Computationally derived structural insights into Rare Earth selectivity in lanmodulin and its variants
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59 BASIC BIOLOGICAL SCIENCES↗
Engineering topics
Park, Dan M.
Publications and source records attributed to Park, Dan M..
EF-Hand Battle Royale: Hetero-ion Complexation in Lanmodulin
The lanmodulin (LanM) protein has emerged as an effective means for rare earth element (REE) extraction and separation from complex feedstocks without the use of organic solvents. Whereas the binding of LanM to individual REEs has been well characterized, little is known about the thermodynamics of mixed metal binding complexes (i.e., heterogeneous ion complexes), which limits the ability to accurately predict separation performance for a given metal ion mixture. In this paper, we employ the law of mass action to establish a theory of perfect cooperativity for LanM-REE complexation at the two highest-affinity binding sites. The theory is then used to derive an equation that explains the nonintuitive REE binding behavior of LanM, where separation factors for binary pairs of ions vary widely based on the ratio of ions in the aqueous phase, a phenomenon that is distinct from single-ion-binding chemical chelators. We then experimentally validate this theory and perform the first quantitative characterization of LanM complexation with heterogeneous ion pairs using resin-immobilized LanM. Importantly, the resulting homogeneous and heterogeneous constants enable accurate prediction of the equilibrium state of LanM in the presence of mixtures of up to 10 REEs, confirming that the perfect cooperativity model is an accurate mechanistic description of REE complexation by LanM. We further employ the model to simulate separation performance over a range of homogeneous and heterogeneous binding constants, revealing important insights into how mixed binding differentially impacts REE separations based on the relative positioning of the ion pairs within the lanthanide series. In addition to informing REE separation process optimization, these results provide mathematical and experimental insight into competition dynamics in other ubiquitous and medically relevant, cooperative binding proteins, such as calmodulin.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Scalable and Consolidated Microbial Platform for Rare Earth Element Leaching and Recovery from Waste Sources
Not Available
54 ENVIRONMENTAL SCIENCES↗
Protein-based approach for high-purity Sc, Y, and grouped lanthanide separation
Rare earth elements (REEs: Sc, Y, La- Lu) are irreplaceable components in many clean energy and consumer technologies. However, the extraction and subsequent separation of individual REEs from ore-based feedstocks remains a significant economic and environmental challenge. Here in this work, we investigated the intra-REE separation potential of lanmodulin (LanM), a natural protein from Methylorubrum extorquens that has emerged as a sustainable potential alternative to conventional solvent extraction-based separation. By determining the intra-REE selectivity of immobilized LanM and systematically testing pH-based and small chelator-based (i.e., citrate and malonate) desorption processes, we established the framework and methodology for achieving select individual and grouped REE separations from a mixed REE feedstock. We show that Sc forms the tightest complex with LanM among REEs but can be readily and selectively desorbed using malonate to generate high-purity Sc (>99 % purity, >99 % yield) in a single adsorption/desorption cycle. We further show that the intrinsic REE selectivity of LanM is sufficient to achieve heavy REE (HREE) separation from light and middle REEs (L-MREEs), yielding an yttrium-enriched product. This separation effect is further magnified by pairing LanM’s unique M-LREE preference with a HREE-preferring chelator in the desorption process, which enriches HREE and MREE fractions relative to low value, abundant La/Ce. Finally, by combining pH- and citrate-based desorption processes in a two-cycle separation scheme, we demonstrate the generation of fractions highly enriched in Y, Gd-Lu, Pr-Eu, and La-Ce. Collectively, these data support the application of a LanM-based approach for achieving impactful REE separations from mixed REE feedstocks.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Enhanced rare-earth separation with a metal-sensitive lanmodulin dimer
Technologically critical rare-earth elements are notoriously difficult to separate, owing to their subtle differences in ionic radius and coordination number. The natural lanthanide-binding protein lanmodulin (LanM) is a sustainable alternative to conventional solvent-extraction-based separation. Here we characterize a new LanM, from Hansschlegelia quercus (Hans-LanM), with an oligomeric state sensitive to rare-earth ionic radius, the lanthanum(III)-induced dimer being >100-fold tighter than the dysprosium(III)-induced dimer. X-ray crystal structures illustrate how picometre-scale differences in radius between lanthanum(III) and dysprosium(III) are propagated to Hans-LanM’s quaternary structure through a carboxylate shift that rearranges a second-sphere hydrogen-bonding network. Comparison to the prototypal LanM from Methylorubrum extorquens reveals distinct metal coordination strategies, rationalizing Hans-LanM’s greater selectivity within the rare-earth elements. Finally, structure-guided mutagenesis of a key residue at the Hans-LanM dimer interface modulates dimerization in solution and enables single-stage, column-based separation of a neodymium(III)/dysprosium(III) mixture to >98% individual element purities. This work showcases the natural diversity of selective lanthanide recognition motifs, and it reveals rare-earth-sensitive dimerization as a biological principle by which to tune the performance of biomolecule-based separation processes.
36 MATERIALS SCIENCE↗
Comparison of Kill Switch Toxins in Plant-Beneficial Pseudomonas fluorescens Reveals Drivers of Lethality, Stability, and Escape
Kill switches provide a biocontainment strategy in which unwanted growth of an engineered microorganism is prevented by expression of a toxin gene. A major challenge in kill switch engineering is balancing evolutionary stability with robust cell killing activity in application relevant host strains. Understanding host-specific containment dynamics and modes of failure helps to develop potent yet stable kill switches. To guide the design of robust kill switches in the agriculturally relevant strain Pseudomonas fluorescens SBW25, we present a comparison of lethality, stability, and genetic escape of eight different toxic effectors in the presence of their cognate inactivators (i.e., toxin–antitoxin modules, polymorphic exotoxin–immunity systems, restriction endonuclease–methyltransferase pair). We find that cell killing capacity and evolutionary stability are inversely correlated and dependent on the level of protection provided by the inactivator gene. Decreasing the proteolytic stability of the inactivator protein can increase cell killing capacity, but at the cost of long-term circuit stability. By comparing toxins within the same genetic context, we determine that modes of genetic escape increase with circuit complexity and are driven by toxin activity, the protective capacity of the inactivator, and the presence of mutation-prone sequences within the circuit. Here, the results of our study reveal that circuit complexity, toxin choice, inactivator stability, and DNA sequence design are powerful drivers of kill switch stability and valuable targets for optimization of biocontainment systems.
59 BASIC BIOLOGICAL SCIENCES↗