N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119334, Russia.
Spectrochim Acta A Mol Biomol Spectrosc. 2021 Dec 15;263:120171. doi: 10.1016/j.saa.2021.120171. Epub 2021 Jul 12.
Spectral-fluorescent and photochemical properties (photoisomerization and generation of the triplet state) of meso-substituted cationic carbocyanine dyes, 3,3'-di-(β-hydroxyethyl)-5,5'-dimethoxy-9-ethylthiacarbocyanine iodide (K1) and 3,3'-di-(β-hydroxyethyl)-9-methylthiacarbocyanine iodide (K2), have been studied in solutions and in the presence of DNA. In solutions, on passing from acetonitrile to dioxane, a growth of fluorescence of the dyes is observed due to a shift of the equilibrium of cis/trans isomers toward the fluorescent trans-isomer. Upon flash photolysis of dye solutions in dioxane, the formation and subsequent decay of the cis-photoisomers of the dyes are observed. In aqueous solutions, the interaction with DNA leads to the formation of noncovalent complexes of K1 and K2 with DNA, which is accompanied by a significant increase in the fluorescence intensity. The results of the molecular docking experiments showed the possibility of several types of binding, which was confirmed by the data obtained from other experiments. The effects of temperature and additions of NaCl on the stability of the dye-DNA complexes were studied. The spectral-fluorescent data were used to estimate the binding constants of the dyes with DNA and other characteristics of the dyes that are important for their use as probes. Upon flash photolysis of the dyes in complexes with DNA, photoisomerization is not observed, but the quantum yield of intersystem crossing to the triplet state increases. The decay of the triplet states occurs by a two-exponential law. The rate constants for quenching of the triplet states of the dyes complexed with DNA by oxygen were found to be lower than the expected values for diffusion-controlled quenching (taking into account the spin statistical factor 1/9), which is explained by the steric factor of complexation.
介晶取代阳离子碳菁染料 3,3'-二-(β-羟乙基)-5,5'-二甲氧基-9-乙基噻嗪碳菁碘化物(K1)和 3,3'-二-(β-羟乙基)-9-甲基噻嗪碳菁碘化物(K2)的光谱荧光和光化学性质(光异构化和三重态的产生)已在溶液中和 DNA 存在下进行了研究。在溶液中，从乙腈向二氧六环转变时，染料的荧光强度增加，这是由于顺/反异构体平衡向荧光反式异构体移动所致。在二氧六烷溶液中用光瞬间照射染料时，观察到染料顺式光异构体的形成和随后的衰减。在水溶液中，与 DNA 的相互作用导致 K1 和 K2 与 DNA 形成非共价复合物，这伴随着荧光强度的显著增加。分子对接实验的结果表明存在几种结合类型的可能性，这得到了其他实验数据的证实。研究了温度和添加 NaCl 对染料-DNA 复合物稳定性的影响。光谱荧光数据用于估计染料与 DNA 的结合常数和对其作为探针使用很重要的染料的其他特性。在与 DNA 形成复合物的染料的光瞬间照射下，没有观察到光异构化，但到三重态的系间窜跃量子产率增加。三重态的衰减按双指数规律发生。发现与 DNA 络合的染料的三重态由氧猝灭的速率常数低于扩散控制猝灭的预期值(考虑到自旋统计因子 1/9)，这是由络合的空间位阻因素解释的。
