Read the accessible HTML protocol
ABMIUM laboratory protocol
A complete immunoprecipitation workflow covering lysate preparation, antibody binding, immune-complex capture, washing, elution, controls and troubleshooting.
Application overview | Download linked PDF | Browse research antibodies | Ask technical support
Introduction
Immunoprecipitation (IP) is a widely used biochemical technique for the selective isolation and removal of enrichment of a target protein from complex biological samples using antigen-antibody interactions. The method enables downstream applications such as Western blotting, mass spectrometry, and functional assays. Variants of IP, including co-immunoprecipitation (co-IP), are particularly valuable for studying protein-protein interactions under native or near-physiological conditions.
Principle
Immunoprecipitation is based on the specific binding between an antibody and its antigen. The antibody - antigen complex is captured using Protein A/G-conjugated beads, which bind to the Fc region of antibodies. Following binding, the immune complexes are separated from the lysate by centrifugation, washed to remove non-specifically bound proteins, and eluted for further analysis.
Source: Principle of Immunoprecipitation | BioRender Science Templates
Materials Required
Equipment
Refrigerated centrifuge
Microcentrifuge tubes (1.5 - 2 mL)
Rotary mixer/rotator
Pipettes and sterile tips
Ice bucket
Mortar and pestle (for tissue samples)
Liquid nitrogen container
Heating block or water bath (for SDS elution)
Reagents Required
Lysis buffer (e.g., NP-40, Triton X-100, or RIPA buffer)
Protease inhibitor cocktail
Phosphate-buffered saline (PBS)
Wash buffer (e.g., PBS with 0.1% Tween-20 or lysis buffer with adjusted salt concentration)
Protein A/G Sepharose beads
Target-specific primary antibody
Control IgG antibody
SDS-PAGE loading buffer (2X)
Glycine buffer (100 mM, pH 2.5 - 3.0)
Tris-HCl (1 M, pH 8.5 for neutralization)
Sample preparation
Cell Extracts
Adherent cells:
Remove media and wash cells with PBS.
Place the culture plate on ice, add a cold lysis buffer supplemented with protease inhibitor cocktail and keep the plate on ice for 1 - 2 min.
Scrape the cells and gently transfer the disrupted cell suspension into a chilled microcentrifuge tube.
Mix on a rotary mixer for 30 min at 4°C.
Centrifuge at 10,000 × g for 10 minutes at 4°C and transfer the cell extract to chilled fresh tubes.
Suspension Cells:
Collect cells by centrifugation (500×g for 5 min), Wash the cells with cold PBS and collect cells again by centrifugation.
Drain the PBS carefully, add a cold lysis buffer and keep the cells on ice for 1-2 minutes.
Repeat steps 4 - 5
Tissue Extracts
Snap freeze the dissected tissue and immediately grind it into a fine powder using a mortar and pestle in a liquid nitrogen bath.
Transfer the ground tissue to a pre-weighed chilled tube. Weigh the powder and store at −80 °C until use
Add 300 µL lysis buffer supplemented with protease inhibitor cocktail per 5 mg tissue powder. Mix on a rocker at 4 °C for about an hour.
Pass the lysate through a 25 gauge needle 3 times.
Collect the lysate and centrifuge at high speed (10,000 x g) for 5 minutes at 4˚C to remove cell debris.
Transfer the tissue extract (supernatant) to a fresh tube.
Determine protein concentration using a BCA or Bradford assay.
Adjust all samples to the same protein concentration using a lysis buffer.
(Optional but recommended) Pre-clearing
This step reduces non-specific binding.
Add 20 - 30 µL Protein A/G beads to lysate.
Incubate for 30-60 minutes at 4°C with rotation.
Centrifuge (2,000 X g, 2 min) and transfer supernatant to a new tube.
Antibody Binding
Add 1 - 5 µg antibody per 500 - 1000 µg total protein (as recommended by the antibody vendor or as determined by user titration) against the target to a known amount (µg) of sample (standardized by the user).
Make up the volume to 500 µL with a lysis buffer containing protease inhibitor cocktail I.
Gently mix for 3 - 4 hours or overnight at 4°C on a rotary mixer.
Preparation of Protein A/G Beads
Wash the Protein A/G Sepharose beads (25 - 40 µL/reaction) twice with 1 mL Wash Buffer, centrifuging at 2000 x g for 2 minutes and aspirating the supernatant in between washes.
Note: 25 µL Protein A/G Sepharose Beads I can bind over 500 µg IgG.
Suspend as 50% slurry in a 1× wash buffer.
Bead Capture
After antibody binding, add 25-40 µL of Protein A/G Sepharose Beads I slurry to each tube and gently mix for 1 hour at 4°C on a rotary mixer.
Collect the Protein A/G Sepharose Beads by low-speed centrifugation at 4°C (e.g., 2000 x g for 2 minutes).
Wash Protein A/G Sepharose Beads I beads 3 times with 1 mL 1× wash buffer, collecting the Protein A/G Sepharose Beads I by low-speed centrifugation at 4°C and aspirating the supernatant in between washes.
After the last wash, remove as much of the 1× wash buffer as possible, making sure that the beads never dry completely.
Elution
Functional Assay
The beads with the antigen-antibody (Ag-Ab) complex may be used directly for an activity assay provided the antibody does not block the active site of the protein being assayed.
SDS Buffer (denaturing) elution:
To elute the complex, add 40 µL 2X SDS-PAGE loading buffer to the beads and boil for 5 min.
Centrifuge to collect eluent. Eluent can be stored on ice for same day analysis or frozen at -80˚C for future SDS-PAGE analysis.
Low-pH (non-denaturing) elution:
Add 40 µL low pH glycine buffer (100 mM glycine/HCl, pH 2.5 - 3.0, not provided) and incubate for 10 min at room temperature with agitation.
Centrifuge to collect the eluent. Perform an additional elution as needed. Add 1/10th the volume of 1M Tris-HCl pH 8.5 (not provided) to the eluent to neutralize the pH and store the eluent at -80°C until use.
This buffer disrupts most protein - protein and antigen - antibody interactions while partially preserving protein structure.Some antibodies and proteins may be damaged by low pH.
The affinity purified protein may be used for an activity assay.
Limitations
Requires high-quality, specific antibodies
Weak or transient interactions may be lost
Non-specific binding can increase background
Epitope masking may prevent binding
Denaturing conditions prevent functional assays
Antibody heavy/light chains may interfere in detection
Troubleshoot
Closing Statement:
Immunoprecipitation is an important technique for isolating and enriching specific proteins from complex biological samples for downstream applications such as Western blotting, mass spectrometry, and functional assays. The effectiveness of the method depends on proper sample preparation, high-quality antibodies, optimized binding and washing conditions, and careful handling to preserve protein integrity while minimizing non-specific interactions. When performed under appropriate conditions, immunoprecipitation provides reliable and reproducible results for studying protein expression, protein - protein interactions, and functional characteristics in molecular and cellular research.
Problem
Possible Cause
Solution
Low or no target protein
Poor antibody affinity or low expression
Increase antibody amount, verify expression (input), extend incubation
High background
Non-specific binding
Pre-clear lysate, increase wash stringency, reduce antibody
Low signal in downstream detection
Low protein recovery
Load more sample, increase starting material
Heavy/light chain interference
Antibody contamination
Use crosslinked beads or light-chain-specific secondary antibodies
Loss of protein activity
Harsh elution conditions
Use non-denaturing (low pH) elution
Viscous lysate
DNA contamination
Shear through needle or add DNase
Loss of protein interactions
Stringent washes
Reduce salt/detergent concentration
Products and support for this protocol
Browse research antibodies. Confirm application validation, species reactivity, sample type and detection requirements before selection.
Contact ABMIUM scientific support for product selection and troubleshooting.
For research use only. This protocol is general guidance and does not replace product-specific instructions, institutional safety procedures or local risk assessments.
ABMIUM laboratory protocol
A complete immunoprecipitation workflow covering lysate preparation, antibody binding, immune-complex capture, washing, elution, controls and troubleshooting.
Application overview | Download linked PDF | Browse research antibodies | Ask technical support
Introduction
Immunoprecipitation (IP) is a widely used biochemical technique for the selective isolation and removal of enrichment of a target protein from complex biological samples using antigen-antibody interactions. The method enables downstream applications such as Western blotting, mass spectrometry, and functional assays. Variants of IP, including co-immunoprecipitation (co-IP), are particularly valuable for studying protein-protein interactions under native or near-physiological conditions.
Principle
Immunoprecipitation is based on the specific binding between an antibody and its antigen. The antibody - antigen complex is captured using Protein A/G-conjugated beads, which bind to the Fc region of antibodies. Following binding, the immune complexes are separated from the lysate by centrifugation, washed to remove non-specifically bound proteins, and eluted for further analysis.
Source: Principle of Immunoprecipitation | BioRender Science Templates
Materials Required
Equipment
Refrigerated centrifuge
Microcentrifuge tubes (1.5 - 2 mL)
Rotary mixer/rotator
Pipettes and sterile tips
Ice bucket
Mortar and pestle (for tissue samples)
Liquid nitrogen container
Heating block or water bath (for SDS elution)
Reagents Required
Lysis buffer (e.g., NP-40, Triton X-100, or RIPA buffer)
Protease inhibitor cocktail
Phosphate-buffered saline (PBS)
Wash buffer (e.g., PBS with 0.1% Tween-20 or lysis buffer with adjusted salt concentration)
Protein A/G Sepharose beads
Target-specific primary antibody
Control IgG antibody
SDS-PAGE loading buffer (2X)
Glycine buffer (100 mM, pH 2.5 - 3.0)
Tris-HCl (1 M, pH 8.5 for neutralization)
Sample preparation
Cell Extracts
Adherent cells:
Remove media and wash cells with PBS.
Place the culture plate on ice, add a cold lysis buffer supplemented with protease inhibitor cocktail and keep the plate on ice for 1 - 2 min.
Scrape the cells and gently transfer the disrupted cell suspension into a chilled microcentrifuge tube.
Mix on a rotary mixer for 30 min at 4°C.
Centrifuge at 10,000 × g for 10 minutes at 4°C and transfer the cell extract to chilled fresh tubes.
Suspension Cells:
Collect cells by centrifugation (500×g for 5 min), Wash the cells with cold PBS and collect cells again by centrifugation.
Drain the PBS carefully, add a cold lysis buffer and keep the cells on ice for 1-2 minutes.
Repeat steps 4 - 5
Tissue Extracts
Snap freeze the dissected tissue and immediately grind it into a fine powder using a mortar and pestle in a liquid nitrogen bath.
Transfer the ground tissue to a pre-weighed chilled tube. Weigh the powder and store at −80 °C until use
Add 300 µL lysis buffer supplemented with protease inhibitor cocktail per 5 mg tissue powder. Mix on a rocker at 4 °C for about an hour.
Pass the lysate through a 25 gauge needle 3 times.
Collect the lysate and centrifuge at high speed (10,000 x g) for 5 minutes at 4˚C to remove cell debris.
Transfer the tissue extract (supernatant) to a fresh tube.
Determine protein concentration using a BCA or Bradford assay.
Adjust all samples to the same protein concentration using a lysis buffer.
(Optional but recommended) Pre-clearing
This step reduces non-specific binding.
Add 20 - 30 µL Protein A/G beads to lysate.
Incubate for 30-60 minutes at 4°C with rotation.
Centrifuge (2,000 X g, 2 min) and transfer supernatant to a new tube.
Antibody Binding
Add 1 - 5 µg antibody per 500 - 1000 µg total protein (as recommended by the antibody vendor or as determined by user titration) against the target to a known amount (µg) of sample (standardized by the user).
Make up the volume to 500 µL with a lysis buffer containing protease inhibitor cocktail I.
Gently mix for 3 - 4 hours or overnight at 4°C on a rotary mixer.
Preparation of Protein A/G Beads
Wash the Protein A/G Sepharose beads (25 - 40 µL/reaction) twice with 1 mL Wash Buffer, centrifuging at 2000 x g for 2 minutes and aspirating the supernatant in between washes.
Note: 25 µL Protein A/G Sepharose Beads I can bind over 500 µg IgG.
Suspend as 50% slurry in a 1× wash buffer.
Bead Capture
After antibody binding, add 25-40 µL of Protein A/G Sepharose Beads I slurry to each tube and gently mix for 1 hour at 4°C on a rotary mixer.
Collect the Protein A/G Sepharose Beads by low-speed centrifugation at 4°C (e.g., 2000 x g for 2 minutes).
Wash Protein A/G Sepharose Beads I beads 3 times with 1 mL 1× wash buffer, collecting the Protein A/G Sepharose Beads I by low-speed centrifugation at 4°C and aspirating the supernatant in between washes.
After the last wash, remove as much of the 1× wash buffer as possible, making sure that the beads never dry completely.
Elution
Functional Assay
The beads with the antigen-antibody (Ag-Ab) complex may be used directly for an activity assay provided the antibody does not block the active site of the protein being assayed.
SDS Buffer (denaturing) elution:
To elute the complex, add 40 µL 2X SDS-PAGE loading buffer to the beads and boil for 5 min.
Centrifuge to collect eluent. Eluent can be stored on ice for same day analysis or frozen at -80˚C for future SDS-PAGE analysis.
Low-pH (non-denaturing) elution:
Add 40 µL low pH glycine buffer (100 mM glycine/HCl, pH 2.5 - 3.0, not provided) and incubate for 10 min at room temperature with agitation.
Centrifuge to collect the eluent. Perform an additional elution as needed. Add 1/10th the volume of 1M Tris-HCl pH 8.5 (not provided) to the eluent to neutralize the pH and store the eluent at -80°C until use.
This buffer disrupts most protein - protein and antigen - antibody interactions while partially preserving protein structure.Some antibodies and proteins may be damaged by low pH.
The affinity purified protein may be used for an activity assay.
Limitations
Requires high-quality, specific antibodies
Weak or transient interactions may be lost
Non-specific binding can increase background
Epitope masking may prevent binding
Denaturing conditions prevent functional assays
Antibody heavy/light chains may interfere in detection
Troubleshoot
Closing Statement:
Immunoprecipitation is an important technique for isolating and enriching specific proteins from complex biological samples for downstream applications such as Western blotting, mass spectrometry, and functional assays. The effectiveness of the method depends on proper sample preparation, high-quality antibodies, optimized binding and washing conditions, and careful handling to preserve protein integrity while minimizing non-specific interactions. When performed under appropriate conditions, immunoprecipitation provides reliable and reproducible results for studying protein expression, protein - protein interactions, and functional characteristics in molecular and cellular research.
Problem
Possible Cause
Solution
Low or no target protein
Poor antibody affinity or low expression
Increase antibody amount, verify expression (input), extend incubation
High background
Non-specific binding
Pre-clear lysate, increase wash stringency, reduce antibody
Low signal in downstream detection
Low protein recovery
Load more sample, increase starting material
Heavy/light chain interference
Antibody contamination
Use crosslinked beads or light-chain-specific secondary antibodies
Loss of protein activity
Harsh elution conditions
Use non-denaturing (low pH) elution
Viscous lysate
DNA contamination
Shear through needle or add DNase
Loss of protein interactions
Stringent washes
Reduce salt/detergent concentration
Products and support for this protocol
Browse research antibodies. Confirm application validation, species reactivity, sample type and detection requirements before selection.
Contact ABMIUM scientific support for product selection and troubleshooting.
For research use only. This protocol is general guidance and does not replace product-specific instructions, institutional safety procedures or local risk assessments.