MICROSTRUCTURE FORMATION PROPERTIES OF -THIA-PENTACOSA-10,12-DIYNOYL)-SN-3-PHOSPHOCHOLINE - AN ACYL-CHAIN MODIFIED DIACETYLENIC PHOSPHOLIPID

An acyl chain modified diacetylenic phospholipid containing a sulfur b eta to the diacetylene, thia-pentacosa-10,12-diynoyl)-sn-3-phosphochol ine, was synthesized. Comparisons of the UV spectra of the lipid, the diacetylenic carboxylic acid precursor, and the unmodified diacetyleni c lipid 1,2-bis(tricosa-10,12-diynoyl)-sn-3-phosphocholine reveal that the sulfur acts as an auxochrome resulting in bathochromic shifts and higher intensities for the absorption peaks. Differential scanning ca lorimetry was used to determine the acyl chain melting transition temp eratures of -thia-pentacosa-10:12-diynoyl)-sn-3-phosphocholine in wate r (31.2 degrees C) and 70:30 ethanol:water mixture (28.7 degrees C) an d revealed that the lipid packed more homogeneously in the ethanol:wat er mixture. Subsequent dispersal of the lipid in water produced ribbon s with diameters ranging from 0.01-0.1 mu m while dispersal in 70:30 e thanol:water leads to formation of tubules with diameters ranging from 0.6-0.8 mu m. A gel comprised of interwoven ribbons was formed from a n equimolar mixture of the lipid and 1,2-bis(nonoyl)-sn-glycero-3-phos phocholine (DNPC) in 0.1 M aqueous NaCl.