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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    A protein mines, sorts rare earths better than humans, paving way for   
   green tech    
      
     Date:   
         May 31, 2023   
     Source:   
         Penn State   
     Summary:   
         Rare earth elements, like neodymium and dysprosium, are a critical   
         component to almost all modern technologies, from smartphones to   
         hard drives, but they are notoriously hard to separate from the   
         Earth's crust and from one another. Scientists have discovered   
         a new mechanism by which bacteria can select between different   
         rare earth elements, using the ability of a bacterial protein to   
         bind to another unit of itself, or 'dimerize,' when it is bound   
         to certain rare earths, but prefer to remain a single unit, or   
         'monomer,' when bound to others.   
      
      
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   FULL STORY   
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   Rare earth elements, like neodymium and dysprosium, are a critical   
   component to almost all modern technologies, from smartphones to hard   
   drives, but they are notoriously hard to separate from the Earth's crust   
   and from one another.   
      
   Penn State scientists have discovered a new mechanism by which bacteria   
   can select between different rare earth elements, using the ability of   
   a bacterial protein to bind to another unit of itself, or "dimerize,"   
   when it is bound to certain rare earths, but prefer to remain a single   
   unit, or "monomer," when bound to others.   
      
   By figuring out how this molecular handshake works at the atomic level,   
   the researchers have found a way to separate these similar metals from   
   one another quickly, efficiently, and under normal room temperature   
   conditions. This strategy could lead to more efficient, greener mining   
   and recycling practices for the entire tech sector, the researchers state.   
      
   "Biology manages to differentiate rare earths from all the other metals   
   out there -- and now, we can see how it even differentiates between   
   the rare earths it finds useful and the ones it doesn't," said Joseph   
   Cotruvo Jr., associate professor of chemistry at Penn State and lead   
   author on a paper about the discovery published today (May 31) in the   
   journal Nature. "We're showing how we can adapt these approaches for rare   
   earth recovery and separation."  Rare earth elements, which include the   
   lanthanide metals, are in fact relatively abundant, Cotruvo explained,   
   but they are what mineralogists call "dispersed," meaning they're mostly   
   scattered throughout the planet in low concentrations.   
      
   "If you can harvest rare earths from devices that we already have,   
   then we may not be so reliant on mining it in the first place," Cotruvo   
   said. However, he added that regardless of source, the challenge of   
   separating one rare earth from another to get a pure substance remains.   
      
   "Whether you are mining the metals from rock or from devices, you are   
   still going to need to perform the separation. Our method, in theory,   
   is applicable for any way in which rare earths are harvested," he said.   
      
   All the same -- and completely different In simple terms, rare earths   
   are 15 elements on the periodic table -- the lanthanides, with atomic   
   numbers 57 to 71 -- and two other elements with similar properties that   
   are often grouped with them. The metals behave similarly chemically,   
   have similar sizes, and, for those reasons, they often are found together   
   in the Earth's crust. However, each one has distinct applications in   
   technologies.   
      
   Conventional rare earth separation practices require using large amounts   
   of toxic chemicals like kerosene and phosphonates, similar to chemicals   
   that are commonly used in insecticides, herbicides and flame retardants,   
   Cotruvo explained. The separation process requires dozens or even hundreds   
   of steps, using these highly toxic chemicals, to achieve high-purity   
   individual rare earth oxides.   
      
   "There is getting them out of the rock, which is one part of the problem,   
   but one for which many solutions exist," Cotruvo said. "But you run into   
   a second problem once they are out, because you need to separate multiple   
   rare earths from one another. This is the biggest and most interesting   
   challenge, discriminating between the individual rare earths, because   
   they are so alike.   
      
   We've taken a natural protein, which we call lanmodulin or LanM, and   
   engineered it to do just that."  Learning from nature Cotruvo and his lab   
   turned to nature to find an alternative to the conventional solvent-based   
   separation process, because biology has already been harvesting and   
   harnessing the power of rare earths for millennia, especially in a class   
   of bacteria called "methylotrophs" that often are found on plant leaves   
   and in soil and water and play an important role in how carbon moves   
   through the environment.   
      
   Six years ago, the lab isolated lanmodulin from one of these bacteria,   
   and showed that it was unmatched -- over 100 million times better -- in   
   its ability to bind lanthanides over common metals like calcium. Through   
   subsequent work they showed that it was able to purify rare earths as   
   a group from dozens of other metals in mixtures that were too complex   
   for traditional rare earth extraction methods. However, the protein was   
   less good at discriminating between the individual rare earths.   
      
   Cotruvo explained that for the new study detailed in Nature, the team   
   identified hundreds of other natural proteins that looked roughly like   
   the first lanmodulin but homed in on one that was different enough   
   -- 70% different -- that they suspected it would have some distinct   
   properties. This protein is found naturally in a bacterium (Hansschlegelia   
   quercus) isolated from English oak buds.   
      
   The researchers found that the lanmodulin from this bacterium exhibited   
   strong capabilities to differentiate between rare earths. Their studies   
   indicated that this differentiation came from an ability of the protein   
   to dimerize and perform a kind of handshake. When the protein binds   
   one of the lighter lanthanides, like neodymium, the handshake (dimer)   
   is strong. By contrast, when the protein binds to a heavier lanthanide,   
   like dysprosium, the handshake is much weaker, such that the protein   
   favors the monomer form.   
      
   "This was surprising because these metals are very similar in size,"   
   Cotruvo said. "This protein has the ability to differentiate at a scale   
   that is unimaginable to most of us -- a few trillionths of a meter,   
   a difference that is less than a tenth of the diameter of an atom."   
   Fine-tuning rare earth separations To visualize the process at such   
   a small scale, the researchers teamed up with Amie Boal, Penn State   
   professor of chemistry, biochemistry and molecular biology, who is a   
   co-author on the paper. Boal's lab specializes in a technique called   
   X-ray crystallography, which allows for high-resolution molecular imaging.   
      
   The researchers determined that the protein's ability to dimerize   
   dependent on the lanthanide to which it was bound came down to a single   
   amino acid -- 1% of the whole protein -- that occupied a different   
   position with lanthanum (which, like neodymium, is a light lanthanide)   
   than with dysprosium.   
      
   Because this amino acid is part of a network of interconnected amino   
   acids at the interface with the other monomer, this shift altered how   
   the two protein units interacted. When an amino acid that is a key player   
   in this network was removed, the protein was much less sensitive to rare   
   earth identity and size.   
      
   The findings revealed a new, natural principle for fine-tuning rare earth   
   separations, based on propagation of miniscule differences at the rare   
   earth binding site to the dimer interface.   
      
   Using this knowledge, their collaborators at Lawrence Livermore National   
   Laboratory showed that the protein could be tethered to small beads in   
   a column, and that it could separate the most important components of   
   permanent magnets, neodymium and dysprosium, in a single step, at room   
   temperature and without any organic solvents.   
      
   "While we are by no means the first scientists to recognize that metal-   
   sensitive dimerization could be a way of separating very similar   
   metals, mostly with synthetic molecules," Cotruvo said, "this is   
   the first time that this phenomenon has been observed in nature with   
   the lanthanides. This is basic science with applied outcomes. We're   
   revealing what nature is doing and it's teaching us what we can do better   
   as chemists."  Cotruvo believes that the concept of binding rare earths   
   at a molecular interface, such that dimerization is dependent on the   
   exact size of the metal ion, can be a powerful approach for accomplishing   
   challenging separations.   
      
   "This is the tip of the iceberg," he said. "With further optimization of   
   this phenomenon, the toughest problem of all -- efficient separation of   
   rare earths that are right next to each other on the periodic table --   
   may be within reach."  A patent application was filed by Penn State based   
   on this work and the team is currently scaling up operations, fine-tuning   
   and streamlining the protein with the goal of commercializing the process.   
      
   Other Penn State co-authors are Joseph Mattocks, Jonathan Jung, Chi-Yun   
   Lin, Neela Yennawar, Emily Featherston and Timothy Hamilton. Ziye Dong,   
   Christina Kang-Yun and Dan Park of the Lawrence Livermore National   
   Laboratory also co- authored the paper.   
      
   The work was funded by the U.S. Department of Energy, the National   
   Science Foundation, the National Institutes of Health, the Jane Coffin   
   Childs Memorial Fund for Medical Research, and the Critical Materials   
   Institute, an Energy Innovation Hub funded by the DOE, Office of Energy   
   Efficiency and Renewable Energy, Advanced Materials and Manufacturing   
   Technologies Office. Part of the work was performed under the auspices   
   of the DOE by Lawrence Livermore National Laboratory.   
      
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   Story Source: Materials provided by Penn_State. Original written by   
   Adrienne Berard. Note: Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Mattocks, J.A., Jung, J.J., Lin, CY. et al. Enhanced rare-earth   
         separation with a metal-sensitive lanmodulin dimer. Nature, 2023   
         DOI: 10.1038/s41586-023-05945-5   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230531150125.htm   
      
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