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Compaction Process of Calf Thymus DNA by Mixed Cationic−Zwitterionic Liposomes: A Physicochemical Study
journal contribution
posted on 2008-02-21, 00:00 authored by Alberto Rodríguez-Pulido, Emilio Aicart, Oscar Llorca, Elena JunqueraThe compaction of calf thymus DNA (CT-DNA) by cationic liposomes constituted by a 1:1 mixture of a
cationic lipid, 1,2-distearoyl-3-(trimethylammonio)propane chloride (DSTAP), and a zwitterionic lipid, 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE, null net charge at pH = 7.4), has been evaluated in
aqueous buffered solution at 298.15 K by means of conductometry, electrophoretic mobility, cryo-TEM, and
fluorescence spectroscopy techniques. The results reveal that DSTAP/DOPE liposomes are mostly spherical
and unilamelar, with a mean diameter of around 77 ± 20 nm and a positively charged surface with a charge
density of σζ = (21 ± 1) × 10-3 C m-2. When CT-DNA is present, the genosomes DSTAP/DOPE/CT-DNA,
formed by means of a surface electrostatic interaction, are generally smaller than the liposomes. Furthermore,
they show a tendency to fuse forming cluster-type structures when approaching isoneutrality, which has been
determined by the electrochemical methods at around (L/D)φ = 5.6. The analysis of the decrease on the
fluorescence emission of the fluorophore ethidium bromide, EtBr, initially intercalated between DNA base
pairs, as long as the genosomes are formed has permitted us to confirm the electrostatic character of the
DNA−liposome interaction.
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298.15 Kcationic liposomescharge densitycationic lipidPhysicochemical StudyThe compactionfluorophore ethidium bromideCompaction Processinteractiongenosomefluorescence emissionfluorescence spectroscopy techniquesDSTAPzwitterionic lipidcalf thymus DNAsurfaceelectrochemical methodsDOPEDNA base pairsCalf Thymus DNAelectrophoretic mobility