Researchers from ORNL recorded the vibrational spectra of an α amino acid with damage-free electron energy-loss spectroscopy
A team of researchers from the Department of Energy's Oak Ridge National Laboratory (ORNL) described the first use of an electron microscope to directly identify isotopes in amino acids at the nanoscale without damaging the samples. The method does not damage amino acids and aid in real-space observation of dynamic chemistry. According to Jordan Hachtel, ORNL postdoctoral fellow and lead author, the method allows to track isotopic labels directly with the electron microscope. The experiment was conducted at ORNL's Center for Nanophase Materials Sciences and the findings were published in the journal Science on February 1, 2019.
The team used monochromated electron energy-loss spectroscopy (EELS), in a scanning transmission electron microscope (STEM). The technique is sensitive enough to distinguish between molecules that differ by a single neutron on a single atom. The team used EELS to capture the minute vibrations in the molecular structure of an amino acid. Juan Carlos Idrobo, ORNL staff scientist and corresponding author stated that although mass spectrometry has high mass resolution, it does not have nanometer spatial resolution. The new electron microscopy technique offers a gentler approach. In the technique, the electron beam is positioned extremely close to the sample (without direct contact) and the electrons can excite and detect the vibrations without destroying the sample. This in turn allows to observe biological samples at room temperature over longer periods of time.
According to the researchers, the new technology can complement mass spectrometry and other conventional optical and neutron-based techniques currently used to detect isotopic labels. Hachtel stated that the technique is the perfect complement to a macroscale mass spectrometry experiment and the pre-knowledge of the mass spectrometry can be used to spatially resolve the effects on the isotopic labels in a real-space sample. The technique can be used in the field of life sciences along with other soft matter such as polymers. It can also find application in quantum materials in which isotopic substitution contribute in controlling superconductivity.
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