Sturcture and thermotropic properties of 1,3-dipalmitoyl-glycero-2-phosphocholine

• Published in: Journal of molecular biology Vol. 170; no. 1; pp. 155 - 174
• Main Authors: Serrallach, EN, Dijkman, R, de Hass, GH, Shipley, G G
• Format: Journal Article
• Language: English
• Published: 01.01.1983
• Subjects: 1,3-dipalmitoyl-glycero-2-phosphocholine; differential scanning calorimetry; lipid bilayers; X-ray diffraction
• ISSN: 0022-2836

The structure and thermotropic properties of hydrated 1,3-dipalmitoyl-glycero-2-phosphocholine ( beta -DPPC) have been studied by X-ray diffraction and differential scanning calorimetry. After prolonged storage at -3 degree C, differential scanning calorimetry heating scans exhibit endothermic transitions at 27 degree C and 37 degree C, with transition enthalpies, Delta H = 9 multiplied by 1 and 10 multiplied by 5 kcal/mol beta -DPPC, respectively (1 cal = 4 multiplied by 184 J). Upon cooling, the high temperature transition is completely reversible, whereas the low temperature transition is not. Prolonged incubation of hydrated beta -DPPC at low tempertures is necessary in order to regain the full enthalpy of the low temperature transition, indicating metastability of the low temperature form. X-ray diffraction studies indicate three different lamellar phases upon heating equilibrated beta -DPPC from -3 degree C: below 18 degree C, a hydrated "crystalline" bilayer phase, L sub(c), with an ordered hydrocarbon chain-packing mode and a bilayer periodicity d = 58 angstrom: between 30 degree C and 35 degree C, a hydrated gel phase; above 37 degree C, a highly hydrated (48 mol water/mol beta -DPPC) liquid crystalline bilayer phase, L sub(a), with d = 65 angstrom.