Effects of hydrostatic pressure on the molecular structure and endothermic phase transitions of phosphatidylcholine bilayers: a Raman scattering study

Abstract

The temperature dependences of the Raman spectra of aqueous dispersions of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were monitored at different but constant pressures between 1 and 1210 bar. The changes observed in these Raman spectra are discussed in terms of the effects of high pressure on the phase state and molecular structure of lipid bilayers. It is demonstrated that the temperature of the endothermic gel to liquid-crystal phase transition, as well as the temperature of the pretransition, increases linearly with increasing hydrostatic pressure. The dTm/dP values obtained from a wide range of pressures are 20.8 degrees C X kbar-1 for DPPC and 20.1 degrees C X kbar-1 for DMPC. The dTp/dP value for DPPC is 16.2 degrees C X kbar-1. It is also shown that the volume change that occurs at the gel to liquid-crystal transition is not constant; i.e., d delta Vm/dP decreases by 6.2% (DPPC) or 6.3% (DMPC) per kilobar pressure. The volume change at the pretransition is also pressure dependent; the d delta Vp/dP value of DPPC decreases by 4.7% per kilobar pressure.

Comprehensive characterization of temperature- and pressure-induced bilayer phase transitions for saturated phosphatidylcholines containing longer chain homologs

“…On the other hand, the L ␤ I phase is also induced by an application of pressure. It was found that bilayers of CnPCs, such as dimyristoyl-PC (DMPC: C14PC) and dipalmitoyl-PC (DPPC: C16PC), form the fully L ␤ I phase under high pressure [10][11][12][13][14][15][16][17][18]. In the L ␤ I phase, hydrocarbon chains of the CnPC molecules in one of the monolayers constituting a bilayer extend beyond the region of the bilayer midplane and alternately interpenetrate into the other opposing monolayer.…”

Chain elongation of diacylphosphatidylcholine induces fully bilayer interdigitation under atmospheric pressure

“…Lipid bilayer membranes of diacylphosphatidylcholines (diacylPCs), of which two identical saturated fatty-acid chains are bound to the glycerol backbone by ester linkage, have been thoroughly examined by several physico-chemical techniques [1][2][3][4][5][6][7][8][9]. Such bilayer membranes form various kinds of phases depending upon experimental conditions, and the characteristic gel-phase polymorphism is observed.…”

Ordering Phenomena in Surfactant Systems: From Micellar Solutions to Gel and Crystalline Phases

“…Consequently, this is a transition into a viscous gel phase similar to what has been observed in phospholipid dispersions either under pressure or at low temperatures (e.g. [9][10][11][12][13][14]). The formation of a gel-like structure of OTAB was also suggested by [15] who observed a heat signal in differential scanning calorimetry.…”