Mass spectrometry of oligosaccharides
Authors: Zaia Joseph 
Published: February 2004

I.
Introduction
162

 II.
CHARACTERISTICS OF TANDEM MASS SPECTRA OF CARBOHYDRATES
163

A.  Ionization of Carbohydrates
163

    1.  Electrospray Ionization (ESI)
163

    2.  Matrix‐Assisted Laser Desorption/Ionization (MALDI)
163

B.  Nomenclature for the Fragmentation of Glycoconjugates
164

C.  Tandem MS of Native Oligosaccharide Molecular Ions
165

    1.  Protonated Ions
165

    2.  Deprotonated Ions
166

    3.  Alkali and Alkaline Earth Adducted Ions
166

D.  Tandem MS of Permethylated and Peracetylated Oligosaccharides
169

E.  Tandem MS of Reductively Aminated Carbohydrates
170

F.  Discrimination of Monosaccharide Linkages
171

G.  Gas‐Phase Degradation of Oligosaccharides
178

H.  Computer‐Based Approaches for Interpretation of Oligosaccharide Product‐Ion Mass Spectra
181

I.  Internal Residue Loss Rearrangements of Oligosaccharide Ions During CID
183

J.  Conclusions
184

 III.
ANALYZERS FOR MASS SPECTROMETRY OF CARBOHYDRATES
186

A.  Analysis of Permethylated Carbohydrates Using High Temperature GC/MS
186

B.  Analysis of Carbohydrates with MALDI‐TOF MS
186

C.  Analysis of Carbohydrates with MALDI Q‐oTOF MS
187

D.  Analysis of Carbohydrates with ESI Q‐oTOF MS
187

E.  Analysis of Carbohydrates with QIT MS
187

F.  Analysis of Glycoconjugates with FT MS
188

G.  Conclusions
188

 IV.
TANDEM MASS SPECTROMETRY OF GLYCOPEPTIDES
189

A.  Ionization of Glycopeptides
189

B.  CID of Glycopeptides
190

    1.  Selective Identification of Glycopeptides with Tandem MS
190

    2.  CID of O‐Linked Glycopeptides
191

    3.  CID of N‐Linked Glycopeptides
191

C.  Electron Capture Dissociation of Glycopeptides
193

D.  Conclusions
193

 V.
MASS SPECTROMETRY OF SIALYLATED GLYCOCONJUGATES
195

A.  Permethylation of Sialylated Oligosaccharides
195

B.  MALDI‐MS of Sialylated Glycoconjugates
195

    1.  Anionic Dopants for Analysis of Sialylated Glycoconjugates
196

    2.  Methyl Esterification to Stabilize Sialic Acid Residues
196

    3.  Perbenzolylation to Stabilize Sialic Acid Residues
196

    4.  High‐Pressure MALDI of Sialylated Glycoconjugates
196

C.  ESI MS of Sialylated Oligosaccharides
197

D.  Tandem MS of Sialylated Oligosaccharides
198

E.  Conclusions
199

 VI.
MASS SPECTROMETRY OF SULFATED OLIGOSACCHARIDES
199

A.  Derivatization
199

B.  Ionization Methods
199

    1.  Fast Atom Bombardment
199

    2.  MALDI
202

        a.  MALDI of Sulfated Peptides
202

        b.  Direct MALDI of Sulfated Oligosaccharides
202

        c.  Use of Basic Peptides for MALDI of Polysulfated Oligosaccharides
203

        d.  MALDI Analysis of Protein‐Sulfated Oligosaccharide Complexes
204

    3.  ESI of Sulfated Oligosaccharides
205

    4.  On‐Line Separation Systems for Sulfated Carbohydrates
206

C.  Tandem MS of Sulfated Oligosaccharides
206

    1.  Lessons from CID of Sulfated Peptides
206

    2.  Tandem MS of Mono‐ and Di‐Sulfated Oligosaccharides
207

    3.  Precursor‐Ion and Neutral‐Loss Scans for Sulfated Glycoconjugates
208

    4.  Determination of Positional Sulfation Isomers in GAG Disaccharides
208

    5.  Tandem Mass Spectrometric Quantification of GAG Disaccharides
209

    6.  Tandem Mass Spectrometric Analysis of GAG Oligosaccharides
211

        a.  CS Oligosaccharides
211

        b.  Heparin/HS Oligosaccharides
214

D.  Conclusions
214

 VII.
OVERALL CONCLUSIONS
215

 VIII.
ABBREVIATIONS
215

References
216

Glycosylation is a common post‐translational modification to cell surface and extracellular matrix (ECM) proteins as well as to lipids. As a result, cells carry a dense coat of carbohydrates on their surfaces that mediates a wide variety of cell–cell and cell–matrix interactions that are crucial to development and function. Because of the historical difficulties with the analysis of complex carbohydrate structures, a detailed understanding of their roles in biology has been slow to develop. Just as mass spectrometry has proven to be the core technology behind proteomics, it stands to play a similar role in the study of the functional implications of carbohydrate expression, known as glycomics. This review summarizes the state of knowledge for the mass spectrometric analysis of oligosaccharides with regard to neutral, sialylated, and sulfated compound classes. Mass spectrometric techniques for the ionization and fragmentation of oligosaccharides are discussed so as to give the reader the background to make informed decisions to solve structure‐activity relations in glycomics. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 23:161–227, 2004.