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 Novel Affinity Tag System

CaptureSelect C-tag/C-tagXL is a novel affinity tag system offering unique selectivity for a small 4 amino acid peptide tag: E-P-E-A (glutamic acid - proline - glutamic acid - alanine), which enables simple purification of C-tagged proteins.

CaptureSelect C-tag Resin

  • Smallest affinity tag available: 4 residues: E-P-E-A
  • High binding affinity when E-P-E-A tag displayed at C-terminus of protein
  • High selectivity for recombinant protein purification
  • Binding under both physiological and denaturing conditions (up to 8 M urea)
  • Crude feed stock can be applied
  • A variety of mild elution buffers can be used to elute the product
  • Robust and reusable affinity matrix
  • Biotin anti-C-tag conjugate available for detection purposes (ELISA, western)
Product Characteristics
CaptureSelect C-tagXL Affinity Matrix Improved version of CaptureSelect C-tag Affinity Matrix, which features a significant increased binding capacity and better scalable base matrix. The specificity, and the binding and elution conditions did not change.
CaptureSelect C-tagXL Affinity Matrix (pre-packed)
1 mL and 5mL columns pre-packed with the CaptureSelect C-tagXL affinity matrix

CaptureSelect C-tag Affinity Matrix

Binds the short C-tag sequence E-P-E-A (glutamic acid - proline - glutamic acid – alanine) when this affinity tag is fused at the C-terminus of a target protein
CaptureSelect C-tag Affinity Matrix (pre-packed) 1 mL columns pre-packed with the CaptureSelect C-tag affinity matrix
CaptureSelect Biotin Anti-C-tag Conjugate Binds the short C-tag sequence E-P-E-A (glutamic acid - proline - glutamic acid – alanine) when this affinity tag is fused at the C-terminus of a target protein
CaptureSelect C-tagXL Ligand Leakage ELISA Kit

Complements the CaptureSelect C-tagXL affinity matrix


Figure 1. GFP-EPEA purification with >90% recovery. Samples from E. coli-derived feed stocks were applied batch-wise to spin columns (400 µL crude sample with 100 µL CaptureSelect C-tag Affinity Matrix). Elution: 20 mM Tris, 2 M MgCl2, pH 7. Regeneration/strip: 0.1 M glycine, pH 2.

This shows a green fluorescent protein (GFP) containing a GYQDY-EPEA C-terminal tag purified using CaptureSelect C-tag affinity matrix from an E. coli cytoplasmatic fraction. Protein gel analysis of the elution clearly illustrates the recovery of the GFP, as indicated by the green fluorescent signal present in the elution fraction.


Additional reading

Application note

Reinventing Affinity Tags


Accelerating the clinical development of protein-based vaccines for malaria by efficient purification using a four amino acid C-terminal ‘C-tag’

The Biotechnological Applications of Recombinant Single-Domain Antibodies are Optimized by the C-Terminal Fusion to the EPEA Sequence (C Tag)

Discovery of C-tag: Structure and properties of a complex of α-synuclein and a single-domain camelid antibody


Anti-C-tag affinity ligand

In addition to the CaptureSelect C-tag affinity resin, the anti-C-tag affinity ligand is also available as conjugated ligand (conjugated to Biotin). This facilitates easy detection and or quantitation of EPEA C-tagged proteins using techniques such as ELISA, Western blot, and label-free platforms (Biacore™ and Octet®).