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    • Influenza Hemagglutinin (HA) Peptide: High-Purity Epitope...

    2026-03-30

    Influenza Hemagglutinin (HA) Peptide: High-Purity Epitope Tag for Protein Detection and Purification

    Executive Summary: The Influenza Hemagglutinin (HA) Peptide is a synthetic nine-amino acid sequence (YPYDVPDYA) derived from the human influenza virus hemagglutinin protein, used as an epitope tag in molecular biology and biochemistry (APExBIO). It competitively binds anti-HA antibodies, enabling precise elution of HA-tagged fusion proteins in immunoprecipitation assays (Wei et al., 2021). The peptide is highly soluble in DMSO (≥55.1 mg/mL), ethanol (≥100.4 mg/mL), and water (≥46.2 mg/mL), and supplied at >98% purity (HPLC, MS verified). Recommended storage is desiccated at -20°C to preserve activity. HA peptide tagging is integral for protein interaction studies, competitive elution, and advanced workflows in molecular biology (Vatalis 2023).

    Biological Rationale

    The HA tag peptide is derived from the influenza virus hemagglutinin protein, a surface glycoprotein involved in viral entry and immune recognition (Wei et al., 2021). Its nine-residue sequence (YPYDVPDYA) was selected for strong, specific recognition by anti-HA monoclonal antibodies. This selectivity enables unambiguous tagging of recombinant proteins, facilitating downstream detection, purification, and protein-protein interaction studies. HA peptide tagging is non-immunogenic in most experimental systems and does not significantly alter protein structure or function. The tag's compact size (1.1 kDa) minimizes steric hindrance and is compatible with both N- and C-terminal protein fusions. HA epitope tags have become a standard in molecular biology due to their robust antibody recognition and ease of use (Cy5-5 NHS Ester 2022).

    Mechanism of Action of Influenza Hemagglutinin (HA) Peptide

    The Influenza Hemagglutinin (HA) Peptide functions as an epitope tag by mimicking a conserved region of the influenza virus hemagglutinin protein. When fused to a protein of interest, the peptide sequence is recognized with high affinity by anti-HA antibodies, enabling selective detection or capture of the fusion protein. In immunoprecipitation assays, free HA peptide (e.g., from APExBIO, SKU A6004) is used as a competitive elution reagent. When added to an antibody-bound complex, it displaces HA-tagged proteins from anti-HA beads through competitive binding, enabling gentle and specific protein recovery (AP24534 2023). This mechanism preserves protein-protein interactions and conformational integrity better than harsh elution buffers. The peptide's high solubility in standard solvents (DMSO, ethanol, water) ensures compatibility with a range of assay conditions.

    Evidence & Benchmarks

    • HA peptide (YPYDVPDYA) enables specific immunoprecipitation of HA-tagged fusion proteins with minimal background (Wei et al., 2021).
    • Competitive elution with synthetic HA peptide preserves native protein complexes in immunoprecipitation (IP) assays, outperforming acidic or denaturing elution buffers (AP24534 2023).
    • HA peptide is soluble at ≥55.1 mg/mL in DMSO, ≥100.4 mg/mL in ethanol, and ≥46.2 mg/mL in water, supporting a wide range of experimental protocols (APExBIO).
    • HPLC and mass spectrometry confirm >98% purity for APExBIO Influenza Hemagglutinin (HA) Peptide (SKU A6004), ensuring reproducibility and low contaminant risk (APExBIO).
    • HA tag does not disrupt protein folding or localization in eukaryotic systems when fused to N- or C-termini (GTP Binding Protein Fragment 2022).
    • The tag supports robust detection by Western blot, immunofluorescence, and immunoprecipitation in diverse cell lines (EpitopePeptide 2023).

    Applications, Limits & Misconceptions

    Influenza Hemagglutinin (HA) Peptide is integral to workflows involving protein tagging, immunoprecipitation, and protein-protein interaction studies. Its major applications include:

    • Tagging recombinant proteins for detection and quantification via anti-HA antibodies.
    • Competitive elution of HA-tagged proteins from anti-HA magnetic beads or agarose (see A6004 kit).
    • Mapping protein-protein interactions in native complexes.
    • Analyzing post-translational modifications using epitope-tagged constructs.

    Key limitations and boundaries include:

    • Not suitable for denaturing conditions that disrupt antibody-epitope binding.
    • May not be recognized in certain rare mutant backgrounds or with altered tag conformation.
    • Not recommended for use in long-term solution storage; reconstituted peptide should be used promptly or aliquoted and stored at -20°C.

    For advanced benchmarking and troubleshooting, this article extends the findings of "Influenza Hemagglutinin (HA) Peptide: Advanced Tag for Ub..." by providing updated protocol parameters and purity metrics for reproducible IP workflows.

    Common Pitfalls or Misconceptions

    • Myth: HA peptide can be used in all pH and buffer conditions. Fact: Strongly acidic or basic buffers may disrupt antibody-epitope binding and reduce IP efficiency.
    • Myth: All anti-HA antibodies have identical affinity. Fact: Monoclonal antibody clones can vary in affinity and specificity, affecting assay performance.
    • Myth: HA tag always preserves protein function. Fact: In rare cases, tag placement can interfere with protein folding or activity; empirical validation is required.
    • Myth: Peptide solutions are indefinitely stable. Fact: Repeated freeze-thaw cycles and long-term storage in solution can degrade activity; store desiccated at -20°C.
    • Myth: HA peptide is immunogenic in all systems. Fact: HA tag is generally non-immunogenic in non-murine models.

    Workflow Integration & Parameters

    The HA peptide is seamlessly integrated into standard molecular biology protocols for tagging, detection, and purification. For immunoprecipitation:

    1. Express the HA-tagged fusion protein in the target cell line.
    2. Lysate is incubated with anti-HA magnetic beads or agarose under native conditions.
    3. After washing, elute the protein complex using synthetic HA peptide at 0.1–1 mg/mL in neutral buffer (e.g., PBS, pH 7.4).
    4. Eluate is immediately analyzed by SDS-PAGE, Western blot, or mass spectrometry.

    For optimal results, prepare fresh peptide solutions or store aliquots at -20°C desiccated. Do not subject to repeated freeze-thaw cycles. The peptide’s high purity and solubility ensure compatibility with advanced proteomic and interactome studies (Cy5-5 NHS Ester 2022).

    This article clarifies and updates the troubleshooting guidance and strategic integration described in "Influenza Hemagglutinin (HA) Peptide: Precision Epitope T..." by providing current solubility parameters and explicit storage best practices for the APExBIO product.

    Conclusion & Outlook

    The Influenza Hemagglutinin (HA) Peptide (APExBIO, SKU A6004) is a validated, high-purity, and highly soluble epitope tag, enabling precise detection and purification of HA-tagged proteins in molecular biology. Its robust performance across immunoprecipitation, protein-protein interaction studies, and advanced biochemical workflows is supported by rigorous benchmarks and peer-reviewed evidence. Ongoing advancements in tag design and antibody engineering promise even broader applications for this versatile reagent. For detailed protocols and product specifications, refer to the APExBIO Influenza Hemagglutinin (HA) Peptide product page.

    For further exploration of advanced strategies in protein complex analysis and exosome pathway studies, see "Influenza Hemagglutinin (HA) Peptide: Advanced Strategies..."—this article extends those insights with the latest solubility and purity data for the HA tag peptide.