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DNA Packing in Stable Lipid Complexes Designed for Gene Transfer Imitates DNA Compaction in Bacteriophage
M. Schmutz, D. Durand, A. Debin, Y. Palvadeau, A. Etienne and A. R. Thierry
Proceedings of the National Academy of Sciences of the United States of America
Vol. 96, No. 22 (Oct. 26, 1999), pp. 12293-12298
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/49340
Page Count: 6
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The structure of complexes made from DNA and suitable lipids (lipoplex, Lx) was examined by cryo-electron microscopy (cryoEM). We observed a distinct concentric ring-like pattern with striated shells when using plasmid DNA. These spherical multilamellar particles have a mean diameter of 254 nm with repetitive spacing of 7.5 nm with striation of 5.3 nm width. Small angle x-ray scattering revealed repetitive ordering of 6.9 nm, suggesting a lamellar structure containing at least 12 layers. This concentric and lamellar structure with different packing regimes also was observed by cryoEM when using linear double-stranded DNA, single-stranded DNA, and oligodeoxynucleotides. DNA chains could be visualized in DNA/lipid complexes. Such specific supramolecular organization is the result of thermodynamic forces, which cause compaction to occur through concentric winding of DNA in a liquid crystalline phase. CryoEM examination of T4 phage DNA packed either in T4 capsides or in lipidic particles showed similar patterns. Small angle x-ray scattering suggested an hexagonal phase in Lx-T4 DNA. Our results indicate that both lamellar and hexagonal phases may coexist in the same Lx preparation or particle and that transition between both phases may depend on equilibrium influenced by type and length of the DNA used.
Proceedings of the National Academy of Sciences of the United States of America © 1999 National Academy of Sciences