High Magnetic Field Science and Its Application in the United States Current Status and Future Directions (2013) / Chapter Skim
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3 High Magnetic Fields in Chemistry, Biochemistry, and Biology
3 High Magnetic Fields in Chemistry, Biochemistry, and Biology
Pages 67-79
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From page 67... ...
Field strengths in NMR magnets are limited by the properties of these materials, making high-field NMR one of the important scientific drivers for the continuing development of advanced superconducting materials and magnet technology. The National High Magnetic Field Laboratory (NHMFL)
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From page 68... ...
In an external magnetic field, interaction between nuclear magnetic moments and the external field causes the nuclei to align with the field direction. NMR is a phenomenon in which the application of radio-frequency (RF)
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From page 69... ...
Higher magnetic fields lead to better NMR data for two main reasons. The first is spectral resolution: The NMR frequency of the nucleus of a particular atom in a molecule or material is proportional to the strength of the external field but is also affected by the atom's local chemical and structural environment.
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From page 70... ...
to the magnetic field direction using a pneumatic turbine system, approximates the effects of rotational diffusion, producing solid state NMR linewidths that can approach the linewidths in solution NMR spectra. Some of the most exciting applications of solid-state NMR are possible only at very high magnetic fields.
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From page 71... ...
Among these are the development of multidimensional NMR techniques that allow NMR frequencies of essentially all 1H, 15N, and 13C nuclei within a protein or nucleic acid to be measured and assigned to specific atoms; the identification and characterization of a variety of nuclear spin interactions that can be measured through NMR signals and interpreted as experimental constraints on molecular structure; and the development of highly stable and homogeneous superconducting magnets with fields up to 23.5 T Some of the most significant new trends in biomolecular NMR that have appeared since the NRC report Opportunities in High Magnetic Field Science (NRC, 2005)
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From page 72... ...
Improvements in MAS technology allow sample rotation frequencies above 50 kHz to be achieved routinely; solid state NMR probes (the devices that contain the circuitry for application of RF pulses and detection of NMR signals) that work efficiently at the high NMR frequencies of high-field magnets have been developed; new isotopic labeling approaches have been introduced that lead to tractable solid-state NMR spectra for large proteins; new techniques for assigning solid-state NMR signals to specific atomic sites and for obtaining molecular structural constraints have been developed.
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From page 73... ...
for sensitivity enhancements. DNP is a process in which the large polarizations of electron spins in a strong magnetic field are partially transferred to nuclear spins by irradiation of EPR transitions, resulting in large enhancements of nuclear spin polarizations and hence NMR signals.
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From page 74... ...
NMR magnet in Europe, at a new NMR center in the Netherlands. Additional 1.2 GHz NMR magnets are under negotiation for other European sites.
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From page 75... ...
In addition, as magnet technology improves to meet the challenges of the next generation of NMR magnets, the cost of moderately high-field instruments, which are more widely distributed among individual research labs and institutions, is likely to decrease. The cost of a 1.2 GHz NMR magnet is approximately $20 million.
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From page 76... ...
. In biological applications, FT-ICR mass spectrometry has emerged as a tool with immense impact in metabolomics (see discussion of NMR in metabolomics above)
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From page 77... ...
Nonetheless, high-field EPR is a growing field with important applications in chemistry and biology, as higher fields produce greater spectral resolution and provide sensitivity to molecular motions on a wider variety of timescales. In particular, in structural biology, measurements of magnetic dipole-dipole couplings between electron spins, using pulsed EPR techniques, have become increasingly common as a means of determining distances in the 10-100 Å range between electron spin labels in proteins and nucleic acids.
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From page 78... ...
However, the highest-field NMR magnets in this country are limited to the 900-950 MHz range (21.1-22.3 T) , while a 1.0 GHz NMR system (23.5 T)
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From page 79... ...
2011. Fast characterization of functionalized silica materials by silicon-29 surface-enhanced NMR spectroscopy using dynamic nuclear polarization.
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