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The mucin-type O-glycome in cancer aberrantly expresses the truncated glycans Tn (GalNAcα1-Ser/Thr) and STn (Neu5Acα2,6GalNAcα1-Ser/Thr). However, the role of Tn and STn in cancer and other diseases is not well understood. Our recent discovery of the self-binding properties (carbohydrate-carbohydrate interactions, CCIs) of Tn (Tn-Tn) and STn (STn-STn) provides a model for their possible roles in cellular transformation. We also review evidence that Tn and STn are members of a larger family of glycan tumor antigens that possess CCIs, which may participate in oncogenesis.

Scleroglucan is a (1,3)-β-D-glucan polysaccharide produced by the fungus Sclerotium. Dissolved in water at room temperature it adopts a linear, rigid, triple helical structure. Gelation of scleroglucan can be obtained by Schiff-base formation between partly periodate oxidized scleroglucan and the primary amine groups of chitosan. The scleraldehyde-chitosan gels exhibit a collapse transition when exposed to volume fractions of isopropanol, Wp, larger than 65%. The aim of the present study is to provide structural information concerning the local polymer distribution and the collapse transition in (1,3)-β-D-glucan-chitosan gels. Small angle x-ray scattering was used to investigate solutions and gels of scleroglucan in water, as well as in an aqueous mixture containing 65% isopropanol. The results reveal that in aqueous solution, the polysaccharide scleroglucan chains have an approximately cylindrical cross section of external diameter close to 17 Å. The gels display the same local structure, but form clusters on a longer distance scale. For the collapsed gels in the water-isopropanol mixture, partial phase separation occurs in which ordered domains of approximate size of 110 Å develop. This study indicates that local ordering in liquid-crystalline-type domains is a possible molecular mechanism contributing to the collapse of gels composed of semiflexible polymers. The triple helical structure of the molecule appears not to be conserved in the majority phase in this solvent, but it is conserved in the liquid crystalline domains. [ABSTRACT FROM AUTHOR]

Abstract: Recent advances regarding toroids of stiff polyelectrolytes include determination of the hexagonal polymer chain packing of compacted λ-phage DNA at the single-toroid level. Additionally, the crucial influence of chain stiffness in the formation of the toroidal geometry in the collapsed state has been experimentally demonstrated using the stiff polysaccharide xanthan. [Copyright &y& Elsevier]

Abstract: Comb-like branched (1→3)-β-d-glucans dissolve in water as stiff triple-helical structures. Dissociation followed by re-association leads to the formation of a blend of various macromolecular topologies, where the cyclic species make up a significant fraction. In this study, the molecular properties of these nanosized cyclic structures of (1→3)-β-d-glucans were probed using a combination of AFM and SEC-MALLS. The cyclic structures were obtained by subjecting linear triple-helical molecules of (1→3)-β-d-glucans to a denaturation–renaturation cycle, and the fraction of cyclic structures in the renatured sample was determined by AFM. Samples containing different known fractions of linear and circular molecules were studied by SEC with online multi-angle laser-light scattering and viscometric detectors. The molecular weight and the radius of gyration of the molecules eluting from the SEC column, as well as the concentration and the intrinsic viscosity, were determined simultaneously. By extrapolating the results to a situation of only circular species, the results allowed to determine the linear mass per unit length (ML) of not only the linear but also the circular morphologies of the (1→3)-β-d-glucans. The values obtained were ML=2140±180gmol−1nm−1 for the circular species and 2045±80gmol−1nm−1 for the linear species. This is the first direct determination of the ML parameter of the circular topology, and the results indicate that the reassociation of the individual chains yield a triplex structure also for the circular morphology, similar to the initial triple helix. [Copyright &y& Elsevier]

Techniques used in studies of polysaccharides, including chemical composition, linkage pattern, and higher order structures are in constant development. They provide information necessary for understanding of the polysaccharide properties and functions. Here, recent advancements in studies of the polysaccharides at the single-molecule level are highlighted. Over the last few years, single-molecule techniques such as force spectroscopy have improved in sensitivity and can today be used to detect forces in the pN range. In addition, these techniques can be used to investigate properties of single molecules close to physiological conditions. The challenges in the interpretation of the observations are aided by control experiments using well-characterised polysaccharides and by data provided by complementary methods. This field is expected to have increasing impact on the further advancement of the molecular understanding of the role of polysaccharides in various biological processes such as recognition and cell adhesion. [Copyright &y& Elsevier]