Effect of DMSO on Protein Structure and Interactions Assessed by Collision-Induced Dissociation and Unfolding.

Given the frequent use of DMSO in biochemical and biophysical assays, it is desirable to understand the influence of DMSO concentration on the dissociation or unfolding behavior of proteins. In this study, the effects of DMSO on the structure and interactions of avidin and Mycobacterium tuberculosis (Mtb) CYP142A1 were assessed through collision-induced dissociation (CID) and collision-induced unfolding (CIU) as monitored by nanoelectrospray ionization-ion mobility-mass spectrometry (nESI-IM-MS). DMSO concentrations higher than 4% (v/v) destabilize the avidin tetramer toward dissociation and unfolding, via both its effects on charge state distribution (CSD) as well as at the level of individual charge states. In contrast, DMSO both protects against heme loss and increases the stability of CYP142A1 toward unfolding even up to 40% DMSO. Tandem MS/MS experiments showed that DMSO could modify the dissociation pathway of CYP142A1, while CIU revealed the protective effect of the heme group on the structure of CYP142A1.