Chain flexibility and branching effects on arabinogalactan conformation in solution

The structural and conformational characteristics of three arabinogalactans were investigated in aqueous and aprotic organic solutions using small-angle X-ray scattering (SAXS), dynamic light scattering, and viscosity measurements. This study aimed to clarify the dimensional and hydrodynamic properties related to the branching structure of a type II arabinogalactan extracted from jasmine tea leaves by comparing it with linear arabinogalactan (LG) and highly branched larch arabinogalactan (LAG60) samples. The obtained form factor P(q) and the radius of gyration R_g for LG were analyzed in terms of the wormlike chain model with the Kuhn segment length of 2.80 nm, a measure of chain stiffness. This result indicates higher chain flexibility than that of polysaccharides whose backbone consists of 1,4-linked hexoses in a good solvent. The P(q) data of the other two arabinogalactans, LAG60 and JSP-1a, which have short branches, were well described by the hyperbranched chain model. This model considers the fractal dimensions of partial chains in good solvent systems. The model uses a fixed number of branching points that exclude the contribution of single-sugar-residue branches. In addition, the hydrodynamic properties and the second virial coefficient were consistent with the P(q) and R_g results.