Dr. Tuo Wang, Associate Professor
Department of Chemistry
Louisiana State University

Complex Carbohydrates in Plant Biomass, Microalgae, and Fungal Pathogens Investigated Using Solid-State NMR 

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 three carbohydrate-rich biosystems: fungal pathogens, plant biomass, and microalgae. 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. First, 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. Second, in another photosynthetic system, the microalgae, we have revealed the polymorphic structure of carbohydrate components in the crystalline starch, the heterogeneous cell walls, and the dynamic glycolipids. Third, the cell wall of a major fungal pathogen Aspergillus fumigatus is found to contain hydrophobic scaffolds of chitin and α-glucans, which are enclosed in a soft matrix of β-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. The in-depth understanding of microbes’ armor, lignocellulose, and microalgae will facilitate the development of antifungal drugs and better technology for the production of biofuel and high-value biopolymers.