MEM-PFA

Recipe

Reagent	Quantity (for 100 mL)	Final concentration
MOPS (1 M, pH 7.4)	10 mL	0.1 M
NaCl (5 M)	10 mL	0.5 M
EGTA (0.5 M, pH 8.0)	200 μL	1 mM
MgSO₄ (1 M)	200 μL	2 mM
Paraformaldehyde (PFA)	4 g	4% (w/v)
Tween 20 (100%)	50 L	0.05% (v/v)
H₂O	to 100 mL

To prepare MEM-PFA, transfer 4 g of PFA to a 200-mL Erlenmeyer flask, add 50 mL of warm H₂O, and stir. Add 20 μL of 10 N NaOH. When the PFA has dissolved (within a few minutes), put the flask on ice. Add the remaining ingredients except Tween 20, and bring the volume to 100 mL in a graduated cylinder with H₂O. Mix the solution well and filter through a folded, pre-wet filter. Add 50 μL of Tween 20 and stir. Store at 4°C protected from light and use within 1 wk.