Capillary isoelectric focusing (cIEF) protocol

Sodium hydroxide, phosphoric acid, glacial acetic acid, urea, iminodiacetic acid, 2-mercaptoethanol and L-arginine were from Sigma Aldrich (St. Louis, MO, USA). The Pharmalyte 3–10 was from GE Healthcare (Chicago, IL, USA). The cIEF Gel; the pI markers of the pI Peptide Marker kit; the Fast Glycan kit; and the SDS-MW Analysis Assay kit including the SDS-MW Gel Buffer, Sample Buffer and 10 kDa protein standard along with the 50 µm ID NCHO and BFS capillaries were from Bio-Science Kft (Budapest, Hungary). The hIgG1 test sample was from Molecular Innovations (Novi, MI, USA). The commercial PNGase F enzyme was from New England Biolabs (Ipswich, MA, USA). The in-house produced 6His-PNGase F (production described in detail in [20 (link)] and this enzyme featured 3 months of shelf life) was from University of Pannonia (Veszprem, Hungary).