Dimethyl sulfoxide favours the covalent phosphorylation and not the binding of Pi to sarcoplasmic reticulum ATPase.

Competition between Ca2+ binding and Pi phosphorylation showed that the affinity of Ca(2+)-ATPase for Pi was not changed by 20% DMSO. Thus, the enhancement of Pi phosphorylation in the presence of DMSO should not be attributed to a solvent effect on the affinity for Pi, but rather on the phosphorylation reaction itself.