Cooperativity and Site-Selectivity of Intramolecular Hydrogen Bonds on the Fluorescence Quenching of Modified GFP Chromophores

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• 作者：Deng-Hsiang Chang ; Chun-Lin Ou ; Hung-Yu Hsu ; Guan-Jhih Huang ; Chen-Yi Kao ; Yi-Hung Liu ; Shie-Ming Peng ; Eric Wei-Guang Diau ; Jye-Shane Yang
• 刊名：Journal of Organic Chemistry
• 出版年：2015
• 出版时间：December 18, 2015
• 年：2015
• 卷：80
• 期：24
• 页码：12431-12443
• 全文大小：792K
• ISSN：1520-6904

文摘

This paper provides the first example of experimentally characterized hydrogen-bond cooperativity on fluorescence quenching with a modified green fluorescence protein (GFP) chromophore that contains a 6-membered C鈺怤路路路H鈥揙 and a 7-membered C鈺怬路路路H鈥揙 intramolecular H-bonds. Variable-temperature ¹H NMR and electronic absorption and emission spectroscopies were used to elucidate the preference of intra- vs intermolecular H-bonding at different concentrations (1 mM and 10 渭M), and X-ray crystal structures provide clues of possible intermolecular H-bonding modes. In the ground state, the 6-membered H-bond is significant but the 7-membered one is rather weak. However, fluorescence quenching is dominated by the 7-membered H-bond, indicating a strengthening of the H-bond in the excited state. The H-bonding effect is more pronounced in more polar solvents, and no intermediates were observed from femtosecond fluorescence decays. The fluorescence quenching is attributed to the occurrence of diabatic excited-state proton transfer. Cooperativity of the two intramolecular H-bonds on spectral shifts and fluorescence quenching is evidenced by comparing with both the single H-bonded and the non-H-bonded counterparts. The H-bond cooperativity does not belong to the conventional patterns of 蟽- and 蟺-cooperativity but a new type of polarization interactions, which demonstrates the significant interplay of H-bonds for multiple H-bonding systems in the electronically excited states.