X-ray crystallographic structure of LBT5 complexed with Tb3+ (from Imperiali et al.).
A lanthanide binding tag (LBT) is a specially designed peptide sequence derived from the structure of calcium-binding proteins’ EF-hand, a common protein structural element found in calcium-binding proteins, which consists of a helix-loop-helix structure that forms a pocket for calcium ion loops. LBTs have the ability to selectively bind to rare-earth elements (REEs), particularly lanthanides, due to a specific molecular structure that creates a tight binding pocket for these ions.
The design of LBTs is inspired by the EF-hand motifs. LBTs, which show promise as biomolecular REE extractants, have a ride range of critical applications, including biochemistry, materials science, and environmental monitoring, where selective detection and binding of lanthanides are crucial.
But mainstream purification methods rely on organic solvents in processes that are neither sustainable nor efficient.
A team of researchers studied LBTs optimized for coordination to Tb3+ using luminescence spectroscopy, surface tensiometry, x-ray reflectivity (XR), and x-ray fluorescence near total reflection (XFNTR). (Tb3+ is a terbium ion with an electron configuration of 4f8 and S = 3. It’s a rare earth ion that’s used as a luminescent activator in many materials.) The XR and XFNTR measurements were obtained at the NSF’s ChemMatCARs 15-ID-C insertion device x-ray beamline at the U.S. Department of Energy’s Advanced Photon Source at Argonne National Laboratory.
Their study demonstrates that LBTs are surface active; in solution LBTs complex selectively to a REE cation, and the resulting peptide-metal diffuses (migrates) to an air/water interface to an air/water interface enabling an all-aqueous, green, energy-efficient, interfacial separation process. By carefully modifying the amino acid residues of the peptide, researchers can engineer LBTs to selectively deliver REEs to air-aqueous interfaces for interfacial separation.
See: Luis E. Ortuno Macias1, Felipe Jiménez-Ángeles2, Jason G. Marmorstein3, Yiming Wang3, Stephen A. Crane3, Surabh K. T.1, Pan Sun4, Bikash Sapkota4, Eshe Hummingbird3, Woojin Jung3, Baofu Qiao2, Daeyeon Lee3, Ivan J. Dmochowski3, Robert J. Messinger1, Mark L. Schlossman4, Cesar de la Fuente-Nunez3, Ravi Radhakrishnan3, E. James Petersson3, Monica Olvera de la Cruz2, Wei Bu5, Mrinal Bera5, Binhua Lin5, Raymond S. Tu1, Kathleen J. Stebe3a, and Charles Maldarelli1b, “Lanthanide binding peptide surfactants at air–aqueous interfaces for interfacial separation of rare earth elements,” Proc. Nat. Acad. Sci. USA 121 (52), e2411763121 (2024).
Author affiliations: 1The City College of New York, 2Northwestern University, 3University of Pennsylvania, 4University of Illinois at Chicago, 5The University of Chicago
Correspondence: akstebe@seas.upenn.edu, bmaldarelli@ccny.cuny.edu
This work has been financially supported by the Department of Energy under the Basic Energy Sciences Award No. DESC0022240. NSF’s ChemMatCARS is supported by the Divisions of Chemistry, and Materials Research, National Science Foundation (NSF), under Grant No. NSF/CHE-1834750 and NSF/CHE-2335833. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DEAC02-06CH11357. The MALDI MS instrument for peptide characterization was supported by NIH S10 OD030460.
For information on Liquid Surface/Interface X-ray Scattering program at NSF’s ChemMatCARS contact:
Wei Bu
(630) 252-0470
weibu@uchicago.edu