Co-IP Immunoprecipitation: Practical Walkthrough and Key Points

critical

No Target Protein or Insufficient Yield

Western blot shows no visible band for the target protein, or the band intensity is much weaker than expected, indicating little or no protein was eluted from the immunoprecipitation.

💡 7 · ✓ 8

severe

High Background with Nonspecific Bands

Western blot shows high background signal with multiple nonspecific bands, obscuring the target protein band and making interpretation difficult.

💡 6 · ✓ 6

severe

Bead-Antibody Isotype Incompatibility

No or very weak target protein signal despite using adequate antibody concentration, suggesting inefficient antibody capture by the beads due to isotype incompatibility.

💡 5 · ✓ 5

severe

Protein Complex Disruption in Co-IP

In co-immunoprecipitation experiments, expected interacting proteins are not detected on Western blot, suggesting protein-protein complexes were disrupted during sample handling.

💡 3 · ✓ 3

moderate

Accidental Bead Loss During Aspiration

Inconsistent or absent target protein signal across replicate samples, with visible reduction in bead pellet volume, indicating beads were aspirated during wash or supernatant removal steps.

💡 3 · ✓ 4