Carbohydrates, branched-chain properties

Polysaccharides are the most abundant constituents of living matter. They are in principle built up in the same manner as oligosaccharides. The chain molecules can be either linear or branched, a fact that markedly affects the physical properties of the polysaccharides. The carbohydrate material in plants is largely composed of cellulose and hemicelluloses. Chapter 3 deals with their structure and properties. 

Alditols polyols are readily renewable, inexpensive and harmless to the environment. By incorporation of polyols into aliphatic polyesters, functional linear or hyperbranched polymers can be prepared with specific biological activities and/or that respond to environmental stimuli. Polyesters with carbohydrate or polyol repeat units in chains have been prepared by chemical methods. " In some cases, the reaction conditions led to hyperbranched polymers (HBPs). The highly branched architecture of HBPs leads to unusual mechanical, rheological and compatibility properties. " These distinguishing characteristics have garnered interest for their use in numerous industrial and biomedical fields. Chemical routes to linear polyol-polyesters require elaborate protection-deprotection steps ". Furthermore, condensation routes to hyperbranched polymers generally require harsh reaction conditions such as temperatures above 150 C and highly acidic catalysts ". ... 

The unique advantages of NMR in the analysis of carbohydrate structure are only fully apparent in consideration of points 3 and 4. In contrast to the unbranched polymeric nature of polypeptide and nucleic acid chains, carbohydrates may be branched structures, capable of substitution at several points. The monosaccharide constituents are polymerized in nature by a non-template directed, enzymatic process the resulting oligosaccharides are often heterogeneous, differing in detail from a consensus structure. NMR is particularly efficient at investigating the solution conformations, and the dynamic properties of such molecules. 

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