title: Binary mixtures of saturated and unsaturated mixed-chain phosphatidylcholine. A differential scanning calorimetry study.
abstract: High-resolution differential scanning calorimetry (DSC) has been used to study the aqueous dispersions of mixed-chain phosphatidylcholines prepared from colyophilized mixtures of C(18):C(11:1 delta 10) PC/C(18):C(10)PC and C(18):C(11:1 delta 10) PC/C(18):C(11)PC of various molar ratios. These mixed-chain phospholipids are characterized by a marked disparity in their acyl-chain lengths; however, the sn-1 acyl chain in the fully extended conformation is about twice as long as the sn-2 acyl chain. Their thermotropic behavior was determined, and the phase diagrams of these two mixtures were constructed from the calorimetric data. Results indicate that C(18):C(11:1 delta 10)PC/C(18):C(10)PC and C(18):C-(11:1 delta 10)PC/C(18):C(11)PC are miscible in all proportions with a near-ideal behavior of mixing in the gel and liquid-crystalline phases. Equimolar mixtures of diC(14)PC/C(18):C(11:1 delta 10)PC, diC(14)PC/C(18):C(10)PC, and diC(14)PC/C(18):C(11)PC have also been studied by DSC. These phosphatidylcholines in the 1:1 mixture differ in Tm by less than 11 degrees C; however, they exhibit gel-phase immiscibility in the plane of the bilayer. Taken together, these studies suggest that C(18):C(11)PC and C(18):C(11:1 delta 10)PC are packed similarly to C(18):C(10)PC in excess water as mixed interdigitated bilayers, at T less than Tm, which transform into partially interdigitated bilayers when heated above Tm.
authors.affiliation: Department of Biochemistry, University of Virginia School of Medicine, Charlottesville 22908.
authors.forename: S
authors.initials: S
authors.lastname: Ali
authors.forename: H N
authors.initials: HN
authors.lastname: Lin
authors.forename: R
authors.initials: R
authors.lastname: Bittman
authors.forename: C H
authors.initials: CH
authors.lastname: Huang
mesh_terms: D002152:Calorimetry, Differential Scanning; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D013329:Structure-Activity Relationship
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines