title: Structural polymorphism of DNA-dendrimer complexes.
abstract: DNA condensation in vivo relies on electrostatic complexation with small cations or large histones. We report a synchrotron x-ray study of the phase behavior of DNA complexed with synthetic cationic dendrimers of intermediate size and charge. We encounter unexpected structural transitions between columnar mesophases with in-plane square and hexagonal symmetries, as well as liquidlike disorder. The isoelectric point is a locus of structural instability. A simple model is proposed based on competing long-range electrostatic interactions and short-range entropic adhesion by counterion release.
authors.affiliation: Materials Department, Physics Department, and Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Evans
authors.forename: A
authors.initials: A
authors.lastname: Ahmad
authors.forename: K
authors.initials: K
authors.lastname: Ewert
authors.forename: T
authors.initials: T
authors.lastname: Pfohl
authors.forename: A
authors.initials: A
authors.lastname: Martin-Herranz
authors.forename: R F
authors.initials: RF
authors.lastname: Bruinsma
authors.forename: C R
authors.initials: CR
authors.lastname: Safinya
mesh_terms: D002412:Cations / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D006657:Histones / Q000737:chemistry; D008954:Models, Biological; D008958:Models, Molecular; D011126:Polypropylenes / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D002412:Cations; D006657:Histones; D011126:Polypropylenes; D004247:DNA