Electron microscopy and biochemical properties of polyamine-compacted DNA

Abstract

We have obtained polyamine-compacted DNA and analyzed it by electron microscopy employing the method described by Dubochet, suitable for the study of complexes in which the main interactions are of ionic character. In addition, we have developed a simple biochemical method, based on the action of pancreatic DNase I, to demonstrate the condensation of DNA with spermidine. DNA-spermidine complexes are resistant to the action of DNase I, and there is a strong correlation between the presence of condensed DNA forms, both as toroids and as cylinders, and the insensitivity to DNase I activity. We have also shown that pBR322 DNA-spermidine complexes are transcriptionally active in the presence of Escherichia coli RNA polymerase. This supports the data concerning the biological activity of spermidine-condensed DNA.

A novel N-acyl phosphatidylethanolamine-containing delivery vehicle for spermine-condensed plasmid DNA

“…Since the direct condensation with spermine at high plasmid concentration yielded aggregates even larger than the original 0.5-1 m average length of the free plasmid, 32,34 it was necessary to find another way to condense plasmid DNA for potential encapsulation into liposomes. In the commonly used water-in-oil emulsion methods for liposomal preparation, 35,36 phospholipids stabilize reverse micelles before solvent is removed.…”

“…[28][29][30][31] DNA condensed in vitro with spermidine has shown higher transcriptional activity than uncondensed DNA. 32 Therefore, the polyamines may constitute one particularly useful class of condensing agents for liposomal delivery systems.…”

Supramolecular structure and nuclear targeting efficiency determine the enhancement of transfection by modified polylysines

“…Various ligands have been covalently attached to pLy as a means to link these molecules to DNA, [1][2][3][4][5][6] and thereby effect cell-specific delivery and uptake of plasmid DNA. pLy has been shown to form condensed toroids of 80-100 nm with DNA 1 to confer resistance to DNase, 7 with multi-step condensation reported in the presence of high NaCl concentrations. 8 Condensation of plasmid DNA by pLy appears to correlate with improved gene transfer efficiency.…”

Interfacial engineering of core/shell heterostructured nanocrystal quantum dots for light-emitting applications

“…Nanocrystal quantum dots (NQDs) [1] exhibit narrow emissions upon a broad range of excitation wavelengths and high luminescence efficiencies, making them promising for use in various light-emitting applications, including displays [2][3][4][5][6][7][8][9][10][11], solar concentrators [12][13][14][15], and lasers [16][17][18]. In the last two decades, the structures of NQDs evolved into sophisticated heterostructures, boosting their optical performances and photophysical stabilities [19][20][21][22][23][24][25][26][27].…”