Conformation of polysaccharides

IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN), Symbols for specifying the conformation of polysaccharide chains (Recommendations 1981), Eur. J. Biochem, 131, 5-7, (1983) Pure Appl. Chem., 55,1269-1272 (1983) ref. 2, pp. 177-179. 

Conversely, if we know the molecular weight we can make inferences about the conformation of polysaccharides in solution using Eq. 13 and other power-law relations. We will consider this in more detail after we have considered further molecular weight measurement by absolute (i.e. without assumptions concerning conformation) procedures. 

In 1963, V.S.R. Rao undertook a more ambitious task the prediction of the likely conformations of polysaccharides from a computerized survey of model structures ( ). As a result of atomic overlap, some model conformers had higher energies than others, a criterion by which most models could be rejected. These predictions were not accompanied by experimental data for the subject molecules, leaving to experimentalists the task of corroboration or refutation. Although many advances in computers and methods have occurred in the intervening decades, predicting polysaccharide conformations based upon relative conformational energies continues to be of substantial interest. 

CA of Polysaccharides. Polysaccharides adopt a wide variety of shapes that depend on their composition and their environment. In solution, polymers are almost always random coils that have local regions that might be similar to conformations that are found in the solid state. The chapter by Brant and Christ discusses conformations of polysaccharides in solutions both in terms of these local regions and by the overall shape of the random coil in terms of end-to-end distance, etc. The following discussion concerns only linear (unbranched) molecules, and refers only to regular polymers, i.e., those that have repeated sequences of monomeric residues located by screw-axis (helical) symmetry. 

Eur. J. Biochem. (1980) 111, 295-298 Nomenclature of unsaturated monosaccharides Eur. J. Biochem. (1981) 119, 1-3 Nomenclature of branched-chain monosaccharides Eur. J. Biochem. (1981) 119, 5-8 Abbreviated terminology of oligosaccharide chains /. Biol Chem. (1982) 257, 3347-3351 Polysaccharide nomenclature /. Biol Chem. (1982) 257, 3352-3354 Symbols for specifying the conformation of polysaccharide chains... 

Progress in the i.r. and Raman spectroscopy of polysaccharides was reviewed by Blackwell.194 In this review, work on polymorphic forms of amylose, on oriented films of glycosaminoglycans, and on bacterial polysaccharides was summarized. The usefulness of the vibrational spectra in determining the conformations of polysaccharides was shown. 

These structures and conformations of polysaccharide molecules and their intermolecular associations give polysaccharide solutions, polysaccharide dispersions, and polysaccharide gels their special properties in biologic systems and in industrial usage. The ease with which polysaccharides dissolve is related to their conformation and structure in many the same ways as is their solution behavior. 

Symbols for Specifying the Conformation of Polysaccharide Chains http //www. chcm.qmul.ac.uk/iupac/misc/psac.html... 

Wang Q, Cui SW (2005) Understanding the conformations of polysaccharides. In Cui SW (ed) Food carbohydrates. Taylor Francis, Boca Raton, FL, p 219... 

Finally, there is a pressing need for more-detailed information on the molecular fine-structure, or conformation, of polysaccharides in solution. The potential of small-angle x-ray diffraction for distinguishing between a random coil and a broken or partial helix in solution has been established. A better definition of the helical conformation of dissolved polysaccharides, which, because of basic chemical asymmetry, have a favored chirality ( handedness ), is awaited. This area of x-ray study is only beginning to be developed. ... 

Quantum mechanical and semi-empiiical calculations support this suggestion. For example, it has been shown that, contrary to earlier suggestions, lysozyme does not distort the chair conformation of polysaccharide pyranoside units [32]. Similarly, it has been suggested that the serine proteases distort the trigonal planar arrangement around the carbonyl carbon of amides and peptides (XVII) to a non-planar conformation which resembles the tetrahedral intermediate (XVIII). Support for this hypothesis came from X-ray studies of the trypsin-trypsin inhibitor complex [33]. 

At the molecular level, various specific and non-specific solvent-solute interactions may occur in polysaccharide solutions that may result in a change in the conformational shape, solubility, viscosity and other hydrodynamic and thermodynamic properties. Hydrophilic interactions such as hydrogen bonding and electrostatic interactions are believed to be factors that influence the conformation of polysaccharides in solution, although the question is being raised (more and more) as to the implication of patches of hydrophobic intermolecular interactions, especially for chain aggregations. One important feature is the... 

SOLVENT EFFECT ON CHAIN DIMENSIONS AND CONFORMATIONS OF POLYSACCHARIDES... 

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