Nuclear magnetic resonance (NMR) spectroscopy represents a technique that is dependent on the magnetic properties of the atomic nucleus. When positioned in a strong magnetic field, certain nuclei resonate at a specific frequency in the radio frequency range of the electromagnetic spectrum. Slight variations in those frequencies provide detailed information about the molecular structure in which the atom resides.
During the past decades there has been a tremendous progress in NMR, which took place both in experimental instrumentation and in theoretical approaches that help extracting indispensable molecular information from the special parameters known as “high-resolution NMR parameters”. That broadened the scope of this spectroscopy for studying a large series of molecular problems.
NMR spectroscopy complements other analytical and structural techniques such as X-ray crystallography and mass spectrometry. The advantage of this technique is the distinctive ability of a nuclear spectrometer to enable both the quantitative and non-destructive study of molecules in solution and in solid state, but also to allow the study of biological fluids.
NMR spectroscopy is most often used by biochemical scientists to interrogate characteristics of organic molecules, albeit the technique is appropriate to all kind of samples that contain nuclei possessing spin. Nevertheless, the future of NMR spectroscopy may be in personalized medicine and in portable devices.
NMR: A Trend in Medical Research
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NMR spectroscopy has already been successfully used to screen for biomarker profiles that denote sub-phenotypes of various diseases, laying the foundation for the development of new and targeted drugs, but also potentially enabling the physicians to come up with “the specific therapy for the specific patient”.
The first step is to create a database of metabolic profiles in samples under kindred conditions – which represents a process known as metabolomics – with subsequent analysis of the spectra to determine any predilections towards disease. If a large group of people is followed and the analysis is repeated after a certain time period, the changing NMR spectra will exhibit changes in the phenotype of each individual.
The gathered information can then be used to pinpoint environmental factors that can contribute to specific phenotype changes, and to establish which phenotype changes could result in which disease. This will in turn allow physicians to comprehend the causes of a specific disease and to identify a personalized cure.
At the moment, NMR spectroscopy can detect practically all proton-containing metabolites in a sample,
i.e. various molecules that produce different signals in the spectrum. The advantages are that this technique is fast and non-selective, without the need for sample preparation.
Most of the characteristics that will soon enable its use in personalized medicine can already be found in the Avance III HD NanoBay NMR device from the company Bruker, which is currently the most highly integrated state-of-the-art broadband NMR spectrometer. It delivers high quality information and includes most compact and stable Ascend magnet technology.
Portable NMR Spectroscopy
The traditional NMR system can be quite large and bulky due to the size of the magnets used; nevertheless, advances in the technology for producing magnets resulted in smaller permanent magnets, which in turn facilitated the implementation of tabletop spectrometers that we see in modern analytical laboratories, such as Bruker's Fourier 300 compact NMR spectrometer.
A research team from Harvard University took a step further and paved the way for a truly portable NMR spectrometer. They managed to integrate the spectrometer electronics into a 4 mm2 silicon chip, which was operated with a compact permanent magnet (0.51-T Hallbach magnet).
Such portable systems will facilitate the implementation of NMR spectroscopy in instances where expensive and large conventional NMR spectrometers cannot be stationed, yet on-demand or online analysis is necessary. A bundle of spectrometer electronics chips and micro-coils have the possibility to counter the inherent slowness of individual experiments, thus enabling high-throughput analysis for metabolomics, structural biology and pharmaceutical screening.
http://www.vanderbilt.edu/AnS/Chemistry/Rizzo/chem220a/Ch13slides.pdf Keeler J. Understanding NMR Spectroscopy, Second Edition. John Wiley & Sons, Inc., 2011
Jacobsen NE. NMR Spectroscopy Explained: Simplified Theory, Applications and Examples for Organic Chemistry and Structural Biology. John Wiley & Sons, Inc., 2007; pp. 1-38.