We describe an NMR analysis of liposomes obtained from two phosphatidy
l nucleosides, namely 5'-(1-palmitoyl-2-oleoyl-sn-glycero(3)phosp (1)
and 5'-(1-palmitoyl-2-oleoyl-sn-glycero(3)ph inosine (2). This analysi
s is mostly based on 1D- and 2D-H-1-N-MR at high field and is aimed at
investigating intramolecular interactions between groups within the s
ame lipid molecule and intermolecular interactions between neighboring
lipid molecules in the liposome aggregate. Particular care was taken
to choose mixing times which reduce the possibility of spin diffusion
effects. The presence of particular cross peaks in 2D-H-1-NOESY experi
ments permits us to assess the presence of syn- and anti-conformations
of the aromatic head groups both in the monomeric nucleotides and in
the liposomes. The lack of any particular ring effect in liposomes sug
gests that no stacking interactions of the nucleobases are present. On
the other hand, the presence of other distinct cross peaks indicates
short interatomic distances between a given aromatic base and the suga
r moiety of an adjacent phosphatidyl nucleoside headgroup. These data
permit one to draw a structural model of the liposome surface which ac
counts for the poor binding characteristics of phosphatidyl nucleoside
liposomes toward complementary oligonucleotide strands.