Dimethyl Sulfoxide is used as a reaction solvent in the solid phase synthesis of peptides, during coupling operations between resin-bound fragments and activated carboxyl groups on the incoming fragment.
A variety of coupling agents have been reported in this step, including TBTU/HOBt/DIPEA, DIC/DHBt, and HBTU/ HOBt/DIPEA.

In a recent review of strategies for the convergent synthesis of proteins, it was reported that performing the coupling step in DMSO using a DCC/HOBt coupling system resulted in a low degree of product epimerization:

Adapted from Barlos, K.; Gatos, D. Biopolymers (Peptide Science), Vol. 51, 266-278 (1999)

Solubilizing Peptides and Proteins. DMSO is widely used to dissolve proteins / peptides for purification via preparative HPLC in reverse-phase mode. It is also used as a reaction solvent for protein modification reactions due to the ability to dissolve high molecular weight peptides when other solvents fail.

Related Resources

DMSO in the Pharmaceutical Industry: More about the use of DMSO “From Benchtop to Bedside”

DMSO PharmaSolvent: The high purity of this product make it solvent of choice for the synthesis of Active Pharmaceutical Ingredients, and intermediates