SM buffer with gelatin

Recipe

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, dissolve the NaCl and MgSO₄·7H₂O in 800 ml of H₂O; add the Tris-Cl and gelatin; and adjust the volume to 1 liter with H₂O. Sterilize the buffer by autoclaving for 20 minutes at 15 psi (1.05 kg/cm²) on liquid cycle. After the solution has cooled, dispense 50-ml aliquots into sterile containers. SM buffer with gelatin may be stored indefinitely at room temperature. Discard each aliquot after use to minimize the chance of contamination.