Researchers from MIT developed an approach to significantly enhance the sensitivity of nuclear magnetic resonance spectroscopy
A team of researchers from Massachusetts Institute of Technology (MIT) developed a new low-power pulsed Dynamic Nuclear Polarization (DNP) sequence for static samples that is composed of a train of microwave pulses. This approach is expected to enhance the sensitivity of Nuclear Magnetic Resonance Spectroscopy (NMR). According to Robert Griffin, the Arthur Amos Noyes Professor of Chemistry, the new method can be used to analyze structures in a few minutes. The approach relies on short pulses of microwave power, which can allow to determine structures for several complex proteins.
The sensitivity of NMR relies on the atoms' polarization, which is a measurement of the difference between the population of ‘up’ and ‘down’ nuclear spins in each spin ensemble. Another approach developed by the team further enhances the polarization with the help of DNP. DNP involves transferring polarization from the unpaired electrons of free radicals to hydrogen, carbon, nitrogen, or phosphorus nuclei in the sample being studied. This leads to an increase in polarization and makes it easier to identify the molecule's structural features. DNP includes continuous irradiation of the sample with high-frequency microwaves with the help of a gyrotron. Although, this improves NMR sensitivity by around 100-fold, the method requires high amount of power and is inefficient at higher magnetic fields.
To address the issue, the team developed an approach to deliver short pulses of microwave radiation at a specific frequency. This enabled the team to enhance polarization by a factor of up to 200, which is similar to the improvement achieved with conventional DNP and requires only 7% of the power and can be implemented at higher magnetic fields. According to the researchers, the improvement in sensitivity can lead to analysis of samples in a single day that would previously have taken around 110 years. To demonstrate the technique, the team used it to analyze standard test molecules such as a glycerol-water mixture. The research was published in the journal Sciences Advances on January 18, 2019.
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