MES monohydrate is a buffering agent used in biochemistry and molecular biology that was selected and described by Good et al. It is a zwitterionic, morpholinic buffer that is useful for a pH range of 5.5 – 6.7 and commonly used for cell culture media, as a running buffer in electrophoresis, and for protein purification in chromatography. MES lacks the ability to form a complex with most metal ions and is recommended for use as a non-coordinating buffer in solutions with metal ions. MES is often used in buffered culture media for bacteria, yeast, and mammalian cells. It is toxic towards plants at high concentrations, but can be used in culture media at lower concentrations for plants. Due to low ionic mobility, MES is regarded as an excellent buffer for use in capillary electrochromatography. MES is often employed as a substitute for the highly toxic cacodylate, as well as a substitute for the non-zwitterionic buffers citrate and malate. MES complexes with some organotin(IV) molecules that are being explored as antitumor agents.

MES free acid or MES free acid monohydrate can be mixed with MES sodium salt to acquire desired pH. Alternatively, MES free acid or MES free acid monohydrate can be titrated with sodium hydroxide to attain desired pH.

Product SpecificationsMES Free Acid, Monohydrate, Ultra Pure2-(N-Morpholino)ethanesulfonic acid, Monohydrate

Formula: C₆H₁₃NO₄S ∙ H₂O

MW: 213.25 g/mol

Storage/Handling: Store in a dry and well-ventilated place.

PubChem Chemical ID: 16218417

Note: MES Hydrate (CAS# 1266615-59-1) and MES Monohydrate (CAS# 145224-94-8) differ only in the number of water molecules associated with the buffer in powder form. Regardless of the number of water molecules present, these buffers are identical when dissolved into an aqueous solution.