Western Blot Stripping Buffer — Mild + Harsh Recipes

This page covers formulations for both mild and harsh stripping buffers, step-by-step protocols for membrane stripping and reprobing, considerations specific to proteinase detection (MMPs, cathepsins, ADAMs), and common failure modes when working with low-abundance targets or high-affinity rabbit polyclonals.

Mild Stripping Buffer Recipe

Mild stripping relies on low pH to disrupt antibody-antigen interactions without denaturing proteins on the membrane. This approach preserves antigenicity better than harsh methods and is the first choice when reprobing for a second target of similar or higher abundance.

Standard mild stripping buffer formulation:

• 15 mM glycine
• 0.1% SDS (w/v)
• 1% Tween-20 (v/v)
• Adjust to pH 2.2 with HCl

Prepare fresh or store at room temperature for up to one week. The low pH is critical—if pH drifts above 2.5, stripping efficiency drops significantly, particularly for rabbit polyclonals with nanomolar affinity constants. SDS aids in antibody dissociation, while Tween-20 reduces nonspecific reabsorption during the stripping incubation.

Protocol: After imaging your blot, rinse the membrane twice in TBS-T for 5 min each. Submerge in mild stripping buffer with gentle agitation for 15–30 min at room temperature. For rabbit polyclonal antibodies raised against linear epitopes (common in Triple Point Biologics' proteinase catalog), 20 min is typically sufficient. Rinse extensively in TBS-T (3 × 10 min), block again in 5% non-fat dry milk or BSA for 1 h, then reprobe. Always test stripping efficiency on a duplicate blot when establishing a new protocol—residual primary antibody can produce artifactual signal when the secondary alone is applied.

Harsh Stripping Buffer Recipe

Harsh stripping uses reducing agents and detergent at elevated temperature to denature and remove antibodies irreversibly. This method is necessary for high-affinity rabbit polyclonals targeting conformational epitopes, or when mild stripping leaves detectable residual signal.

Harsh stripping buffer formulation (Restore™-type):

• 62.5 mM Tris-HCl, pH 6.8
• 2% SDS (w/v)
• 100 mM β-mercaptoethanol

Prepare fresh before use; β-mercaptoethanol oxidizes rapidly in aqueous solution. Some protocols substitute DTT at 50–100 mM, though β-mercaptoethanol is more effective for IgG heavy-light chain dissociation. Handle in a fume hood.

Protocol: Rinse blot briefly in deionized water. Submerge in harsh stripping buffer prewarmed to 50°C and incubate for 30 min at 50°C with occasional agitation (water bath or hybridization oven). For especially tenacious antibodies—such as rabbit polyclonals affinity-purified against recombinant proteinase domains—increase temperature to 62°C or extend time to 45 min. After stripping, wash extensively in TBS-T (4 × 10 min) to remove residual β-mercaptoethanol, which can interfere with HRP activity. Re-block and reprobe as above.

Harsh stripping typically reduces total protein signal by 10–30% depending on membrane type (PVDF retains protein better than nitrocellulose). When detecting low-abundance proteinases such as pro-MMP-2 or cathepsin X, consider loading additional sample on a parallel blot rather than stripping if quantitative comparison is required.

How to Strip a Western Blot Membrane: Step-by-Step Protocol

The general workflow applies to both mild and harsh methods, with buffer-specific modifications noted above.

1. Image and document original blot. Capture chemiluminescent or fluorescent signal at multiple exposures. Record all antibody identities, dilutions, and exposure times for your records.
2. Rinse membrane. Wash 2 × 5 min in TBS-T to remove residual detection reagent (HRP substrate or fluorophore). If using ECL, residual luminol can cause background in subsequent imaging.
3. Apply stripping buffer. Use sufficient volume to cover the membrane with agitation (10–15 mL per mini blot in a small tray). For mild stripping, incubate 15–30 min at room temperature. For harsh stripping, incubate 30 min at 50°C.
4. Wash thoroughly. TBS-T washes (3 × 10 min for mild, 4 × 10 min for harsh) remove stripped antibodies and prevent carryover. Change wash buffer between steps.
5. Re-block. Treat the membrane as if starting fresh—block in 5% milk or BSA for 1 h at room temperature or overnight at 4°C.
6. Reprobe with second primary antibody. Use standard Western blot conditions. If probing for a loading control (actin, GAPDH, tubulin), verify that stripping was successful by incubating a test strip in secondary antibody alone—any signal indicates incomplete stripping.

For proteinase Western blots where you are comparing activation states (e.g., pro-MMP-9 vs active MMP-9), strip and reprobe for total proteinase first, then strip again and probe for a phospho-specific or cleavage-specific epitope. Reversing this order often leads to loss of the lower-abundance activated form.

Reprobing Western Blots: Best Practices

Successful reprobing depends on antibody affinity, target abundance, and membrane handling.

Antibody compatibility: Rabbit polyclonal antibodies—especially those affinity-purified against recombinant protein—often have dissociation constants in the low nanomolar range and may require harsh stripping. Mouse monoclonals with moderate affinity (Kd 10–50 nM) typically strip with mild buffer. If you are reprobing after detecting a proteinase with a rabbit polyclonal from Triple Point Biologics' MMP or cathepsin range, plan for harsh stripping if your first-pass signal was strong.

Probing order: Always probe for the lowest-abundance target first. Stripping reduces total protein on the membrane; if your second target is a loading control at high abundance (actin, GAPDH), the signal loss is inconsequential. Conversely, probing for a constitutive housekeeping protein first and then stripping to detect a low-copy proteinase will often yield weak or absent signal on the reprobe.

Membrane choice: PVDF tolerates multiple strip-reprobe cycles better than nitrocellulose. If planning to strip, transfer to 0.45 µm PVDF and keep membranes hydrated between steps (store in TBS at 4°C, sealed, for up to one week). Nitrocellulose becomes brittle and protein retention drops after a single harsh strip.

Control wells: Reserve one lane for a stripping control—after stripping, probe this lane with secondary antibody only. Any bands indicate incomplete primary removal and will produce artifacts in the reprobe, particularly if both primary antibodies are from the same host species.

Stripping Buffer for Proteinase Western Blots

Proteinases present specific challenges for membrane stripping due to their propensity for autocatalysis, zymogen activation, and the presence of multiple isoforms or cleavage products on a single blot.

When detecting MMPs, cathepsins, ADAMs, or other proteinases, you often resolve both the proform and active form in separate bands. If you strip to reprobe for total proteinase or a different epitope, be aware that partially active enzyme may degrade antibodies or membrane-bound protein during the stripping incubation. Adding a protease inhibitor cocktail to your stripping buffer is generally unnecessary—most proteinases are inactive at pH 2.2 or denatured at 50°C in SDS—but if you observe smearing or band loss after stripping a cathepsin blot, consider including 1 mM PMSF or a cysteine protease inhibitor (E-64, 10 µM) during washes.

For serine proteinase inhibitors (serpins), note that serpin-enzyme complexes are SDS-stable and migrate as high-molecular-weight bands. Stripping will not dissociate the covalent complex; reprobing for the serpin or the target proteinase will still detect the complex band. If you need to distinguish free vs complexed forms, run parallel blots rather than strip-reprobe the same membrane.

Triple Point Biologics' rabbit polyclonal antibodies targeting proteinase prodomains (e.g., pro-MMP-2, pro-cathepsin L) are raised against recombinant zymogens and often exhibit high specificity for the proform. After stripping a blot probed with such an antibody, reprobing with a neoepitope antibody (recognizing the active-site cleavage) will reveal activation status on the same sample set. This workflow is routine in activation time-course experiments.

Comparing Mild vs Harsh Stripping Efficiency

The decision between mild and harsh stripping should be informed by a pilot experiment on a duplicate blot.

Mild stripping advantages: Preserves membrane-bound protein, faster workflow, less hazardous reagents. Effective for monoclonal antibodies and polyclonals with moderate affinity (Kd >10 nM). Lower risk of losing low-abundance targets.

Mild stripping limitations: Incomplete removal of high-affinity rabbit polyclonals, particularly those recognizing structured epitopes. Residual primary can cause false positives if the second primary is from the same host species (e.g., rabbit-to-rabbit reprobing).

Harsh stripping advantages: Near-complete antibody removal, even for high-affinity reagents. Suitable for serial reprobing (three or more cycles). Denatures and removes nonspecific binders.

Harsh stripping limitations: Protein loss from membrane (10–30%), potential for target denaturation (especially problematic for phospho-epitopes or conformation-dependent antibodies), longer protocol, and requires temperature control.

Testing stripping efficiency: After stripping, incubate the membrane in blocking buffer, then apply only the HRP-conjugated secondary antibody that matches the first primary (e.g., goat anti-rabbit IgG-HRP if your first antibody was a rabbit polyclonal). Develop with ECL. Any bands visible above background indicate incomplete stripping. If present, repeat the stripping step or switch to harsh stripping before reprobing.

For quantitative Western blots where you are normalizing proteinase expression to a loading control, the protein loss from harsh stripping is acceptable as long as you reprobe the same membrane—this maintains the proportional relationship between target and control.

Common Pitfalls

• Residual primary antibody after mild stripping: High-affinity rabbit polyclonals may not fully dissociate at pH 2.2. Solution: Test stripping efficiency with secondary-only control. If bands remain, use harsh stripping or increase mild stripping time to 45 min.
• Protein loss during harsh stripping: Extended incubation or temperatures above 62°C can strip target protein from the membrane along with antibodies. Solution: Limit harsh stripping to 30 min at 50°C and use PVDF instead of nitrocellulose. For irreplaceable samples, run a parallel blot rather than stripping.
• Ghost bands from residual HRP activity: If ECL substrate is not fully washed away before stripping, residual HRP can produce faint bands in the reprobe. Solution: Wash blot extensively in TBS-T after imaging, before adding stripping buffer. Store stripped membranes in TBS at 4°C, not in azide (which inhibits HRP).
• Incomplete re-blocking: Stripping exposes hydrophobic patches on the membrane, increasing nonspecific binding in the reprobe. Solution: Block for a full 1 h after stripping, using fresh blocking buffer. If background is high, switch from milk to 3% BSA or add 0.05% Tween-20 to the blocking buffer.
• Cross-reactivity between first and second antibody: Reprobing with a second rabbit polyclonal after stripping a rabbit polyclonal can produce ambiguous results if stripping is incomplete. Solution: Use antibodies from different host species when possible (e.g., rabbit for target, mouse for loading control), or validate complete stripping with secondary-only control before reprobing.
• Loss of phospho-epitopes during harsh stripping: Heating to 50–62°C in the presence of SDS can promote dephosphorylation or epitope denaturation. Solution: Use mild stripping for phospho-specific antibodies, or run a separate blot for phospho-targets rather than reprobing.

References

1. Alegria-Schaffer A, Lodge A, Vattem K. Performing and optimizing Western blots with an emphasis on chemiluminescent detection. Methods Enzymol. 2009;463:573-599.
2. Mahmood T, Yang PC. Western blot: technique, theory, and trouble shooting. N Am J Med Sci. 2012;4(9):429-434.
3. Towbin H, Staehelin T, Gordon J. Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc Natl Acad Sci U S A. 1979;76(9):4350-4354.
4. Gallagher S, Winston SE, Fuller SA, Hurrell JGR. Immunoblotting and immunodetection. Current Protocols in Molecular Biology. 2008;Chapter 10:Unit 10.8.