Polysaccharides derivatives, chemically reactive

Deoxy sugars. See Sugars, deoxy. Derivatives, chemically reactive, of polysaccharides, 29, 305—405 Desulfurization,... 

Kennedy, John F., Chemically Reactive Derivatives of Polysaccharides, 29, 305-405... 

Kennedy, J. F., Chemically reactive derivatives of polysaccharides. Advances Carbohydrate Chem. Biochem., ... 

It is important to compare the structural features of proteins with those of synthetic polymers or of polysaccharides in order to determine the specific properties of the derivative materials. Contrary to homopolymers or copolymers in which one or two monomers are repeated, proteins are heteropolymers consisting of amino acids. Proteins have a specific amino acid sequence and spatial conformation which determine their chemical reactivity and thus their potential for the formation of linkages that differ with respect to their position, nature and/or energy. This heterogenic structure provides many opportunities for potential crosslinking or chemical grafting—it even facilitates modification of the film-forming properties and end-product properties. 

The compositional studies discussed in this paper have provided some insights into the DOM cycle. For example, monomer level studies have shown that the chemical composition of HMWDOM is homogeneous in the surface ocean (Aluwihare et al, 1997 McCarthy et al, 1996). Compositional differences between the surface and deep ocean have demonstrated that polysaccharides are reactive and removed with depth (Aluwihare et al, 2002 Benner et al, 1992) furthermore, the relative abundance of amides resembhng those found in N-acetyl glucosamine also decreases with depth suggesting that these compounds are reactive and likely derived from surface ocean productivity (Aluwihare et al, 2005 Benner and Kaiser, 2003). Amino acid compositions and quantities exhibit no vertical trend and certain amino acids could have a common source throughout the ocean (McCarthy et al, 1998). D enantiomers of several amino acids are also ubiquitous in HMWDOM and indicate the presence of dissolved peptides derived from bacteria. 

During the past ten years, the l,6-anhydro-/3-D-hexopyranoses have found wide application in the synthesis of hexoses and their derivatives, and of oligosaccharides, and for polymerization to polysaccharides. They can be used as model compounds in studying the physical and chemical properties of monosaccharides, as has been shown, for example, by nuclear magnetic resonance (n.m.r.) studies, and also by studies of (a) their chiroptical properties, (b) the partial reactivity of hydroxyl groups, and (c) their ability to form complexes. 

In the years since controversies concerning the chemical structure of such major polysaccharides as cellulose and starch were resolved, the polysaccharide chemist has had little need for x-ray information in working out details of chemical structure. Indeed, the number of detailed x-ray studies on polysaccharides is so much smaller than the number of chemical studies that it is easy to understand why this subject has not been reviewed in this Series previously. Nevertheless, the great commercial importance of cellulose fibers and cellulose derivatives, and the influence of fiber morphology on reactivity, have resulted in a considerable volume of x-ray work relative to this particular material. A review on polymer unit-... 

In addition, because of the presence of —OH groups, natural polysaccharides may be modified by controlled chemical reaction to give derivatives with new specific properties industrial derivatives are mainly obtained from cellulose (qv), starch (qv), and chitin and chitosan (qv). The presence of these —OH functional groups is also the origin of interaction with water molecules (hydrophilic character of oligo- and polysaccharides) and intra- and interchain H-bond network formation playing a role in reactivity control, swelling, or dissolution rate. 

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