Medical research

New test helps drug discoverers identify future cancer treatments

Researchers have developed an investigative procedure that makes the early stages of drug discovery more efficient. This test can help scientists identify new biologically active compounds that can be used to develop effective ...


SARS-CoV-2: The grasping fingers of the viral N protein

Immediately after the infection of a cell in the throat or lungs, the SARS-CoV-2 virus works very hard to replicate, using the human cell's metabolic pathways to produce its proteins and make sure that its genetic material ...


Refining NMR technique to work toward new drug testing tool

University of Canterbury Chemical and Process Engineering Professor Daniel Holland and his team are refining a technique called nuclear magnetic resonance (NMR) and plan to use it to measure the content and concentration ...

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Nuclear magnetic resonance

Nuclear magnetic resonance (NMR) is a property that magnetic nuclei have in a magnetic field and applied electromagnetic (EM) pulse, which cause the nuclei to absorb energy from the EM pulse and radiate this energy back out. The energy radiated back out is at a specific resonance frequency which depends on the strength of the magnetic field and other factors. This allows the observation of specific quantum mechanical magnetic properties of an atomic nucleus. Many scientific techniques exploit NMR phenomena to study molecular physics, crystals and non-crystalline materials through NMR spectroscopy. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI).

All nuclei that contain odd numbers of nucleons have an intrinsic magnetic moment and angular momentum, in other words a spin > 0. The most commonly studied nuclei are 1H (the most NMR-sensitive isotope after the radioactive 3H) and 13C, although nuclei from isotopes of many other elements (e.g. 2H, 10B, 11B, 14N, 15N, 17O, 19F, 23Na, 29Si, 31P, 35Cl, 113Cd, 195Pt) are studied by high-field NMR spectroscopy as well.

A key feature of NMR is that the resonance frequency of a particular substance is directly proportional to the strength of the applied magnetic field. It is this feature that is exploited in imaging techniques; if a sample is placed in a non-uniform magnetic field then the resonance frequencies of the sample's nuclei depend on where in the field they are located. Since the resolution of the imaging techniques depends on how big the gradient of the field is, many efforts are made to develop more powerful magnets, often using superconductors. The effectiveness of NMR can also be improved using hyperpolarization, and/or using two-dimensional, three-dimensional and higher dimension multi-frequency techniques.

The principle of NMR usually involves two sequential steps:

The two fields are usually chosen to be perpendicular to each other as this maximises the NMR signal strength. The resulting response by the total magnetization (M) of the nuclear spins is the phenomenon that is exploited in NMR spectroscopy and magnetic resonance imaging. Both use intense applied magnetic fields (H0) in order to achieve dispersion and very high stability to deliver spectral resolution, the details of which are described by chemical shifts, the Zeeman effect, and Knight shifts (in metals).

NMR phenomena are also utilized in low-field NMR, NMR spectroscopy and MRI in the Earth's magnetic field (referred to as Earth's field NMR), and in several types of magnetometers.

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