Cytosine rich DNA sequences can fold into a non-canonical four stranded intercalated i-motif structure. We investigated Htel-iM, an i-motif structure of the human telomeric DNA region that plays an important role in cell division, cancer diseases and aging. A high pressure up to 1 Gpa was applied to reveal the volumetric changes during unfolding. Thermal transitions at different pressures were followed by infrared and fluorescence spectroscopy. We demonstrated that Htel-iM unfolds in two steps. First the outer hydrogen bonds break in which C(2)O(2) and the N(4)H₂ amino group is involved, subsequently the hydrogen bond involving N(3)⁺ becomes broken. Htel-iM was destabilized by pressure and unfolded with a negative volume change.

中文翻译：

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揭示人类端粒i-基序DNA的展开步骤和体积变化

富含胞嘧啶的DNA序列可以折叠成非规范的四链插入的i-基序结构。我们研究了Htel-iM，这是人类端粒DNA区域的i-基序结构，在细胞分裂，癌症和衰老中起着重要作用。施加高达1 Gpa的高压以显示展开过程中的体积变化。在不同压力下的热转变之后是红外和荧光光谱。我们证明了Htel-iM分两步展开。首先，外部氢键断裂，其中涉及C（2）O（2）和N（4）H ₂氨基，随后涉及N（3）⁺的氢键断裂。Htel-iM在压力作用下不稳定，并且在体积变化为负的情况下展开。