Song Xinbo, Bian Hui, Wang Chao, Hu Mingyu, Li Ning, Xiao Yi
State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian 116024, P.R. China.
Org Biomol Chem. 2017 Oct 4;15(38):8091-8101. doi: 10.1039/c7ob01698k.
Near-infrared (NIR) fluorescent probes are advantageous over visible ones, for they can avoid the interference from the short-wavelength background emission in biological systems. However, there are a very limited number of NIR probes that can specifically label target proteins in living cells. In this work, a series of long-wavelength dyes (N-NIR, S-NIR, and K-NIR) analogous to the novel Changsha NIR family are synthesized conveniently through a new approach that is different from the previously reported one. These three dyes have similar conjugation structures but exhibit tunable photophysical properties. N-NIR and S-NIR have large extinction coefficients over 100 000, and high fluorescence quantum yields. Although NIR absorption and emission of K-NIR are inferior to the former two, it emits in a much longer wavelength region. And all the three dyes can easily pass through the cell membranes to obtain the high-resolution NIR fluorescence images. Furthermore, N-NIR is chosen as the NIR fluorophore to develop a protein-labeling reagent PYBG-D, since it demonstrates the highest fluorescence quantum yield of up to 0.4 (in methanol). PYBG-D is efficiently synthesized through Sonogashira coupling between bromo-substituted N-NIR and alkyne-substituted benzylguanine (PYBG). The conjugate PYBG-D proves to be a specific and efficient label for O-alkylguanine-DNA alkyltransferase (SNAP-tag) that fused to target proteins in living cells, which contributes to high resolution NIR fluorescence images under a laser confocal microscope.
近红外（NIR）荧光探针比可见光探针更具优势，因为它们可以避免生物系统中短波长背景发射的干扰。然而，能够特异性标记活细胞中靶蛋白的近红外探针数量非常有限。在这项工作中，通过一种不同于先前报道的新方法，方便地合成了一系列与新型长沙近红外家族类似的长波长染料（N-NIR、S-NIR和K-NIR）。这三种染料具有相似的共轭结构，但表现出可调的光物理性质。N-NIR和S-NIR具有超过100000的大消光系数和高荧光量子产率。尽管K-NIR的近红外吸收和发射不如前两者，但其发射波长区域更长。并且这三种染料都可以轻松穿过细胞膜以获得高分辨率的近红外荧光图像。此外，由于N-NIR表现出高达0.4（在甲醇中）的最高荧光量子产率，因此选择它作为近红外荧光团来开发一种蛋白质标记试剂PYBG-D。通过溴代取代的N-NIR与炔基取代的苄基鸟嘌呤（PYBG）之间的Sonogashira偶联高效合成了PYBG-D。共轭物PYBG-D被证明是一种特异性且高效的O-烷基鸟嘌呤-DNA烷基转移酶（SNAP-tag）标记物，该酶与活细胞中的靶蛋白融合，这有助于在激光共聚焦显微镜下获得高分辨率的近红外荧光图像。
