N-linked glycans were released from chicken ovalbumin by hydrazinolysis and
examined by matrix-assisted laser desorption/ionization mass spectrometry.
Postsource decay analysis showed that most fragment ions arose as the resu
lt of internal glycosidic cleavages involving loss of nonreducing terminal
residues from ions that had lost one or both GlcNAc residues from the chito
biose core [GlcNAc beta(1 --> 4)GlcNAc]. Cross-ring fragments were abundant
from the reducing-terminal GlcNAc but other cross-ring fragments were weak
. The ion found to be most useful for determining the composition of the an
tennae attached to the 3- or 6-linked core mannose residues was an internal
cleavage ion formed by loss of both the chitobiose core and the antenna li
nked to the 3-position of the core branching mannose. This ion was observed
to lose water in the absence of a "bisecting" GlcNAc residue (beta 1 --> 4
linked to the core mannose) and to lose a GlcNAc molecule (221 mass units)
when a bisecting GlcNAc residue was present. (J Am Soc Mass Spectrom 2000,
11, 572-577) (C) 2000 American Society for Mass Spectrometry.