Polysaccharide classification

There is no ideal system of polysaccharide classification [3]. The best system should be that based on chemical structure. However, because of their polymolecularity, which limits descriptions to statistical structures in many cases, and the great variety of structures, classifying polysaccharides in this way has limitations. Combinations of the following categories are used [3] ... 

Table 1. Classification of Selected, Native Polysaccharides by Structure...

Within the scope of this review, the contributions of the last decade concerning cell-wall polysaccharides isolated from woody and other plant tissues will be reviewed according to the above-proposed classification of hemicelluloses including larch arabinogalactans. The present review article updates and extends previous reviews [3-5] and will focus in particular on new investigated plant sources, isolation methods, structural features, physicochemical and various functional properties of hemicelluloses. Attention will also be paid to the modification of isolated hemicelluloses or hemicellulosic materials and the appHcation possibiUties of hemicelluloses and their derivatives, including their use for the production of composite materials and other biomaterials. 

Once a general conformation type or preliminary classification has been established it is possible to use sedimentation data to obtain more detailed information about polysaccharide conformation. For example, the low value of ks/[v 0 25 found for the bacterial polysaccharide xylinan has been considered to be due to asymmetry [115]. If we then assume a rigid structure the approximate theory of Rowe [36,37] can be applied in terms of a prolate ellipsoid of revolution to estimate the aspect ratio p L/d for a rod, where L is the rod length and d is its diameter) 80. 

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. 

The molecules that form the foundation of living systems are often organized into four categories. They are the primary metabolites nucleic acids, proteins, carbohydrates, and lipids. The categories can be grouped together in different ways, based on features that they have in common. For example, nucleic acids, proteins, and polysaccharides are polymeric. Nucleic acids and proteins are further related because they are templated polymers. Other classification systems are also possible.1 Interest in the development of size-expanded versions of biomolecules has grown over the past... 

An attempt has been made to classify gums into two main groups (a) real gums which are those plant products which form a clear solution in water and (b) vegetable mucilages which are those which swell but do not dissolve completely in water. This classification is useful but not entirely satisfactory since there are exceptions. Thus gum traga-canth, a tree exudate and a true plant gum, is only partially soluble in water and exhibits those properties normally attributed to mucilages. In this section of the article the term plant gum will be restricted to those complex acid polysaccharides which are exuded from trees either spontaneously or after mechanical injury. 

Hegnauer, R. and Grayer-Barkmeijer, R.J., Relevance of seed polysaccharides and flavonoids for the classification of the Leguminosae a chemotaxonomic approach. Phytochemistry, 34, 3, 1993. 

Blake and Richards26 carefully examined all of the steps involved in the analysis of complex polysaccharides, and preferred to use the alditol acetates in studies on the classification,428 fractionation,427 and molecular aggregation428 of hemicelluloses and speargrass xylan.420,430... 

The suggested classification of polysaccharide structures seems to be useful for prediction of the mechanisms of chain assembly. Investigation of these mechanisms for other types of polysaccharide chains, especially for the very frequent UT type, should be particularly interesting. 

The serogroup classification of Salmonella bacteria, according to the Kauffmann-White scheme (2), is based on the antigenic specificities which reside in the polysaccharide chain (the... 

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