Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: Atomic force microscopy and static molecular modelling

Peter Cooper, Kolin Harinda Rajapaksha, Thomas Barclay, Milena Ginic-Markovic, Andrea Gerson, Nikolai Petrovsky

    Research output: Contribution to journalArticlepeer-review

    18 Citations (Scopus)

    Abstract

    Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would 'lock in' each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts.

    Original languageEnglish
    Pages (from-to)964-972
    Number of pages9
    JournalCARBOHYDRATE POLYMERS
    Volume117
    DOIs
    Publication statusPublished - 6 Mar 2015

    Keywords

    • Adjuvant
    • Isoform
    • Model
    • Structure
    • Vaccine

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