NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Part III: Studies on keto esters and acids

Michal Afri, Carmit Alexenberg, Pinchas Aped, Efrat Bodner, Sarit Cohen, Michal Ejgenburg, Shlomi Eliyahu, Pessia Gilinsky-Sharon, Yifat Harel, Miriam E. Naqqash, Hani Porat, Ayala Ranz, Aryeh A. Frimer

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

The development of "molecular rulers" would allow one to quantitatively locate the penetration depth of intercalants within lipid bilayers. To this end, an attempt was made to correlate the 13C NMR chemical shift of polarizable "reporter" carbons (e.g., carbonyls) of intercalants within DMPC liposomal bilayers - with the polarity it experiences, and with its Angstrom distance from the interface. This requires families of molecules with two "reporter carbons" separated by a known distance, residing at various depths/polarities within the bilayer. For this purpose, two homologous series of dicarbonyl compounds, methyl n-oxooctadecanoates and the corresponding n-oxooctadecanoic acids (n = 4-16), were synthesized. To assist in assignment and detection several homologs in each system were prepared 13C-enriched in both carbonyls. Within each family, the number of carbons and functional groups remains the same, with the only difference being the location of the second ketone carbonyl along the fatty acid chain. Surprisingly, the head groups within each family are not anchored near the lipid-water interface, nor are they even all located at the same depth. Nevertheless, using an iterative best fit analysis of the data points enables one to obtain an exponential curve. The latter gives substantial insight into the correlation between polarity (measured in terms of the Reichardt polarity parameter, ET(30)) and penetration depth into the liposomal bilayer. Still missing from this curve are data points in the moderate polarity range.

Original languageEnglish
Pages (from-to)105-118
Number of pages14
JournalChemistry and Physics of Lipids
Volume184
DOIs
StatePublished - Dec 2014

Bibliographical note

Publisher Copyright:
© 2014 Elsevier Ireland Ltd. All rights reserved.

Keywords

  • C NMR
  • DMPC
  • E
  • Liposome
  • Molecular ruler
  • Oxooctadecanoates

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