The majority of proteins are posttranslationally modified, the most significant change being glycosylation, i.e., the attachment of one or more oligosaccharide chains. Because of their long history, but also relative neglect until recently, the terminology for saccharides is diverse. Also a major problem in the glycosciences is that many different methods are necessary for oligosaccharide analysis, and this does not at first seem straightforward. I hope this chapter will demystify the structures and the analysis of glycoconjugates (glycoproteins, GPI-anchored proteins, glycolipids, and proteoglycans). The terminology is in fact easy to follow. It has simple beginnings: from glucose comes the generic term glycose, which is used in words such as glycosidic ring, glycoprotein, and so forth; from sucrose (a disaccharide of glucose and fructose) comes the word saccharide and, hence, oligosaccharide chain. In addition to glucose (Glc), there are seven other possible orientations of hydroxyl groups in hexoses of the formula C₆H₁₂O₆ (from whence comes the term carbohydrate) in the series allose (All), altrose (Alt), Glc, mannose (Man), gulose (Gul), idose (Ido), galactose (Gal), talose (Tal). However, in addition to hydroxyl groups on the ring carbons, there are also acetamido groups (Fig. 1), e.g., at C-2 in n-acetylglucosamine (GlcNAc) and n-acetylgalactosamine (GalNAc), and at C-5 in n-acetylneuraminic acid (NeuAc). There may also be present sulfate and phosphate esters. Other commonly occurring monosaccharides are the 6-deoxyhexose fucose (Fuc), the pentose xylose (Xyl), and the C-6 carboxyl uranic acids, glucuronic acid (GlcA), iduronic acid (IdoA), and galacturonic acid (GalA). The monosaccharides are linked together between the hydroxyl groups numbered around the glycosidic ring as shown in Fig. 1 and with α or β (anomeric) configuration, depending on the ring geometry (⁴C₁ or ¹C₄ for hexopyranoside rings) and linkage above or below the plane of the ring (Fig. 1).

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