Hydration effects on spacing of primary-wall cellulose microfibrils: a small angle X-ray scattering study |
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Authors: | Craig J Kennedy Adriana ?turcová Michael C Jarvis Timothy J Wess |
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Institution: | (1) Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff, Wales, UK;(2) Chemistry Department, Glasgow University, Glasgow, G12 8QQ Scotland, UK |
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Abstract: | Celery collenchyma cell walls are typical of primary plant cell walls in their composition but contain unusually well-oriented
cellulose microfibrils that are packed with more regularity than normal, permitting small-angle X-ray scattering (SAXS) experiments
that would not otherwise be possible. Small-angle scattering data were obtained for the cell walls in essentially their native
state and for isolated cellulose, in a fibrous form that retained the physical shape and microfibril orientation of the native
cell walls. The scattering patterns showed a distinct peak attributed to the interference contribution to the convolution
of form and interference functions. The position of the peak attributed to the interference function implied a mean centre-to-centre
microfibril spacing of approximately 3.2 nm in dry isolated cellulose and 3.8 nm in dry cell walls. Hydration increased the
mean microfibril spacing in the cell walls to 5.4 nm but had only a small effect on the mean microfibril spacing of isolated
cellulose. In the scattering profile from intact, hydrated cell walls it was just possible to discern the position of the
first Bessel minimum, from which a microfibril diameter in the range 3.1–3.6 nm may be estimated. This estimate is likely
to include attached hemicellulose chains. Porod plots of scattering intensity indicated a relatively sharp interface between
microfibrils and their immediate surroundings. The SAXS data imply that cellulose microfibrils 2.6–3.0 nm in diameter are
not quite in lateral contact with one another in the isolated cellulose and are augmented by hemicelluloses and separated
by readily hydrated matrix polysaccharides in the native plant cell wall. |
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Keywords: | Cellulose Microfibrils SAXS Primary cell wall |
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