Makarov V L, Dimitrov S I, Petrov P T
Eur J Biochem. 1983 Jul 1;133(3):491-7. doi: 10.1111/j.1432-1033.1983.tb07491.x.
The chromatin structure in solution has been studied by the flow linear dichroism method (LD) in a wide range of ionic strengths. It is found that increasing the ionic strength from 0.25 mM Na2EDTA, pH 7.0 to 100 mM NaCl leads to a strong reduction of the LD amplitude of chromatin and inversion of the LD sign from negative to positive at 2 mM NaCl. Chromatin exhibits a positive LD maximum value at 10-20 mM NaCl. These data enable us to conclude that in very low ionic strength (0.25 mM Na2EDTA) the nucleosome discs are oriented with their flat faces more or less parallel to the chromatin filament axis. Increasing ionic strength up to 20 mM NaCl leads to reorientation of the nucleosome discs and to formation of chromatin structures with nucleosome flat faces inclined to the fibril axis. A conformational transition of that kind is not revealed in H1-depleted chromatin. The condensation of the chromatin filaments with increasing concentration of NaCl from 20 mM to 100 mM slightly influences the orientation of the nucleosomes.
利用流动线性二色性方法（LD）在广泛的离子强度范围内研究了溶液中的染色质结构。研究发现，将离子强度从pH 7.0的0.25 mM Na2EDTA增加到100 mM NaCl，会导致染色质LD振幅大幅降低，并且在2 mM NaCl时LD信号从负变为正。染色质在10 - 20 mM NaCl时呈现正的LD最大值。这些数据使我们能够得出结论，在极低的离子强度（0.25 mM Na2EDTA）下，核小体盘的平面或多或少与染色质丝轴平行排列。将离子强度增加到20 mM NaCl会导致核小体盘重新定向，并形成核小体平面相对于纤维轴倾斜的染色质结构。在缺乏H1的染色质中未发现这种构象转变。随着NaCl浓度从20 mM增加到100 mM，染色质丝的凝聚对核小体的定向影响较小。
