Carpenter B G, Baldwin J P, Bradbury E M, Ibel K
Nucleic Acids Res. 1976 Jul;3(7):1739-46. doi: 10.1093/nar/3.7.1739.
There is considerable current interest in the organisation of nucleosomes in chromatin. A strong X-ray and neutron semi-meridional diffraction peak at approximately 10 nm had previously been attributed to the interparticle specing of a linear array of nucleosomes. This diffraction peak could also result from a close packed helical array of nucleosomes. A direct test of these proposals is whether the 10 nm peak is truly meridional as would be expected for a linear array of nucleosomes or is slightly off the meridian as expected for a helical array. Neutron diffraction studies of H1-depleted chromatin support the latter alternative. The 10 nm peak has maxima which form a cross-pattern with semi-meridional angle of 8 to 9 degrees. This is consistent with a coil of nucleosomes of pitch 10 nm and outer diameter of approximately 30 nm. These dimensions correspond to about six nucleosomes per turn of the coli.
当前人们对染色质中核小体的组织形式极为关注。此前，在约10纳米处出现的一个强烈的X射线和中子半子午线衍射峰被归因于核小体线性阵列的粒子间间距。这个衍射峰也可能由核小体紧密堆积的螺旋阵列产生。对这些推测的直接检验是，10纳米的峰是否真的如核小体线性阵列所预期的那样位于子午线方向，还是如螺旋阵列所预期的那样稍微偏离子午线。对H1缺失染色质的中子衍射研究支持了后一种可能性。10纳米的峰具有最大值，这些最大值形成了一个半子午线角度为8至9度的交叉图案。这与螺距为10纳米、外径约为30纳米的核小体螺旋结构相符。这些尺寸对应于每圈螺旋约六个核小体。
