Ikuo Yamamoto

Surface charge modulation of liposomes by enzymatic hydrolysis of macrocyclic 1,2-dotriacontanedioyl-sn-glycero-3-phosphocholine

1,2-Dotriacontanedioyl-sn-glycero-3-phosphocholine (dTPC) was synthesized, and by a sonication method, dTPC was transformed into liposomes with physical features (charge, size, gel-to-liquid crystalline phase transition constants, etc.) similar to those of liposomes made of acyclic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Quantitative enzymatic assays using phospholipases A2 and C showed that dTPC was comparable with or better than DPPC as a substrate. Remarkably, the liposomes assembled from a mixture of dTPC and 1,2-distearyl-sn-glycero-3-phosphocholine were converted rapidly into anionic liposomes at pH 7 by the action of phospholipase A2, keeping their vesicular structure and exposing CO2H groups of the lysolipids of dTPC on the membrane surface. The use of dTPC is discussed in conjunction with the enzyme-catalyzed modification of the liposomes.

Very long single-alkyl chain amphiphiles : planar membranes from triacontylphosphorylcholine

Abstract Unlike conventional double-chain amphiphiles, triacontylphosphorylcholine gave planar membranes upon sonication of the aqueous dispersion. The membranes had a thickness of about 50 A and underwent gel-to-liquid crystalline phase transition at 39°C (Tm) with ΔH of 2–3 kcal/mol. The membrane morphology was explained by monomolecular organization of the amphiphiles on the basis of transmission electron microscopy, X-ray diffraction and effects of additives such as cholesterol.

Modification of neutral (isoelectric) liposomes to anionic liposomes by phospholipase A2: the use of macrocyclic 1,2-dotriacontanedioyl-sn-glycero-3-phosphocholine

1,2-Dotriacontanedioyl-sn-glycero-3-phosphocholine (dTPC) has been synthesized; liposomes containing dTPC were converted rapidly into anionic liposomes at pH 7 by the action of phospholipase A2, retaining the vesicular structure and exposing the CO2H groups of the lysolipids on the membrane surface.