Paraformaldehyde (4% in MEM)

• 1. Add 4 g of paraformaldehyde to a beaker containing 80 mL of distilled H₂O. Cover with foil and heat to 60°C in a chemical fume hood with constant stirring. Do not let the temperature rise above 65°C.

• 2. Add 1 N NaOH drop-wise, while stirring, until the solution just clears. Cool the solution on ice to room temperature.

• 3. When cool, add 10 mL of MEM salts stock buffer (10×).

• 4. Bring the volume to 100 mL with dH₂O.

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