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Accelerated Light-Induced Aging of Α-, Β-, and Γ-13C-Enriched Cell Wall-Dehydrogenation Polymers Studied With Solid State 13C NMR spectroscopy

Published

Author(s)

J Parkas, David L. VanderHart, U Westermark

Abstract

Light-induced aging of lignocellulosic materials has been studied with a new technique involving selectively alpha-, beta-, and gamma-13C-enriched cell wall-dehydrogenation polymers (CW-DHP:s) and solid state 13C NMR spectroscopy. The results from cross-polarization magic angle spinning (CP/MAS) 13C NMR experiments of unirradiated and irradiated CW-DHP have revealed mainly a decrease in the amount of end-groups of both coniferaldehyde and coniferyl alcohol type. The results suggest that these end-groups become saturated and that the terminal functionalities, i.e., gamma-aldehyde and gamma-hydroxymethyl groups, at least to some extent, are retained. The results indicate further that no detectable cleavage of the beta-O-4 bonds occurs in the examined lignocellulosic model. In terms of proposed mechanisms of yellowing, there is marginal evidence that up to 2% ofthe alpha-labeled sites are converted by irradiation to alpha-carbonyls (aldehyde or ketones); moreover, we cannot dismiss the possibility that the precursor structures giving rise to these few a-carbonyls are beta-O-4 structures.The 13C-enriched CW-DHP was formed directly on spruce (Picea abies) wood tissue (differentiating xylem) by administering selectively 13C-labeled coniferin at pH 6.0 in the presence of glucose oxidase and beta-glucosidase, i.e., no phenol-oxidizing enzyme was added and the wood cells own enzymes polymerized the precursor.
Citation
Journal of Wood Chemistry and Technology
Volume
22 No. 4

Keywords

aging C13, cell wall-dehydrogenation, enrichment, light, ligin, NMR, spruce, yellowing

Citation

Parkas, J. , VanderHart, D. and Westermark, U. (2002), Accelerated Light-Induced Aging of &#913;-, &#914;-, and &#915;-<sup>13</sup>C-Enriched Cell Wall-Dehydrogenation Polymers Studied With Solid State <sup>13</sup>C NMR spectroscopy, Journal of Wood Chemistry and Technology (Accessed February 22, 2024)
Created December 31, 2001, Updated October 12, 2021