3-Morpholinopropanesulfonic Acid (CAS 1132-61-2): Industry Application and Supply Guide

3-Morpholinopropanesulfonic Acid

   A postdoctoral researcher at a university molecular biology lab in Germany spent nearly three weeks chasing what she thought was a sample preparation error before a collaborator from a neighboring lab finally suggested the real problem. She was running denaturing RNA gel electrophoresis using a phosphate-based buffer system — cheaper to prepare and familiar from her previous lab — and the RNA bands from her total RNA extractions kept showing aberrant migration patterns, with the 28S ribosomal band running in an unexpected position relative to the 18S band. The gel images looked degraded, even though the RNA integrity measured fine on the nanodrop. Her collaborator, who had been doing RNA work for fifteen years, immediately recognized the problem: phosphate at the concentration being used was interacting with the formaldehyde in the denaturing gel system, interfering with the denaturation of RNA secondary structure. He handed her a bottle of MOPS buffer stock and told her to redo the gel. The next morning she had clean, sharp bands with the expected 2:1 intensity ratio between 28S and 18S. The three weeks of troubleshooting could have been avoided if she had known from the start that 3-morpholinopropanesulfonic acid — MOPS — is the standard choice for RNA electrophoresis and not an interchangeable substitute for phosphate.

  3-Morpholinopropanesulfonic acid, better known by the acronym MOPS, carries the molecular formula C7H15NO4S and the CAS number 1132-61-2. It is one of the Good’s buffers — a series of zwitterionic biological buffers developed by Norman Good and colleagues in the 1960s and published in Biochemistry in 1966. The design goal for the series was a set of compounds that would maintain stable pH in the physiological range — approximately 6 to 8 — without interfering with biological systems, metal chelation, enzymatic reactions, or common spectrophotometric assays. MOPS has a pKa of approximately 7.20 at 25 degrees Celsius, which places it in the mid-physiological range and makes it well suited to reactions and preparations that need buffering around neutral pH.
 
  The structure of MOPS combines a morpholine ring — a six-membered ring with one nitrogen and one oxygen — with a propanesulfonic acid chain attached to the ring nitrogen. The sulfonate group carries the negative charge that balances the protonated nitrogen in the zwitterionic form. This charge distribution means MOPS does not penetrate cell membranes effectively, which is one reason it does not disrupt cellular processes the way simpler buffers sometimes do. The molecular weight of 209.26 grams per mole means that a 1 molar stock solution requires about 209 grams per liter — a straightforward preparation that dissolves readily in water at room temperature.
  The RNA electrophoresis application is perhaps the most widely recognized use in academic and research settings. The standard MOPS-formaldehyde denaturing gel system for RNA analysis relies on the buffer maintaining pH stability throughout the run, preventing the formaldehyde from causing off-target interactions that would smear the bands. The fact that MOPS does not absorb at 254 nm allows it to be used in UV-monitored systems without contributing background signal. Researchers preparing MOPS running buffer for RNA gels typically work with a 10x stock — usually 0.2 M MOPS, 50 mM sodium acetate, 10 mM EDTA, adjusted to pH 7.0 — that gets diluted into the gel and running buffer at time of use.
 
  In cell culture and fermentation, MOPS is used to stabilize pH in media formulations that are not CO2-buffered, or in situations where bicarbonate buffering is insufficient or incompatible with the experiment. This comes up frequently in microbiological work where bacteria are cultured in small volumes on a shaker without a CO2 incubator, and pH drift during growth would otherwise affect the results. The non-toxicity of MOPS to most microbial species at working concentrations makes it a reliable choice for defined media formulations.
  Industrial process chemistry applications for MOPS are narrower but consistent. It appears in electroplating bath formulations where stable pH control prevents uneven metal deposition, and in certain specialty coating formulations where the pH needs to remain stable across temperature fluctuations. The high water solubility and the fact that MOPS does not complex with most common metal cations — in contrast to phosphate, which precipitates calcium and many divalent metals — makes it useful in situations where metal compatibility is required.
 
  The purity requirements for MOPS used in research and cell biology applications are high. Biochemical-grade MOPS should be tested for heavy metals, for residual synthesis byproducts, and for freedom from compounds that might interfere with enzyme activity or cell viability assays. The lot-to-lot consistency of pKa and solubility is also important, since buffer capacity depends on both the concentration and the actual ionization behavior of the compound.
3-Morpholinopropanesulfonic Acid
Shandong Lookchemical Co, Ltd. supplies 3-morpholinopropanesulfonic acid (CAS 1132-61-2) with documented purity and conductivity specifications. The material is characterized by HPLC and confirmed for heavy metal content by ICP. Lot-specific CoA documentation accompanies each shipment. Technical queries on grade selection for specific biological or industrial applications can be addressed to the sales team.
 

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