Department of Molecular Biophysics and Polymer Physics, Saint-Petersburg State University, Universitetskaya nab. 7/9 , 199034 St. Petersburg, Russia.
P.N. Lebedev Physical Institute, Russian Academy of Sciences, 53 Leninsky Pr., 119991 Moscow, Russia.
J Phys Chem B. 2024 May 9;128(18):4377-4384. doi: 10.1021/acs.jpcb.4c01127. Epub 2024 Apr 24.
We have studied the excited states and structural properties for the complexes of cytosine (dC) chains with silver ions (Ag) in a wide range of the Ag to DNA ratio () and pH conditions using circular dichroism, steady-state absorption, and fluorescence spectroscopy along with the ultrafast fluorescence upconversion technique. We also calculated vertical electronic transition energies and determined the nature of the corresponding excited states in some models of the cytosine-Ag complexes. We show that (dC) chains in the presence of silver ions form a duplex stabilized by C-Ag-C bonds. It is also shown that the i-motif structure formed by (dC) chains is destabilized in the presence of Ag ions. The excited-state properties in the studied complexes depend on the amount of binding ions and the binding sites, which is supported by the calculations. In particular, new low-lying excited states appear when the second Ag ion interacts with the O atom of cytosine in the C-Ag-C pairs. A similar picture is observed in the case when one Ag ion interacts with one cytosine via the N7 atom.
我们使用圆二色性、稳态吸收和荧光光谱以及超快荧光上转换技术，研究了在广泛的银与 DNA 比（）和 pH 条件下，胞嘧啶（dC）链与银离子（Ag）复合物的激发态和结构性质。我们还计算了垂直电子跃迁能量，并确定了一些胞嘧啶-Ag 复合物模型中相应激发态的性质。我们表明，在银离子存在下，（dC）链形成由 C-Ag-C 键稳定的双链。还表明，在银离子存在下，由（dC）链形成的 i -motif 结构不稳定。研究复合物中的激发态性质取决于结合离子和结合位点的数量，这得到了计算的支持。特别是，当第二个 Ag 离子与 C-Ag-C 对中的胞嘧啶的 O 原子相互作用时，会出现新的低能激发态。当一个 Ag 离子通过 N7 原子与一个胞嘧啶相互作用时，也会观察到类似的情况。
