Molecular mechanisms underlying amylose aggregation and gelation

The molecular origin of the aqueous aggregation and gelation behavior of amylose is shown to lie in the formation of interchain double helices. Gelation is shown to be possible from "dilute" nonentangled amylose solutions, and no correlation is found between critical gelling concentrations and coil overlap concentrations for a range of amylose chain lengths. NMR and X-ray diffraction experiments show that amyloses precipitated from dilute aqueous solution contain only B-type aggregated double helices and that amylose gels contain rigid double-helical "junction zones" interconnected by more mobile amorphous single-chain segments. Optical rotation results suggest that the double-helix structure underlying amylose aggregation and gelation may have a left-handed conformation.