MOPS sodium salt 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 6.5 – 7.9 and commonly used for cell culture media, as a running buffer in electrophoresis and for protein purification in chromatography. MOPS 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. MOPS is often used in buffered culture media for bacteria, yeast, and mammalian cells. MOPS is regarded as an excellent buffer for use in separating RNA in agarose gels. It is recommended to sterilize MOPS buffers by filtration rather than with autoclave due to the unknown identity of yellow degradation products that occur after sterilization of MOPS with autoclave. It is suitable for use in the bicinchoninic acid (BCA) assay. MOPS sodium salt can be mixed with MOPS free acid to attain desired pH. Alternatively, MOPS free acid can be titrated with sodium hydroxide to attain desired pH.