With about 4 % abundance in the genome 5‐methylcytosine (5mC) is one of the most important epigenetic modifications. Change in DNA hypermethylation levels has even been linked to resistances to cisplatin treatment of cancer cells. This work aimed at the synthesis and full characterization of 5mC‐cisplatin adducts as well as for the examination of possible side‐reactions and transformations. We report the first X‐ray crystal structure of a cis‐[PtCl(5mC)(NH₃)₂]Cl complex and the formation of [PtCl(5mC)(NH₃)₂]⁺ and [PtCl(5mC)₂(NH₃)]⁺ with HR‐ESI mass spectrometry. Further, we explore complex formation and dynamics using ¹H, ¹⁹⁵Pt, and DOSY NMR spectroscopy. UV/Vis absorption and EPR spectroscopy also confirmed the formation of trace amounts of paramagnetic Pt‐blue species. In the process, a hemiprotonated 5mC dimer, 5mC‐5mCH⁺, reminiscent of the “i‐motif” in DNA tetramers, was structurally characterized.

中文翻译：

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与表观遗传上相关的碱基5-甲基胞嘧啶形成顺铂加合物

5-甲基胞嘧啶（5mC）在基因组中的丰度约为4％，是最重要的表观遗传修饰之一。DNA高甲基化水平的变化甚至与顺铂治疗癌细胞的耐药性有关。这项工作旨在合成和完整表征5mC-顺铂加合物，以及检查可能的副反应和转化。我们报道了顺式[PtCl（5mC）（NH ₃）₂ ] Cl配合物的第一个X射线晶体结构以及[PtCl（5mC）（NH ₃）₂ ] ⁺和[PtCl（5mC）₂（ NH₃）] ⁺和HR‐ESI质谱。此外，我们使用¹ H，¹⁹⁵ Pt和DOSY NMR光谱研究了复合物的形成和动力学。紫外/可见吸收和EPR光谱也证实了痕量的顺磁性Pt-blue物种的形成。在此过程中，对半质子化的5mC二聚体5mC - 5mC H ⁺进行了结构表征，使人联想到DNA四聚体中的“ i-基序”。