Electrospray Ionization Mass Spectrometry Conditions

The acquisition range was m/z 1,200–1,900. The mass spectrometer was calibrated via a tune mix (Thermo Scientific). Mass spectra were viewed and analyzed via software Xcalibur V2.2. Additionally, Glycoworkbench software was used to annotate and visualize the structures of N-glycans as described in previous article (Pedersen et al., 2017; Lucas et al., 2018, 2019).

The relative abundance of the different N-glycans under lead stresses was based on the signal intensities of the corresponding Fmoc-labeled N-glycans obtained from ESI-MS analysis as previously described (Nakano et al., 2009; Mathieu-rivet et al., 2013). Briefly, each signal intensity of N-glycans was used to calculate their relative abundance compared with the total signal intensity of all identified N-glycans.