Scientists at Lawrence Livermore National Laboratory (LLNL) and Penn State University are modifying and improving natural molecules that would help target specific radioactive elements that are found in nuclear waste or used in nuclear medicine.
Even the most effective molecules for such tasks which evolved over billions of years can still be improved for non-natural applications. Lanthanides are natural elements used in numerous items like computer hard drives and magnets. The team bioengineered nature’s most potent protein for attaching to lanthanides which is called lanmodulin in order to make it even more selective for actinide elements. Actinides are radioactive metals that a present in nuclear waste such as uranium, plutonium and americium.
The research by the team of scientists was published in the journal Chemical Science. Their results improve our understanding of how natural compounds can interact with nuclear waste in the environment. They could lead to new molecules for scavenging and detection of specific radioactive metals.
The team designed, synthesized and characterized five variants of lanmodulin (LanM) to decipher and eventually improve its actinide-binding properties. They found that the presence of water molecules that bridge the metal and protein molecule is particularly important for controlling the stability and metal preferences of the metal-protein complexes. This design principle permitted the scientists to improve the protein’s ability to discriminate between actinide and lanthanide elements.
Molecules that are selective for actinides over lanthanides are among the most preferred. This is because these two families of elements are found in nuclear waste. Separating them would allow for a more efficient management of radioactive materials. The team’s discovery could lead to new separation systems for applications in nuclear waste disposal and radiochemistry fields. LanM was discovered by the Penn State University members of the team in 2018. The LLNL-Penn State collaboration has been exploring applications of this important molecule in the field of nuclear sciences.
LLNL scientist Gauthier Deblonde is co-lead author of the study. He said, “This is the first study where someone made changes to lanmodulin to dissect and improve its metal binding properties. As we were tuning the protein’s properties to target radioactive elements, we also learned a lot about the mechanisms by which it binds the metals.”
Classic molecules have a limited set of chemical interactions. The new research showed that macromolecules, such as proteins, have an extended repertoire of chemical interactions that scientists can fine-tune to target specific metals.
Joseph Cotruvo, Jr. is a Penn State assistant professor of chemistry and a co-lead author of the study. He said, “This study uncovers yet another tool that this remarkable protein has at its disposal to discriminate between metals that differ from one another in only very subtle ways. This realization is an important step toward high-performance LanM-based separation methods and molecules custom-designed to bind specific medical isotopes.”
Joseph Mattocks of Penn State also contributed to this work. The work is being funded by the National Nuclear Security Administration’s Office of Defense Nuclear Nonproliferation Research and Development and the U.S. Department of Energy’s Basic Energy Sciences program.