Ding D, Allen F S
Biochim Biophys Acta. 1980 Nov 14;610(1):72-80. doi: 10.1016/0005-2787(80)90057-x.
CD studies of known sequence DNA-like polynucleotide-Hg2+ complexes have established a cross-strand binding of Hg2+ to the two thymines of the base-paired first-neighbor unit TpA, as the type I binding mode of poly[d(A-T) x d(A-T)] and other polynucleotides with high TpA incidence. The amino group of adenine is the most probable Hg2+ site for poly(A) and for the binding mode II of poly[d(A-T) x d(A-T)]. The binding of Hg2+ to the natural DNAs shows two binding modes with two different degrees of CD perturbation. The two proposed binding modes are substantiated by Hg2+ binding studies with the DNa-poly(L-lysine) complexes. The increase of sedimentation coefficient of the nucleosomal core particle-heavy metal ion complexes can be accounted for by the binding of heavy metal ions. From the CD experiments with Hg2+ and Ag+, it is estimated that 80 +/- 10% of the DNA in the nucleosomal core particle is involved in the wrapping around the histone core. An out-of-plane transition of the DNA-Ag+ binding mode II is proposed as the cause for the large CD perturbation at 270 nm, but the origin of optical activity of the DNA-Hg2+ complex is still unknown.
对已知序列的类DNA多核苷酸-Hg2+复合物的圆二色性（CD）研究表明，Hg2+以I型结合模式与碱基配对的第一邻位单元TpA中的两个胸腺嘧啶形成跨链结合，这是聚[d(A-T)×d(A-T)]和其他高TpA发生率的多核苷酸的结合模式。腺嘌呤的氨基是聚(A)以及聚[d(A-T)×d(A-T)]的II型结合模式中最可能的Hg2+结合位点。Hg2+与天然DNA的结合呈现出两种具有不同程度CD扰动的结合模式。通过对DNA-聚(L-赖氨酸)复合物的Hg2+结合研究证实了这两种提出的结合模式。核小体核心颗粒-重金属离子复合物沉降系数的增加可归因于重金属离子的结合。通过对Hg2+和Ag+的CD实验估计，核小体核心颗粒中80±10%的DNA参与了围绕组蛋白核心的缠绕。有人提出DNA-Ag+ II型结合模式的平面外转变是270nm处出现大CD扰动的原因，但DNA-Hg2+复合物光学活性的起源仍然未知。
