A more efficient and cost-effective method of detecting lanthanides, the rare-earth metals used in smart phones and other technologies, could be possible with a new sensor sensor that changes its fluorescence when it binds to these metals. A research team from Penn State developed the sensor from a protein they described recently, and then used it to study the biology of bacteria using lanthanides. A study describing the sensor appears online in the Journal of the American Chemical Society .
"Lanthanides are used in a variety of current technologies, including smart phone screens and electronics, batteries for electric cars, satellites and lasers," said Joseph Cotruvo, Jr., assistant professor and Louis Martarano Penn State chemistry senior development professor Author of the study. "These elements are termed rare earths and in the periodic table comprise chemical elements with an atomic weight of 57 to 71
The research team developed a fluorescence sensor used to detect calcium Part of the sensor that binds to calcium with a protein that has been recently discovered and that binds several million times better to lanthanides than other metals. The protein undergoes a change in shape when it binds to lanthanides. This is the key to activating the fluorescence of the sensor.
"The gold standard for the detection of any element present in a sample is a mass spectrometry technique called ICP-. MS, said Cotruvo. "This technique is very sensitive, but requires special instruments that most laboratories do not have, and it is not cheap." With the protein-based sensor we have developed, we can determine the total amount of lanthanides in a sample, which is not the case identifying each individual element, but this can be done quickly and inexpensively at the sampling site. "
The research team also used the sensor to study the biology of a type of bacteria that uses lanthanides – the bacteria that became the lanthanide binding protein originally discovered. In previous studies, lanthanides had been detected in the periplasm of the bacteria – a gap between membranes outside the cell – but the team also used the sensor to detect lanthanides in the cytosol of the bacterium – the fluid that fills the cell.
"We found that the lightest of the lanthanides – lanthanum through neodymium in the periodic table – enter the cytosol, but the heavier ones do not," said Cotruvo. "We still try to understand exactly how and why it is, but this tells us that there are proteins in the cytosol that deal with lanthanides that we did not know before." It might also be useful to understand what Behind this high uptake selectivity is the development of new ways to separate one lanthanide from another, which is currently a very difficult problem. "
The team also found that the bacteria absorb lanthanides, much like many bacteria absorb iron. They secrete small molecules that bind tightly to the metal, and the entire complex is taken up into the cell. This shows that there are small molecules that are likely to bind even more tightly to lanthanides than the highly selective sensor.
"We hope to continue to study these small molecules and any proteins in the cytosol that may bind better to lanthanides than the protein we used in the sensor," Cotruvo said. "Examining how these lanthanides bind and interact with each other can give us ideas on how to replicate these processes when collecting lanthanides for use in current technologies."
In addition to Cotruvo, Joseph Mattocks and Jackson Ho of Penn belong to the research team's state.
Bacterial protein could help find materials for your next smartphone
Joseph A. Mattocks et al., A Selective Protein-based Fluorescence Sensor with Picomolar Affinity for Rare Earth Elements, Journal of the American Chemical Society (2019). DOI: 10.1021 / jacs.8b12155
New Sensor Detects Rare Metals in Smartphones (2019, April 23)
retrieved on April 24, 2019
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