Conformationally Locked Chromophores as Models of Excited-State Proton Transfer in Fluorescent Proteins
Conformationally Locked Chromophores as Models of Excited-State Proton Transfer in Fluorescent Proteins
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DOI：
10.1021/ja3010144
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发表时间：
2012-04-04
影响因子：
15
通讯作者：
Solntsev, Kyril M.
中科院分区：
文献类型：
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作者：
Baranov, Mikhail S.;Lukyanov, Konstantin A.;Solntsev, Kyril M.
绿色荧光蛋白（GFP）家族的成员通过三个内部氨基酸残基的修饰形成发色团。以前，发色团的许多关键特性是使用模型化合物研究的。然而，没有研究分子间激发态质子转移（ESPT）与GFP样的合成发色团已经进行，因为它们要么是非荧光或缺乏电离的OH基团。本文报道了两个高荧光GFP发色团类似物：p-HOBDI-BF 2和p-HOPyDI：Zn的合成和光化学研究。在已知的荧光化合物中，p-HOBDI-BF 2是天然GFP发色团的最接近的类似物。这些可逆（p-HOBDI-BF 2）和可逆（p-HOPyDI：Zn）锁定的化合物是完全平面的GFP发色团的第一个例子，其中光异构化诱导的失活被抑制，并且观察到质子化光解离。p-HOBDI-BF 2和p-HOPyDI：Zn的光物理行为（激发态pK（α）、溶剂化显色性、动力学和质子转移热力学）揭示了它们的高光酸性，这使它们成为荧光蛋白中分子间ESPT的良好模型。此外，p-HOPyDI：Zn是金属有机络合物中“超级”光酸性的第一个例子。
Members of the green fluorescent protein (GFP) family form chromophores by modifications of three internal amino acid residues. Previously, many key characteristics of chromophores were studied using model compounds. However, no studies of intermolecular excited-state proton transfer (ESPT) with GFP-like synthetic chromophores have been performed because they either are nonfluorescent or lack an ionizable OH group. In this paper we report the synthesis and photochemical study of two highly fluorescent GFP chromophore analogues: p-HOBDI-BF2 and p-HOPyDI:Zn. Among known fluorescent compounds, p-HOBDI-BF2 is the closest analogue of the native GFP chromophore. These irrreversibly (p-HOBDI-BF2) and reversibly (p-HOPyDI:Zn) locked compounds are the first examples of fully planar GFP chromophores, in which photoisomerization-induced deactivation is suppressed and protolytic photodissociation is observed. The photophysical behavior of p-HOBDI-BF2 and p-HOPyDI:Zn (excited state pK(a)'s, solvatochromism, kinetics, and thermodynamics of proton transfer) reveals their high photoacidity, which makes them good models of intermolecular ESPT in fluorescent proteins. Moreover, p-HOPyDI:Zn is a first example of "super" photoacidity in metal-organic complexes.