Introduction to NMR

NMR involves the detection of radiofrequency signals from several types of atoms placed in a magnetic field. At HWB•NMR, NMR spectroscopy is used to reveal the three dimensional structures of proteins, which are composed of thousands of atoms uniquely arranged in space in order to perform a specific biological function within an organism.

 

Diagram of a carbon-13 atom

 

NMR involves the detection of radiofrequency signals from several types of atoms placed in a magnetic field. At HWB•NMR, NMR spectroscopy is used to reveal the three-dimensional structures of biomolecules, which are composed of thousands of atoms uniquely arranged in space in order to perform a specific biological function within an organism.

The nuclei of hydrogen, carbon-13, nitrogen-15 and phosphorus-31 atoms are magnetically active and, when placed in a magnetic field, absorb and release energy at a specific frequency, generating an NMR signal. This is called nuclear magnetic resonance.

The specific frequency of each atomic nucleus depends on its chemical and spatial environment, while other magnetic properties depend on its interaction with other atoms in the molecule. By measuring the frequencies of hundreds of nuclei within a biomolecule, together with other site-specific magnetic properties, the molecular structure of the biomolecule can be deduced. This structure reveals the 3D shape of the biomolecule and the chemical properties of regions which bind other molecules and communicate biological information. This information can then be used to screen for and design inhibitors that block unwanted binding events involved in diseases. In addition, the power of NMR spectroscopy lies in its capability to inform on both structure and dynamics of biomolecules, thus taking into account those dynamic processes that are crucial for all biological functions.

Powerful NMR spectrometers provide more information by separating and detecting the frequency signals of nuclei within even very large molecules. The 1000 MHz magnet provides an extremely strong and stable field that yields stronger and better separated signals, allowing more accurate structures to be determined.

The strength of the NMR spectrometer is specified in terms of the resonance frequency of the hydrogen atoms within its magnetic field, and is expressed in megahertz (MHz). The 1000 MHz spectrometer is equipped with a 23.5 Tesla magnet and is used to characterise demanding targets such as multicomponent enzymes, membrane proteins and nucleic acids.

To yield even better data, sensitivity is boosted by cryogenic probes which reduce the thermal noise when detecting the NMR signals. In addition, liquid handling robots are used to automatically prepare and inject samples, increasing the speed of the experiments in drug screening campaigns and metabolomics studies.

NMR has several unique advantages. It is a non-destructive technique, allowing samples to be regenerated for additional experiments. It is a versatile method, being used to determine concentrations, dynamics, folding, interactions and structures of a wide variety of molecules. NMR experiments are typically performed in solution, which resembles the cellular environment, allowing biologically relevant states to be observed. When performed in solid-state, NMR experiments do not require crystallization, easing the requirements for sample preparation.