Microfibril diameter in celery collenchyma cellulose: X-ray scattering and NMR evidence

Craig J Kennedy, Graeme J Cameron, Adriana Šturcová, David C Apperley, Clemens M Altaner, Timothy J Wess, Michael C Jarvis

    Research output: Contribution to journalArticle

    90 Citations (Scopus)

    Abstract

    Cellulose isolated from celery collenchyma
    is typical of the low-crystallinity celluloses
    that can be isolated from primary cell-walls of
    higher plants, except that it is oriented with high
    uniformity. The diameter of the microfibrils of
    celery collenchyma cellulose was estimated by
    three separate approaches: 13C NMR measurement
    of the ratio of surface to interior chains;
    estimation of the dimensions of the crystalline
    lattice from wide angle X-ray scattering (WAXS)
    measurements using the Scherrer equation; and
    the observation that microfibrils of this form of
    cellulose have the unusual property of packing
    into an irregular array from which small angle
    X-ray scattering (SAXS) shows features of both
    form and interference functions. The interference
    function contributing to the SAXS pattern implied
    a mean microfibril centre-to-centre distance
    of 3.6 nm, providing an upper limit for the
    diameter. However modelling of the scattering
    pattern from an irregular array of microfibrils
    showed that the observed scattering curve could
    be matched at a range of diameters down to
    2.4 nm, with the intervening space more or less
    sparsely occupied by hemicellulose chains. The
    lateral extent of the crystalline lattice normal to
    the 200 plane was estimated as a minimum of
    2.4 nm by WAXS through the Scherrer equation,
    and a diameter of 2.6 nm was implied by the
    surface: volume ratio determined by 13C NMR.
    The WAXS and NMR measurements both
    depended on the assumption that the surface
    chains were positioned within an extension of the
    crystalline lattice. The reliability of this assumption
    is uncertain. If the surface chains deviated
    from the lattice, both the WAXS and the NMR
    data would imply larger microfibril diameters
    within the range consistent with the SAXS
    pattern. The evidence presented is therefore all
    consistent with microfibril diameters from about
    2.4 to 3.6 nm, larger than has previously been
    suggested for primary-wall cellulose. Some degree
    of aggregation may have occurred during the
    isolation of the cellulose, but the larger microfibril
    diameters within the range proposed are a consequence
    of the novel interpretation of the experimental data from WAXS and NMR and
    are consistent with previously published data if
    these are similarly interpreted.
    Original languageEnglish
    Pages (from-to)235-246
    Number of pages12
    JournalCellulose
    Volume14
    Issue number3
    DOIs
    Publication statusPublished - 1 Jun 2007

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