Magnetic phenomena record

The chemical shift of nuclei was one of the first surprises of the physicists starting NMR, which spoiled the picture for them, and made NMR spectroscopy to be a tool for chemists and biochemists. Chemical shift is the property of nuclei to resonate in an external magnetic field at a frequency that depends on the chemical environment. Thus, physically identical nuclei such as in different chemical environments resonate at different frequencies. This phenomenon was first observed in 1950 on the two resonances of ammonium nitrate [20]. The authors did not publish the spectrum obtained. Therefore, a 30-MHz spectrum of EtOH recorded in 1951 is presented here [21] (Fig. 3). For comparison with the 30-MHz spectrum, a H- spectrum of hen egg white lysozyme recorded at 900 MHz in the year 2000 is shown in Fig. 4. With present resolution of spectrometers of 10 , chemical shifts can in principle be resolved at the ppb level. 

Nuclear magnetic resonance (NMR) spectroscopy is at present one of the most widely applied physical techniques in biology, and its potential applications increase day by day, as more sophisticated instrumentation becomes available and deeper theoretical knowledge is obtained. The phenomenon of NMR was discovered simultaneously by Purcell and his associates at Harvard University and by Bloch and co-workers at Stanford University, for which they were jointly awarded the Nobel prize in physics in 1952. In the lipid field there are two main types of NMR spectroscopy that are of interest broad-line experiments, concerned mainly with the spectra obtained from samples in the solid state, or from oriented phases, and narrow-line, or high-resolution, experiments carried out with samples in the liquid, solution or gas phases. Both types of NMR spectroscopy are extremely useful in the study of the lipids. In addition, Fourier transform (FT) NMR has helped increase the sensitivity of the technique and the so-called pulse method of recording spectra has literally widened the prospect of NMR applications in the field of lipid research and industry. The application of NMR to solid fats is still in its infancy (Pines et aL, 1973 Schaefer and Stejskal, 1979 BocieketaL, 1985). 

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