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Alexenberg C, Afri M, Eliyahu S, Porat H, Ranz A, Frimer AA. Locating intercalants within lipid bilayers using fluorescence quenching by bromophospholipids and iodophospholipids. Chem Phys Lipids 2019; 221:128-139. [PMID: 30954536 DOI: 10.1016/j.chemphyslip.2019.03.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 03/17/2019] [Accepted: 03/31/2019] [Indexed: 11/30/2022]
Abstract
In previous work, we have been able to determine the depth of intercalated molecules within the lipid bilayer using the solvent polarity sensitivity of three spectroscopic techniques: the 13C NMR chemical shift (δ); the fluorescence emission wavelength (λem), and the ESR β-H splitting constants (aβ-H). In the present paper, we use the quenching by a heavy atom (Br or I), situated at a known location along a phospholipid chain, as a probe of the location of a fluorescent moiety. We have synthesized various phospholipids with bromine (or iodine) atoms substituted at various locations along the lipid chain. The latter halolipids were intercalated in turn with various fluorophores into DMPC liposomes, biomembranes and erythrocyte ghosts. The most effective fluorescence quenching occurs when the heavy atom location corresponds to that of the fluorophore. The results show that generally speaking the fluorophore intercalates the same depth independent of which lipid bilayer is used. KBr (or KI) is the most effective quencher when the fluorophore resides in or at the aqueous phase. Presumably because of iodine's larger radius and spin coupling constant, the iodine analogs are far less discriminating in the depth range it quenches.
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Affiliation(s)
- Carmit Alexenberg
- The Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel.
| | - Michal Afri
- The Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel.
| | - Shlomi Eliyahu
- The Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel.
| | - Hani Porat
- The Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel.
| | - Ayala Ranz
- The Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel.
| | - Aryeh A Frimer
- The Department of Chemistry, Bar-Ilan University, Ramat Gan, 5290002, Israel.
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Afri M, Alexenberg C, Aped P, Bodner E, Cohen S, Ejgenburg M, Eliyahu S, Gilinsky-Sharon P, Harel Y, Naqqash ME, Porat H, Ranz A, Frimer AA. NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Chem Phys Lipids 2014; 184:105-18. [DOI: 10.1016/j.chemphyslip.2014.07.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Revised: 07/10/2014] [Accepted: 07/21/2014] [Indexed: 01/20/2023]
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NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Part V: A comparison of liposomes, bioliposomes and erythrocyte ghosts. Chem Phys Lipids 2014; 184:52-60. [DOI: 10.1016/j.chemphyslip.2014.10.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 10/06/2014] [Accepted: 10/08/2014] [Indexed: 11/20/2022]
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Afri M, Alexenberg C, Aped P, Bodner E, Cohen S, Ejgenberg M, Eliyahu S, Gilinsky-Sharon P, Harel Y, Naqqash ME, Porat H, Ranz A, Frimer AA. NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Part IV: studies on ketophospholipids. Chem Phys Lipids 2014; 184:119-28. [PMID: 25064026 DOI: 10.1016/j.chemphyslip.2014.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Revised: 06/11/2014] [Accepted: 07/08/2014] [Indexed: 11/17/2022]
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.
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Affiliation(s)
- Michal Afri
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Carmit Alexenberg
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Pinchas Aped
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Efrat Bodner
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Sarit Cohen
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Michal Ejgenberg
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Shlomi Eliyahu
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | | | - Yifat Harel
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Miriam E Naqqash
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Hani Porat
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Ayala Ranz
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
| | - Aryeh A Frimer
- The Department of Chemistry, Bar-Ilan University, Ramat Gan 5290002, Israel.
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Afri M, Naqqash ME, Frimer AA. Using fluorescence to locate intercalants within the lipid bilayer of liposomes, bioliposomes and erythrocyte ghosts. Chem Phys Lipids 2011; 164:759-65. [PMID: 21939642 DOI: 10.1016/j.chemphyslip.2011.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 08/15/2011] [Accepted: 09/06/2011] [Indexed: 11/15/2022]
Abstract
In previous work, we have shown the utility of the "NMR technique" in locating intercalants within the lipid bilayer. We describe herein the development of a more sensitive and complementary "fluorescence technique" for this purpose and its application to liposomes, bioliposomes and erythrocyte ghosts. This technique is based on the observation in selected compounds of an excellent correlation between the emission wavelength (λ(em)) and Dimroth-Reichardt E(T)(30) polarity parameter for the solvent in which the fluorescence emission spectrum was obtained.
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Affiliation(s)
- Michal Afri
- Department of Chemistry, Bar Ilan University, Ramat Gan, Israel.
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Shachan-Tov S, Afri M, Frimer AA. A reinvestigation of the reaction of coumarins with superoxide in the liposomal bilayer: correlation between depth and reactivity. Free Radic Biol Med 2010; 49:1516-21. [PMID: 20801211 DOI: 10.1016/j.freeradbiomed.2010.08.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2010] [Accepted: 08/06/2010] [Indexed: 11/26/2022]
Abstract
Afri et al. reported in this journal (Free Radic. Biol. Med.32:605-618; 2002) that a direct relationship exists between the depth of alkanoylcoumarins 1 within the liposomal lipid bilayer and the rate at which they undergo superoxide-mediated saponification. These results were based on a correlation between the (13)C NMR chemical shift of polarizable carbonyl carbons and the E(T)(30) polarity they sense. Subsequent studies challenged these results, however, demonstrating that, in conjugated ketones and aldehydes, charge separation influences the E(T)(30) polarity measured. To elucidate whether this is true for conjugated esters such as coumarins as well, the nonconjugated analogs 3,4-dihydrocoumarins 11 and 15 were intercalated within DMPC liposomal bilayers and their relative locations within the liposomal bilayer were determined. The length of the alkyl chain substituted at C-4 and C-10 influences the depth of the substrates within the liposome. The location of these 3,4-dihydrocoumarins corresponds well with the conjugated analog coumarin 1-confirming the validity of the abovementioned results of Afri et al. The lack of substantial charge separation in the coumarin 1 system presumably results from the "swamping-out" effect of the ester oxygen. Instead of 1,3-delocalization of charge, typical of conjugated systems, delocalization of the nonbonding pair on the ester oxygen predominates.
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Affiliation(s)
- Sharona Shachan-Tov
- The Ethel and David Resnick Chair in Active Oxygen Chemistry, Department of Chemistry, Ramat Gan 52900, Israel
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Cohen Y, Bodner E, Richman M, Afri M, Frimer AA. NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Chem Phys Lipids 2008; 155:98-113. [DOI: 10.1016/j.chemphyslip.2008.07.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 07/06/2008] [Accepted: 07/08/2008] [Indexed: 10/21/2022]
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