The Thieme Chemistry Journals Award is presented every year to up-and-coming researchers worldwide who are in the early stages of
Electrocatalysis for Chemical Synthesis and Energy Conversion
Professor Shannon Stahl | University of Wisconsin-Madison
Hosted by Professor Charlie Machan
Oxidation and reduction reactions are crucial to the synthesis of organic chemicals, and they also provide the basis for energy production. Electrochemistry is the archetypal method for the removal and delivery of electrons in oxidation and reduction reactions, but electrochemical processes face numerous challenges. Most of the important redox processes involving organic molecules and energy-related small molecules (e.g., H2, O2, CO2, N2) feature the addition or removal of an even number of electrons and protons: 2e–/2H+, 4e–/4H+, 6e–/6H+. Such reactions are not well suited for a direct electrochemical processes, and catalysts are required to enable these reactions proceed with high efficiency and controlled selectivity. This talk will present our recent efforts to develop electrochemical transformations and electrocatalytic methods inspired by biological energy transduction and enzymatic redox processes. Specifically, we take advantage of electron-proton transfer mediators (EPTMs) that couple the movement of both electrons and protons. These mediators avoid unfavorable charge separation associated with independent electron and proton transfer steps, and they introduce new mechanistic pathways to achieve electrode-driven redox reactions. Quinones and organic nitroxyls are especially promising EPTMs, as they mediate hydrogen-atom or other proton-coupled electron transfer reactions with molecules or catalysts in solution, and then are capable of efficient regeneration via proton-coupled electron-transfer at an electrode. These mediator concepts and their use in electrocatalytic reactions will be illustrated through a series of case studies related to chemical synthesis (alcohol oxidation, C–H functionalization) and energy conversion (the oxygen reduction reaction).
Screening, Isolation, and Characterization of Antibiotic Natural Products
Professor Amanda Wolfe | University of North Carolina Asheville
Hosted by Professor Mike Hilinski
The increased emergence of bacterial resistance over the past two decades has greatly reduced the effectiveness of nearly all clinical antibiotics, bringing infectious disease to the forefront as a dire threat to global health. To combat these infections, new antibiotics need to be rapidly discovered, and bacterial natural products have reemerged as an abundant source of novel bioactive molecules. Herein, the isolation and evaluation of over 400 bacteria from bulk and rhizosphere soil native to western North Carolina and the southwestern U.S. in a novel and robust liquid-based high-throughput antagonism assay against Staphylococcus aureus and Escherichia coli is presented. Over 300 bacterial species were screened in monoculture, and 12% and 15% were found to produce antibiotics capable of ≥30% growth inhibition of Staphylococcus aureus or Escherichia coli respectively. 69 of those bacteria were subjected to 16s rRNA sequencing and found to be majority Pseudomonas (30%) and Serratia (17%) bacteria, and Aquitalea, Brevundimonas, Chryseobacterium, Herbaspirillum, and Microbacterium bacteria, which are currently not known to be antibiotic producers. More than 10 producing bacteria have been subjected to large scale culture and extraction techniques to isolate the produced antibiotic. One of those, a Pseudomonas sp., was found to produce the natural product pseudopyronine B, and we have further improved the antibiotic activity of this natural product through SAR evaluation of the alkyl side chains.