Harrington R E
Nucleic Acids Res. 1977 Oct;4(10):3519-35. doi: 10.1093/nar/4.10.3519.
The persistence length of high-molecular-weight, monodisperse-bihelical DNA has been evaluated from low-shear flow birefingence and viscosity data at several temperatures in 2.0 M Nacl neutral pH buffer. At these solvent conditions, both the DNA and histone components of chromatin nu-bodies have structural features similar to those in the intact nucleohistone complex at low ionic strength. The theory of Landau and Lifshitz is used to relate the experimental result to the thermodynamic functions for bending 140 nucleotide pairs of DNA into a plausible model structure: per nu-body, delta Gb=43.8 +/- 5.3 kcal/mole, delta Hb= 45.7 +/- 3.7 kcal/mole, and delta Sb = 6.2 +/- 12.4 entropy units. This bending free energy is comparable to or less than that estimated to be required for a kinked DNA configuration and appears to be well within the range of estimated electrostatic free energies available from DNA-histone interactions in a nu-body assembly.
在2.0M氯化钠中性pH缓冲液中，于几个温度下，通过低剪切流双折射和粘度数据评估了高分子量、单分散双螺旋DNA的持续长度。在这些溶剂条件下，染色质核小体的DNA和组蛋白成分都具有与低离子强度下完整核组蛋白复合物相似的结构特征。利用朗道和利夫希茨理论将实验结果与将140个核苷酸对的DNA弯曲成合理模型结构的热力学函数相关联：每个核小体，ΔGb = 43.8±5.3千卡/摩尔，ΔHb = 45.7±3.7千卡/摩尔，以及ΔSb = 6.2±12.4熵单位。这种弯曲自由能与估计的扭结DNA构型所需的自由能相当或更低，并且似乎完全在核小体组装中DNA-组蛋白相互作用可获得的估计静电自由能范围内。
