Arrival time distributions decided using Thin depend sensitively within the traveling wave speed and amplitude as well as the temperature and pressure of the drift gas, and hence need to be calibrated to obtain collision cross section (CCS) values.51Given a typical deviation of reported CCS values of approximately 2%,52it would be tenuous to identify isomers that have CCSs as close as the species separated here by this method alone, even if done carefully. example. Selective enzymatic synthesis of the G1(1-6)F isomer allows us to assign the peaks in the arrival-time distributions and the infrared spectra to their respective isomeric forms. Moreover, we demonstrate the effect of the sponsor cell collection (CHO and HEK-293) within the IgG G1F gycan profile in the isomer level. This work illustrates the potential of our approach for glycan analysis of mAbs. We apply high-resolution ion mobility combined with cryogenic infrared spectroscopy to distinguish isomeric N-glycans with different terminal galactose positions. == Introduction == Monoclonal antibody (mAb) drugs are used to treat some of the most serious, life-threatening, and chronic diseases, such as cancers,1immune-mediated inflammatory conditions,2and diabetes.3Most of the current therapeutic mAbs are humanized or human immunoglobulins G (IgGs), produced as recombinant glycoproteins in eukaryotic cells.4IgGs are about 150 kDa in size Neratinib (HKI-272) and comprised of two identical heavy chains of 50 kDa and two identical light chains of 25 kDa (Fig. 1).5 == Fig. 1. Schematic structure of IgG antibody. == Immunoglobulin G molecules are glycosylated in the CH2 domains of the Fc region (seeFig. 1), with Neratinib (HKI-272) glycans being covalently attached at the Asn297 residue. The N-glycans of the Fc region contribute approximately 23% to the total mass of the IgG protein.4,5Despite this low percentage, the N-glycan moieties can have a significant impact on the effector functions of antibodies, such as the antibody-dependent cell mediated cytotoxicity (ADCC) and the complement-dependent cytotoxicity (CDC).6,7For example, it has been established that this absence of core fucose (Fuc) residues in the N-glycans of the Fc region substantially increases the ADCC activity.8,9Moreover, a high sialic acid content reduces ADCC activity but at the same time plays an important role in anti-inflammatory responses.10,11Terminal galactose is well known to enhance CDC activity, and its impact on ADCC activity has also been reported.1217However, it has only recently been demonstrated that this terminal galactose position (i.e., on either the core mannose (Man) 1-6 or 1-3 branch) has a significant effect on the effector functions of mAbs. Aoyamaet al.have shown that this G1(1-6)F mAb has higher complement component 1q (C1q)- and Fc gamma receptor (FcR)-binding activities and CDC activity than the G1(1-3)F mAb because of the greater involvement of the galactose around the 1-6 branch in the structural stability of the CH2 domain name.18 It is important to note that protein biotherapeutics such as mAbs generally exhibit micro-heterogeneities that can lead to the presence/absence or different ratios between the N-glycans in the Fc region with terminal Gal on the Man 1-6 and 1-3 arms. Effective tools are thus needed to analyse protein glycoforms, even at the isomer level, for both biological mAbs and biosimilars.1922 Several methods have been implemented to distinguish and identify positional isomers of released N-linked glycans with terminal Gal (1-6/1-3). These include tandem mass spectrometry,23ion mobility spectrometry (IMS),24and various combinations of selective enzymatic digestion or synthesis with nuclear magnetic resonance (NMR) or high-performance liquid chromatographic (HPLC) analysis.2528The most commonly used method currently combines hydrophobic interaction liquid chromatography (HILIC) and mass spectrometry (MS), where the chromatographic peak assignment is based on the previously published work indicating that the glycan with a terminal galactose around the upper Man (1-6) arm elutes prior to that with galactose on the lower Man (1-3) arm.29Despite the potential of this hybrid technique, glycan LC workflows typically involve a derivatization step to label the glycans with a fluorescent tag, since they do not contain a natural chromophore.30While this improves sensitivity and facilitates quantification, it complicates the workflow, and the labels can be expensive. Recently there has been a surge HDAC6 in the application of gas-phase spectroscopy together with ion mobility spectrometry for the structural characterization of glycans.24,3136In the present work, we use a Neratinib (HKI-272) combination of ultrahigh-resolution IMS with cryogenic infrared spectroscopy as a rapid and reliable technique for glycan isomer identification. Our approach allows one to obtain highly resolved, isomer-specific vibrational spectra, even of larger, more complex glycan ions. We have implemented a chemoenzymatic approach37,38to synthesize selectively the glycan isomer G1(1-6)F and characterize it along with the G1(1-3)F isomer by IMS and vibrational spectroscopy. We then demonstrate the impact of the host cell line (CHO and HEK-293) around the ratio of G1F isomers within the glycan profile of IgG. == Experimental approach == == Selective chemoenzymatic synthesis of the G1(1-6)F isomer == The synthesis of G1(1-6)F (Fig. 2) was performed in a total volume of 50 L containing 0.27 mM of an acceptor G-NGA2 N-linked glycan (Dextra Laboratories, UK), 0.54 mM of GDP-Fuc (guanosine 5-diphospho–l-fucose sodium salt) (Sigma-Aldrich), a MES (2-(N-morpholino)ethanesulfonic acid) buffer solution (100 mM, pH 7.0), and 0.12 mg mL1of recombinant human 1,6-fucosyltransferase (FUT8) (Creative BioMart, USA)..