Rau D C, Lee B, Parsegian V A
Proc Natl Acad Sci U S A. 1984 May;81(9):2621-5. doi: 10.1073/pnas.81.9.2621.
We have measured the repulsive force between B-form double helices in parallel packed arrays of polymer-condensed DNA in the presence of 0.005-1.0 M ionic solutions. Molecular repulsion is consistently exponential with a 2.5-3.5 A decay distance, when the separation between DNA surfaces is 5-15 A. Only weakly dependent on ionic strength and independent of molecular size, this intermolecular repulsion does not obey the predictions of electrostatic double-layer theory. Rather, it strongly resembles the "hydration force" first recognized and quantified between phospholipid bilayers. Only beyond 15 A separation between molecules is there evidence of electrostatic double-layer forces. The quantitative failure of electrostatic double-layer theory seen here must gravely affect accepted analyses of other polyelectrolyte systems. Because the packing of condensed DNA resembles the spacings of DNA in many bacteriophages, our results permit estimation of the "DNA pressure" in phage heads.
我们测量了在0.005 - 1.0 M离子溶液存在下，聚合物凝聚DNA平行堆积阵列中B型双螺旋之间的排斥力。当DNA表面间距为5 - 15 Å时，分子排斥始终呈指数形式，衰减距离为2.5 - 3.5 Å。这种分子间排斥仅微弱依赖于离子强度且与分子大小无关，并不遵循静电双层理论的预测。相反，它与首次在磷脂双层之间识别和量化的“水化力”极为相似。只有在分子间距超过15 Å时，才有静电双层力的证据。此处所见静电双层理论的定量失效必定严重影响对其他聚电解质系统的公认分析。由于凝聚DNA的堆积类似于许多噬菌体中DNA的间距，我们的结果允许估算噬菌体头部的“DNA压力”。
