二价反离子介导的DNA-DNA静电相互作用的重入行为
Reentrant behavior of divalent counterion mediated DNA-DNA electrostatic interaction
摘要：
利用计算机模拟研究了二价反离子介导的DNA-DNA相互作用问题。虽然二价抗衡离子不能凝聚游离的DNA分子在溶液中，我们表明，如果DNA构型熵是有限的，二价抗衡离子可以导致DNA折返凝聚所造成的三价或四价抗衡离子类似。DNA-DNA相互作用在小或大的反离子浓度下是强烈排斥的，并且对于在两者之间的浓度是可忽略的或轻微吸引的。我们的研究结果的影响，从噬菌体DNA弹射实验进行了讨论。定量结果有助于理解在其他实验中涉及DNA和二价抗衡离子的静电效应。
英文摘要：
The problem of DNA-DNA interaction mediated by divalent counterions is studied using computer simulation. Although divalent counterions cannot condense free DNA molecules in solution, we show that if DNA configurational entropy is restricted, divalent counterions can cause DNA reentrant condensation similar to that caused by tri- or tetra-valent counterions. DNA-DNA interaction is strongly repulsive at small or large counterion concentration and is negligible or slightly attractive for a concentration in between. Implications of our results to experiments of DNA ejection from bacteriophages are discussed. The quantitative result serves to understand electrostatic effects in other experiments involving DNA and divalent counterions.
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