SDS sample buffer

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For preparation and loading of protein samples onto a gel for SDS-PAGE analysis (Western blot/protein blot).

  • Preparation: SDS contained in the sample buffer makes proteins negatively charged proportionally to their length. 2-mercapto-ethanol/DTT breaks disulphide bonds.
  • Loading: glycerol makes the sample buffer more dense than the surrounding running buffer of the protein gel, enabling easy loading into the gel pockets.


To make 10 mL of 4x stock

  • 2.0 ml 1M Tris-HCl pH 6.8
  • 0.8 g SDS
  • 4.0 ml 100% glycerol
  • 0.4 ml 14.7 M β-mercaptoethanol
  • 1.0 ml 0.5 M EDTA
  • 8 mg bromophenol Blue

Final concentrations (1x)

  • 50 mM Tris-HCl pH 6.8
  • 2% SDS
  • 10% glycerol
  • 1% β-mercaptoethanol
  • 12.5 mM EDTA
  • 0.02 % bromophenol blue

Use of loading buffer

Dilute protein sample 1:3 into 4X sample loading buffer. Load on acrylimide gel in SDS-PAGE buffer.


β-mercaptoethanol is a severe irritant and is readily absorbed through the skin. SDS is a respiratory irritant in solid form and a mask should be worn while weighing it.



  • 5x SDS loading buffer [1]
  • SDS loading buffer, Lynn lab, Uni Kentucky [2]
  • Wikipedia: SDS-PAGE, SDS