Hedenstrom M, Wiklund-Lindstrom S, Oman T, Lu FC, Gerber L, Schatz P, Sundberg B, Ralph J
Identification of lignin and polysaccharide modifications in Populus wood by chemometric analysis of 2D NMR spectra from dissolved cell walls

Molecular Plant: 2009 2:933-942

Abstract
2D 13C–1H HSQC NMR spectroscopy of acetylated cell wallsin solution gives a detailed fingerprint that can be used toassess the chemical composition of the complete wall withoutextensive degradation. We demonstrate how multivariate analysisof such spectra can be used to visualize cell wall changes betweensample types as high-resolution 2D NMR loading spectra. Changesin composition and structure for both lignin and polysaccharidescan subsequently be interpreted on a molecular level. The multivariateapproach alleviates problems associated with peak picking ofoverlapping peaks, and it allows the deduction of the relativeimportance of each peak for sample discrimination. As a firstproof of concept, we compare Populus tension wood to normalwood. All well established differences in cellulose, hemicellulose,and lignin compositions between these wood types were readilydetected, confirming the reliability of the multivariate approach.In a second example, wood from transgenic Populus modified intheir degree of pectin methylesterification was compared tothat of wild-type trees. We show that differences in both ligninand polysaccharide composition that are difficult to detectwith traditional spectral analysis and that could not be a prioripredicted were revealed by the multivariate approach. 2D NMRof dissolved cell wall samples combined with multivariate analysisconstitutes a novel approach in cell wall analysis and providesa new tool that will benefit cell wall research.

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