Oligosaccharides determining structures

The final chapter, by Hounsell (London), also relates to an important aspect of glycoprotein structure, namely the structures and shapes, as determined by physicochemical methods, of oligosaccharide determinants of glycoproteins that are antigens and targets for binding of adhesion molecules. 

Structure A was chosen to have (p ip values near those for the single minimum energy structure determined for globoside using Bock and Lemiuex s HSEA program (39,40). Structure B was chosen because it also has

previous studies of oligosaccharide conformation. Structure C was chosen to have ip values displaced 120° from the other initial structures. 

Fast atom bombardment mass spectrometry (FABMS) has become an important addition to the ionization techniques available to the analytical chemist in recent years. It has been particularly useful in a number of diverse applications which include molecular weight determinations at high mass, peptide and oligosaccharide sequencing, structural analysis of organic compounds, determination of salts and metal complexes, and the analysis of ionic species in aqueous solutions. This paper will focus on some aspects of the quantitative measurement of ionic species in solution. The reader is referred to a more comprehensive review for more details of some of the examples given here as well as other applications (1). 

In many instances, the linkage oligosaccharide is associated with a peptide moiety, and thus the amino acid sequence must be established and, in addition, the structural parameters of the CPL oligosaccharide determined. The latter comprise (i) primary structure, (i i) type and location of noncarbohydrate substituents, and (i i i) the linkage to the peptide backbone. For gaining insight into structure-function relations, it is important for the three-dimensional structure to be determined. 

N.m.r. and mass spectrometric methods have been used to determine structures of 22 neutral oligosaccharides up to octasaccharides obtained from bovine submaxillary-gland mucin glycoprotein. ... 

A further aspect of the wide range of substrates for sialidases has been the analysis of these substrates. The determination of oligosaccharide chain structures has allowed precise study of sialidase specificity. A need for a spectrum of well defined substrates has developed as a prerequisite for the elucidation of sialidase specificity. The large body of data which has accumulated on the sialidases points to a number of characteristics general to sialidase action, and forms the basis of current knowledge about sialidases. 

Hen egg-white lysozyme catalyzes the hydrolysis of various oligosaccharides, especially those of bacterial cell walls. The elucidation of the X-ray structure of this enzyme by David Phillips and co-workers (Ref. 1) provided the first glimpse of the structure of an enzyme-active site. The determination of the structure of this enzyme with trisaccharide competitive inhibitors and biochemical studies led to a detailed model for lysozyme and its hexa N-acetyl glucoseamine (hexa-NAG) substrate (Fig. 6.1). These studies identified the C-O bond between the D and E residues of the substrate as the bond which is being specifically cleaved by the enzyme and located the residues Glu 37 and Asp 52 as the major catalytic residues. The initial structural studies led to various proposals of how catalysis might take place. Here we consider these proposals and show how to examine their validity by computer modeling approaches. 

The precise chemical nature of some of the ligands involved in selectin-ligand interactions has been determined. All three selectins bind sialylated and fucosy-lated oligosaccharides, and in particular all three bind sialyl-Lewis (Figure 47-12), a structure present on both glycoproteins and glycolipids. Whether this compound is the actual ligand involved in vivo is not estab-... 

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