Measurements of absolute CCS values were performed using a Synapt G1 HDMS quadrupole/IMS/oa-ToF instrument (Waters Co., Manchester, U.K.) modified for drift tube operation (Bush, et al., 2010).
Briefly, N-linked glycans were released with hydrazine from the well-characterized glycoproteins ribonuclease B, porcine thyroglobulin, chicken ovalbumin, and bovine fetuin
obtained from Sigma Chemical Co., Ltd. (Poole, Dorset, U.K.) and reacetylated. Sialic acids were removed from the thyroglobulin and fetuin samples by heating with 1% acetic acid for 1 h at 70 °C.
For electrospray analysis, samples were dissolved in water:methanol (1:1, v:v) at ∼1 mg/mL. More information refer to the supplementary section Pagel K and Harvey DJ, Analytical Chemistry 2013.