NMR
Two-dimensional NMR techniques already had advanced the study of protein structures in solutions. In 1988, Richard Ernst’s group published a report in Nature showing how NMR spectroscopy could be used to elucidate structure in three dimensions. Now, studies are underway to increase NMR sensitivity by 100-fold.
Credit: DOE
Of late, the nuclear magnetic resonance community has been buzzing about a technique that can increase NMR sensitivity by 100-fold or more and is opening up new ways to follow biochemical reactions in vitro and in vivo. Called dynamic nuclear polarization (DNP), the technique can be used simply to speed up familiar experiments—data collection that historically took overnight can be done in mere seconds—but it is also making NMR a newly powerful tool for identifying reaction intermediates, probing enzyme kinetics, and imaging in vivo.
The power of NMR lies in its high resolution; it enables researchers to see small differences in chemical environments. NMR is also noninvasive and nonperturbing—it won’t harm whatever sample or organism you’re scanning. At the same time, NMR is “horribly insensitive,” says Lucio Frydman, a chemistry professor at Weizmann Institute of Science, in Israel. NMR insensitivity can be a particular problem for studies of biochemical systems, which are often limited to low concentrations—typically, hundreds of scans must be averaged to bring a signal out of the noise.
NMR basically involves putting a sample in a magnetic field, where the spins of nuclei with odd numbers of protons or neutrons will line up with or against the field direction. Because of the energy difference between these states, proportionately more nuclei align with the field. The population difference leads to a nuclear spin polarization, which is measured by NMR.
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Excerpted with permission, Chemical & Engineering News
Copyright © 2009 American Chemical Society