Jessica Lewer, Graduate Student, Kostal Group & Andrew Kamischke, Graduate Student, Miller Lab, GW Department of Chemistry | Department of Chemistry | Columbian College of Arts & Sciences

Multi-criteria In Silico Framework Guides Rational Design of Photodegradable Pesticides with Minimal Ecotoxicity

Rational design of pesticides with tunable degradation properties and minimal ecotoxicity is among the grand challenges of green and sustainable chemistry. While in silico approaches have gained traction in predictive toxicology, current methods lack the necessary multifaceted approach and design-vectoring tools needed for systems-based development of new chemicals. Here, we report a method for the screening of existing, and design of new pesticides, which combines photodegradation, (eco)toxicity and performance metrics into a single tool. Our multi-tier framework leverages computed kinetics and thermodynamics of indirect photodegradation of pesticides, which are applied in conjunction with ecotoxicity and performance predictions based on cutoff values in key, mechanistically-derived physiochemical properties. Beyond supporting screening of existing pesticides, computational tiers were developed to link structural attributes of pesticides to process-based outcomes, facilitating rational design of new, or redesign of existing, chemicals. Taking advantage of computational efficacy afforded by the tiered approach, our model was applied to all relevant pesticides on the US EPA’s registry, resulting in 16,100 unique assessments. Extensively validated against experimental data, our approach is robust, broadly applicable, and offers a user-friendly roadmap to new-pesticide development. The guidelines presented here clearly identify trade-offs inherent to the design process, and offer a blueprint for developing similar strategies in other chemical sectors

Bio

Jessica received her B.S. in Chemistry from Clarkson University in 2017. From there, she was commissioned into the U.S. Air Force as a 2nd lieutenant chemist where she began her first duty assignment at the Air Force Technical Application Center, Patrick AFB, Florida. For two years she led a chemical modeling and simulation team whose work included atmospheric chemistry, environmental fate, and hydrological transport modeling for DoD compounds of interest. In 2019 she joined George Washington University as a Chemistry Master’s candidate working in Dr. Jakub Kostal’s lab where she is focusing on in silico modeling to support the rational design of photodegradable pesticides with minimal ecotoxicity.

Scattering and Extinction Studies of Carbon Growth in Laminar Nitrogen Diluted Ethylene/Air Diffusion Flames

Combustion processes make up approximately 80% of all primary energy consumption in the United States. Soot, a by-product of incomplete combustion, causes many health and environmental concerns. An understanding of the electronic and optical properties of soot and its precursors can shed light on understanding how it is formed and its interaction with the environment, particularly its role in radiative transfer in the atmosphere.

Previous work in our group used absorption techniques in the visible and infrared regions of the electromagnetic spectrum. Those measurements were used to calculate the spatially resolved AE (Ångström Exponent) of soot and the optical bandgap of soot’s precursors. The latter was correlated with computed HOMO-LUMO gaps of polynuclear aromatic hydrocarbons and oxygen-substituted analogs, and aggregates thereof. In the same flame system under investigation here. To extend these measurements to smaller PAH precursor sizes, we are using an optical parametric oscillator (OPO) light source with a tunable range of 210-2400 nm to collect extinction and fluorescence data. Additionally, scattering data will be collected at various angles and analyzed using Rayleigh-Debye-Gans fractal aggregate theory to determine both primary particle size and the radius of gyration for agglomerated soot particles.

Bio

Andrew received his bachelor’s degree in forensic chemistry with honors from The University of Mississippi in 2018. In fall 2018, Andrew began his PhD in Dr. Houston Miller’s lab at George Washington University to continue research examining the electrical and optical properties of soot.