Title: Direct Determination of Hydroxymethyl Conformations of Plant Cell Wall Cellulose Using ¹H Polarization Transfer Solid-State NMR

Abstract

In contrast to the well-studied crystalline cellulose of microbial and animal origins, cellulose in plant cell walls is disordered due to its interactions with matrix polysaccharides. Plant cell wall (PCW) is an undisputed source of sustainable global energy; therefore, it is important to determine the molecular structure of PCW cellulose. The most reactive component of cellulose is the exocyclic hydroxymethyl group: when it adopts the tg conformation, it stabilizes intrachain and interchain hydrogen bonding, while gt and gg conformations destabilize the hydrogen-bonding network. So far, information about the hydroxymethyl conformation in cellulose has been exclusively obtained from ¹³C chemical shifts of monosaccharides and oligosaccharides, which do not reflect the environment of cellulose in plant cell walls. Here, we use solid-state Nuclear Magnetic Resonance (ssNMR) spectroscopy to measure the hydroxymethyl torsion angle of cellulose in two model plants, by detecting distance-dependent polarization transfer between H4 and H6 protons in 2D ¹³C–¹³C correlation spectra. We show that the interior crystalline portion of cellulose microfibrils in Brachypodium and Arabidopsis cell walls exhibits H4–H6 polarization transfer curves that are indicative of a tg conformation, whereas surface cellulose chains exhibit slower H4–H6 polarization transfer that is best fit to the gt conformation. Joint constraints bymore » the H4–H6 polarization transfer curves and ¹³C chemical shifts indicate that it is unlikely for interior cellulose to have a significant population of the gt and gg conformation mixed with the tg conformation, while surface cellulose may adopt a small percentage of the gg conformation. These results provide new constraints to the structure and matrix interactions of cellulose in plant cell walls, and represent the first direct determination of a torsion angle in an important noncrystalline carbohydrate polymer.« less

Authors:

Phyo, Pyae  ^[1];

• Search DOE PAGES for author "Phyo, Pyae"
• Search DOE PAGES for ORCID "0000-0002-3019-6011"

Wang, Tuo  ^[1];

• Search DOE PAGES for author "Wang, Tuo"
• Search DOE PAGES for ORCID "0000-0002-1801-924X"

Yang, Yu ^[1]; O’Neill, Hugh  ^[2];

• Search DOE PAGES for author "O’Neill, Hugh"
• Search DOE PAGES for ORCID "0000-0003-2966-5527"

Hong, Mei  ^[1]

• Search DOE PAGES for author "Hong, Mei"
• Search DOE PAGES for ORCID "0000-0001-5255-5858"

---

+ Show Author Affiliations

1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Chemistry
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Structural Molecular Biology

Publication Date:

Wed Mar 21 00:00:00 EDT 2018

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Center for Lignocellulose Structure and Formation (CLSF)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1470519

Grant/Contract Number:  

SC0001090

Resource Type:

Accepted Manuscript

Journal Name:

Biomacromolecules

Additional Journal Information:

Journal Volume: 19; Journal Issue: 5; Related Information: CLSF partners with Pennsylvania State University (lead); North Carolina State University; University of Rhode Island; Virginia Tech University; Journal ID: ISSN 1525-7797

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

09 BIOMASS FUELS; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES; biofuels (including algae and biomass); bio-inspired; membrane; carbon sequestration; materials and chemistry by design; synthesis (self-assembly)