Polysaccharide triple helices

Yanaki, T., Norisuye, T., and Fujita, H., Triple helix of schizophyllum commune polysaccharide in dilute solution. 3. Hydrodynamic properties in water, Macromolecules, 13, 1462, 1980. 

Depending upon chemical structure and the conformations that are possible, polysaccharides in solution may develop secondary structures such as helices, tertiary structures formed from junction zones or by double helix or triple helix unions and even quaternary structures from the cross linking of tertiary structures. Polysaccharides thus mimic proteins and nucleic acids, which are specific types of sugar-phosphoric acid copolymers. 

Three potential helical structures of polysaccharides, (a) Single helix with twofold screw axis (cellulose) (b) double helix (amylose) and (c) triple helix (/ , 1-3 glucan) (according to Rees [4]). The particular structure depends largely on the constraints imposed by hydrogen-bonds and rotational freedoms around the glycosidic intermonomer bonds (i. e., O Fig. 3, energy barriers to rotation)... 

Curdlan is a bacterial polysaccharide made by Agrobacterium biovar [87,88,89]. It is a linear (1 3)- -glucan (MW 73,000) that forms a triple helix. Curdlan is insoluble in cold water. When aqueous dispersions of curdlan are heated, two types of gels form. First curdlan dissolves. When the solution reaches 55-66 °C, then is cooled, a reversible gel forms. The gel melts when held at about 60 °C. When the thermoreversible gel is heated to a temperature above 80 °C, an irreversible gel forms. Heating to higher temperatures results in stronger irreversible gels. Transition temperatures are a function of concentration. 

Another polysaccharide which displays interesting hydration phenomena is (l->-3 )-B-D-g 1 ucan, often called paramylon ( ), curdlan ( ) or laminaran (16). The molecular crystalline arrangement o P this polysaccharide consists of a triple helix formed by three intertwining 6j hel ices. (, 23) Two polymorphs... 

Other polysaccharides as well suit the formation of supramolecular structures with carbon nanotubes. For instance, a complex may be formed with schizophyl-lan. This (1-1,3-glucane exists as triple helix and winds around the SWNT accordingly. Functionalizing the termini of the glucane, for example, with ladosides, provides a compound that is soluble in water. Furthermore, it may confer to the product an increased affinity, for example, to lecture. 

Since polysaccharides have polar groups as well as some hydrophobic features, there can be inter residue interactions in a polysaccharide as well, but these attractions are expressed as interactions between different chains giving rise to such phenomena as crystallization which is prominently expressed in chitin and in cellulose. Other types of polysaccharides exhibit multistrand helix formation as in the case of sceleroglucan whose tendency for triple helix formation leads to unusual physical properties. Still other types of polysaccharides can form cross links in a more random way leading to gel formation as in the case of pectin, agarose and alginates. Chain interactions in other polysaccharides such as hyaluronan, chondroitin or... 

A Novel Triple Helix Consisting of One Polynucleotide and Two Polysaccharide Chains... 

Scleroglucan (from Sclerotinia sclemtiomm) is a 1 3 -D-glucan with additional 1 —> 6 (3-links (Fig. 13.9) that confer water solubility to it under ambient conditions, but do not significantly interfere with a triple helix gelling process, similar to that of curdlan [46]. Similar polysaccharides can also be extracted from other sources such as waste yeast. 

Palleschi A., Bocchinfuso G., Coviello T., Alhaique F., Molecular dynamics investigations of the polysaccharide scleroglu-can First study on the triple helix structure, Carbohyd. Res., 340(13), 2005, 2154-2162. 

Polysaccharides are generally indigestible to humans, so their effects are not manifested in the bloodstream. However, their physical movement through the colon appears to trigger certain physiological reactions in humans, possibly due to an immune reaction via the Peyer s patches. Immunostimulatory polysaccharides are large, insoluble, extensively branched molecules often occurring in triple helix formation (Turner 1998). 

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