Computational Evidence for Kinetically Controlled Radical Coupling during Lignification
Name
Gani_manuscript_chemrxiv_rev2.pdf
Description
Submitted version
Size
611.31 KB
Format
Adobe PDF
Checksum (MD5)
79e3a3f4d253333d3a33e458d863be3c
Author(s)
Gani, Terry ZH
Orella, Michael J
Anderson, Eric M
Stone, Michael L
Brushett, Fikile R
Beckham, Gregg T
Román-Leshkov, Yuriy
Date Issued
2019
Journal
ACS Sustainable Chemistry & Engineering
Publisher
American Chemical Society (ACS)
Version
Original manuscript
Abstract
© 2019 American Chemical Society. Lignin is an alkyl-aromatic biopolymer that, despite its abundance, is underutilized as a renewable feedstock because of its highly complex structure. An approach to overcome this challenge that has gained prominence in recent years leverages the plasticity and malleability of lignin biosynthesis to tune lignin structure in planta through genetic approaches. An improved understanding of lignin biosynthesis can thus provide fundamental insights critical for the development of effective tailoring and valorization strategies. Although it is widely accepted that lignin monomers and growing chains are oxidized enzymatically into radicals that then undergo kinetically controlled coupling in planta, direct experimental evidence has been scarce because of the difficulty of exactly replicating in planta lignification conditions. Here, we computationally investigate a set of radical reactions representative of lignin biosynthesis. We show that, contrary to the notion that radical coupling reactions are usually barrierless and dynamically controlled, the computed activation energies can be qualitatively consistent with key structural observations made empirically for native lignin in a variety of biomass types. We also rationalize the origins of regioselectivity in coupling reactions through structural and activation strain analyses. Our findings lay the groundwork for first-principles lignin structural models and more detailed multiscale simulations of the lignification process.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1021/acssuschemeng.9b02506
