glycoproteins, a family of high molecular weight and densely glycosylated biopolymers. Those mucins can act as an infection shield by trapping various viruses in the biopolymer matrix [ 1 ] and they reduce bacterial adhesion to surfaces. [ 2,3 ] Mucins also form highly hydrated and lubricative layers that protect the underlying epithelium from dehydration and shear stress that emerge during eye blinking or when swallowing food. Water typically accounts for up to 95% of the total mass in the mucus gel. [ 4,5 ] Shifts in the mucus water content correlate with substantial changes of the mucus barrier function [6][7][8] and result in important pathological disorders such as dry mouth [ 9 ] and dry eye. [ 10 ] Mucin-associated glycans contribute up to 80% of the molecular weight of mucins [ 11 ] and contain highly hydrated hydroxyl groups. Differences in the amount and composition of glycans from mucins extracted from pig stomachs and mucins from bovine submaxillary glands correlate with their capacity to adsorb water. [ 12 ] However, other properties such as protein composition also differ between these two mucin species, precluding the establishment of a defi nitive link between the presence of mucin glycans and hydration.Mucins, and other well-hydrated molecules such as zwitterionic polymers, polysaccharides, and polyelectrolytes are generally good boundary lubricants when adsorbed [ 13,14 ] or assembled in brush structures [15][16][17][18] on surfaces. Hence, mucin-associated glycans could also be essential for the lubricative function of mucus. In a related system, the mucin-like macromolecule lubricin showed a signifi cant decrease in lubricity when its associated glycans were removed. [ 19 ] Moreover, the lubricity of salivary fi lms, which contain mucins, has also been correlated with the total amount of glycosylation present in the fi lm. However, also here, the complexity of saliva composition precluded the identifi cation of the specifi c role of mucin glycosylation. [ 20 ] Hence, there is a need for a more defi ned experimental system to determine if mucin glycosylation is essential to the hydration and lubrication properties of mucins.This study explores the role of glycosylation in mucin hydration and lubricity, using mucin coatings as a simplifi ed model system. Such mucin coatings can reconstitute levels of surface hydration [ 21,22 ] and lubrication [23][24][25] similar to those found in native mucus. Our data show that the removal of mucin-bound glycans results in a signifi cant reduction in hydration and lubricity of the mucin-coated surface. We show that the hydration and lubricity of deglycosylated mucins can be partially A key property of mucin glycoproteins is their exceptional capacity to hydrate and lubricate surfaces. In vivo, mucins assemble into mucus hydrogels that cover the epithelium and protect it from dehydration and shear stress. A better understanding of the origin of these properties could lead to new treatment strategies for patients with poor mucus coverage, defective mucus produ...