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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #225261
Title: CHARACTERIZATION OF NON-DERIVATIZED PLANT CELL WALLS USING HIGH-RESOLUTION SOLUTION-STATE NMR SPECTROSCOPY

Author
item YELLE, DANIEL - U.S. FOREST PRODUCTS LAB
item Ralph, John
item FRIHART, CHARLES - U.S. FOREST PRODUCTS LAB

Submitted to: Magnetic Resonance in Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2008
Publication Date: N/A
Citation: N/A

Interpretive Summary: Detailed structural examination of plant cell walls can take many months. Recently we provided a breakthrough that we had been seeking for over a decade -- realizing complete dissolution of the whole cell wall without significant degradation. We demonstrated that it was possible for the first time to run NMR (Nuclear Magnetic Resonance) Spectroscopy on the whole cell wall after dissolution and acetylation; the degree of detail proved to be extremely revealing and allowed us to get much of the information that has previously only been garnered from laboriously isolated fractions. Moreover, the potential to characterize the polysaccharide and lignin components was revealed. Here we have in some ways improved on this method by eliminating one step in the preparation of the cell walls for NMR. The walls are dissolved directly for NMR by using deuterated DMSO and deuterated N-methylimidazole (NMI) as the dissolution solvent. Deuterated NMI is not available commercially so had to be synthesized. We demonstrate here that simple dissolution in the solvent system allows detailed NMR spectra to be acquired. In some ways the spectra are even better than for the acetylated cell walls previously used. The resolution of some of the components was better, allowing a more detailed interpretation. Also, as the cell walls are more nearly in their native state, the presence of various cell wall components, such as acetylated sugar units in various polysaccharides, could be readily seen. We think that the methods described here will be particularly useful for plant cell wall research and will allow researchers to analyze, in detail, the whole cell wall by more rapid NMR methods. There is also the possibility to use NMR for screening plants to aid in the selection of optimal biomass species, and for optimizing the conversion of cellulosic biomass to biofuels.

Technical Abstract: A recently described plant cell wall dissolution system has been logically modified to utilize perdeuterated solvents to allow direct in-nmr-tube dissolution and high-resolution solution-state NMR of the whole cell wall without derivatization. Finely ground cell wall material dissolves in a solvent system containing dimethylsulfoxide-d6 (DMSO-d6) and 1-methyl¬imidazole-d6 (NMI-d6) in a ratio of 4:1 (v/v), keeping wood component structures mainly intact in a highly native-state. These two-dimensional (2D) NMR experiments, using gradient-HSQC 1-bond 13C-1H correlation, on non-derivatized cell wall (NDCW) material from a representative gymnosperm (Pinus taeda), an angiosperm (Populus tremuloides), and a herbaceous plant, kenaf (Hibiscus cannabinus) demonstrate the efficacy of the system. We describe a method to synthesize NMI-d6 to a high degree of deuteration, thus allowing cell wall dissolution and characterization of non-derivatized plant cell wall structures through contour assignments using model compound data.