Western blot: high background

1. Ranked causes

   1. Blocking buffer under-concentrated, wrong type, or expiredBackground scales with shorter block times or old milk/BSA lots.
   2. Insufficient washing after primary or secondary antibodyBackground drops after adding 1–2 extra TBST washes.
   3. Antibody concentration too high (primary or secondary lot)Titrating antibodies down 2-fold cleans background without losing the band.
   4. Over-exposure on the imagerShorter exposure recovers dynamic range; bands still present.

2. Recovery steps

   1. Add 2 extra TBST + 0.1% Tween washes (5 min each) after secondaryHighest-yield fix for uniform membrane background.
   2. Re-block 1 h at RT with fresh 5% milk or BSA in TBSTExpired or weak blocker is the second most common cause.
   3. Titrate secondary (and if needed primary) 2-fold downwardCuts nonspecific binding while retaining true signal.
   4. Shorten exposure until background is below the specific bandSeparates chemistry background from camera saturation.

3. Controls first

   • Are blank / no-primary control lanes also high-background?If yes: Wash, block, secondary, or exposure — not antigen-specific binding alone.

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