title: Structure and stability of the complex formed by oligonucleotides.
abstract: Polycations and cationic lipids have been widely used as non-viral vectors for the delivery of plasmid DNA, siRNA and anti-sense oligonucleotides. To demonstrate that one polycation can form a complex with several types of DNA, we conducted a comparative study on the complexation of poly(L-lysine) (PLL) with 2000 bp salmon testes DNA (dsDNA), 21 bp double-stranded oligonucleotides (ds-oligo), and 21 nt single-stranded oligonucleotides (ss-oligo) in PBS buffer. The complexes are prepared by a titration method and the process is monitored by laser light scattering. It was found that in most cases, ss-oligo and ds-oligo form complexes with higher molecular weights than the complex formed by dsDNA at the same +/- ratio immediately after mixing. More importantly, the complexes formed by oligonucleotides are not stable, the scattered intensity gradually decreases to the level of the solvent in weeks. Atomic force microscopy measurements also indicate that the freshly prepared complex is subject to environmental changes and could dissociate very quickly. The behaviour of oligonucleotides cannot be predicted by the classical polyelectrolyte theories.
authors.affiliation: Beijing National Laboratory for Molecular Sciences and the Key Laboratory of Polymer Chemistry & Physics of Ministry of Education, College of Chemistry & Molecular Engineering, Peking University, Beijing, P R China.
authors.forename: Cui
authors.initials: C
authors.lastname: Zheng
authors.forename: Lin
authors.initials: L
authors.lastname: Niu
authors.forename: Jingjing
authors.initials: J
authors.lastname: Yan
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Luo
authors.forename: Dehai
authors.initials: D
authors.lastname: Liang
mesh_terms: D000818:Animals; D004247:DNA / Q000737:chemistry*; D008027:Light; D018625:Microscopy, Atomic Force; D009841:Oligonucleotides / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry*; D012474:Salmon; D012542:Scattering, Radiation
chemical_list: D009841:Oligonucleotides; D011107:Polylysine; D004247:DNA