Phosphonate lipid tubules. 1

We describe a new chiral tubule-forming lipid in which the C-O-P headgroup/ glycerol backbone Linkage of the archetypal tubule-forming phospholipid, 1, 2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine, DC(8,9)PC, is repl aced by a C-C-P linkage. Tubule formation from this phosphonate analogue oc curs under the same mild conditions as with DC(8,9)PC and produces identica l yields, but the phosphonate tubules have cylindrical diameters twice that of DC(8,9)PC tubules. Small-angle X-ray scattering, atomic-force, and opti cal microscopy reveal the new tubules to consist of fewer coaxially nested cylindrical lamellae than DC(8,9)PC tubules; accordingly, the phosphonate t ubules are more fragile. In addition, a small portion of the phosphonate pr ecipitate is in the form of stable open helices, and enantiomerically pure preparations of the new molecule contain significant numbers of helices pos sessing the unexpected sense of handedness.