What to Do After Protein Purification? These Four Validation Methods You Must Know!-Antibody Detection Service Topic-Tekbiotech-Yeast and Phage Display CRO, Expert in Nano-body and Antibody Drug Development

What to Do After Protein Purification? These Four Validation Methods You Must Know!

Recalling our previous discussions on prokaryotic expression systems for recombinant proteins and commonly used protein expression tags, a new question arises: after successful protein purification, what can these precious proteins be used for?

1. Western Blot (WB)

This is the first step and the one most easily overlooked. It helps you confirm whether the purified protein is indeed your target protein, preventing wasted effort. Briefly, proteins are separated by gel electrophoresis, then electro-transferred onto a membrane. Specific binding of an antibody to the target protein is used for colorimetric detection to verify the identity of the target protein.

Steps:Sample Preparation (boil sample in loading buffer) → Electrophoresis (SDS-PAGE to separate proteins) → Transfer (to PVDF or nitrocellulose membrane) → Blocking (with 5% BSA or non-fat milk for 1 hour at room temperature or overnight at 4°C) → Primary Antibody Incubation (overnight incubation at 4°C saves antibody) → Secondary Antibody Incubation → Development (protect from light)

2. Co-Immunoprecipitation (Co-IP)

To determine whether two proteins interact in vivo, Co-IP is your method of choice. In essence, this technique utilizes the specific binding of antigens and antibodies. Antibodies immobilized on beads can pull down the target antigen along with any interacting proteins.

Steps:Pre-clearing (lysate + beads to remove non-specific binders) → Incubation with IP-grade primary antibody (add primary antibody to lysate, incubate overnight at 4°C) → Capture Complex (beads bind to the Fc region of the antibody) → Elution (Antibody A + Protein X + Protein Y) → WB Validation (Co-IP products must be analyzed by WB to confirm the presence of interacting proteins)

3. Chromatin Immunoprecipitation (ChIP)

ChIP is similar in principle to Co-IP, but the subject of study is the interaction between DNA and proteins. It involves crosslinking intracellular DNA-binding proteins with formaldehyde, shearing the DNA, and then using an antibody to enrich the target protein along with the DNA fragments bound to it.

Steps:Crosslinking (fix with formaldehyde) → Sonication (shear DNA into fragments of 200-1000 bp) → Immunoprecipitation (add antibody and beads) → Reverse Crosslinking (heat at 65°C to release DNA) → DNA Purification → PCR Analysis

4. Pull-Down Assay

If you have both Protein A and Protein B and want to know if they interact directly, without any intermediary, choose the pull-down assay. In a nutshell, a tagged protein A (e.g., GST, His) is immobilized on affinity beads, then incubated with Protein B or a cell lysate containing the potential prey protein to directly determine if they interact.

Steps (using GST as an example):Purify Proteins (GST tag and GST-fusion protein) → Incubate with Glutathione Beads → Incubate with Cell Lysate (containing prey protein) → Elution → WB Validation

Reliable experimental results are never obtained from a single technique alone. The following table can help you quickly make decisions. In practice, multiple validation methods are typically combined. For example, interacting proteins identified by Co-IP often still require validation by Western Blot.

TekBiotech has established a comprehensive protein expression and purification platform. We are dedicated to providing high-quality protein expression and purification development services to scientists worldwide, including one-stop solutions such as expression system selection (E. coli, yeast, insect, or mammalian cells), vector construction and design, expression condition optimization, downstream purification, and quality validation. Aligned with the evolving needs of life sciences, we develop innovative biological tools and therapeutic proteins, providing robust support for our clients' research projects.

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