In a Pinch

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Science  28 Jan 2000:
Vol. 287, Issue 5453, pp. 549
DOI: 10.1126/science.287.5453.549f

Complexes of cationic lipids and DNA have been used for gene delivery. For certain concentration ranges, complexes of neutral and cationic lipids with DNA form lamellar structures in which intercalated DNA forms well-ordered two-dimensional arrays.

Analogous complexes have recently attracted interest for protein or drug delivery. Subramanian et al. have now examined the structure of complexes of mixtures of neutral and cationic lipids with a high-molecular-weight peptide (polyglutamic acid) using small-angle x-ray and neutron scattering. Near the isoelectric point of these complexes, dilution with neutral lipids increased the membrane spacing from 4 to 6 nanometers. In their model for these complexes, the interaction of the polypeptide and the lipid layers pinches off pockets of water locally. The authors suggest that these pinched regions could be used, for example, in drug delivery.—PDS

J. Am. Chem. Soc.122, 26 (2000).

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