-packed with the CaptureSelect C-tagXL affinity matrix
CaptureSelect Biotin Anti-C-tag ConjugateBinds the short C-tag sequence E-P-E-A when this affinity tag is fused at the C-terminus of a target protein and facilitates easy detection of C-tagged proteins using techniques such as Western Blot, ELISA, and label free detection platforms.

Purification of a C-tagged protein


Figure 1. Purification of His–EPEA tagged protein from E.coli periplasmic fraction: C-tag outperforming two different Ni-NTA resins

M. Molecular weight marker
1. Starting material (His-EPEA tagged protein)
2. Flow through fraction
3. Wash fraction
4. Elution fraction


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