Properties of phosphatidylcholine in the presence of its monofluorinated analogue

The interdigitated gel phase in mixtures of cationic and zwitterionic phospholipids

“…F-DPPC remains fully interdigitated below the main transition and has no pretransition. The primary reason F-DPPC is fully interdigitated below the main transition (~49°C) is because the highly polar C-F bond at the end of the sn-2 acyl chain is less hydrophobic than DPPC [23,24]. This stabilizes interdigitation since the terminal ends of the acyl chains are exposed within the L β I phase.…”

Differential Scanning Calorimetry Studies of Phospholipid Membranes: The Interdigitated Gel Phase

“…The monofluorinated analogue of DPPC, 1-palmitoyl-2-(16-fluoropalmitoyl)sn-glycero-3-phosphocholine (F-DPPC), spontaneously forms the L I phase below the main transition temperature (Tm) [67][68][69]. The main transition temperature of F-DPPC also occurs at a higher temperature (~50 °C) and with a higher transition enthalpy (9.8 kcal/mol) compared to DPPC [67].…”

“…It is possible that this relates to a conversion from interdigitated to noninterdigitated gel right before the transition into the liquid crystalline phase [67]. The main transition is also characterized by a large main transition hysteresis (Figures 8 and 9) [67,69]. Additionally, the L I phase has high conformational order and tight lipid packing [68].…”

“…DPPC or PE lipids). For example, at equimolar amounts of F-DPPC and DPPC, interdigitated F-DPPCrich domains create a phase-segregated system [69,117]. On DSC scans this manifests itself as multiple peaks (Figure 8).…”

“…The peaks with the greatest transition hysteresis likely correspond to interdigitated domains rich in F-DPPC. When the F-DPPC molar fraction is large, the hysteresis is also increased [69]. Additionally, gel phase coexistence occurs in the mixture of 1,2-dielaidoyl-sn-glycero-3-phosphoethanolamine (DEPE) and EDPPC [95].…”