Morphological Properties of Dispersions of Tubule-Forming Phospholipids (Expedited Award)

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Lipid tubules are rigid, straight, thin-walled, hollow cylinders with a fixed diameter of about 0.75 micrometers and axial ratios as high as 2000:1. The two methods found by the principal investigator for fabricating them rely only on the self-organizing properties of surfactants in solution, and yet allow high yield and good control of the length distribution. Once formed, tubules can be stabilized by polymerization, and further stabilized by coating with some metals. Tubules could potentially replace graphitic fibers in many of their current uses, and they have the added attraction of being intrinsically biocompatible for use in biotechnological and medical applications. Research in this emerging area has concentrated on single-component dispersions of a few similar diacetylenic lecithins which were the first found by the principal investigators to form tubules. Unusual packing of the hydrocarbon chains and head groups in these lipids may lead to the production of a crystalline helical ribbon that can convert to a complete tubule. This project initiates two systematic, exploratory searches based on this theory: one for the thermal and morphological effects of mixing tubule-forming lipids with others not believed to form tubules, and another to determine if lipids not currently known to form tubules will form them if subjected to appropriate conditions. The primary characterization techniques are high power optical microscopy under controlled temperatures, and, for higher resolution,