Field of Science

Least favourite NMR solvent, but a swell liquid nonetheless

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Coronene has a poll on what everyone's least favourite NMR solvent is. I have not used all the solvents on the list, but among the ones I have used, DMSO was probably my least favourite, as it also seems to be for others taking the poll.

In my case, the reason was specific. I needed to do NOESY spectroscopy on a degassed, sealed sample. And even ice kept freezing up the DMSO when we were connecting it to the vacuum. For CDCl3, we could happily use lig. N2 and be happy, but not so for DMSO; we had to patiently do the degassing for almost half an hour. In addition, DMSO is viscous and radically changes the tumbling of molecules, causes aggregation and hydrogen bonding etc. Needless to say, one has to re-experiment with his/her NOESY parameters.

On the other hand, it is instructive to see what a great molecule DMSO is for biological applications. It can be used as a drug-delivery vehicle, although this use is debated. DMSO is widely used as a cryo-protectant, and the serine protease inhibitor PMSF is dissolved in DMSO as it will naturally get inactivated in water.

Ronald Breslow and the late Charlotte Friend also discovered that this simple molecule can induce cell differentiation and later, it was found to be a HDAC (histone deacetylase) inhibitor, a class of molecules that's heavily researched these days. Interaction with HDACs intimately interferes with transcription. For example, the recent celebrity 'wine molecule' resveratrol is purported to increase expression of the HDAC protein SIRT1, possibly affecting longevity.
Incidentally, Breslow's latest paper is an article in Nature Biotechnology, in which DMSO is used as the starting lead to develop SAHA, a HDAC inhibitor which is now in Phase 2 clinical trials as an anticancer agent.

DMSO also "enters the cell and kills the herpes virus". Apparently, this is an 'indisputable fact', and seems to be the basis of scented DMSO creams as the picture above shows. More interesting talk for the cocktail party; guys, beware of the DMSO girl.

A remarkably simple molecule with some remarkable (and occasionally annoying) properties, this DMSO.


  1. We have an outdoor hallway ("breezeway") connecting one half of the chemistry building to the other here. It isn't very long, maybe 20 meters or so. Taking an NMR requires walking down 4 flights of stairs and across the entire building (and breezeway). While it doesn't get that cold in Northern California, if you don't stash your DMSO samples carefully clasped in your warm hands, or stuffed down your pants or something, you will spend all your NMR time trying to thaw out your sample. They freeze solid in that 20 or so meter walk outside.

  2. I like it, nonetheless. I am trying to study hydrogen bonding in small molecules and this is one of the solvents, or sometimes the only one that can dissolve polar amino acid like molecules. The dielectric constant being halfway between water and hydrocarbons DMSO is one of my favorite NMR solvents. Surprisingly, if you mix water with DMSO in right proportion the melting point takes a dip beyond what you'd expect. Surely, this is an interesting molecule.


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