(308f) Selective Separation of Rees Using Peptides Derived from the EF-Hand Loop 1 of Lanmodulin and Controlled Via Hydrophobic Guest Residue

The growing demand for rare earth elements (REEs), combined with their limited supply and the negative environmental impacts of mining calls for innovative, cost-effective, and sustainable methods to recover and recycle these elements from end-of-life products and industrial waste. REEs are essential in applications such as magnets, catalysts, polishing, and metal alloys, and are critical to advancing technologies like electric vehicles, turbines, solar panels, and LED screens. Among many proposed schemes, biosorption using proteins and peptides is a promising approach for the recovery of REEs due to several advantages including low cost, high selectivity, high regeneration, and fast kinetics. Peptides have additional advantages over proteins; being short chains of amino acids makes them easier to tune, the synthesis of peptides is relatively easy, the peptides are robust, and the cost of production can be low.

Recent studies have revealed that peptides derived from the EF-hand loops of the lanmodulin protein show strong binding affinities for rare earth elements (REEs). Motivated by these findings, several peptides based on the EF-hand loop 1 of lanmodulin were designed and examined for their binding affinities towards Ce (III), Nd (III), La (III), and Y (III) in solution. Initially, the binding ability of these peptides to the REEs was confirmed through circular dichroism (CD) and molecular dynamics (MD) simulations. Subsequently, the thermodynamic properties (K_d, ΔH, ΔS, and ΔG) of the binding with ions in solution were evaluated using isothermal titration calorimetry (ITC). A significant correlation between the thermodynamic properties ∆H and ∆S and the relative hydrophobicity of the guest residue in the designed peptide was observed. The peptides showed varying binding affinities and selectivity for REEs, with differences spanning an order of magnitude. The thermodynamic properties were also found to be in a strong correlation with the computationally estimated properties such as solvent-accessible surface area, the water in the hydration shell, and the hydrogen bond decay of water molecules near the peptide.