Resolving disulfide structural isoforms of IgG2 monoclonal antibodies by ion mobility mass spectrometry.

Recombinant monoclonal antibodies are an important class of therapeutic agents that have found widespread use for the treatment of many human diseases. Here, we have examined the utility of ion mobility mass spectrometry (IMMS) for the rapid characterization of disulfide variants in intact IgG2 monoclonal antibodies. It is shown that IMMS reveals 2 to 3 gas-phase conformer populations for IgG2s. In contrast, a single gas-phase conformer is revealed using IMMS for both an IgG1 antibody and a Cys-232 --> Ser mutant IgG2, both of which are homogeneous with respect to disulfide bonding. This provides strong evidence that the observed IgG2 gas-phase conformers are related to disulfide bond heterogeneity. Additionally, IMMS analysis of redox enriched disulfide isoforms allows assignment of the mobility peaks to established disulfide bonding patterns. These data clearly illustrate how IMMS can be used to quickly provide information on the higher order structure of antibody therapeutics.