White Spots or Smudges on Western Blot Membrane (Western Blot (Unusual Gel Band Appearance))

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Uneven white spots, circular patches, or smudged areas appear on the membrane where no signal is detected. These areas correspond to regions where protein transfer did not occur. Common causes: 1) Air bubbles trapped between gel and membrane during transfer assembly 2) Incomplete contact between gel and membrane due to improper stacking 3) Bubbles formed during transfer due to excessive heat generation 4) Transfer stack not properly rolled or compressed before transfer Solutions: 1) Carefully roll out transfer stack with small roller or pipette to remove all air bubbles before transfer 2) Perform Ponceau S staining immediately post-transfer to visualize transferred proteins and identify bubble locations 3) Pre-wet membrane, filter papers, and gel in transfer buffer to minimize air trapping 4) Assemble transfer sandwich under transfer buffer to prevent air bubble incorporation 5) Use cooled transfer buffer (4°C) and perform transfer at 4°C to minimize bubble formation from heat