Thermal phase behaviour and structure of hydrated mixtures between dipalmitoyl- and dihexadecylphosphatidylcholine

✍ Scribed by Karl Lohner; Annemarie Schuster; Gábor Degovics; Karl Müller; Peter Laggner

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 429 KB
• Volume: 44
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(87)90005-3

✦ Synopsis

Mixtures of 1,2-dipahnitoyl-and 1,2-O-dihexadecyl-sn-glycero-3-phosphocholine (DPPC and DHPC) in dispersion with excess water were studied by differential scanning calorimetry (DSC) and X-ray diffraction techniques, The transition parameters of the main gel-to-liquid crystalline transition show a monotonous dependence on the composition, indicating ideal miscibility of the two lipids, in keeping with the closely similar structures of the pure, hydrated lipids in the P~' and La states. The pre-transition shows a depression to a minimum temperature of 23°C occurring around equhnolax mixtures. Below the pre-transition temperatures, the L~' gel phase of DPPC maintains bimolecular structure up to DHPC admixtures of 50 tool%, with adaptations in hydrocarbon chain packing and multihyer periodicity. On the side of DHPC, the interdigitated gel structure shows full solubility for DPPC up to equimolarity without major structural changes. The crystalline Lc-phase of DPPC exhibits immiscibility with DHPC, demonstrated by the fact that the subtransition is abolished already at less than 15 tool% DHPC. DHPC, below its subtransition, can accommodate up to 50 mol% DPPC within an interdigitated layer structure with unperturbed, crystalline hydrocarbon chain packing.