Journal of Energy Bioscience 2024, Vol.15, No.1, 28-31 http://bioscipublisher.com/index.php/jeb 29 Figure 11D1H-13C MultiCP-MAS ssNMR provides a broad overview of lignifed Populus SCWs Note: General assignment regions are indicated for the predominant constituent polymers cellulose (gray), xylan (blue), and lignin (green), along with representative structures and their assignments indicated with color-coding. chemical shift information and peak profles extracted from a combined set of 1d and 2d ssnMR data were used to inform spectral deconvolution efforts used throughout this work; The raw data are shown in black, and the resultant ft is shown in red; c: Cellulose; Xn: Xylan; Ac: Acetyl; GalA: Galacturonic acid (pectin); GlcA: α-d-glucuronic acid; [4OMe] GlcA: (4-O-methyl)-α-d-glucuronic acid Figure 3 Atomistic SCW periodic model variants and comparison of their proximity analyses with ssNMR spin-diffusion experiments Note: Left: Snapshots of several molecular model variants for the poplar ScW. the naming convention is as follows: the letter refers to the relative arrangement of hemicellulose and lignin, where “a” denotes a model with all xylan bound on cellulose, and no xylan interspersed with lignin; “b” denotes a model with 70% hemicellulose bound to cellulose, and the remaining 30% interspersed in the surrounding lignin-xylan matrix; “d” denotes a model with lignin-bound cellulose and with hemicellulose as the surrounding layer; “e” denotes a model with phase-separated hemicellulose and lignin both bound to cellulose at the top and bottom, respectively; “h” denotes a model with hemicellulose interspersed within the 18-chain elementary cellulose fbril leaving room for increased direct lignin-cellulose interaction. the number after the decimal denotes the number of 18-chain elementary fbrils in the model. b.8 and b.10 are larger systems constructed with 70% of xylan bound to cellulose, and the remaining 30% interspersed with lignin and consist of eight and ten 18-chain cellulose elementary fbrils, respectively; Right: Calculated percentage of sink atoms within 1 nm of source atoms in the model variants compared to that obtained from ssnMR spin-diffusion experiments depicted on a polar plot; The four dashed lines originating from the center indicate the four ssnMR magnetization metrics, with the experimental values indicated as black dots and the colors indicating the various models Figure 4 depicts the atomistic model of lignocellulose assembly within Populus secondary cell walls (SCWs), aligning with ssNMR data. Panel A shows the molecular structures of lignin, xylan, and cellulose. Panel B illustrates their macromolecular assembly, where xylan on the cellulose surface adopts an extended configuration, pointing towards lignin. Panel C highlights the cellulose component, comprising two core bundles of four 18-chain elementary fibrils. Panel D focuses on hemicellulose, revealing a nearly complete sheath around cellulose, minimizing direct cellulose-lignin contact and some xylan isolated within core bundles. Panel E indicates that lignin primarily interacts with hemicellulose, with minimal direct contact with cellulose. This model underscores the spatial organization and interactions of these biopolymers, crucial for SCW integrity.
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