Polysaccharides chemical structure

Fig. 8 Preparation of amphiphilic polysaccharide. Chemical structures of deoxycholic acid-modified chitosan (a) and Phe-modified pectin (pectin-gra/t-Phe) (b). SEM image of nanoparticles prepared from pectin-gra/t-Phe (c)...

Of great interest is the possible determination of structures of pneumococcus polysaccharides by comparison with a known chemical structure such as dextran. The extent of the cross-precipitation reactions43 of dextran with various pneumococcus antisera indicates the closeness of the relationships between the structures of dextran and of the various pneumococcus polysaccharides. 

Although polysaccharide metabolic products of molds and yeasts are not strictly bacterial polysaccharides, they are considered briefly here because of similarities in chemical structure (see also page 191). 

Figure 7.7 Structure of a generalized LPS molecule. LPS constitutes the major structural component of the outer membrane of Gram-negative bacteria. Although LPSs of different Gram-negative organisms differ in their chemical structure, each consists of a complex polysaccharide component, linked to a lipid component. Refer to text for specific details...

Investigations conducted at the Canadian Government Research Laboratories in Ottawa on the chemical structures of Neisseria meni-gitidis antigens have mainly been based on the interpretation of 13C-n.m.r. spectra. The polysaccharides of serogroups A, B, C, W135, X, Y,165 29e,166 and BO167 were characterized as complex polysaccharides,... 

Observation of displacement effects resulting from O-substitution, and use of standards, led to the assignment of the chemical structure of the polysaccharide of Neisseria meningitidis serogroup 29e, which consists of 2-acetamido-2-deoxy-D-galactosyl and partly acetylated 3-deoxy-D-manno-octulosylonic acid (KDO) residues.166 The 13C-n.m.r. spectrum of the O-deacetylated polymer (see Fig. 36,B) contained 15 signals out of the possible 16 expected from an alternating structure. Comparison of these resonances with those of the anomers of 2-aceta-... 

Different classifications for the chiral CSPs have been described. They are based on the chemical structure of the chiral selectors and on the chiral recognition mechanism involved. In this chapter we will use a classification based mainly on the chemical structure of the selectors. The selectors are classified in three groups (i) CSPs with low-molecular-weight selectors, such as Pirkle type CSPs, ionic and ligand exchange CSPs, (ii) CSPs with macrocyclic selectors, such as CDs, crown-ethers and macrocyclic antibiotics, and (iii) CSPs with macromolecular selectors, such as polysaccharides, synthetic polymers, molecular imprinted polymers and proteins. These different types of CSPs, frequently used for the analysis of chiral pharmaceuticals, are discussed in more detail later. 

IWo chapters treat widely divergent aspects of the aqueous degradation of carbohydrates. Christopher J. Biermann (Corvallis) discusses aqueous acidic hydrolysis and other cleavages of glycosidic linkages in oligo- and polysaccharides, with specific emphasis on their relation to procedures for determination of chemical structure. In the final chapter, Olof Theander (Uppsala) and David A. Nelson (Richland) provide an informative treatment of the... 

Figure 3.1 Chemical structures of the current most successfully employed derivatised polysaccharide CSPs. (a) CHIRALPAK AD Amylose tris (3,5-dimethylphenylcarbamate) coated onto a silica support, (b) CHIRALPAK AS Amylose tris [(S)-a-methylbenzylcarbamate] coated onto a silica support, (c) CHIRALCEL OD Cellulose tris (3,5-dimethylphenylcarbamate) coated onto a silica support, (d) CHIRALCEL OJ Cellulose tris (4-methylbenzoate) coated onto a silica support.

Fortunately from the chemists point of view, there are polysaccharides with blood group activity more readily accessible than those from erythrocytes, and it is with the former that most chemical investigations have been concerned, although the relationship between these and the blood group substances proper from erythrocytes is not yet clear. Indeed the relationship may be no more than a close similarity in chemical structure of some parts of the molecular complex. 

Contents 1. Introduction to Marine Sulfated Polysaccharides A High Tendency for Regular Chemical Structures in Invertebrates 196... 

INTRODUCTION TO MARINE SULFATED POLYSACCHARIDES A HIGH TENDENCY FOR REGULAR CHEMICAL STRUCTURES IN INVERTEBRATES... 

Non-reserve polysaccharides seem to function in biological tissues through the part they play in cohesion, the retention of water and salts, the physical organization, and the elasticity and general texture. Polysaccharide conformation and association, as well as chemical structure, are obviously involved in the control of such properties. The polysaccharide-polysaccharide interactions considered in this Section can be regarded (in the nomenclature of protein biochemistry) as showing secondary, tertiary, and quaternary structure.4W>2W8 The... 

The specific optical rotation of these polymers ([a]f> + 91° =b 5°) led Schuerch and coworkers 1 to suggest that they contain a minor preponderance of a-D-glucoeidic linkages. Only pyranoid forms were assumed to be present. In view of the finding of furanoid residues in other synthetic polysaccharides,15 1 2 this supposition is no longer valid. Additional experimental data, such as the results of methylation studies, must be acquired before the chemical structure of these complicated polymers can be formulated. 

Depending upon chemical structure and the conformations that are possible, polysaccharides in solution may develop secondary structures such as helices, tertiary structures formed from junction zones or by double helix or triple helix unions and even quaternary structures from the cross linking of tertiary structures. Polysaccharides thus mimic proteins and nucleic acids, which are specific types of sugar-phosphoric acid copolymers. 

Several physicochemical properties of dietary fiber Contribule to its physiological role. Water-holding capacity, ion-exchange capacity, solution viscusity, density, and molecular interactions are characteristics determined by the chemical structure of the component polysaccharides, their crystallinity, and surface area. 

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