Department of Chemistry, McGill University, Montreal, Quebec H3A-0B8, Canada.
Centre de recherche en biologie structural, McGill University, Montreal, Quebec H3G 0B1, Canada.
Bioconjug Chem. 2023 Jun 21;34(6):972-976. doi: 10.1021/acs.bioconjchem.3c00055. Epub 2023 May 17.
A new fluorescent cytosine analog "C" containing a -stilbene moiety was synthesized and incorporated into hemiprotonated base pairs that comprise -motif structures. Unlike previously reported fluorescent base analogs, C mimics the acid-base properties of cytosine (p ≈ 4.3) while exhibiting bright (ε × Φ ≈ 1000 cm M) and red-shifted fluorescence (λ = 440 → 490 nm) upon its protonation in the water-excluded interface of C:C base pairs. Ratiometric analyses of C emission wavelengths facilitate real-time tracking of reversible conversions between single-stranded, double-stranded, and -motif structures derived from the human telomeric repeat sequence. Comparisons between local changes in C protonation with global structure changes according to circular dichroism suggest partial formation of hemiprotonated base pairs in the absence of global -motif structures at pH = 6.0. In addition to providing a highly fluorescent and ionizable cytosine analog, these results suggest that hemiprotonated C:C base pairs can form in partially folded single-stranded DNA in the absence of global -motif structures.
一种新的含 - 二苯乙烯部分的荧光胞嘧啶类似物“C”被合成并掺入由 - 基序结构组成的半质子化碱基对中。与之前报道的荧光碱基类似物不同，C 模拟了胞嘧啶的酸碱性质（p ≈ 4.3），同时在其在水排斥界面中的质子化时表现出明亮的（ε × Φ ≈ 1000 cm M）和红移荧光（λ = 440 → 490nm）。C 发射波长的比率分析有助于实时跟踪来自人端粒重复序列的单链、双链和 - 基序结构之间的可逆转换。根据圆二色性，C 质子化的局部变化与全球结构变化之间的比较表明，在 pH = 6.0 时，在没有全局 - 基序结构的情况下，半质子化碱基对部分形成。除了提供高荧光和可离子化的胞嘧啶类似物外，这些结果表明，在没有全局 - 基序结构的情况下，半质子化的 C:C 碱基对可以在部分折叠的单链 DNA 中形成。
