title: Compaction process of calf thymus DNA by mixed cationic-zwitterionic liposomes: a physicochemical study.
abstract: The 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 sigmazeta = (21 +/- 1) x 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)phi = 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.
authors.affiliation: Departamento de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040-Madrid, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Rodríguez-Pulido
authors.forename: Emilio
authors.initials: E
authors.lastname: Aicart
authors.forename: Oscar
authors.initials: O
authors.lastname: Llorca
authors.forename: Elena
authors.initials: E
authors.lastname: Junquera
mesh_terms: D000818:Animals; D002412:Cations; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003217:Conductometry; D004247:DNA / Q000737:chemistry*; D004587:Electrophoresis, Agar Gel; D008081:Liposomes / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D010714:Phosphatidylethanolamines; D000644:Quaternary Ammonium Compounds; D013050:Spectrometry, Fluorescence; D055672:Static Electricity
chemical_list: C410262:1,2-dioleoyl-glycero-3-phosphatidyl ethanolamine; D002412:Cations; D008081:Liposomes; D010714:Phosphatidylethanolamines; D000644:Quaternary Ammonium Compounds; D004247:DNA; C427203:calf thymus DNA