title: Salt-dependent DNA-DNA spacings in intact bacteriophage λ reflect relative importance of DNA self-repulsion and bending energies.
abstract: Using solution synchrotron x-ray scattering, we measure the variation of DNA-DNA d spacings in bacteriophage λ with mono-, di-, and polyvalent salt concentrations, for wild-type [48.5×10(3) base pairs (bp)] and short-genome-mutant (37.8 kbp) strains. From the decrease in d spacings with increasing salt, we deduce the relative contributions of DNA self-repulsion and bending to the energetics of packaged phage genomes. We quantify the DNA-DNA interaction energies within the intact phage by combining the measured d spacings in the capsid with measurements of osmotic pressure in DNA assemblies under the same salt conditions in bulk solution. In the commonly used Tris-Mg buffer, the DNA-DNA interaction energies inside the phage capsids are shown to be about 1kT/bp, an order of magnitude larger than the bending energies.
authors.affiliation: Department of Physics, George Washington University, Washington, DC 2005, USA.
authors.forename: Xiangyun
authors.initials: X
authors.lastname: Qiu
authors.forename: Donald C
authors.initials: DC
authors.lastname: Rau
authors.forename: V Adrian
authors.initials: VA
authors.lastname: Parsegian
authors.forename: Li Tai
authors.initials: LT
authors.lastname: Fang
authors.forename: Charles M
authors.initials: CM
authors.lastname: Knobler
authors.forename: William M
authors.initials: WM
authors.lastname: Gelbart
mesh_terms: D010582:Bacteriophage lambda / Q000737:chemistry* / Q000235:genetics*; D001665:Binding Sites; D004269:DNA, Bacterial / Q000737:chemistry* / Q000648:ultrastructure; D004735:Energy Transfer; D008954:Models, Biological; D009690:Nucleic Acid Conformation; D012492:Salts / Q000737:chemistry*
chemical_list: D004269:DNA, Bacterial; D012492:Salts