Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 21, 1998
Publication Date: N/A
Technical Abstract: Molecular modeling provides a tool for evaluating hypotheses concerning molecular mechanisms underlying complex interactions among cell wall components that control plant wall structure and function. Recent work has shown cell wall ferulates and dehydrodiferulates are much more prominent than previously measured, suggesting a greater potential role in cross- linking wall polysaccharides and thus altering the physical characteristic of the wall matrix. In grasses, arabinoxylan cross-linking is fairly extensive based on releasable dehydrodiferulates. We have used molecular modeling to help explore the feasibility of cross-linking reactions involving wall bound ferulates. For example, are all dehydrodiferulates the result of intermolecular coupling as opposed to intramolecular bond formation? To answer this question, we modeled a ferulated arabinoxylan (16 xylose residues) with two ferulates positioned at various locations along the backbone and the optimized structure generated using MM2 parameters. When ferulates were separated by > 4 xylose residues, diferulate formation only occurs if the xylan backbone can relax allowing the two ferulates within spatial proximity for bonding. Where ferulates could overlap (< 4 xylose residues), one or both of the ferulates must rotate along the xylan backbone to be properly positioned for radical coupling. In both cases, energy barriers prevented the complete rotation to allow bond formation; therefore, formation of intramolecular dehydrodiferulates seems unlikely. We are also modeling spatial restrictions for intermolecular dehydrodiferulates to determine the maximum distance allowable for radical coupling.