Mandel R, Fasman G D
Nucleic Acids Res. 1976 Aug;3(8):1839-55. doi: 10.1093/nar/3.8.1839.
Chromatin nucleosomes (mononucleosomes through pentanucleosomes) have been isolated by staphylococcal nuclease digestion of calf thymus nuclei. The peak value ellipticity is the same for all oligomers, 1900 deg cm2, mol-1 at 280-nm, 23 degrees C. The dh280/dT vs T show a progressive increase in Tm of the main thermal band (73.5 degrees C, monomer; 79 degrees C, pentamer). Very small amounts of free DNA can be observed in the melting profiles, and shoulders at 60 degrees C and 93 degrees C appear and increase in magnitude as the particle size increases. The magnitude of the change, delta[theta]280, increases with oligomer size. This pattern could result from an initial unfolding of an asymmetric assembly of nucleosomes (polynucleosome superhelix) in addition to the denaturation of the internal nucleosome structure, and a subsequent or simultaneous denaturation of the double strand DNA. The extent of this unfolding appears to depend upon the size of the oligomer and therefore implies interactions between asymmetrically assembled neighboring nucleosomes.
通过用葡萄球菌核酸酶消化小牛胸腺细胞核，已分离出染色质核小体（单核小体至五核小体）。所有寡聚体的峰值椭圆率相同，在280纳米、23摄氏度下为1900度厘米²·摩尔⁻¹。280纳米处吸光度随温度变化率（dh280/dT）与温度（T）的关系表明，主要热吸收带的解链温度（Tm）逐渐升高（单体为73.5摄氏度；五聚体为79摄氏度）。在解链曲线中可观察到极少量的游离DNA，并且随着颗粒大小增加，60摄氏度和93摄氏度处出现肩峰且幅度增大。变化幅度delta[theta]280随寡聚体大小增加。这种模式可能是由于核小体不对称组装体（多核小体超螺旋）的初始解折叠以及内部核小体结构的变性，随后或同时双链DNA变性所致。这种解折叠程度似乎取决于寡聚体的大小，因此意味着不对称组装的相邻核小体之间存在相互作用。
