<br>2-氨基嘌呤的缓冲依赖性光物理学：深入了解荧光猝灭和激发态相互作用,The Journal of Physical Chemistry B

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2-氨基嘌呤的缓冲依赖性光物理学：深入了解荧光猝灭和激发态相互作用
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2024-03-07 , DOI: 10.1021/acs.jpcb.3c07269
Souvik Poddar _{1,

2} , Marcia Levitus _{1,

2}

Affiliation

2-氨基嘌呤 (2AP) 是 DNA 和 RNA 研究中使用最广泛的荧光核碱基类似物。其独特的光物理特性和对环境变化的敏感性使其成为了解核酸动力学和 DNA-蛋白质相互作用的有用工具。我们研究了常用缓冲溶液中存在的离子对 2AP 激发态光物理性质的影响。三（羟甲基）氨基甲烷 (TRIS) 的荧光猝灭可以忽略不计，但对于磷酸盐、碳酸盐、3-(N-吗啉代)丙磺酸 (MOPS) 和 4-(2-羟乙基)-1-哌嗪乙磺酸 (HEPES) 则显着缓冲区。结果表明，2AP的两个互变异构体（7H、9H）被磷酸根离子不同程度地猝灭。对于 7H 互变异构体，H ₂ PO ₄ ^–离子的猝灭作用更明显，而对于 HPO ₄ ^2–离子则相反。对于磷酸盐离子，时间分辨荧光研究的结果不能用简单的碰撞猝灭机制来解释。相反，结果与 2AP 和磷酸根离子之间的瞬时相互作用一致。我们假设 2AP 互变异构体和氢键受体（磷酸盐和碳酸盐）之间的激发态相互作用导致 2AP 的单线激发态显着猝灭。这种相互作用表现为双指数荧光强度随猝灭剂浓度变化的指数前因子的衰减，以及斯特恩-沃尔默图的向下曲率。

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Buffer-Dependent Photophysics of 2-Aminopurine: Insights into Fluorescence Quenching and Excited-State Interactions

2-Aminopurine (2AP) is the most widely used fluorescent nucleobase analogue in DNA and RNA research. Its unique photophysical properties and sensitivity to environmental changes make it a useful tool for understanding nucleic acid dynamics and DNA–protein interactions. We studied the effect of ions present in commonly used buffer solutions on the excited-state photophysical properties of 2AP. Fluorescence quenching was negligible for tris(hydroxymethyl)aminomethane (TRIS), but significant for phosphate, carbonate, 3-(N-morpholino) propanesulfonic acid (MOPS), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffers. Results indicate that the two tautomers of 2AP (7H, 9H) are quenched by phosphate ions to different extents. Quenching by the H₂PO₄^– ion is more pronounced for the 7H tautomer, while the opposite is true for the HPO₄^2– ion. For phosphate ions, the results of the time-resolved fluorescence study cannot be explained using a simple collisional quenching mechanism. Instead, results are consistent with transient interactions between 2AP and the phosphate ions. We postulate that excited-state interactions between the 2AP tautomers and an H-bond acceptor (phosphate and carbonate) result in significant quenching of the singlet-excited state of 2AP. Such interactions manifest in biexponential fluorescence intensity decays with pre-exponential factors that vary with quencher concentration, and downward curvatures of the Stern–Volmer plots.

更新日期：2024-03-07

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