1H–13C HMQC-based pulse scheme used for measuring 1HM-R2 rates. Narrow and wide rectangular pulses are applied with flip angles of 90° and 180°, respectively, along the x-axis unless indicated otherwise. T is the relaxation delay. The delay τ is set to 4 ms. Quadrature detection in t1 is obtained using States-TPPI (Marion et al. 1989) of phase ϕ1. The phase cycling employed is: ϕ1 = (x, −x); ϕ2 = 2(x), 2(y), 2(−x), 2(−y); receiver phase = x, −x, −x, x. The duration and strength of the gradients are as follows: G1, 1 ms, 15 G/cm; G2, 0.5 ms, 20 G/cm