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Preparation of SM buffer (lambda diluent)

SM buffer is primarily used in biology laboratories, and its main function, like any other buffer, is to stabilize the pH. That is, it can withstand minor pH changes, increasing the stability of biological materials or molecules. When performing an experimental task, it is critical to keep all other variables constant and only vary the tested variables. This emphasizes the significance of keeping the pH stable through reliable and consistent methods such as buffer systems. SM buffer is one of them and is used for routine phage suspension manipulation. You can make SM buffer with or without gelatin. During storage, the gelatin in SM buffer stabilizes phage particles.

SM buffer container-preparation of SM buffer

Preparation of SM Buffer


Reagent Amount  Final concentration
NaCl 5.8 g 100 mM
MgSO4·7H2O 2 g 8 mM
Tris-Cl (1 M, pH 7.5) 50 ml 50 mM
Gelatin (2%, w/v) 5 ml 0.01% (w/v)
H2O to 1 liter


To prepare 1 liter of SM buffer with gelatin, 

  1. Dissolve the NaCl and MgSO4·7H2O in 800 ml of H2O; 
  2. Add the Tris-Cl and gelatin,
  3. Adjust the volume to 1 liter with H2O. 
  4. Sterilize the buffer by autoclaving for 20 minutes at 15 psi (1.05 kg/cm2) on a liquid cycle. 
  5. After the solution has cooled, dispense 50-ml aliquots into sterile containers.

Storage condition

SM buffer with gelatin may be stored indefinitely at room temperature

NOTE: Discard each aliquot after use to minimize the chance of contamination
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