Nitrogen Relaxation in Large Molecules The Isotopic Substitution Method

4 Nitrogen Relaxation in Large Molecules. The Isotopic Substitution Method 

Nitrogen NMR acquires its structural dimension with the investigations of large molecules containing several nitrogen atoms, and much work has been done to improve this field. 

Fortunately, the inconvenience resulting from the poor efficiency of the N-H dipolar relaxation is rapidly attenuated as the molecular reorientation becomes slower, i.e. as the molecular weight of the investigated compounds increases. As shown in Fig.2.3, rapidly decreases to- 

Another severe limitation to the investigation of biopolymers is caused by the dipolar broadening which accompanies the increase in 

C signals (Fig. 2.1). Moreover, it should be noted that in a certain range of correlation times, the lines are expected to be sharper in superconducting spectrometers (Fig. 2.3b). However, the dipolar effect may be a severe impediment to the resolution of nitrogen lines of proteins, for example. 

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