Phase Characteristics of Positional Isomers of 1,2-di(heptacosadiynoyl)-sn-glycero-3-phosphocholine; Tubule-Forming Phosphatidylcholines.

摘要

We have examined the phase behavior of positional isomers of a polymerizable diacetylenic phospholipid, 1,2-di(heptacosadiynoyl)-sn-glycero-3-phosphocholine which has the diacetylene in varying position along the acyl chains. Upon cooling multilamellar vesicles (MLVs) through the liquid-crystalline to gel phase transition, all isomers examined spontaneously formed hollow, cylindrical microstructures (or tubules). Differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR) have been used to characterize positional isomers of this lipid in an effort to understand the effect of diacetylenic position on the molecular characteristics of tubule formation. Calorimetric results indicate that moving the position of the diacetylene along the acyl chain results in the alternation of the exotherm observed for the hydrated transition temperature associated with tubule formation, with higher transition temperatures (Tm) observed from isomers with an even number of methylenes between the diacetylene groups abd the glycerol backbone. (JS)