Locating intercalants within lipid bilayers using fluorescence quenching by bromophospholipids and iodophospholipids.

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 C NMR chemical shift (δ); the fluorescence emission wavelength (λ), and the ESR β-H splitting constants (a). 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.

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 (13)C 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.

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

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 (13)C NMR chemical shift of polarizable "reporter" carbons (e.g.

NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Part IV: studies on ketophospholipids.

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.