Oligosaccharides carbohydrate structures

The larger oligosaccharides are present as a branched chain. Carbohydrate attached to threonine or serine generally occurs as a short oligosaccharide. Carbohydrate structures present in human IgG or IgM, worked out by Dr. Stuart Komfeld and his associates, are shown in Fig. 

In order to investigate, and deduce, the complex carbohydrate structures of glycoproteins, it must be possible to release, and isolate, the oligosaccharide chain(s) from the glycoprotein. Following this, the structure is usually deduced by a combination of enzymic, chemical, and instrumental methods.34-36... 

Ester-type dimers illustrate the four-step approach for identification of carbohydrate structural elements in the oligosaccharide cores by NMR spectroscopy. Eor these type of compounds, edited NMR sub-spectra have permitted the assignment of all of the resonances in both monomeric units (22, 78). Spectroscopic simulation of the coupling constants can be deduced for proton resonances with a non-first-order resolution. Figure 2 illustrates this approach for batatin 1 (230) the... 

Duus J0, Gotfredsen CH, Bock K (2000) Carbohydrate Structural Determination by NMR Spectroscopy Modem Methods and Limitations. Chem Rev 100 4589 Agrawal PK, Pathak AK (1996) Nuclear Magnetic Resonance Spectroscopic Approaches for the Determination of friterglycosidic Linkage and Sequence in Oligosaccharides. Phytochem Anal 7 113... 

Nonetheless, there is one macromolecule — the Fc fragment of the human IgGj Immunoglobulin — with a complex carbohydrate structure attached to it which allowed the determination of the decasaceharide conformation down to atomic resolution [37, 38] (cf. below). Another system which allowed the resolution of the oligosaccharide structure is the rabbit IgGx Fc-fragment [39]. 

O-type oligosaccharides form another important group of carbohydrate structures found as parts of glycoproteins. They are either linked to serine or threonine of the protein backbone. 

Many proteins synthesized by the ribosomes of the RER contain short chains of carbohydrates (oligosaccharides) and are called glycoproteins. The oligosaccharides are of two main types O-linked (to the OH side chain of Ser or Thr) and N-linked (to the NH2 side chain of Asn). Some proteins are attached to the plasma membrane by a third type of carbohydrate structure called a glycosyl phosphatidylinositol (GPI) anchor. 

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