Glycoconjugates and Carbohydrates

Glycoconjugates and Carbohydrates

Glycosaminoglycan Polysaccharide chain found in proteoglycans. Has a linear structure that features a repeating disaccharide unit comprised of glucosamine or galactosamine and a uronic acid or galactose. The amino sugars are generally N-acetylated and contain ester sulfate. The pattern of sulfation varies and may confer specific biological properties. Glycoside Acetal or ketal formed by substitution […]

Important Terms (Glycoconjugates and Carbohydrates)

Aglycone Group attached to the hydroxyl of a furanose or pyranose sugar to form a glycoside. Can vary from a simple methyl group to other sugars to complex alkaloids. Aldose Polyhydroxy aldehyde with three or more carbon atoms. When of sufficient length will form five-or six-membered ring (furanose or pyranose) hemiac-etals. Designated d- or l- […]

Glycoconjugates and Carbohydrates

THE UTILIZATION of carbohydrates as food sources, sweetening agents, and clothing materials dates back several thousand years. Likewise, the production of beer and wine was known in ancient times although the relationship to saccharides and fermentation was not appreciated then. Manufacture of sugar as a sweetener including refinements such as decolorization with charcoal also has […]

MONOSACCHARIDES Part 1 (Glycoconjugates and Carbohydrates)

It is generally accepted that monosaccharides, or simple sugars, may have three to nine carbon atoms in a linear chain. Thus the nomenclature aldotriose, aldotetrose, al-dopentose, etc., or ketotetrose, ketopentose, etc. The vast majority of naturally occurring sugars contain five or six carbon atoms. These saccharides are classified as d- or l-if they can be […]

MONOSACCHARIDES Part 2 (Glycoconjugates and Carbohydrates)

B. Chemical Transformations The chemistry of carbohydrates involves transformations at both the carbonyl function and the chain hydroxyl groups. The presence of multiple species of simple sugars in aqueous solution gives rise to complex reaction patterns wherein product distribution may well be determined by kinetic rather than thermodynamic considerations. 1. Reactions at the Carbonyl Group […]

OLIGOSACCHARIDES (Glycoconjugates and Carbohydrates)

The ability of the anomeric hydroxyl group of a sugar to be substituted with another sugar (via one of its hydroxyl groups), and for this process to be iterated leads to formation of di- and higher saccharides. Because several hydrox-yls are available for such linkages and the anomeric configuration can vary as well, the number […]

POLYSACCHARIDES (Glycoconjugates and Carbohydrates)

Polymeric saccharides can have 10,000 or more sugar units, four or five different sugars, and a branched structure. The diversity that can be envisioned is huge and much of it is actually observed. Classification of polysaccha-rides differentiates homopolymers (a single sugar type) and heteropolymers (two or more sugar types) with subtypes reflecting linear or branched […]

GLYCOCONJUGATES

Structural analysis of proteins has shown that up to half of naturally occurring proteins are subject to post-translational modifications with the vast majority glyco-sylated. 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. The glycoproteins may […]

ANALYTICAL METHODS (Glycoconjugates and Carbohydrates)

Classical methods for the determination of saccharide structures are rarely employed at this time. Thus, methyla-tion and periodate analyses, once the mainstay of carbohydrate work, have been superseded by mass spectrometry and nuclear magnetic resonance (NMR). Consider the typical problem—that of defining the complete structure of an oligosaccharide (polysaccharide), free or combined. Unlike procedures for […]