Jim Parkås, Magnus Paulsson, Ulla Westermark, Noritsugu Terashima
Solid State NMR Analysis of ?-13C-Enriched Lignocellulosic Material During Light-Induced Yellowing
Summary
Photoyellowing of lignocellulosic materials has been studied with a new technique based on solid state
13C-NMR analysis of 13C-enriched DHP in cell wall tissue. The selectively 13C-enriched cell wall-dehydrogenation
polymer (CW-DHP) was prepared directly on differentiating xylem from spruce (Picea
abies) at pH 6.0 by administering ?-13C-enriched coniferin in an enzymatic system consisting of glucose
oxidase, ?-glucosidase, and the naturally occurring water-insoluble enzymes remaining in the cell wall.
The bonding pattern of the formed CW-DHP was found to be: 42% ?-?, ?-5, and ?-1 substructures; 36%
?-O-4 derived substructures; and 22% coniferyl alcohol and coniferaldehyde end-groups. The 13C-NMR
analysis of unirradiated and irradiated tissue revealed a decrease in the relative amount of coniferaldehyde
and/or coniferyl alcohol end-groups during irradiation. Prolonged irradiation also introduced new
signals centered at 37, 70, and 102 ppm. The results indicate that the present technique, with the formation
of DHP in a naturally lignifying carbohydrate environment, has the potential of being a valuable
tool for the study of structural changes of lignin during light-induced yellowing.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 55, 04/2001
Pages: 276 - 282
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