Lipid/DNA complexes

Bergen M, Chen R, Gonzalez R (2003) Efficacy and safety of HLA-B7/beta-2 microglobulin plasmid DNA/lipid complex (Allovectin-7) in patients with metastatic melanoma. Expert Opin Biol Ther 3 377-384... 

Okahata Y, Kawasaki T (2005) Preparation and Electron Conductivity of DNA-Aligned Cast and LB Films from DNA-Lipid Complexes. 260 57-75 Otto D, see Ihmels H (2005) 258 161-204... 

Preparation and Electron Conductivity of DNA-Aligned Cast and LB Films from DNA-Lipid Complexes... 

Keywords Anisotropic electron conductivity Cast film DNA-lipid complex ... 

A DNA-lipid complex was prepared by simply mixing two aqueous solutions of DNA and cationic lipids as follows. An aqueous solution of DNA Na" from salmon testes (ca. 30 000 bps or 500 bps) and an aqueous solution of 1.1 eq. mol of cationic amphiphiles were mixed at room temperature and... 

Figure 4 shows CD spectra of (a) the DNA-lipid complex in organic solution containing a small amount of water (CHCl3/Et0H/Fl20 =4 1 0.07, 790 mM of H2O), and (b) native DNA in an aqueous buffer solution (20 mM NaCl, 10 mM Tris, pH 7.8). The DNA-lipid complex shows a positive Cotton effect at 270 nm and a negative Cotton effect at 245 nm similar to native DNA in aqueous solution, which indicates the B-form structure for the DNA strands [11]. Thus, the DNA-lipid complex forms a double helical B-form... 

Fig. 4 CD spectra of a DNA-lipid complex in CHCl3/Et0H/H20 = 4 1 0.07, and b native DNA in aqueous buffer solution (20 mM NaCl, pH 7.8, 10 mM Tris, [DNA] = 50 riMbp 23 °C)...

Fig. 5 Effect of water contents on CD spectra of the DNA-lipid complex in CHCI3 /EtOH (4 1) solution ([DNA] = 50 p.Mbp , 23 °C)...

The CHCl3/Et0H/H20 (4 1 0.07) solution of the DNA-lipid complex (0.25 g) was cast on a Teflon plate and the solvent was evaporated slowly under the saturated vapor at room temperature. The obtained self-standing film was (ca. 60 xm thick) water-insoluble, and physically stable (Fig. 6a). The DNA film can be obtained also from the hot-press method. Here, the powder of the DNA-lipid complex was hot-pressed at 120 °C for 1 min under... 

Fig. 6 A DNA-lipid cast film prepared from a solution of DNA-lipid complexes...

Fig. 7 X-ray diffraction patterns of a the as-cast film, b the stretched film of the DNA-lipid complex in water moisture, and c the stretched DNA-lipid film in the dry state. Open, two-headed arrows show the stretching direction of the film. Closed arrows show the incident beam of the X-rays. X-ray photographs of a and c were enlarged to show diffraction more clearly...

When the stretched film was dried in air (simply applying a hair-dryer for 2 min), only diffraction on the equator as two spots of 41 A was observed but not diffraction on the meridian for base-pairs (Fig. 7c). This suggests that the orientation of the base pairs is not perpendicular to the stretched direction, although the DNA strands are aligned parallel to the stretched direction. Figure 8 shows CD spectra of the cast film of the DNA-lipid complex in wet (a) and dry states (b). The CD spectrum of the wet film was consistent with a B-form structure of native DNA in fibers obtained from aqueous solution [1-3]. On the contrary, the CD spectrum in the dry state resembles the A-form of DNA in which the base pairs slant to the axis of the strands [2,3]. These results are consistent with CD spectra of the DNA-lipid complex in an organic solution DNA exists in the B-form in the presence of water and the C-form in the ab-... 

Fig. 8 CD spectra of the cast film of the DNA-lipid complex a in water and b in the dry state (23 °C, film thickness 3 jlM)...

Successful gene delivery by use of cationic liposomes requires the following conditions (134) (1) condensation of DNA into the complex and its protection from degradation by intracellular nucleases (2) adhesion of DNA-lipid complex onto the cellular surface (3) complex internalization (4) fusion of an internalized DNA-cationic liposome complex with the endosome membrane (5) escape of DNA from the endosome (6) entry of DNA into the nucleus followed by gene expression. 

Theoretical work on CL/DNA complexes has also led to the realization of a variety of novel new phases of matter in DNA— lipid complexes (O Hem and Lubensky, 1998 Golubovic and Golubovic, 1998). In particular, a novel new sliding columnar phase , is predicted, where the positional coherence between DNA molecules in adjacent layers is lost without destroying orientational coherence of the chains from layer to layer. 

May, S. and Ben-Shaul, A. (1997) DNA-lipid complexes stability of honeycomb-like and spaghetti-like structures. Biophys. J., 73, 2427-2440. 

Song, Y.K. and Liu, D. (1998a) Free liposomes enhance the transfection activity of DNA/ lipid complexes in vivo by intravenous administration. Biochim. Biophys. Acta., 1372, 141-150. 

Liu et al. [7] found significant differences between the disposition of complexed and uncomplexed [1251]-labeled plasmid DNA in mice. An equal amount of radioactivity was found in blood and liver at 15 min after injection of naked plasmid DNA. In contrast, at the same time-point, a major portion of injected DNA was in the lung when DNA-lipid complexes were injected. 

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