Changes in hydrocarbon chains and head groups in distearoyl phosphatidylcholine at 4th and 3rd transitions under high pressure

The highly ordered conformation of hydrocarbon chain packing with orthorhom bic symmetry in L-alpha-distearoyl phosphatidylcholine under high pressure is confirmed using wide angle X-ray diffraction and Raman scattering, With an increase in temperature under high pressure, two phase transitions (the 4th and 3rd counted from the well known main and pre-transitions) convert t he hydrocarbon chain packing from orthorhombic to quasi-hexagonal via, brie fly; quasi-orthorhombic symmetry. This behavior is closely related to the m ovement of the head group and the occurrence of the gauche bond in the intr achain of phospholipids. These phenomena occur alter the phospholipid is pr essed above about 250 MPa and heated once above its melting point.