LIPOSOMES CONTAINING PURINE AND PYRIMIDINE-BASES - STABLE UNILAMELLARLIPOSOMES FROM PHOSPHATIDYL NUCLEOSIDES

With the aim of investigating the behavior of liposomes bearing nuclei c acid bases in their double-layered spherical structure, 1-palmitoyl- 2-oleoyl-sn-glycero(3)phospho)cytidine (1) and 5'-(1-palmitoyl-2-oleoy l-sn-glycero(3 )phospho)inosine (2) have been synthesized and unilamel lar liposomes have been prepared by extrusion of a slightly alkaline a queous lipid dispersion through polycarbonate membranes. The liposomes were characterized by electron microscopy, dynamic light scattering ( LS), and circular dichroism (CD) spectroscopy. LS studies showed that the liposomes are monodisperse; those from 1 remained stable for over one week, the liposomes from 2 alone are less stable, whereas liposome s of equimolar mixtures of 1 and 2 are again characterized by a good s tability. CD studies of liposomes of 1 showed a positive Cotton effect in the region of the cytidine absorption, and the significant differe nces with respect to the spectrum of cytidine monophosphate are seen a s a result of the supramolecular structure of the liposomes. More in g eneral, this study shows that it is possible to insert complementary p urine and pyrimidine nucleosides into the spherical organization of li posomes.