Structure of polymerizable lipid bilayers. I—1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine, a tubule-forming phosphatidylcholine

✍ Scribed by David G. Rhodes; Steven L. Blechner; Paul Yager; Paul E. Schoen

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 727 KB
• Volume: 49
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(88)90062-x

✦ Synopsis

This report presents the first X-ray diffraction data on diacetylenic phospholipids. The tubule-forming polymerizable lipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DCs.gPC), was studied by low angle X-ray diff3"action from partially dehydrated oriented multibilayers in both polymerized and unpolymerized form. Bilayers of this material were found to be highly ordered, yielding as many as 16 orders of lamellar diffraction, in both the polymerized and unpolymerized states. The unit cell dimension was very small for a lipid of this size. In addition to the features usually observed in the electron density profile structure of phospholipid bilayers, the electron-dense diacetylenic portions of the fatty acyl chain produced electron density maxima at two well-defined levels on each side of the bilayer approximately 15/~ and 9 ~ from the bilayer midplane. A model molecular conformation deduced from the one-dimensional electron density map features all-lrans acyi chains tilted at approximately 28 ° from the bilayer normal that are interdigitated with chains of the opposing monolayer by approximately two carbons at the brayer center. The linear diacetylene moieties on /3-and T-chains appear at different positions along the bilayer normal axis and are roughly parallel to the bilayer surface. This model is discussed in terms of a polymerization mechanism.