MALDI-TOF-MS Profiling of Serum N-Glycans

MALDI-TOF-MS in reflection positive-ion mode was used for the serum N-glycans profiling (17 (link)). 1 μL of glycan samples was mixed with 1 μL of matrix containing 5 mg/mL super-DHB with 1 mM NaOH in 50% ACN on the AnchorChip target plate (Bruker Daltonics, Bremen, Germany) and the mixture was dried by air for 2 h. The N-glycomes were detected using a rapifleXtreme MALDI-TOF mass spectrometer with a Smartbeam-3D laser, controlled by flexControl 4.0 (Bruker Daltonics). A peptide calibration standard (Bruker Daltonics) was used for the calibration of the instrument. The mass range was set from m/z 1000 to m/z 5000. Laser shots were accumulated 5000 times for each spectrum. We chose an automatic acquisition mode and random walk pattern at a laser frequency of 5000 Hz for the acquisition of sample spectra (17 (link)).