某些核蛋白的巨大负圆二色光谱研究。
Investigation of huge negative circular dichroism spectra of some nucleoproteins.
作者信息
Li H J, Epstein P, Yu S S, Brand B
出版信息
Nucleic Acids Res. 1974 Nov;1(11):1371-83. doi: 10.1093/nar/1.11.1371.
Under certain conditions of preparation, DNA, whether free or complexed with polylysine or histone KAP (I, fl), produce huge negative circular dichroism (CD) spectra with maxima at about 270nm. In order to investigate the cause of these spectra, reconstituted polylysine-DNA complex was used as a model system. It was found that the CD change of DNA in the complex is not a linear function of the fraction of base pairs bound. Such a CD spectrum is not changed despite dilution up to 128 folds for as long as 12 hours. Difference CD spectra taken between free DNA and any of the complexes are qualitatively the same, and are similar to those of free DNA and nucleohistone KAP (Fasman et al., Biochemistry 9, 2814-2822, 1970), free DNA and direct mixed polylysine-DNA complexes, or free DNA in high salt (Chang et al., Biochemistry12, 3028-3032, 1973). The suggestion is made that this CD spectrum might be caused by specific conformational changes in DNA, perhaps belonging to the family of B to C transitions followed by a further structural distortion of DNA due to aggregation of the nucleoprotein molecules.
在特定的制备条件下，DNA无论是游离状态还是与聚赖氨酸或组蛋白KAP（I，β）复合，都会产生巨大的负圆二色性（CD）光谱，其最大值在约270nm处。为了研究这些光谱产生的原因，将重组的聚赖氨酸-DNA复合物用作模型系统。研究发现，复合物中DNA的CD变化不是结合碱基对比例的线性函数。只要长达12小时，即使稀释至128倍，这种CD光谱也不会改变。游离DNA与任何一种复合物之间的差示CD光谱在性质上是相同的，并且与游离DNA和核组蛋白KAP（法斯曼等人，《生物化学》9，2814 - 2822，1970）、游离DNA和直接混合的聚赖氨酸-DNA复合物，或高盐溶液中的游离DNA（张等人，《生物化学》12，3028 - 3032，1973）的光谱相似。有人提出，这种CD光谱可能是由DNA中特定的构象变化引起的，可能属于从B型到C型转变的家族，随后由于核蛋白分子的聚集导致DNA进一步的结构扭曲。
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