32.19: Applications Of NMR In Biology
Nuclear magnetic resonance (NMR) spectroscopy is a very valuable analytical technique for researchers. It has been used for more than 50 years as an analytical tool. F. Bloch and E. Purcell formulated NMR in 1946 and won the 1952 Nobel Prize in Physics for their work. Biological macromolecules such as proteins, nucleic acids, lipids, and organic molecules including pharmaceutical compounds, can be studied using this versatile tool that exploits the magnetic properties of certain nuclei.
The basic principle of this technique is that nuclei, in addition to their electric charge, also have a spin. Nuclei with an odd atomic number or mass possess this property of spin, which is vital for the NMR technique. The spin is random and in random directions, similar to a spinning top. Hence, when placed under an external magnetic field, these nuclei align themselves with or against the applied field. These nuclei return to their original orientation when the external field is removed. The energy gap is then translated into a spectra that depends on the nature of the environment of the atoms, and the distance between nuclei. The resulting spectra helps study different parameters like the structure, dynamics, and properties of the samples. Properties such as reaction state,chemical environment, and interactions of the samples are examples of investigational results that can be studied with this technique.
In biology, 13C, 1H, 2H 15N, 31P, 23Na, and 19F are important biologically relevant NMR-active nuclei that help understand biochemical pathways involved in amino acid, lipid, and carbohydrate metabolism. Also, NMR offers a window into observing and quantifying numerous compounds in biological fluids, cell extracts, and tissues without the need for complex sample preparation or fractionation.
Over the past two decades, NMR has been developed to produce detailed images in a process now called magnetic resonance imaging (MRI), a name coined to avoid the use of the word “nuclear” and the concomitant implication that nuclear radiation is involved. MRI is based on NMR, in which an externally applied magnetic field interacts with the nuclei of certain atoms, particularly those of hydrogen (protons) of the body tissue.
Numerous applications of this technique, including its pivotal role in drug discovery and proteomics, are helping advance research to new heights, benefiting humanity.