Carbohydrate linkages, structural analysis

V. Structural Analysis of Glycopeptides and Glycoproteins Containing Unusual Carbohydrate-Protein Linkages... 

Multiple-ion monitoring is, however, of considerable value in structural studies, but only if model compounds of known structure are available for comparison. Such an approach has been used in the study of the carbohydrate structures of glycoproteins from different tissues.50 Separation of glycopeptides obtained from various tissues was performed on columns of concanavalin A-Sepharose. Structural analysis by multiple-ion monitoring of partially methylated, alditol acetates derived from the various fractions indicated that the glycopeptides were separated according to the linkage pattern of mannose (see Fig. 1). 

Carpita NC, Shea EM (1989) Linkage structure of carbohydrates by gas chromotography-mass spectrometry (GC-MS) of partially methylated alditol acetates. In Biermann CJ, McGinnis GD (eds) Analysis of carbohydrates by GLC and MS. CRC Press, Boca Raton, FL, p 157... 

The present article summarizes the data on application of hydrogen fluoride for structural analysis of polysaccharides, primarily those of bacterial origin. Some regularities in the stability of glycosidic linkages of different monosaccharides, and the mechanism of interaction between hydrogen fluoride and carbohydrates, are briefly discussed. The experimental technique for carrying out solvolysis is also described. 

Practical applications are again stressed in the Chapter by Lonngren and Svensson (Stockholm) on Mass Spectrometry in Stmctural Analysis of Natural Carbohydrates. They build on the fundamentals of carbohydrate mass spectrometry, as laid down by Kochetkov and Chizhov in Volume 21, and demonstrate the profound analytical value of mass spectrometry for structural analysis of complex polysaccharides. In particular, this tool has dramatically increased the scope of the traditional methylation linkage-analysis procedure, especially when used in conjunction with gas-liquid chromatographic methods of separation. The latter topic is the subject of complementary Chapters by Dutton, one already published in Volume 28 and the other scheduled for publication in Volume 30. 

Fractionated LCC [22] 5 + 2 Suitable to address LCC heterogeneities in terms of lignin and carbohydrates structures analysis of LCC linkages is problematic... 

Also, they are used for the structural analysis of carbohydrates (117). The information obtained is not limited to that obtained by analysis of the hydrolysis fragments because the specificity of enzyme action, a specificity based on type of monosaccharide and type of linkage, leads to significant data being obtained, by a process of elimination, from enzyme resistant structures and partially hydrolyzed structures. The enzymes which hydrolyse polysaccharides are divided into two groups, endo- and exo-polysaccharide hydrolases. Endo- polysaccharide hydrolases are specific for linkage and... 

Although beyond the scope of this chapter, it is worth remembering that El has enjoyed considerable success in the analysis of small carbohydrates, particularly monosaccharides, and is still valuable as the ionization method in combined gas chromatography/mass spectrometry (GC/MS) systems for the determination of composition and linkage. Methylation analysis whereby polysaccharides are permethylated, hydrolyzed and then further acetylated is still a valuable technique for structural investigation and should not be discarded in the light of the more recently developed techniques such as ESI and MALDI. Methods for permethylation of carbohydrates have recently been reviewed. ... 

Structural analysis of proteins has shown that up to half of naturally occurring proteins are subject to post-translational modifications with the vast majority glycosylated. These covalent linkages involve several amino acids and have distinct structrual characteristics. In addition, a large number of lipids have covalently attached carbohydrate, necessary for their biological functions. 

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