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Title

Characterization of protein amino acid residues and a monolignol conjugate in whole plant cell walls by solution-state 2D NMR and their interference with authentic p-hydroxyphenyl (H) unit estimation

AuthorsKim, Hoon; Padmakshan, D.; Li, Yanding; Rencoret, Jorge ; Karlen, S.D.; Hatfield, R.D.; Ralph, John
Issue Date18-Mar-2018
PublisherAmerican Chemical Society
CitationAbstracts of papers of the American Chemical Society (218): CELL 217 pág. 41 (2018)
AbstractProtein polymers exist in every plant cell wall preparation, and they interfere with lignin characterization and quantification. The current solution-state 2D NMR technique for whole plant cell wall structural profiling provides detailed information regarding cell walls. However, certain components intrude on lignin structural analysis. Here we report the structural characterization of the residual protein peaks in 2D NMR spectra in corn cob and kenaf samples, and note that aromatic amino acids are ubiquitous and evident in spectra from various other plants and tissues. The aromatic correlations from amino acid residues were identified and assigned as phenylalanine and tyrosine. Phenylalanine’s 3/5 correlation peak is superimposed on the peak from typical lignin p-hydroxyphenyl (H-unit) structures, causing an overestimation of the H units. Similarly, protein residues in many species also result in incorrect values for lignin analyses by the Klason method. Protein contamination also occurs when using cellulases to prepare enzyme lignins from virtually protein-free wood samples. We used a protease to remove the protein residues from the ballmilled cell walls, and we were able to reveal H-unit structures in lignins more clearly in the 2D NMR spectra, providing a better basis for their estimation. We also recently characterized a new monolignol conjugate, ML-benzoate (BA), in the cell wall samples of leaf tissues from Canary Island date palm (Phoenix canariensis). These NMR correlations have not been observed from other plant families including commelinid monocotyledons, such as the Poaceae (grasses, e.g., maize, rice, brachypodium). The presence of lignin-bound benzoates BA in the palms (Arecaceae) is very distinguishable. However, benzoate’s 3/5 correlation peak is virtually superimposed on the peak from typical lignin p-hydroxyphenyl (H-unit) structures, also causing an overestimation of the H units.Protein polymers exist in every plant cell wall preparation, and they interfere with lignin characterization and quantification. The current solution-state 2D NMR technique for whole plant cell wall structural profiling provides detailed information regarding cell walls. However, certain components intrude on lignin structural analysis. Here we report the structural characterization of the residual protein peaks in 2D NMR spectra in corn cob and kenaf samples, and note that aromatic amino acids are ubiquitous and evident in spectra from various other plants and tissues. The aromatic correlations from amino acid residues were identified and assigned as phenylalanine and tyrosine. Phenylalanine’s 3/5 correlation peak is superimposed on the peak from typical lignin p-hydroxyphenyl (H-unit) structures, causing an overestimation of the H units. Similarly, protein residues in many species also result in incorrect values for lignin analyses by the Klason method. Protein contamination also occurs when using cellulases to prepare enzyme lignins from virtually protein-free wood samples. We used a protease to remove the protein residues from the ballmilled cell walls, and we were able to reveal H-unit structures in lignins more clearly in the 2D NMR spectra, providing a better basis for their estimation. We also recently characterized a new monolignol conjugate, ML-benzoate (BA), in the cell wall samples of leaf tissues from Canary Island date palm (Phoenix canariensis). These NMR correlations have not been observed from other plant families including commelinid monocotyledons, such as the Poaceae (grasses, e.g., maize, rice, brachypodium). The presence of lignin-bound benzoates BA in the palms (Arecaceae) is very distinguishable. However, benzoate’s 3/5 correlation peak is virtually superimposed on the peak from typical lignin p-hydroxyphenyl (H-unit) structures, also causing an overestimation of the H units.
DescriptionResumen de la comunicación presentada en el 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water (New Orleans), LA 18-22, march 2018
URIhttp://hdl.handle.net/10261/167369
ISSN0065-7727
Appears in Collections:(IRNAS) Artículos
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