High pressure FT-IR spectra of aqueous systems: Applications to biomembranes

Abstract

In order to compare the effects ofcis andtrans unsaturation on the structure and packing of phospholipid bilayers, infrared spectra of aqueous dispersions of DOPC and DEPC were measured as a function of pressure up to 36 kbar. Below their respective critical pressures of the liquid crystalline to gel phase transitions, the infrared spectra of DOPC and DEPC are essentially indistinguishable, whereas above these pressures, there are very pronounced differences in the barotropic behavior of these lipids [6]. In particular, the absence of correlation field splittings of the CH₂ scissoring and rocking modes of DOPC up to 36 kbar suggests that the bent oleoyl chains are closely packed with all chains parallel to each other.