Western blot full protocol: Protein extraction to chemiluminescence

critical

No bands at all (blank membrane)

Membrane is completely blank — neither target protein nor housekeeping control shows any signal after ECL exposure.

💡 5 · ✓ 5

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

critical

Severe protein degradation

SDS-PAGE shows obvious low-MW degradation bands and a smear/tail. Target band is faint or absent on Western.

💡 5 · ✓ 5

severe

Protein concentration is too low

Nanodrop reads A280 ≈ 0.09, concentration ≈ 0.05 mg/mL; SDS-PAGE shows very faint overall bands; BCA quantification confirms low yield.

💡 5 · ✓ 5

severe

Incomplete lysis — visible debris or turbid supernatant

After homogenization / lysis there are visible chunks or debris in the tube and the supernatant is turbid; SDS-PAGE shows missing or weak bands.

💡 5 · ✓ 5

severe

HRP Activity Inhibition by Sodium Azide

Western blot shows no signal or extremely weak signal when using HRP-conjugated secondary antibodies. Chemiluminescent substrate fails to produce expected light emission even with adequate antibody binding and exposure time.

💡 4 · ✓ 5

severe

Temperature-Dependent Sample Degradation

Protein degradation, dephosphorylation, or denaturation occurs when samples are kept above 4°C throughout the protocol, resulting in high background or loss of target bands.

💡 3 · ✓ 3

severe

Uneven Bands Due to Improper Gel Polymerization

Bands appear distorted, wonky, or uneven across lanes. In extreme cases, the same protein appears at different molecular weights in different lanes due to irregular gel matrix formation.

💡 4 · ✓ 4

severe

Multiple Low Molecular Weight Bands or Smearing Below Expected Band

Multiple bands appear at molecular weights lower than the expected target protein, often accompanied by smearing or streaking below the primary band. This pattern suggests progressive breakdown of the intact protein.

💡 4 · ✓ 4

severe

White Bands or Ghost Bands with ECL Detection

Target protein bands appear white or light-colored instead of dark on film or imager. The bands are present but show inverted contrast, appearing as 'ghost bands' where signal should be strongest.

💡 5 · ✓ 6

severe

No Signal or Weak Signal

No bands or very faint bands appear on the western blot after detection

💡 5 · ✓ 5

severe

Overexposed / signal saturation

Bands look thick and bloated, edges spill out, strong-signal differences are masked; not suitable for densitometry quantification because the linear range is lost.

💡 3 · ✓ 4

severe

Band smearing / streaking

Bands have blurred edges, show vertical smearing or the entire lane is hazy; background is fogged, making band intensity comparisons unreliable.

💡 4 · ✓ 4

severe

Insufficient Protein Sample Loading

Western blot shows weak or no signal for target protein. Loading controls may also appear faint, indicating insufficient total protein loaded per lane. This is particularly problematic for low-abundance target proteins.

💡 4 · ✓ 5

moderate

Viscous sample — stringy lysate, hard to pipette

Lysate is stringy/sticky, pipettes slowly, sticks to the tip, and gives unreliable BCA quantification and bad SDS-PAGE loading.

💡 4 · ✓ 4

moderate

Weak or Absent Signal Due to Insufficient Exposure

Western blot film shows very faint bands or no visible bands after initial exposure. The membrane may contain protein and antibody binding has occurred, but the chemiluminescent or colorimetric signal is not captured adequately on film.

💡 4 · ✓ 4

moderate

Bands Appear Lower Than Expected Molecular Weight

All protein bands or the target band migrate further down the membrane than expected based on the predicted molecular weight. Coomassie blue staining of the membrane confirms abnormally low band positions before immunostaining.

💡 4 · ✓ 4

moderate

Low Acrylamide Percentage for Target Protein Size

Lower molecular weight proteins migrate excessively fast through the gel, resulting in poor resolution and bands appearing at the bottom of the membrane or running off entirely.

💡 3 · ✓ 4

moderate

Electrophoresis Time Not Optimized for Target Protein

Protein bands do not align with expected molecular weight markers, with systematic upward or downward shifts affecting all bands uniformly. Pre-staining reveals migration issues before antibody detection.

💡 4 · ✓ 5

moderate

Band Warping from Well Overloading

Individual lanes show warped or distorted bands while adjacent lanes appear normal. Affected lanes may show smearing, broadening, or lateral spreading of protein bands.

💡 4 · ✓ 4

moderate

Black Dots or Speckled Background on Western Blot

Non-specific dark dots or speckled pattern appear across the membrane background, not localized to protein bands. The signal appears as discrete spots rather than uniform background.

💡 5 · ✓ 5

moderate

Dark or Black Blot with Ghost Bands

Entire membrane appears dark or black after chemiluminescent detection, often with white 'ghost' bands where protein bands should appear. Background signal is saturated across the whole blot.

💡 4 · ✓ 5

moderate

Extra Bands at 50 kDa and 25 kDa Masking Target

Western blot shows strong bands at approximately 50 kDa (heavy chain) and 25 kDa (light chain) that may mask or interfere with the target protein band of interest.

💡 3 · ✓ 3

moderate

Inactive Chemiluminescent Detection

No signal detected when using chemiluminescent detection method despite proper procedure

💡 3 · ✓ 3

moderate

Enzyme Inhibitor Interference

No signal or very weak signal despite proper antibody binding

💡 2 · ✓ 2

moderate

Weak bands (faint signal)

Bands are visible but barely detectable; long exposure times are needed, and the internal control also appears weak.

💡 5 · ✓ 5

moderate

Bands Appear Higher Than Expected Molecular Weight

All protein bands or the target band remain near the top of the membrane, migrating less than expected based on the predicted molecular weight. Coomassie blue staining confirms abnormally high band positions before immunostaining.

💡 4 · ✓ 4

moderate

Weak Lysis Method Causing Nonspecific Bands

Insufficient lysis strength results in incomplete protein extraction, leading to weak target signal and increased nonspecific bands from partially solubilized proteins.

💡 3 · ✓ 3

moderate

Smile Effect on Western Blot Bands

Bands appear curved in a smile-shaped pattern across the gel, with edges migrating faster than the center. This distortion affects all lanes uniformly and compromises molecular weight estimation.

💡 4 · ✓ 4

moderate

Streaking and Uneven Migration from Buffer Issues

Bands show streaking, smearing, or uneven migration patterns. Multiple bands may merge or appear poorly resolved with inconsistent migration across the gel.

💡 5 · ✓ 5

moderate

Non-Specific Signal from Insoluble Protein in Well or Dye Front

Strong signal appears at the top of the gel (in or near the loading well) or at the bottom (dye front), unrelated to the expected molecular weight of the target protein. This is especially common for very high molecular weight proteins (>250 kDa).

💡 4 · ✓ 5

moderate

Protein Band Smearing on Western Blot

Protein bands appear as vertical smears rather than discrete sharp bands. Smearing may occur above or below the expected molecular weight, making band interpretation difficult.

💡 4 · ✓ 5

minor

Smiling bands (curved bands)

Bands curve upward at the edges of the gel, appearing like a smile — the middle of the lane runs faster than the sides.

💡 4 · ✓ 4