NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Part V: A comparison of liposomes, bioliposomes and erythrocyte ghosts

Afri et al. (2014a,b) have recently reported their mapping of DMPC liposomes using C-13 NMR in conjunction with a wide range of difunctional intercalants: n-ketoesters, n-ketoacids and n-ketophosphatidylcholines. The present study initiates a comparable study of bioliposomes and erythrocyte ghosts. This required the C-13 NMR characterization of these systems for the first time, and further involved a determination of the signals of three doubly C-13-labeled intercalants, in particular, n-ketophosphatidylcholines where n =4, 8 and 12. This study reveals that DMPC liposomes, bioliposomes and erythrocyte ghosts, with all their structural differences, are not radically different from the perspective of polarity gradient. Any differences observed reflect the additives often naturally present in these lipid systems. (C) 2014 Elsevier Ireland Ltd. All rights reserved.