Read C M, Crane-Robinson C
Eur J Biochem. 1985 Oct 1;152(1):143-50. doi: 10.1111/j.1432-1033.1985.tb09174.x.
Chicken erythrocyte chromatin was depleted of histones H1, H5, H2A and H2B. The resulting (H3/H4)-containing chromatin was digested with micrococcal nuclease to yield monomer, dimer, trimer etc. units, irregularly spaced on the DNA, with even-number multimers being more prominent. Sucrose density gradient centrifugation separated monomers and dimers (7.7 S and 10.5 S). Sodium dodecyl sulphate gel electrophoresis and cross-linking indicated: the monomer contains 50-base-pair (bp), 60-bp and 70-bp DNA and the dimer 125-bp DNA; the monomer contains a tetramer and the dimer an octamer of H3 and H4. Partial association of monomer units to dimers inhibits structural studies of monomers. The internal structure of the dimer, i.e. and (H3/H4)4-125-bp-DNA particle, was studied using circular dichroism, thermal denaturation and nuclease digestion. Both micrococcal nuclease and DNase I digestion indicate that, unlike core particles, accessible sites occur in the centre of the particle and it is concluded that the (H3/H4)4-125-bp-DNA particle is not a 'pseudo-core particle' in which the 'extra' H3 and H4 replace H2A and H2B. It is proposed that the octamer particle is formed by the sliding together of two 'monomer' units, each containing the (H3/H4)2 tetramer and 70 bp of DNA. Excision of this dimer unit with micrococcal nuclease results in the loss of 10 readily digestible base pairs at each end, leaving 125 bp.
鸡红细胞染色质去除了组蛋白H1、H5、H2A和H2B。所得的含（H3/H4）的染色质用微球菌核酸酶消化，产生单体、二聚体、三聚体等单位，在DNA上间隔不规则，偶数多聚体更为突出。蔗糖密度梯度离心分离出单体和二聚体（7.7S和10.5S）。十二烷基硫酸钠凝胶电泳和交联表明：单体含有50碱基对（bp）、60bp和70bp的DNA，二聚体含有125bp的DNA；单体含有一个四聚体，二聚体含有一个H3和H4的八聚体。单体单元部分缔合形成二聚体阻碍了单体的结构研究。利用圆二色性、热变性和核酸酶消化研究了二聚体的内部结构，即（H3/H4）4-125bp-DNA颗粒。微球菌核酸酶和DNase I消化均表明，与核心颗粒不同，可及位点出现在颗粒中心，由此得出结论，（H3/H4）4-125bp-DNA颗粒不是一个“假核心颗粒”，其中“额外”的H3和H4取代了H2A和H2B。有人提出，八聚体颗粒是由两个“单体”单元滑动结合形成的，每个单元含有（H3/H4）2四聚体和70bp的DNA。用微球菌核酸酶切除这个二聚体单元会导致两端各丢失10个易于消化的碱基对，剩下125bp。
