Engineering Novel Proteins for the Sustainable Extraction of Rare-Earth Metals

Date of Award

12-1-2023

Degree Name

M.S. in Chemistry

Department

Department of Chemistry

Advisor/Chair

Advisor: Kevin Hinkle

Abstract

Rare earth elements are found in relative ubiquity within the earth’s crust and have a multitude of application to both everyday life and military defense. On the periodic table, rare earth elements consist of all 15 lanthanides, along with scandium and yttrium. These elements have a wide variety of application, spanning from private and public sector applications, all the way to military defense, thus making them highly desirable metals for eventual utilization. Current methods of rare earth element extraction and purification involve environmentally harmful processes, leading to North America’s decision to not mine for rare earth elements within its territories. This decision has created a distinct lack of self-sufficiency in rare earth element production, currently resulting in a complete reliance of rare earth element imports from other countries, namely China. Due to the current processes of rare earth element extraction and purification posing large detriment to environmental stability along with a decrease in U.S. autonomy, determination of new, safer routes of rare earth element processing is of utmost priority. Specific proteins are known to bind metal ions, which has provided the scientific foundation for a protein-based extraction and purification method targeting rare earth elements. Previous research has identified a protein which is known to bind lanthanides, providing a high potential prospect for the solution to this problem. The protein of interest, named lanmodulin (LanM), contains four regions, denoted as EF hands, with three of which being involved in lanthanide binding. Building upon the previously mentioned solution is a thioredoxin protein found in the extremophile Pyrococcus furiosus. P. furiosus thioredoxin has shown the ability to stably accept newly introduced peptide sequences within its native amino acid sequence. The area of insertion possesses closely located cysteine residues which show potential to form a disulfide bond, effectively increasing rigidity to the binding site’s structure. The Air Force Research Labs have successfully cloned the lanthanide binding loops from LanM to the thioredoxin protein, possibly allowing for a one step extraction/purification process of rare earth elements. The focus of this research is to build upon previous findings using computational chemistry tools and designed simulation experiments. Molecular modeling simulations have provided accurate calculations of energy requirements for both lanthanide ions binding to the proteins along with the energy required to remove the lanthanides from their respective binding pockets. Simulations are also being used for determination of binding loop selectivity and overall effects of the proteins’ conformational changes upon ion binding and ultimate removal. Conclusions drawn from this research will provide a stable foundation to build upon in the coming years within this field. Committee

Keywords

Rare Earth Elements, Lanmodulin (LanM), Pyrococcus Furiosus Thioredoxin (PfTrx), Lanthanides, Molecular Dynamics (MD)

Rights Statement

Copyright © 2023, author.

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