Exchange-transferred CCR etCCR

As described in Section 9.2.4.5, CCR can be used to obtain dihedral angular information. Since CCR processes depend linearly on the correlation time, the requirements for exchange-transferred spectroscopy are fulfilled similarly to the etNOE. 

The first etCCR application has been reported for a partially C— N-labeled phosphotyrosine peptide derived from interleukin-4 receptor ligated to STAT-6 [107] and subsequent studies involve nucleotide cofactors ligated to human recombinant deoxycytidine kinase [108] and epothilone A bound to tubulin [109]. Since etCCR usually involves isotope-labeling schemes for the ligand, its applicability is limited to specific molecular classes. 

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