Honors Theses


Justin Biffinger, Ph.D.



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Honors Thesis


The selective sequestration and purification of rare earth elements (REE) from environmental and waste sources represents a frontier in protein-based hydrometallurgy. REEs present several research challenges based on the strong water binding affinities to REE ions, expanded metal centered coordination environments up to 8, low solubility, and literally accessing the physical location of deposits on earth. Recently, a highly selective lanthanide binding protein labeled as Lanmodulin (LanM) was discovered, isolated, and cloned from Methylorubrum extorquens AM1 and represents a transformational advance for selectively isolating REEs from mixed metal streams and ores. We present here an approach to isolate and purify 6xHIS-tagged LanM (LanM6xHIS) without time and resources intensive size exclusion chromatography steps to purities of > 95% using heat treatment of the cell lysate prior to Ni-NTA affinity chromatography. We did not observe a difference in the final LanM yield using the heat treatment approach and the metal binding selectivity for Eu(III) and Fe(III) was unaffected by heat treatment. Heat treated LanM also absorbed statistically higher concentration of Eu(III) based on results from a xylenol orange (XO) colorimetric assay. The ratio of total moles of Eu(III) removed per mole of LanM was 1.8 for the heat treat preparation compared to 1.3 for the non-heat-treated preparation. These data also confirmed that all purified native LanM solutions form soluble LanM aggregates based on SDS-PAGE and Native-PAGE results. To the best of our knowledge, this is the first report of aggregation of LanM and a purification method to isolate >95% pure LanM without size exclusion chromatography.

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Undergraduate research

Embargoed until Tuesday, June 22, 2123