Speaker: Tuo Wang, Assistant Professor, Dept of Chemistry, Louisiana State Univ
Title: Structural Investigations of Plant Biomass and Fungal Cell Walls by Solid-State NMR and Dynamic Nuclear Polarization
Abstract: Complex carbohydrates play crucial roles in energy storage, cell recognition, and structural building. The structure and assembly of these molecules are highly polymorphic and disordered in cellular environments. Here we present the recent progress in investigating two carbohydrate-rich biosystems: fungal pathogens and plant biomass. Using isotopically enriched whole-cell samples, we determined the conformation, packing, hydration, and motion of polysaccharides and associated biomolecules. Dynamic Nuclear Polarization (DNP) is required for overcoming the sensitivity limitation for probing the polymer interface. The cell wall of a major fungal pathogen Aspergillus fumigatus is found to contain hydrophobic scaffolds of chitin and ±-glucans, which are enclosed in a soft matrix of ²-glucans and glycoproteins. We have identified a uniquely hydrophobic and stiff cell wall architecture in those fungal cells exposed to echinocandin drugs or high salinity and those mutants devoid of major carbohydrate components. This novel mechanism helps the microbes resist external stresses and retain structural integrity. In intact plant stems, aromatic-edited experiments were conducted to understand the interaction between carbohydrates and lignin. Lignin preferentially binds to the non-flat region of xylan, which is linked to the flat-ribbon xylan domains that are coating the even surface of cellulose microfibrils. Molecules are better mixed in woody plants, resulting in stronger interactions between lignin and the cellulose-xylan junctions. The in-depth understanding of microbes’ armor and lignocellulose will facilitate the development of antifungal drugs and biofuel production technology.
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