University of Minnesota Duluth
University of Minnesota Department of Chemistry and Biochemistry
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Friday, March 24, 2017; 2:00 p.m.; Chem 200


Department of Chemistry & Biochemistry Welcomes:


Master Student, Valerie Bruner, Department of Chemistry & Biochemistry, University of Minnesota Duluth, Research Advisor: Katie Schreiner

“Chemical Characterization of the Degradation of Necromass from Four Ascomycota Fungi: Implications for Soil Organic Carbon Turnover and Storage”

Terrestrial soils store vast amounts of organic carbon, approximately twice as much carbon as is currently in the atmospheric CO2 pool. Soil carbon can release into the atmosphere as CO2 through respiration and erosion due to climate warming and land use change. Despite its importance in the global carbon cycle, much is still unknown about the source, turnover, and stability of this soil organic carbon (SOC) pool. For example, fungi are known to play an important role in shaping the chemistry of SOC by degrading common biopolymers, and fungal biomass has been found to be a significant portion of living microbial SOC, forming the majority of biomass in some soils. And yet, despite growing evidence that microbial necromass (i.e., dead microbial tissue) may be a larger contributor to SOC than previously thought, very little is known about the specific degradation patterns of fungal necromass and subsequently its potential chemical contributions to long-lived SOC pools. This study addresses these knowledge gaps through a time-series analysis of the degradation patterns of fungal tissue from four different saprotrophic Ascomyota species in temperate restored prairie soils. Fungal tissue was buried in soils and harvested at intervals from one day to one month. After harvest, chemical analysis of the dried tissue by thermochemolysis pyrolysis-GCMS was used for examining changes within the fungal tissue chemistry that occurs during degradation. This study (1) shows that a small portion of fungal necromass persists in the environment even after the period of the experiment and could serve as a contributor to long-lived SOC, (2) provides quantitative information on the contribution of fungal tissue to SOC pools, and (3) examines the chemical persistence of various organic compounds throughout degradation.



Department of Chemistry & Biochemistry Welcomes:


Master Student, Adam Jersett, Department of Chemistry & Biochemistry, University of Minnesota Duluth, Research Advisor: Dr. Alessandro Cembran

Sulfur Oxidation Effects on Methionine-Aromatic Interactions

The methionine-aromatic motif, in which methionine’s sulfur interacts with a nearby aromatic residue, was previously found to occur in approximately 33% of the protein crystal structures in the PDB. This interaction was shown to increase stabilization in protein structure and to play an important role in protein function and protein-protein recognition. In oxidative biological environments, however, methionine’s sulfur can be oxidized, with unknown effects on the stability of the sulfur-aromatic interaction. Our initial hypothesis was that oxidation of sulfur interferes with protein function by weakening the methionine-aromatic interaction. The quantum mechanical work reported here, instead, shows that methionine oxidation strengthens this interaction by about 1.5 kcal/mol. We further test this finding by investigating the effects of methionine oxidation on the complex between lymphotoxin-α (LTα) and the tumor necrosis factor receptor 1 (TNFR1). Our results show that complex formation is disrupted upon oxidation by the stronger methionine-aromatic interactions, which result in an alteration of the binding interface.