This experiment measures the relaxation rate constants of the 15N TROSY and anti-TROSY lines (along with the rate constant for longitudinal two-spin order). The three rates are used to obtain both R2 and ηxy to allow identification of chemical exchange in large molecules
The experiment normally is performed using protein samples that are perdeuterated at carbon sites [U-D,U-15N] to reduce 1H-1H dipole interactions.
C. Wang, M. Rance, and A. G. Palmer, Mapping chemical exchange in proteins with MW > 50 kD, J. Am. Chem. Soc. 125, 8968-8969 (2003).