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MALDI MS In-Source Decay of Glycans Using a Glutathione-Capped Iron Oxide Nanoparticle Matrix
journal contribution
posted on 2014-08-19, 00:00 authored by Qiaoli Liang, Thomas Macher, Yaolin Xu, Yuping Bao, Carolyn
J. CassadyA new matrix-assisted laser desorption
ionization (MALDI) mass
spectrometry matrix is proposed for molecular mass and structural
determination of glycans. This matrix contains an iron oxide nanoparticle
(NP) core with gluthathione (GSH) molecules covalently bound to the
surface. As demonstrated for the monosaccharide glucose and several
larger glycans, the mass spectra exhibit good analyte ion intensities
and signal-to-noise ratios, as well as an exceptionally clean background
in the low mass-to-charge (m/z)
region. In addition, abundant in-source decay (ISD) occurs when the
laser power is increased above the ionization threshold; this indicates
that the matrix provides strong energy transfer to the sample. For
five model glycans, ISD produced extensive glycosidic and cross-ring
cleavages in the positive ion mode from singly charged precursor ions
with bound sodium ions. Linear, branched, and cyclic glycans were
employed, and all were found to undergo abundant fragmentation by
ISD. 18O labeling was used to clarify m/z assignment ambiguities and showed that the majority
of the fragmentation originates from the nonreducing ends of the glycans.
Studies with a peracetylated glycan indicated that abundant ISD fragmentation
occurs even in the absence of hydroxyl groups. The ISD product ions
generated using this new matrix should prove useful in the sequencing
of glycans.
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GSHiron oxide nanoparticlenonreducing endsionization thresholdanalyte ion intensitiesISD product ionsmass spectrometry matrixmolecules covalentlyISD fragmentationmonosaccharide glucoseMSsodium ionsNPhydroxyl groupsmodel glycansmass spectra exhibitcyclic glycansprecursor ionsperacetylated glycanenergy transferion modelaser power18 OMALDI
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