Deuterium quadrupolar splittings for GW4,20ALP23 in oriented DLPC, DMPC, and DOPC bilayers for samples oriented with β = 90°. The 2H-labeled alanine identities are, from top to bottom, (5,7), (9,11), (13,15), (17,19), and (3,21), with the first alanine of each pair 100% deuterated and the second alanine 50% deuterated.