Methods
The analysis of the N- glycans was performed using matrix-assisted
laser desorption ionization mass spectrometry on single tear samples.
Tears from control normal subjects (CTRL), VKC and AKC patients were
processed and treated with peptide N-glycosidase F (PNGase F) to
deglycosylate N- glycoproteins. Released N- glycans were
purified, permethylated and analyzed by Matrix-Assisted Laser
Desorption/Ionization-Time Of Flight Mass Spectrometry and tandem Mass
Spectrometry (MALDI-TOF MS and MALDI-TOF MS/MS).