Nuclear magnetic resonance radio frequency effect

Abbreviations NMR, nuclear magnetic resonance 2D-NMR, two-dimensional NMR HOHAHA, 2D-NMR homonuclear Hartman-Hahn spectroscopy NOE, nuclear Overhauser effect NOESY, 2D-NMR nuclear Overhauser effect spectroscopy rf, radio frequency FID, free induction decay CD, circular dichroism PF4, platelet factor-4 IL-8, interleukin-8 Gro-a, growth-related protein a. 

A2. Alderman, D. W., Improvement of signal-to-noise ratio in continuous-wave nuclear magnetic resonance at liquid-helium temperature by using a metal oxide semiconductor field-effect-transistor radio-frequency amplifier. Rev. Set. Instrum. 41, 192-197 (1970). 

NMR Spectroscopy The three dimensional structures of small proteins containing about as many as 200 amino acids can be studied with nuclear magnetic resonance (NMR) spectroscopy. In this technique, a concentrated protein solution Is placed in a magnetic field and the effects of different radio frequencies on the spin of different atoms are measured. The behavior of any atom Is Influenced by neighboring atoms In adjacent residues, with closely spaced residues being more perturbed than distant residues. From the magnitude of the effect, the distances between residues can be calculated these distances are then used to generate a model of the three-dimensional structure of the protein. 

The spectrometer is a radio receiver, and we change the frequency to tune in each nucleus at its characteristic frequency, just like the stations on your car radio. Because the resonant frequency is proportional to the external magnetic field strength, all of the resonant frequencies above would be increased by the same factor with a stronger magnetic field. The relative sensitivity is a direct result of the strength of the nuclear magnet, and the effective sensitivity is further reduced for those nuclei that occur at low natural abundance. For example, 13C at natural abundance is 5700 times less sensitive (1/(0.011 x 0.016)) than H when both factors are taken into consideration. 

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