Molecular modeling of substituted polysaccharides

X-ray diffraction patterns of gellan, high acyl native gellan and branched polymer welan correspond to polycrystalline and well oriented specimens. Their molecular structures are strikingly similar, but their packing arrangements are not. The benzyl ester of gellan diffracts like gellan implying that a gellan-like double helix can sustain this substitution. Likewise, the benzyl ester of hyaluronan can adopt any of the reported single- and double-helical forms of hyaluronan itself. Carboxymethylhydroxypropyl guaran (CMHPG) diffracts similarly to guaran. The hydroxypropyl and carboxymethyl groups can cause favorable association of a pair of CMHPG chains which can further be stabilized by divalent cations, one for two carboxymethyl groups belonging to different chains. X-ray data combined with modeling calculations have revealed the details of the molecular architectures in each case to varying extents.