Mono- and trivalent ions around DNA: a small-angle scattering study of competition and interactions.
The presence of small numbers of multivalent ions in DNA-containing solutions results in strong attractive forces between DNA strands. Despite the biological importance of this interaction, e.g., DNA condensation, its physical origin remains elusive. We carried out a series of experiments to probe interactions between short DNA strands as small numbers of trivalent ions are included in a solution containing DNA and monovalent ions. Using resonant (anomalous) and nonresonant small angle x-ray scattering, we coordinated measurements of the number and distribution of each ion species around the DNA with the onset of attractive forces between DNA strands. DNA-DNA interactions occur as the number of trivalent ions increases. Surprisingly good agreement is found between data and size-corrected numerical Poisson-Boltzmann predictions of ion competition for non- and weakly interacting DNAs. We also obtained an estimate for the minimum number of trivalent ions needed to initiate DNA-DNA attraction.
Andresen
Kurt
K
School of Applied and Engineering Physics, Cornell University, Ithaca, New York.
Qiu
Xiangyun
X
Pabit
Suzette A
SA
Lamb
Jessica S
JS
Park
Hye Yoon
HY
Kwok
Lisa W
LW
Pollack
Lois
L
D001665:Binding Sites; D003198:Computer Simulation; D004247:DNA / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction / Q000379:methods*
D007477:Ions; D004247:DNA