Andresen Kurt, Qiu Xiangyun, Pabit Suzette A, Lamb Jessica S, Park Hye Yoon, Kwok Lisa W, Pollack Lois
School of Applied and Engineering Physics, Cornell University, Ithaca, New York.
Biophys J. 2008 Jul;95(1):287-95. doi: 10.1529/biophysj.107.123174. Epub 2008 Mar 13.
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.
含DNA的溶液中存在少量多价离子会导致DNA链之间产生强大的吸引力。尽管这种相互作用在生物学上很重要，例如DNA凝聚，但其物理起源仍然难以捉摸。我们进行了一系列实验，以探究在含有DNA和单价离子的溶液中加入少量三价离子时短DNA链之间的相互作用。利用共振（反常）和非共振小角X射线散射，我们将DNA周围每种离子的数量和分布的测量与DNA链之间吸引力的出现进行了协调。随着三价离子数量的增加，DNA与DNA之间发生相互作用。令人惊讶的是，对于非相互作用和弱相互作用的DNA，数据与离子竞争的尺寸校正数值泊松-玻尔兹曼预测之间发现了很好的一致性。我们还获得了引发DNA与DNA吸引力所需的三价离子最小数量的估计值。
