Pressure effects on the Raman spectra of phospholipid membranes: Pressure induced phase transitions and structural changes in 1,2-dimyristoyl 3-s n-phosphatidylcholine water dispersions

Abstract

In a study of the pressure dependence of the Raman spectrum of an aqueous dispersion of dimyristoyl phosophatidylcholine from ambient pressure up to 5 kbar, three phase transitions have been observed at 150 bar and at 1 and 2.6 kbar. From the behavior of the spectrum, a correlation may be made between these phase transitions and temperature-induced changes observed at 24, 14, and −60 °C, respectively. The major cause of the pressure-induced frequency shift of all the Raman bands is the pressure-enhanced interchain anharmonic interaction rather than the pressure-induced compression of intramolecular bonds. It is further shown that the large angle reorientational fluctuations about the long axes of the acyl chains decrease with increasing pressure.