SELF-ASSEMBLED MICROSTRUCTURES FROM 1,2-ETHANEDIOL SUSPENSIONS OF PURE AND BINARY-MIXTURES OF NEUTRAL AND ACIDIC BIOLOGICAL GALACTOSYLCERAMIDES

Optical and electron microscopy were employed to characterize microstr uctures formed by thermal-mechanical treatment of glycol suspensions o f various pure and binary mixtures of the brain-derived galactosphingo lipids hydroxy fatty acid cerebroside (HFA-Cer), non-hydroxy fatty aci d cerebroside (NFA-Cer) and sulfatide (S-Cer). Negative staining indic ated some new features of the neutral cerebroside suspensions in glyco l. HFA-Cer formed a small fraction of both unilamellar cylinders (ULCs ) (lumina ca. 27 nm) and giant multilamellar cochleates in addition to the typical nonhelical multilamellar cylinders (MLCs) (lumina ca. 10- 30 nm). NFA-Cer formed a gel composed of a significant fraction of ver y long ULCs (lumina ca. 17 nm) without helical substructure, in additi on to multilamellar helical structures such as ribbons and cylinders ( lumina ca. 70 nm). Anisotropic lamellar micelle-shards of NFA-Cer were also detected by negative staining. S-Cer formed short ULCs (lumina c a. 44 nm) with no obvious helical substructure. Complex mixture data a re thought to result from thermodynamic and kinetic factors. HFA-Cer i s highly insoluble and promotes a network of rigid intralamellar hydro gen bonding that tends to exclude other lipids. NFA-Cer stabilizes hel ical defects in the lamellae, and S-Cer enhances disorder or micelliza tion. The processes of microstructure nucleation and lipid phase separ ation were affected by mixtures such that metastable microstructures w ere trapped or the length of lamellar cylinders was altered.