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The other mops [1]

MOPS is the common name for the buffering compound in MOPS buffer. MOPS stands for 3-(N-morpholino) propanesulfonic acid, and with a pKa of 7.20, makes a good buffering agent for many biological systems requiring neutral pH. HEPES is a chemically similar pH buffering compound.

Recipe for 10x MOPS buffer, 1 L

chemical structure of MOPS, 3-(N-morpholino) propanesulfonic acid
  • 83.7 g MOPS; MW 209.3 g/mol
  • 13.6 g Sodium Acetate, trihydrate; MW 136.1 g/mol (watch out: NaAc, anhydrous is only 82 g/mol or 8.2g)
  • 3.7 g EDTA, disodium dihydrate; MW 372.24 g/mol (again check MW of the salt you stock)

  • add 800 ml of nuclease free distilled water; mix to dissolve
  • adjust to pH 7 with NaOH (prepared in nuclease free distilled water)
  • fill to the final volume of 1000 ml

  • filter sterilise or autoclave
  • store at room temperature
  • protect from light; do not use if the solution is dark (yellow is ok)

Final concentration in 10x stock

  • 400 mM MOPS (buffering)
  • 100 mM NaAc
  • 10 mM EDTA (nuclease inhibition by Mg2+ chelation)


Some protocols use a less concentrated MOPS buffer

  • 200 mM MOPS - 41.9 g in 1 L
  • 20 mM NaAc - 2.7 g
  • 10 mM EDTA - 3.7 g

Stability of MOPS

Contrary to common belief, MOPS is sufficiently heat-stable to be autoclaved. Solution will turn yellow but this does not interfere with its buffering capacity. See, for example, Farrell RNA methods, p201 [2]. Straw coloured buffer is good but do not use darker buffer.

Some OWW protocols which use MOPS

External links