IM-MS is a promising technique that fills an important gap within the Glycomics toolbox, namely identifying and differentiating the three-dimensional structure of chemically similar carbohydrates and glycoconjugates. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.

To quantify the measurable structural heterogeneity of a biopharmaceutical product and the effect of glycosylation on this we systematically evaluate three lots of Herceptin®, two mAb standards and an intact 5 Fc-hinge fragment.

In the development of therapeutic antibodies and biosimilars, an appropriate biopharmaceutical CMC control strategy that connects critical quality attributes with mechanism of action should enable product assessment at an early stage of development in order to mitigate risk. Here we demonstrate a new analytical workflow using trastuzumab which comprises "middle-up" analysis using a combination of IdeS and the endoglycosidases EndoS and EndoS2 to comprehensively map the glycan content. Enzymatic cleavage between the two N-acetyl glucosamine residues of the chitobiose core of N-glycans significantly simplifies the oligosaccharide component enabling facile distinction of GlcNAc from GlcNAc with core fucose. This approach facilitates quantitative determination of total Fc-glycan core-afucosylation, which was in turn correlated with receptor binding affinity by surface plasmon resonance and in vitro ADCC potency with a cell based bioassay. The strategy also quantifies Fc-glycan occupancy and the relative contribution from high mannose glycans.

The effect of temperature on the stability of proteins is well explored above 298 K, but harder to track experimentally below 273 K. Variable-temperature ion mobility mass spectrometry (VT IM-MS) allows us to measure the structure of molecules at sub-ambient temperatures. Here we monitor conformational changes that occur to two isotypes of monoclonal antibodies (mAbs) on cooling by measuring their collision cross sections (CCS) at discrete drift gas temperatures from 295 to 160 K. The CCS at 250 K is larger than predicted from collisional theory and experimental data at 295 K. This restructure is attributed to change in the strength of stabilizing intermolecular interactions. Below 250 K the CCS of the mAbs increases in line with prediction implying no rearrangement. Comparing data from isotypes suggest disulfide bridging influences thermal structural rearrangement. These findings indicate that in vacuo deep-freezing minimizes denaturation and maintains the native fold and VT IM-MS measurements at sub ambient temperatures provide new insights to the phenomenon of cold denaturation.