Description of NMR
Nuclear Magnetic Resonance, or NMR as it is usually called, was developed in its present form in 1945 by the physicists Bloch and Purcell. They hoped to be able to use it to obtain precise information about the nuclear properties of spin and magnetic moment. When it turned out that the experiment was compromised by the chemical environment in which the nuclei found themselves, most physicists lost interest in NMR. Their loss was the chemists’ gain. Almost immediately, NMR began to develop into the prime choice for analysis of chemical identity and structure. Over the years, a succession of seemingly endless advancements and applications has developed.
Biochemists use NMR to determine the three-dimensional structure of large biologically important molecules, such as DNA, RNA and proteins. Solid-state NMR helps probe the structure and motion in a wide variety of solid materials. Magnetic Resonance Imaging (MRI) locates nuclear spins spatially and thus permits detailed, non-invasive, three-dimensional images of objects from the size of a single cell to an entire human body. These later advancements have been made possible by the development of new methodologies and highly sophisticated instrumentation.
NMR is a manifestation of the fact that many atomic nuclear isotopes have both an intrinsic angular momentum (spin) and a magnetic moment. Two common examples are the abundant spin 1H (ordinary hydrogen nuclei) and the rare spin 13C (rare compared to ordinary carbon nuclei, 12C). When placed in a magnetic field, the combination of spin and magnetic moment causes the nuclei to precess about the field, or resonate. Typically the resonant frequencies are in the radiofrequency (rf) range in magnetic fields readily available in the laboratory. Various rf methods are available to detect this resonance. Because the magnetic field seen by individual nuclei is modified by their chemical environment (chemical shielding), a chemically complex substance will exhibit a spectrum of resonances. This is where the journey begins... [Note: In the description of an NMR experiment, it is customary to specify both the nature of the NMR experiment and the strength and specifications of the magnet. Thus, for example, one speaks of a simple one-dimensional (1D), fourier-transform (FT) NMR experiment on fluorine (19F) in a high-resolution, wide-bore 300 MHz magnet. Other variables, such as temperature, may also be specified. Magnet strength is always indicated by the resonance frequency of 1H in that magnet, regardless of the nucleus under study. We follow this convention in what follows.]
The NCSU NMR Facility provides modern NMR capabilities for the facility’s users, who represent the faculty, staff, and students of other departments at NCSU, researchers at other smaller colleges and universities in North Carolina, researchers at local governmental agencies, and our industrial collaborators. The NMR Facility’s 4 high resolution NMR spectrometers are used for detailed structural studies of molecules ranging from small organic molecules to macromolecules, such as polymers.