DOPE–oleic acid–Ca2+ as DNA condensing agent

Phospholipid-based non-viral carriers composed of neutral phospholipid dioleoylphosphatidylethanolamine (DOPE) and the binary mixture DOPE-oleic acid (OA) are examined as potential DNA delivery vectors. The process of DNA condensation in the presence of Ca2+ions has been monitored through changes in emmision intensity of fluorescent probe ethidium bromide. The decline in fluorescence intensity with increasing Ca2+concentration at two different time intervals was correlated with the binding capacity of complexes and possible release of DNA from the complex. The microstructure of DOPE-OA mixtures at different OA/DOPE molar ratios and that of DOPE-OA-DNA-Ca2+complexes were determined using synchrotron small angle X-ray diffraction (SAXD). We identified inverted hexagonal phase HIIas the dominant structure. OA affects the lattice parameter of HIIformed by DOPE. With the increasing OA/DOPE molar ratio, the lattice parameter decreases, which results in significantly lower fraction of DNA bound to the OA-enriched complexes

Lipid bilayer - DNA interaction mediated by divalent metal cations: SANS and SAXD study

The structure of aggregates formed due to DNA interaction with dipalmitoylphosphatidylcholine (DPPC) in presence of Ca2+ and Zn2+ is examined using small-angle synchrotron X-ray diffraction (SAXD) and small-angle neutron scattering (SANS). SAXD detected two structures: LC - condensed lamellar phase and LX - lamellar phase with DNA strands intercalated between the adjacent lipid bilayers, without regular packing at low cation concentration (~1 mM). The high concentration of Zn2+ induces a macroscopic phase separation in mixtures. The SANS curves of DPPC+ions2+ vesicles evaluated using the strip function model have shown different modes of cations binding to the DPPC bilayers.Peer reviewed: YesNRC publication: Ye

Characterization of the PEG layer of sterically stabilized liposomes: a SAXS study

Synchrotron small-angle X-ray scattering analysis of the bilayer structure of a pharmacologically relevant sterically stabilized liposome system is presented. Describing the electron density profile of the bilayer with the superposition of Gaussian functions, the contribution of the poly(ethylene glycol) (PEG) layers to the total electron density was identified. The changes in the thickness of the PEG layer as well as the distribution of the PEG chains among the outer and inner leaflets of the bilayers were followed by changing the molar ratio of the PEG-lipid and the molar weight of the PEG molecule

The effects of cholesterol and beta-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

The structures of DMPC and DPPC bilayers in unilamellar liposomes, in the presence of 33.3 mol% cholesterol or the plant sterol β-sitosterol, have been studied by small-angle neutron scattering. The bilayer thickness d(L) increases in a similar way for both sterols. The repeat distance in multilamellar liposomes, as determined by small-angle X-ray diffraction, is larger in the presence of β-sitosterol than in the presence of cholesterol. We observe that each sterol modifies the interlamellar water layer differently, cholesterol reducing its thickness more efficiently than β-sitosterol, and conclude that cholesterol suppresses bilayer undulations more effectively than β-sitosterol