Distribution of ions around DNA, probed by energy transfer.
Distribution of ions around DNA, probed by energy transfer.
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通过能量转移探测 DNA 周围离子的分布。
DOI：
10.1073/pnas.83.10.3267
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发表时间：
1986
影响因子：
11.1
通讯作者：
Matthew,JB
中科院分区：
文献类型：
--
作者：
Wensel,TG;Meares,CF;Vlachy,V;Matthew,JB
测量 DNA 对离子之间双分子能量转移速率的影响，可以直接指示阳离子如何在 DNA 附近区域聚集以及阴离子如何从同一区域被排斥。发光镧系元素离子（在“快速扩散”极限）的能量转移探测取决于离子平衡空间分布的碰撞频率。在 2 mM 盐溶液中添加 1 mM DNA（磷酸盐）可使单价阳离子之间的总体碰撞频率增加 6 +/- 1.5 倍；它将二价-单价阳离子碰撞频率提高了 29 +/- 3 倍；并且它使二价阳离子-一价阴离子碰撞频率降低了 0.24 +/- 0.03 倍。与几种不同的离子分布理论描述预测的碰撞频率的变化进行了比较。基于 B-DNA 的详细分子模型，通过静态可及性修改离散电荷计算获得了与 1 mM DNA 的单价离子实验结果最接近的一致性。在高 DNA 浓度 (10 mM) 下，通过 DNA“软棒”模型的泊松-玻尔兹曼方程的数值解获得最佳结果。 “硬棒”模型的泊松-玻尔兹曼计算大大高估了 DNA 对碰撞频率的影响，基于反离子凝聚理论的计算也是如此。
Measurements of the effect of DNA on rates of bimolecular energy transfer between ions provide a direct indication of how cations cluster in regions near DNA and how anions are repelled from the same regions. Energy transfer from luminescent lanthanide ions (in the "rapid-diffusion" limit) probes collision frequencies that are dependent on the equilibrium spatial distributions of ions. The addition of 1 mM DNA (phosphate) to a 2 mM salt solution increases the overall collision frequency between monovalent cations by a factor of 6 +/- 1.5; it increases the divalent-monovalent cation collision frequency by a factor of 29 +/- 3; and it decreases the divalent cation-monovalent anion collision frequency by a factor of 0.24 +/- 0.03. Comparisons are made with the changes in collision frequencies predicted by several different theoretical descriptions of ion distributions. The closest agreement with experimental results for monovalent ions at 1 mM DNA is obtained with a static accessibility-modified discrete charge calculation, based on a detailed molecular model of B-DNA. At high DNA concentration (10 mM), the best results are obtained by numerical solutions of the Poisson-Boltzmann equation for a "soft-rod" model of DNA. Poisson-Boltzmann calculations for a "hard-rod" model greatly overestimate the effects of DNA on collision frequencies, as does a calculation based on counterion-condensation theory.