Handbook of Solvents - George Wypych - ChemTech - Ventech!

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Figure 12.2.2. (a) Snapshot of random chains of homoglucans obtained from Monte Carlo calculation and (b) ordered
helical structures of the same polymers as measured by X-ray diffraction method.
cal properties, which form the basis of the industrial applications of polysaccharides are directly
related to the structure/conformation of the chain.
Many biological macromolecules in the solid state assume regular helices, which can
be represented by means of a few geometrical parameters and symmetry relations. These
helical structures originate from the stereo regularity of backbone monomers and are easily
described, conceptually simple, and therefore used (all too often) as an idealized model for
all the actual shapes. Elements of helical regularity are essential in the description of the
structure of nucleic acids and polypeptides. Some biopolymers, e.g., globular proteins, almost
completely preserve their structural regularity in solution. Such globular structures are
not known in polysaccharides. Nonetheless, helical conformations have been proposed to
represent the structure of many polysaccharides, microbial glycans in particular. An excellent
overview of the stereo-regular helical conformations of polysaccharides deduced from
X-ray fiber diffraction studies has recently been published. 6