NMR of Fully and Partially 13 C-Enriched Biomass Enhances Pendent Group Structural Characterization
| Authors: | John Ralph, Guy Lippens, Marco Tonelli, Charles G. Fry, Clemens Anklin, Fachuang Lu, Vitaliy I. Timokhin, Nuoendagula, Rebecca A. Smith, Sarah Liu, Sally Ralph, Wu Lan, Yuki Tobimatsu, Fengxia Yue, Yanding Li, Mirko Bunzel, Mathias Sorieul, Stefan Hill, Shawn D. Mansfield, Wout Boerjan, Marc Van Montagu, Jorge Rencoret, José C. del Río, Yu Gao, Jenny C. Mortimer |
| Year: | 2026 |
| Type: | Scientific Journal |
| Station: | Forest Products Laboratory |
| DOI: | https://doi.org/10.1021/acs.analchem.5c08043 |
| Source: | Analytical Chemistry |
Abstract
Traditional solution-state NMR experiments may either fail or yield unsatisfactory results when employing fully-13C-labeled biomass due to complications arising from 13C−13C coupling. Constant-time analogs of HSQC experiments mitigate such issues and deliver enhanced sensitivity. A rarely reported CTHSQC- TOCSY experiment allows the proton coupling network to deliver much of the same value as the parent experiment on unlabeled or 10−15%-13C-labeled biomass polymers but with enhanced sensitivity. In the absence of a viable HMBC analog for long-range correlations, a relayed C−C experiment, i.e., via directly bonded 13C-labeled networks, enables the reliable assignment of coupled carbons, with the added advantage of correlating the more elusive quaternaries. A C−C-FLOPSY experiment takes advantage of fully-13C-labeled materials for mapping extensive carbon networks in the complex polymer mixtures inherent in biomass. Various pendent groups (tricin units, cis- and trans-p-coumarates, and p-hydroxybenzoates) that adorn lignins, and the cis- and trans-ferulates on arabinoxylan polysaccharides, are exquisitely revealed in spectra from isolated lignins or whole-cell-wall materials from maize, sorghum, and poplar.