title: Association of DNA with multivalent organic counterions: from flowers to rods and toroids.
abstract: In this study, complexes of DNA with different organic di- and tetravalent counterions were systematically investigated in solution and on a surface. The complexation behavior was studied by dynamic light scattering, static light scattering, atomic force microscopy, analytical ultracentrifugation, and UV-vis spectroscopy. Results show that both divalent and tetravalent counterions can induce the formation of DNA complexes. Divalent counterions cause aggregation only at high counterion excess, with charge ratios of 50:1 for supercoiled DNA and 200:1 for linear DNA, while for different tetravalent counterions aggregation is already observed for charge ratios of about 1:1. Flower-like aggregates are observed with divalent counterions. For a tetravalent perylene based counterion, a transition from flower-like aggregates at low charge ratios to toroids and rods at high charge ratios is observed. A transition regime for intermediate charge ratios is found. The influence of concentration, added salt, and preparation method is also discussed. It is concluded that it is the interplay of electrostatics and component architectures that directs the structure formation.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, Germany.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.forename: Umit Hakan
authors.initials: UH
authors.lastname: Yildiz
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
authors.forename: Franziska
authors.initials: F
authors.lastname: Gröhn
mesh_terms: D004247:DNA / Q000737:chemistry*; D015394:Molecular Structure; D009930:Organic Chemicals / Q000737:chemistry*; D010316:Particle Size; D010569:Perylene / Q000031:analogs & derivatives / Q000737:chemistry*; D010957:Plasmids / Q000737:chemistry; D012492:Salts / Q000737:chemistry; D013499:Surface Properties
chemical_list: D009930:Organic Chemicals; D012492:Salts; D010569:Perylene; D004247:DNA