UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, TN, United States of America; Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, United States of America. Electronic address: [Email]
BACKGROUND : Lignin, the second most abundant biopolymer on earth, plays a major structural role in plants, conferring mechanical strength and regulating water conduction. Understanding the three-dimensional structure of lignin is important for fundamental reasons as well as engineering plants towards lignin valorization. Lignin lacks a specific primary sequence, making its average chemical composition the focus of most recent studies. However, it remains unclear whether the 3D structure of lignin molecules depends on their sequence. METHODS : We performed all-atom molecular dynamics simulation of three S/G-lignin molecules with the same average composition but different sequence. RESULTS : A detailed statistical analysis of the radius of gyration and relative shape anisotropy reveals that the lignin sequence has no statistically significant effect on the global three-dimensional structure. We found however, that homopolymers of C-lignin with the same molecular weight have smaller radii of gyration than S/G-lignin. We attribute this to lower hydroxyl content of C-lignin, which makes it more compact and rigid. CONCLUSIONS : The 3D structure of lignin is influenced by the overall content of monomeric units and interunit linkages and not by its precise primary sequence. CONCLUSIONS : Lignin is assumed to not have a well-defined primary structure. The results presented here demonstrate there are no significant differences in the global 3D structure of lignin molecules with the same average composition but different primary sequence.