Polysaccharides relative reactivities

Stacey, M. See also, Foster, A. B. Stacey, M. See also, Overend, W. G. Stoloff, Leonard, Polysaccharide Hydrocolloids of Commerce, 13, 265-287 SuGiHARA, James M., Relative Reactivities of Hydroxyl Groups of Carbohydrates, 8,1-44... 

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. 

We have studied the relative reactivity of cellulose and mixed polysaccharides (III) and (IV) in reactions with aqueous and alcoholic solutions of NaOH. The data on the composition of alkali compounds of polysaccharides are given in Table 6. As seen from the data presented in Table 6, the amount of bound alkali in preparations of alkaline compounds of mixed polysaccharides is le than in alkali cdlulose obtained under the same conditions, the DS with respect to NaOH decreasing with increasing content of altrose units in polysaccharide (III) and of 3,6-anhydroglucose units in polysaccharide (IV). 

During our studies on cellulose chemistry ), we have encountered an unusual pattern of solubilities of various celluloses and related polysaccharides in one of the nonaqueous cellulose solvent systems we investigated, the S02-diethylamine(DEA)-dimethyl-sulfoxide(DMSO) system. In this paper, we propose an interpretation of this pattern in terms of intra- and intermolecular hydrogen bonds in native, mercerized and regenerated celluloses. We also consider parallels with the relative reactivities of hydroxyl groups in glucose residues of cellulose toward etherification, under basic conditions, and the data from solid-state C-NMR reported by Atalla and others ( - ) ... 

The saturated hydrocarbon moieties give lipids an aliphatic character, and thus hydro-phobic properties, which limit their loss from artefacts by water leaching. However, they are subject to chemical and microbiological alterations since they have a limited number of reactive sites, they are relatively less susceptible to structural modification and degradation than polysaccharides, proteins and nucleotides. 

A very interesting group of polysaccharides isolated from cornstarch hydrolysates are known as cyclodextrins. One of these compounds, cyclohexaamylose, is a large doughnut-shaped molecule with a central cavity that literally can engulf a small, relatively nonpolar organic molecule and hold it in water solution, similar to a micelle (Section 18-2F). As with micelles, unusual reactivity is exhibited by the bound molecules. An example is the change in the ortho-para... 

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-... 

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