Institute of Biomedical Engineering and Nanomedicine , National Health Research Institutes , Miaoli 35053 , Taiwan (ROC).
J Am Chem Soc. 2018 Apr 18;140(15):5224-5234. doi: 10.1021/jacs.8b01159. Epub 2018 Apr 4.
In this paper, we present a novel charge-free fluorescence-switchable near-infrared (IR) dye based on merocyanine for target specific imaging. In contrast to the typical bathochromic shift approach by extending π-conjugation, the bathochromic shift of our merocyanine dye to the near-IR region is due to an unusual S- cis diene conformer. This is the first example where a fluorescent dye adopts the stable S- cis conformation. In addition to the novel bathochromic shift mechanism, the dye exhibits fluorescence-switchable properties in response to polarity and viscosity. By incorporating a protein-specific ligand to the dye, the probes (for SNAP-tag and hCAII proteins) exhibited dramatic fluorescence increase (up to 300-fold) upon binding with its target protein. The large fluorescence enhancement, near-IR absorption/emission, and charge-free scaffold enabled no-wash and site-specific imaging of target proteins in living cells and in vivo with minimum background fluorescence. We believe that our unconventional approach for a near-IR dye with the S- cis diene conformation can lead to new strategies for the design of near-IR dyes.
在本文中，我们提出了一种基于甲川菁的新型无电荷荧光开关近红外（IR）染料，用于靶向特定成像。与通过扩展π共轭来实现典型红移的方法不同，我们的甲川菁染料的红移到近红外区域是由于一种不寻常的 S-顺式二烯构象。这是第一个采用稳定 S-顺式构象的荧光染料的例子。除了新颖的红移机制外，该染料还表现出对极性和粘度的荧光开关特性。通过将蛋白质特异性配体与染料结合，探针（用于 SNAP 标签和 hCAII 蛋白）在与靶蛋白结合时表现出显著的荧光增强（高达 300 倍）。大的荧光增强、近红外吸收/发射和无电荷支架使目标蛋白在活细胞和体内的无冲洗和特异性成像成为可能，背景荧光最小。我们相信，我们对于具有 S-顺式二烯构象的近红外染料的非常规方法可以为近红外染料的设计带来新的策略。
