Targeting radioactive metals beyond nature’s molecules

The natural protein lanmodulin (depicted in navy blue) was bioengineered by a collaboration of scientists from LLNL and Penn State University to better scavenge and separate elements found in nuclear waste, such as the actinides and their lanthanide fission products. Credit: Gauthier Deblonde/LLNL

LLNL scientists and Penn State University colleagues are enhancing natural compounds that target radioactive elements in nuclear waste or nuclear medicine.

Even the most effective natural compounds can be improved for non-natural uses. For lanthanides —natural elements utilised in many goods like computer hard drives and magnets— the researchers bioengineered nature’s most potent protein (lanmodulin). Actinides are radioactive metals like uranium, plutonium, and americium found in nuclear waste.

Chemical Science publishes the study. The findings help scientists better understand how natural compounds interact with radioactive waste in the environment and may lead to new molecules for scavenging and detection.

The researchers created, synthesised, and analysed five lanmodulin (LanM) variations to better understand its actinide-binding properties. The presence of water molecules that bridge the metal and protein molecule controls the stability and metal preferences of metal-protein complexes. This design idea helped scientists improve the protein’s actinide-lanthanide discrimination.

These two groups of elements are found in nuclear waste and separating them would allow for more efficient management of radioactive materials. The discovery could lead to new nuclear waste and radiochemistry separation systems. Penn State found LanM in 2018, and LLNL and Penn State are studying its nuclear uses.

“This is the first work to dissect and improve lanmodulin’s metal binding characteristics,” said LLNL scientist Gauthier Deblonde. “We learned a lot about metal binding mechanisms while tailoring the protein’s characteristics to target radioactive elements.”

Classic molecules have a restricted variety of chemical interactions, while macromolecules like proteins have an extended repertoire that scientists may fine-tune to target certain metals.

“This study reveals another tool this extraordinary protein uses to distinguish between metals with tiny differences. This is a step toward LanM-based separation technologies and molecules designed to bind medicinal isotopes “Penn State assistant chemistry professor and study co-author Joseph Cotruvo Jr.

Further information: Joseph A. Mattocks et al, Engineering lanmodulin’s selectivity for actinides over lanthanides by controlling solvent coordination and second-sphere interactions, Chemical Science (2022). DOI: 10.1039/D2SC01261H

Journal information: Chemical Science

Source: Lawrence Livermore National Laboratory