Chemical Services, NMR Unit High Resolution NMR Facility

What is NMR?

Nuclear Magnetic Resonance (NMR) is a powerful spectroscopic technique that provides information about the structural and chemical properties of molecules. NMR is one of the few non-destructive methods for analyzing structure and molecular dynamics. NMR exploits the behavior of certain atoms when they are placed in a very strong magnetic field. For biochemists these are mainly ¹H, ¹⁵N, ¹³ C and ³¹ P. ¹H and ³¹ P are highly abundant isotopes whilst ¹⁵ N and ¹³ C are present at only low levels < 1%. Studies using these nuclei generally require isotopic enrichment by production of the molecule from media that has been enriched in these isotopes.

In simple terms, when the sample is placed in the magnet the nuclei of the atoms align with the magnetic field in the same way that the needle of a compass aligns itself in the earth's magnetic field. Typically the magnets used in NMR spectroscopy are 10,000-15,000 times stronger than the earth’s magnetic field. The NMR experiment generally consists of applying short bursts or pulses of energy in the radio frequency (RF) range, typically 40-800 MHz, to the sample. These pulses of RF cause the nuclei to rotate away from their equilibrium position and they start to precess (rotate) around the axis of the magnetic field. The exact frequency at which the nuclei precess is related to both the chemical and physical environment of the atom in the molecule. By using different combinations of RF pulses and delays it is possible to determine how each atom in the molecule interacts with other atoms in the molecule. Using a large set of these interactions it is possible to calculate the three-dimensional structures of molecules.

NMR can also be used to look at dynamic processes. These include internal motions within regions of larger molecules such as loops in a protein or the base pairs in DNA or RNA. NMR can also be used to monitor chemical reactions. In fact there are many ways that NMR may be able to help in your research. If you wish to discuss the possibility of using NMR please contact the NMR staff.


The NMR Spectrometer is composed of the following:

Superconducting Magnet, which provides a strong, extremely homogenous magnetic field into which the sample is placed. The strength of the NMR spectrometer is typically specified in terms of the resonance frequency for the hydrogen atom, expressed in MHz.

NMR Probe, which holds the sample and is placed into the bore of the magnet. The probe also contains the antennae for irradiating the sample with radio frequency energy and for receiving the very weak RF resonance back from the sample.

NMR Console, which is the component that generates and controls short bursts (pulses) of high-power RF energy used to excite the sample in the probe. The NMR console also receives and detects the very weak signals coming back from the probe. The performance of the RF system (stability, speed, and accuracy) is a very important factor.

Computer Workstations and software that are used in the NMR spectrometers, both for the control of the various RF pulses, as well as for the storage and processing of the NMR data. The NMR signals are subjected to complex digital signal processing algorithms including the Fourier Transform to convert the NMR information into a form that is easily interpreted by the end user.