Structural Characterization of Neutral Oligosaccharides by Laser-Enhanced In-Source Decay of MALDI-FTICR MS

Abstract

MALDI in-source decay (ISD) technique described to date has proven to be a convenient and rapid method for sequencing purified peptides and proteins. However, the general ISD still can not produce adequate fragments for the detailed structural elucidation of oligosaccharides. In this study, an efficient and practical method termed the laser-enhanced ISD (LEISD) technique of MALDI-FTICR MS allows highly reliable and abundant fragmentation of the neutral oligosaccharides, which was attributed to the ultrahigh irradiation laser of mJ level. The yield of ISD fragmentation was evaluated under different laser powers for 7 neutral oligosaccharides using DHB as matrix. Better quality ISD spectra including fragment ions in low-mass region were obtained at higher laser power. Results from the LEISD of oligosaccharides demonstrated that a significantly better signal-to-noise ratio (S/N) and more structural information could be obtained in comparison to the conventional CID. It was also suggested that the valuable A ions derived from cross-ring cleavage of the linear oligosaccharides allowed the distinction among α(1→4)-, α(1→6)-, β(1→4)-, and β(1→3)-linked isobaric structures according to fragment types and intensities. In addition, ideal fragmentation ions observed by LEISD method facilitated the determination of the sequences and branched points of complex oligosaccharides from human milk.

Differentiation of Disaccharide Isomers by Temperature-Dependent In-Source Decay (TDISD) and DART-Q-TOF MS/MS

“…Inversely, the ratio value is much less than 1 in Figure 5b. It is speculated that the results are due to the fact that β glycosidic bonds were more stable than the corresponding α-linked ones [22,35]. In addition, the other eight disaccharides were also studied under the same conditions.…”

“…The structures of the oligosaccharides are in many cases related to their multiple important biological functions, while structural analysis of carbohydrates is still challenging because of the enormous structural diversity and microheterogeneity [16][17][18]. With the development of MS, MS-based technology has become a pivotal methodology for structural elucidation of carbohydrates [19][20][21][22][23][24][25][26][27][28]. In our recent reports [22][23][24], oligosaccharide isomers were successfully distinguished by laserenhanced in-source decay (LEISD) of matrix-assisted laser desorption/ionization (MALDI) MS or 1-phenyl-3-methyl-5-pyrazolone labeling technique in conjunction with electrospray ionization (ESI) tandem mass spectrometry.…”

“…With the development of MS, MS-based technology has become a pivotal methodology for structural elucidation of carbohydrates [19][20][21][22][23][24][25][26][27][28]. In our recent reports [22][23][24], oligosaccharide isomers were successfully distinguished by laserenhanced in-source decay (LEISD) of matrix-assisted laser desorption/ionization (MALDI) MS or 1-phenyl-3-methyl-5-pyrazolone labeling technique in conjunction with electrospray ionization (ESI) tandem mass spectrometry. The monosaccharide structural isomers could exhibit different mobility drift times in both drift tube and traveling wave ion mobility mass spectrometry, depending on differences in their anomeric and stereochemical configurations [26].…”

MALDI In-Source Decay, from Sequencing to Imaging

“…As glycans can be easily isolated and purified, the ISD and pMS 3 -sequencing approaches were also employed to characterize thoroughly the structures of both native [43,[54][55][56][57][58][59][60] and permethylated glycans [61][62][63][64][65][66], allowing unambiguous discrimination of isobaric species. In ref.…”

Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry: Mechanistic Studies and Methods for Improving the Structural Identification of Carbohydrates

“…[138][139][140] ISD ions are promptly produced by thermal activation and/or chemical reactions during desorption/ionization processes in the source region, such as hydrogen radical mediated 141) and/or free electron mediated reactions. 142,143) More energy input 144) and higher energy-coupling e ciency between matrices and analytes 89) enhance the ISD process. Because ISD ions receive the full acceleration energy in the ion source, they can be well resolved in the mass spectra.…”