Harrington R E
Biochemistry. 1982 Mar 16;21(6):1177-86. doi: 10.1021/bi00535a011.
Optical modeling of the DNA conformation has been used to interpret the results of highly sensitive flow birefringence and extinction angle studies on nucleosome core particles over a range of counterion strength (using KCl as the supporting electrolyte) from less than 0.15 mM to greater than 0.6 M. Results are consistent with an oblate disk or wedge of axial ratio p-1 congruent to 2 over an intermediate salt concentration range from about 1.5 to 450 mM. Below approximately 1.5 mM, the particle appears to unfold into an extended prolate or oblate structure which can be modeled as a uniform superhelix of DNA. Above approximately 0.45 M, the particle unfolds into a conformation which is hydrodynamically similar to but optically quite different from the low-salt structure. This form can be modeled as a partially unfolded disk in which only the nucleosomal DNA ends become dissociated and the central region remains bound to the histone core. A description of the optical modeling methods is presented, and the results are correlated with hydrodynamic property changes.
DNA构象的光学建模已被用于解释在一系列抗衡离子强度（使用KCl作为支持电解质）下，对核小体核心颗粒进行的高灵敏度流动双折射和消光角研究的结果，抗衡离子强度范围从小于0.15 mM到大于0.6 M。在约1.5至450 mM的中间盐浓度范围内，结果与轴向比p-1约等于2的扁盘或楔形体一致。在约1.5 mM以下，颗粒似乎展开成一种伸长的长扁体或扁球体结构，可将其建模为DNA的均匀超螺旋。在约0.45 M以上，颗粒展开成一种构象，其在流体动力学上与低盐结构相似，但在光学上有很大不同。这种形式可建模为部分展开的盘，其中只有核小体DNA的末端解离，而中心区域仍与组蛋白核心结合。本文介绍了光学建模方法，并将结果与流体动力学性质变化相关联。
