Influence of phospholipid composition on the properties of reconstituted surfactants

The influence of phospholipids on the ultrastructure and metabolism of reco nstituted surfactants has not been well defined. The aim of this study was to determine if changes in the phospholipid composition of reconstituted su rfactants altered their biophysical properties, ultrastructure, and convers ion to light subtype by cycling. We prepared various surfactants containing radiolabeled dipalmitoylphosphatidylcholine ([C-14]DPPC). The addition of phosphatidylglycerol (PG) or dipalmitoylphosphatidic acid (PA) to DPPC incr eased conversion to light subtype. In contrast, the addition of dipalmitoyl phosphatidylglycerol (DPPG) to DPPC markedly reduced conversion to light su btype on cycling. DPPC and DPPC+PG produced large liposomes (similar to 1,0 00 nm), whereas DPPC+PA or DPPC+DPPG formed multilamellar membranes. Mixtur es of DPPC and PA were highly surface active in vitro, whereas the surface activity of DPPC+DPPG was similar to that of DPPC. In conclusion, the ultra structure, metabolism, and surface active properties of DPPC+PG mixtures we re influenced markedly by alterations in the fatty acid composition or pola r head group of PG.