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

• DMPC, bioliposomes and erythrocyte ghosts were characterized by 13C NMR.
• Doubly 13C-labeled n-ketophosphatidylcholines (n = 4, 8 and 12) were prepared.
• The ketoPCs were intercalated into the bilayers of these three lipid systems.
• These systems are similar from the perspective of polarity gradient.
• Differences reflect the additives naturally present in these lipid systems.

Afri et al., 2014a and Afri et al., 2014b have recently reported their mapping of DMPC liposomes using 13C 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 13C NMR characterization of these systems for the first time, and further involved a determination of the signals of three doubly 13C-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.

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