Lignin is a recalcitrant, aromatic heteropolymer, one of the 3 primary components of biomass. Lignin provides structure to plants, water and nutrient transport through plant tissues, and a highly effective defense against pathogens. As the largest reserve of aromatics in the biosphere, lignin has a great potential as a feedstock for industrial processes, if only if its native recalcitrance could be addressed. To better understand the origins of lignin’s recalcitrance, it is imperative to know its 3D structure as it relates to lignin composition and linkage. However, computational modeling all of lignin’s diversity to this point has been limited by the available lignin forcefields, which lack explicit parameterization for emerging lignin structures both from natural variants and engineered lignin structures. Since polymerization of lignin occurs via radical intermediates, multiple C-O and C-C linkages have been isolated, and the current force field only represents a small subset of lignin the diverse lignin structures found in plants.<br/> <br/>In order to take into account the wide range of lignin polymerization chemistries, monomers and dimer combinations of C-, H-, G-, and S-lignins as well as with hydroxycinnamic acid linkages were subjected to extensive quantum mechanical calculations to establish target data from which to build a complete molecular mechanics force field tuned specifically for diverse lignins. By parameterizing lignin specifically, we are able to more accurately represent the interactions and conformations of lignin monomers and dimers relative to a general force field. Coupled with structure building advances also presented, this new force field will enables computational researchers to study the effects of different linkages on the structure of lignin, as well as construct more accurate plant cell wall models based on observed statistical distributions of lignin that differ between disparate feedstocks, and guide further lignin engineering efforts.

Development progress in constructing atomic scale models of diverse lignins

255th National Meeting (2018)

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