Complexes of nucleolipid liposomes with single-stranded and double-stranded nucleic acids

We report on the association of anionic liposomes from POP-Ade:POPC (1-palmitoyl-2-oleoyl-phosphatidyladenosine and 1-palmitoyl-2-oleoyl-phosphatidylcholine, respectively) with single- and double-strand nucleic acids, mediated by Ca(2+) bridging. The structural and dynamical features of such complexes are compared with those displayed when the nucleolipid is replaced by POPG (1-palmitoyl-2-oleoyl-sn-phosphatidyl-glycerol), characterized by the same apolar skeleton and negative charge as POP-Ade, but lacking the nucleic polar head. For single-stranded nucleic acids, we demonstrate that specific interactions drive the formation of complexes with nucleolipid liposomes, while no association is present for POPG-based samples. For double-stranded nucleic acids, Ca(2+) bridging promotes association with both liposomal formulations, but the corresponding complexes have different structural features, in terms of size, overall charge and internal liquid-crystalline structure.