Fast MAS ¹H-¹³C correlation NMR for structural investigations of plant cell walls

Plant cell walls consist of a mixture of polysaccharides that render the cell wall a strong and dynamic material. Understanding the molecular structure and dynamics of wall polysaccharides is important for understanding and improving the properties of this energy-rich biomaterial. So far, solid-state NMR studies of cell wall structure and dynamics have solely relied on ¹³C chemical shifts measured from 2D and 3D correlation experiments. To increase the spectral resolution, sensitivity and upper limit of measurable distances, it is of interest to explore ¹H chemical shifts and ¹H-detected NMR experiments for analyzing cell walls. Here we demonstrate 2D and 3D ¹H-¹³C correlation experiments at both moderate and fast MAS frequencies of 10-50 kHz to resolve and assign ¹H chemical shifts of matrix polysaccharides in Arabidopsis primary cell walls. Both ¹³C-detected and ¹H-detected experiments are implemented and are shown to provide useful and complementary information. Using the assigned ¹H chemical shifts, we measured long-range correlations between matrix polysaccharides and cellulose using ¹H-¹H instead of ¹³C-¹³C spin diffusion, and the 2D experiments can be conducted with either ¹³C or ¹H detection.