title: NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Part IV: studies on ketophospholipids.
abstract: In our companion paper, we described the preparation and intercalation of two homologous series of dicarbonyl compounds, methyl n-oxooctadecanoates and the corresponding n-oxooctadecanoic acids (n=4-16), into DMPC liposomes. (13)C NMR chemical shift of the various carbonyls was analyzed using an E(T)(30) solvent polarity-chemical shift correlation table and the corresponding calculated penetration depth (in Å). An iterative best fit analysis of the data points revealed an exponential correlation between E(T)(30) micropolarity and the penetration depth (in Å) into the liposomal bilayer. However, this study is still incomplete, since the plot lacks data points in the important area of moderately polarity, i.e., in the E(T)(30) range of 51-45.5 kcal/mol. To correct this lacuna, a family of ketophospholipids was prepared in which the above n-oxooctadecanoic acids were attached to the sn-2 position of a phosphatidylcholine with a palmitic acid chain at sn-1. To assist in assignment and detection several derivatives were prepared (13)C-enriched in both carbonyls. The various homologs were intercalated into DMPC liposomes and give points specifically in the missing area of the previous polarity-penetration correlation graph. Interestingly, the calculated exponential relationship of the complete graph was essentially the same as that calculated in the companion paper based on the methyl n-oxooctadecanoates and the corresponding n-oxooctadecanoic acids alone. The polarity at the midplane of such DMPC systems is ca. 33 kcal/mol and is not expected to change very much if we extend the lipid chains. This paper concludes with a chemical ruler that maps the changing polarity experienced by an intercalant as it penetrates the liposomal bilayer.
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: Michal.Afri@biu.ac.il.
authors: Michal
authors: M
authors: Afri
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: C_Eliasi@walla.com.
authors: Carmit
authors: C
authors: Alexenberg
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: Pinchas.Aped@biu.ac.il.
authors: Pinchas
authors: P
authors: Aped
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: Efrat.Bodner@biu.ac.il.
authors: Efrat
authors: E
authors: Bodner
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: SaritCohen84@gmail.com.
authors: Sarit
authors: S
authors: Cohen
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: MichalDomb@gmail.com.
authors: Michal
authors: M
authors: Ejgenberg
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: ShlomiEliyohu@gmail.com.
authors: Shlomi
authors: S
authors: Eliyahu
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: Pessia.Sharon@biu.ac.il.
authors: Pessia
authors: P
authors: Gilinsky-Sharon
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: IfatAsh@Yahoo.com.
authors: Yifat
authors: Y
authors: Harel
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: MiriamNaqqash@gmail.com.
authors: Miriam E
authors: ME
authors: Naqqash
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: HaniPorat@gmail.com.
authors: Hani
authors: H
authors: Porat
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: Ayala.Ranz@gmail.com.
authors: Ayala
authors: A
authors: Ranz
authors: The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel. Electronic address: Aryeh.Frimer@biu.ac.il.
authors: Aryeh A
authors: AA
authors: Frimer
mesh_terms: D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D007364:Intercalating Agents / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D010713:Phosphatidylcholines / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D007364:Intercalating Agents; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D004134:Dimyristoylphosphatidylcholine
keywords: (13)C NMR; DMPC; E(T); Ketophospholipids; Liposome; Molecular ruler