Many experimental investigations show that lignin, from various sources, exhibits antibacterial properties. Lignin in its native state is a complex polymer consisting mainly of three phenylpropanoid monomer units: p-coumaryl alcohol (PCA), coniferyl alcohol (CFA), and sinapyl alcohol (SA). Using molecular dynamics simulations and free energy calculations we investigate the interaction, absorption, and partitioning behavior of monolignols and dilignols in various lipid bilayers. Given its prevalent occurrence in natural lignin, the β-O-4 linkage was used in dilignols. The model membranes investigated consist of DPPC, DOPC, DOPE, and a mixture of 86% DOPE + 14% DOPG lipid bilayers. The mixed lipid bilayer system is considered because of its resemblance to the E. coli inner membrane. The MD simulations show that when placed in aqueous solutions both monomers and dimers absorb very rapidly to the bilayer-water interface. The free energy (PMF) curves indicate that the dilignols adsorb to the bilayer-water interface, but have very little affinity for the membrane interior. The PMF profiles for monolignols show deeper bilayer penetration and lower energy barriers for flipping across the bilayer centers. In addition, our MD simulations of bilayers in the presence of high concentrations of modified dilignols (25 mol% dilignols/lipids) shows that they can have a strong effect on bilayer structure and permeation properties. Specifically, at large concentrations, the dilignols can penetrate deep into bilayers and even flip-flop between bilayer leaflets. Other bilayer structural parameters such as area per lipid, and deuterium and nematic order parameters, show significant changes in the presence of large concentrations of the dilignols.

Molecular dynamics simulation study of interaction of lignin monomers and dimers with lipid bilayers

255th National Meeting (2018)

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