Oligosaccharide derived from glycoproteins

Ion-exchange chromatography combined with pulsed amperometric detection has been successfully employed for the analysis of neutral oligosaccharides (see Section 3.3.5.3). This method can be used for the separation of both oligosaccharides and glyco-peptides derived from glycoproteins, especially when they differ only in their oligosaccharide moiety. This method is also suitable for the identification and determination of 

Another example of the high selectivity of a latexed anion exchanger for the analysis of structurally isomeric oligosaccharide side chains of a glycoprotein is the chromatogram in Fig. 3-121. It shows the separation of mannose hexamers with terminal N- 

The different linkage of the individual mannose residues allows a baseline-resolved separation of both isomers under isocratic conditions. 

Surprisingly, the retention time does not simply increase with the molecular size. Thus, in comparison to the trisaccharide 1, only a slightly higher retention is observed for the nonasaccharide 9. Compared with the non-fucosylated heptasaccharide 7, the nonasaccharide has a markedly lower retention which can be traced back to the fucosyl substitution at C-3 of the N-acetylglucosamine residues and to steric problems between their acetamido groups and the hydroxide groups at C-2 of the fucose residue. 

The influence of the high acidity of an anomeric hydroxide group on retention is demonstrated by the retention behavior of compounds 4 and 5. The mere conversion of the pentasaccharide 5 to the corresponding sugar alcohol 4 leads to a decrease in retention time of about 15 minutes. This is probably due to a conformational transition of the branching mannose residue from the chair form, which is typical for pyranoses, into an open-chain structure. 

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The term mucolipidosis was introduced to denote diseases that combined features common to both mucopolysaccharidoses and sphingolipidoses (Chapter 24). Three mucolipidoses are listed in Table 48—7. In sialidosis (mucolipidosis I, ML-I), various oligosaccharides derived from glycoproteins and certain ganglio-sides can accumulate in tissues. I-cell disease (ML-II)... 

Structural Analysis of Oligosaccharides Derived from Glycoproteins... 

Figure 3.256 Separation of neutral oligosaccharides derived from glycoproteins. Separator column CarboPac PA100 eluent (A)...

The MALDI spectrum of a mixture of four oligosaccharides derived from the cleavage of a glycoprotein. Reproduced from Finnigan MAT documentation, with permission. 

Van Halbeek H, Breg J, Vliegenthart JE, Klein A, Lamblin G, Roussel P. Isolation and structural characterization of low-molecular-mass monosialyl oligosaccharides derived from respiratory-mucus glycoproteins of a patient suffering from bronchiectasis. Eur. J. Biochem. 1988 177(2) 443 60. 

While a limited number of apphcations of actual on-hne LC-MS in the characterization of oligosaccharides have been described (Ch. 20.4), numerous studies describe the utilization of liquid sample introduction into an ESI-MS system for the characterization of (mixtures of) oligosaccharides, eventually after prefractionation or preparative LC. Some examples in the characterization of oligosaccharides not derived from glycoproteins are highhghted in this section. Stractural characterization of glycans from glycoproteins is discussed in Ch. 19.4.2. 

K. Bock, J. Arnarp, J. Lonngren. The preferred conformation of oligosaccharides derived from the complex-type carbohydrate portion of glycoproteins. Eur. J. Biochem. 1982,129, 171-178. 

Y. Mechref, M. V. Novotny. Mass spectrometric mapping and sequencing of N-linked oligosaccharides derived from submicrogram amounts of glycoproteins. Anal. Chem. 1998, 70,455-463. 

Figure 3.249 Schematic representation of oligosaccharides derived from human glycoproteins. In A/-glycosidically bound oligomers, di-A/-acetylchitobiose together with three mannose residues are forming the core of the mannose (a), the complex (b), or the hybrid...

Due to the high number and complexity of potential carbohydrate compounds, a number of methods have been developed that allow identification of carbohydrate structures, depending on the analytical problem and conditions, either directly or in combination with other techniques. In general, oligosaccharide analysis derived from glycoproteins is divided into three phases ... 

A. Dell, H.R. Morris, R.L. Easton, M. Panico, M. Patankar, S. Oehninger, R. Koistinen, H. Koistinen, M. Seppala and G.F. Qark, Structural analysis of the oligosaccharides derived from glycodelin, a human glycoprotein with potent immunosuppressive and contraceptive activities. J. Biol Chem., 1995, 270, 24116 24126. 

Degradation of Free Polymannose-Type Oligosaccharides Derived from A -Linked Glycoproteins During Biosynthesis... 

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