MOPS

The other mops

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

chemical structure of MOPS, 3-(N-morpholino) propanesulfonic acid

• 41.2 g 3-(N-morpholino) propanesulfonic acid (MOPS); MW 209.3 g/mol
• 10.9 g Sodium Acetate, 3- hydrate; MW 136.1 g/mol

(watch out: NaAc, anhydrous is lighter with MW = 82 g/mol)

• 3.7 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

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

Stability of MOPS

Contrary to common belief, MOPS is sufficiently heat-stable to be autoclaved. This will not interfere with its buffering capacity. See, for example, Farrell RNA methods, p201 [1]

Some OWW protocols which use MOPS

• Jacobs:Protocol RNA Agarose Gel
• Knight:NuPAGE electrophoresis
• Sauer:bis-Tris SDS-PAGE, the very best

External links

• Wikipedia MOPS