Hardware Requirements for Biological NMR

The availability of pulsed-field gradients makes it possible to automatically shim using NMR imaging techniques. In MRI we rely on the dominance of water in the human body to obtain 

By now you may have realized that there is a continuum of water molecules in the sample at all levels, not just at the 17 discreet levels we considered above. We can simulate the spectrum we expect by adding together a very large number of NMR peaks, starting at the 

If the arctan (inverse tangent) function is defined to give values between +90° and —90°, we would have b moving linearly from -90° to +90° and then suddenly jumping back to -90°, but the software can unravel these discontinuities to generate a smooth field map. A control experiment is done with r = 0, and the control field map is subtracted from the field map generated with the delay r. 

---

Solid-state F NMR of biological samples has been reviewed by Ulrich. The methodological aspects were the focus of this review article, with an emphasis on designated techniques for studying biomembranes. The unique properties of the F nucleus, the most informative NMR parameters, the special hardware requirements, and appropriate pulse sequences were considered. Following these experimental aspects, several applications of F NMR have been highlighted, for example, for the characterisation of the F CSA tensors of relevant amino acids and for the examination of the behaviour of drugs in lipid bilayers. 

---