Archives

  • 2026-04
  • 2026-03
  • 2026-02
  • 2026-01
  • 2025-12
  • 2025-11
  • 2025-10
  • 2025-09
  • 2025-03
  • 2025-02
  • 2025-01
  • 2024-12
  • 2024-11
  • 2024-10
  • 2024-09
  • 2024-08
  • 2024-07
  • 2024-06
  • 2024-05
  • 2024-04
  • 2024-03
  • 2024-02
  • 2024-01
  • 2023-12
  • 2023-11
  • 2023-10
  • 2023-09
  • 2023-08
  • 2023-06
  • 2023-05
  • 2023-04
  • 2023-03
  • 2023-02
  • 2023-01
  • 2022-12
  • 2022-11
  • 2022-10
  • 2022-09
  • 2022-08
  • 2022-07
  • 2022-06
  • 2022-05
  • 2022-04
  • 2022-03
  • 2022-02
  • 2022-01
  • 2021-12
  • 2021-11
  • 2021-10
  • 2021-09
  • 2021-08
  • 2021-07
  • 2021-06
  • 2021-05
  • 2021-04
  • 2021-03
  • 2021-02
  • 2021-01
  • 2020-12
  • 2020-11
  • 2020-10
  • 2020-09
  • 2020-08
  • 2020-07
  • 2020-06
  • 2020-05
  • 2020-04
  • 2020-03
  • 2020-02
  • 2020-01
  • 2019-12
  • 2019-11
  • 2019-10
  • 2019-09
  • 2019-08
  • 2019-07
  • 2019-06
  • 2019-05
  • 2019-04
  • 2018-11
  • 2018-10
  • 2018-07

    • FLAG tag Peptide (DYKDDDDK): High-Purity Epitope Tag for ...

    2025-11-05

    FLAG tag Peptide (DYKDDDDK): High-Purity Epitope Tag for Recombinant Protein Purification

    Executive Summary. The FLAG tag Peptide (DYKDDDDK) is an 8-amino acid epitope tag widely used for the purification and detection of recombinant proteins in various expression systems. Its sequence encodes an enterokinase cleavage site, enabling gentle elution from anti-FLAG M1 and M2 affinity resins (A6002 technical data). The peptide exhibits high solubility: >210.6 mg/mL in water and >50.65 mg/mL in DMSO, supporting broad compatibility with biochemical workflows (A6002). High purity (>96.9%) is confirmed by HPLC and mass spectrometry. The FLAG tag Peptide is not suitable for eluting 3X FLAG-tagged fusion proteins; specialized peptides are required in such cases (A6002). These properties establish the FLAG tag as a standard for specific, reversible protein affinity capture (ter Beek et al., 2019).

    Biological Rationale

    The FLAG tag Peptide (DYKDDDDK) is engineered as an epitope tag to enable affinity-based purification and detection of recombinant proteins. It is composed of eight amino acids (Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys). The sequence is not commonly found in native eukaryotic or prokaryotic proteins, ensuring high specificity for anti-FLAG antibodies (A6002). Its small size minimizes structural disruption when fused to target proteins (related review). The embedded enterokinase site (DDDDK) permits controlled enzymatic cleavage and release of the tagged protein. FLAG tagging is a non-immunogenic, non-toxic approach, compatible with bacterial, yeast, insect, and mammalian expression systems. The tag’s negative charge (at neutral pH) improves solubility and accessibility on protein surfaces, facilitating efficient antibody binding and elution.

    Mechanism of Action of FLAG tag Peptide (DYKDDDDK)

    The FLAG tag Peptide works by providing a unique, surface-exposed epitope recognized by high-affinity monoclonal antibodies (M1, M2, or M5). When a recombinant protein is engineered with the FLAG tag at its N- or C-terminus, anti-FLAG affinity resin can selectively capture the fusion protein from complex lysates. The tag’s DYKDDDDK sequence includes a consensus enterokinase cleavage motif (DDDDK), allowing release of the fusion protein by enzymatic treatment or competitive elution with synthetic FLAG peptide. This mechanism enables purification under mild conditions, preserving protein function and structure (protocol guide). FLAG tag-based detection is compatible with Western blotting, immunoprecipitation, ELISA, and immunofluorescence assays.

    Evidence & Benchmarks

    • FLAG tag Peptide (DYKDDDDK) enables high-purity protein recovery (>95%) when eluted from anti-FLAG M2 resin under native conditions (A6002 datasheet).
    • The solubility of the peptide is >210.6 mg/mL in water, 50.65 mg/mL in DMSO, and 34.03 mg/mL in ethanol, supporting diverse buffer usage (A6002).
    • Mass spectrometry and HPLC confirm >96.9% purity of the synthetic peptide, ensuring minimal contaminants in sensitive workflows (A6002).
    • Epitope tagging with DYKDDDDK does not interfere with the activity of DNA polymerase ε catalytic domain, as shown by functional complementation assays in yeast (ter Beek et al., 2019).
    • Anti-FLAG M2 antibody affinity is unaffected by the position (N or C terminus) of the FLAG tag (ter Beek et al., 2019).
    • The peptide does not elute 3X FLAG fusion proteins; a 3X FLAG peptide is required for displacement in these contexts (A6002).

    Applications, Limits & Misconceptions

    The FLAG tag Peptide (DYKDDDDK) is used in:

    • Affinity purification of recombinant proteins from cell lysates.
    • Detection in Western blotting, immunoprecipitation, and ELISA.
    • Quantitative pull-down assays for protein-protein or protein-nucleic acid interaction studies.
    • Engineering fusion constructs for structural and biochemical analysis.

    Its high solubility and synthetic purity minimize aggregation or interference in downstream assays. The standardized sequence and commercial availability (e.g., A6002 kit) support reproducibility across laboratories. Recent comparative analyses indicate the FLAG tag's specificity and elution gentleness often outperform larger or more hydrophobic tags (contrast: mechanistic review). This article extends these insights by detailing quantitative solubility and purity metrics, as well as storage and workflow caveats.

    Common Pitfalls or Misconceptions

    • The FLAG tag Peptide (DYKDDDDK) does not effectively elute 3X FLAG-tagged proteins; a 3X FLAG peptide is required (A6002).
    • The peptide should not be stored in solution long-term; use solid storage at -20°C for stability (A6002).
    • Excess peptide in elution buffers may interfere with downstream mass spectrometry if not removed.
    • Not all anti-FLAG antibodies recognize internal FLAG tags; position-dependent effects may occur with some antibody clones.
    • The enterokinase cleavage site is functional only if accessible; buried tags may not be cleaved efficiently.

    Workflow Integration & Parameters

    The recommended working concentration for FLAG tag Peptide (DYKDDDDK) in elution buffers is 100 μg/mL (A6002). For optimal solubility, dissolve in water or DMSO immediately before use. Store the lyophilized peptide desiccated at -20°C. Peptide solutions should be prepared fresh for each use; avoid repeated freeze-thaw cycles (detailed storage insights). For affinity purification, incubate lysate with anti-FLAG resin, wash under native or denaturing conditions, and elute with peptide or enterokinase as appropriate. The peptide is compatible with most common buffer systems (e.g., Tris, PBS, HEPES) and maintains stability over short-term use. Shipping is performed on blue ice to preserve peptide integrity.

    This article extends previous discussions (biochemical basis) by providing quantitative storage, solubility, and purity parameters critical for reproducible protein science workflows.

    Conclusion & Outlook

    The FLAG tag Peptide (DYKDDDDK) remains a gold standard for recombinant protein purification and detection. Its unique combination of small size, high solubility, and sequence-specific antibody recognition underpins its widespread adoption. The product’s robust manufacturing and QC pipeline (HPLC/mass spectrometry verified purity) ensure minimal batch variability (A6002). Researchers should heed boundaries such as incompatibility with 3X FLAG systems and solution storage limitations. As protein science advances, the modular, reversible nature of FLAG tagging continues to empower new applications in proteomics, structural biology, and synthetic biology (ter Beek et al., 2019).