MOPS
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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, MOPS is an good buffer for many biological systems at almost neutral pH. HEPES is a chemically similar pH buffering compound.
Recipe for 10x MOPS buffer
- 41.9 g MOPS; MW 209.3 g/mol
- 2.7 g Sodium Acetate, trihydrate; MW 136.1 g/mol (watch out: NaAc, anhydrous is only 82 g/mol or 1.6g)
- 2.9 g EDTA, sodium salt; MW 292.2 g/mol
- 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 appears yellow
Final concentration of active compounds in 10x stock
- 200 mM MOPS (buffering)
- 20 mM NaAc
- 10 mM EDTA (nuclease inhibition by Mg2+ chelation)
Note: Farrell uses higher concentrations for 10x stock: 400 mM MOPS, 100 mM NaAc, 10 mM EDTA
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 [1]. Straw coloured buffer is but do not use darker buffer.
Some OWW protocols which use MOPS
- Jacobs:Protocol RNA Agarose Gel
- Knight:NuPAGE electrophoresis
- Sauer:bis-Tris SDS-PAGE, the very best
