Transverse relaxation processes

If the approximate magnitude of coupling constants /( Sn, H) is known, polarization transfer pulse sequences such as INEPT or DEPT ° can be successfully applied in order to enhance the sensitivity of the NMR experiments. These techniques, if applied correctly with optimized setting of the spectrometer, normally give Sn NMR signals for which the line widths are mainly governed by natural transverse relaxation processes (see Figs 1 and 2). 

Referring to transverse relaxation processes that give rise to loss of phase coherence, three motional domains can be defined fast tumbling, where the intrinsic linewidth is Lorentzian in character slow tumbling, where the rotational correlation time is comparable to the inverse of the anisotropy of the magnetic interaction very slow tumbling, where the intrinsic linewidth is once again Lorentzian, but the observed linewidth is simply a powder pattern. 

As discussed above, most of the systems used to reconstitute a membrane protein sample for solution NMR create large, slowly tumbling complexes that suffer from rapid transverse relaxation processes. Size estimations of some of these... 

Mixed Echo Decay. The mixed echo amplitude decay can be expressed in terms of the autocorrelation function of the dipolar Hamiltonian (64). Transverse relaxation processes described by a single correlation time are rarely found in amorphous polymers including elastomers. If a normalized distribution of correlation times (tc) is introduced, than the mixed echo decay is given by (64)... 

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