The transverse relaxation rate R-2 of single quantum coherences, the relaxation rate R-LLC of long-lived coherences (LLC), and the ratio R-2/R-LLC have been studied by experiment, simulation and theory in the two-spin system formed by the Glycine aliphatic protons of the dipeptide Alanine-Glycine as a function of the correlation time of rotational diffusion. (C) 2010 Elsevier Inc. All rights reserved.