- Shih-Hsein Liu, The University of Tennessee, Knoxville
This seminar covers two topics:
1. Citrus greening
Citrus greening, a devastating threat to the citrus industry in the United States, is caused by Candidatus liberibacter, a phloem-limited gram-negative bacteria spread by the Asian citrus psyllid. One cure employs multifunctional surface/subsurface/systemic therapeutic technology. A ternary solution, the systemic component of technology, contains zinc nitrate, urea, and hydrogen peroxide in an aqueous solution. All-atom classical molecular dynamics simulations were performed to better understand the behavior of the ternary solution. The analyses reveal strong binding between zinc ion and oxygen in urea and no association between zinc ions. Free energy of binding of urea to zinc ion in solution was also calculated to quantify the stability of urea-zinc complex. Future studies aim at resolving the interactions of the ternary solution with lignin and cellulose in plant cell walls and, ultimately, the bacteria in phloem.
2. Poplar lignin acetylation
Research was carried out to study the effect of poplar lignin acetylation behavior in various solution environments: water, tetrahydrofuran, and mixture of water and tetrahydrofuran. The force fields associated with acetylation groups were first parameterized, and classical molecular dynamics simulations were performed to analyze their radius of gyration as a function of time. Further analyses are being conducted to compare simulation results with small-angle neutron scattering experiments to resolve poplar lignin structures for more efficient biomass breakdown.
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