Conformationally Locked Chromophores as Models of Excited-State Proton Transfer in Fluorescent Proteins

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• 作者：Mikhail S. Baranov ; Konstantin A. Lukyanov ; Alexandra O. Borissova ; Jordan Shamir ; Dmytro Kosenkov ; Lyudmila V. Slipchenko ; Laren M. Tolbert ; Ilia V. Yampolsky ; Kyril M. Solntsev
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：April 4, 2012
• 年：2012
• 卷：134
• 期：13
• 页码：6025-6032
• 全文大小：424K
• 年卷期：v.134,no.13(April 4, 2012)
• ISSN：1520-5126

文摘

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鈥檚, 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 鈥渟uper鈥?photoacidity in metal鈥搊rganic complexes.