COLL 416 |
| Mark S. Spector, Center for Bio/Molecular Science and Engineering, Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Code 6910, 4555 Overlook Avenue SW, Washington, DC 20375-5320 |
| The self-assembly of molecules into helical aggregates is ubiquitous in nature. The key characteristic of chirality in biological systems is enantiomeric specificity, which in the case of biological polymers lead to chiral secondary structures such as helical conformations. On the other hand, cellular membranes are composed of chiral molecules such as phospholipids and cholesterol, but the homochirality of these constituents is not manifested in the membrane's structure. However, in certain cases biological membranes exhibit a distinct helical or twisted structure reflecting the underlying handedness of the individual constituents. The helicity of these mesoscopic aggregates is revealed using electron microscopy and probed spectroscopically using circular dichroism. Among the most interesting systems are synthetic phospholipids containing diacetylenic moieties in their acyl chain, which self-assembly into hollow, cylindrical tubules in the liquid crystalline Lβ’ phase. Nanoscale structures have been found to self-assemble in a binary mixture of the diacetylenic phospholipid and a short chain, saturated lipid. Nanotubules with diameters of 50 nm are found at low temperature, twisted ribbons at intermediate temperatures, and microtubules at higher temperatures. Unusual chiral-optical signatures of nanotubule, twisted ribbon, and microtubule morphologies are observed that can be used to monitor their temporal and thermal stability. |
|
Surface and Colloid Chemistry Award Symposium Honoring Joseph Zasadzinski
2:00 PM-5:00 PM, Wednesday, March 31, 2004 Marriott -- Orange County 3, Oral
Division of Colloid and Surface Chemistry |