Soft X-ray induced chemical modification of polysaccharides in vascular plant cell walls |
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Authors: | George D Cody Jay Brandes Chris Jacobsen Susan Wirick |
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Institution: | aGeophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC 20015, United States;bSkidaway Institute of Oceangraphy, Savannah, GA, United States;cDepartment of Physics, State University of New York, Stony Brook, NY, United States |
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Abstract: | Scanning transmission X-ray microscopy and micro carbon X-ray Absorption Near Edge Spectroscopy (C-XANES) can provide quantitative information regarding the distribution of the biopolymers cellulose, hemicellulose, and lignin in vascular plant cell walls. In the case of angiosperms, flowering plants, C-XANES may also be able to distinguish variations in lignin monomer distributions throughout the cell wall. Polysaccharides are susceptible to soft X-ray irradiation induced chemical transformations that may complicate spectral analysis. The stability of a model polysaccharide, cellulose acetate, to variable doses of soft X-rays under conditions optimized for high quality C-XANES spectroscopy was investigated. The primary chemical effect of soft X-ray irradiation on cellulose acetate involves mass loss coincident with de-acetylation. A lesser amount of vinyl ketone formation also occurs. Reduction in irradiation dose via defocusing does enable high quality pristine spectra to be obtained. Radiation induced chemical modification studies of oak cell wall reveals that cellulose and hemicellulose are less labile to chemical modification than cellulose acetate. Strategies for obtaining pristine C-XANES spectra of polysaccharides are presented. |
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Keywords: | Polysaccaride Cellulose acetate Scanning transmission X-ray microscopy Carbon XANES Radiation damage |
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