Department of Materials Science & Engineering, Seoul National University, San 56-1, Sillim 9-dong, Gwanak-gu, Seoul 151-744, Korea.
Inorg Chem. 2012 Aug 20;51(16):8760-74. doi: 10.1021/ic300476e. Epub 2012 Apr 25.
A new fluorescent zinc sensor (HNBO-DPA) consisting of 2-(2'-hydroxy-3'-naphthyl)benzoxazole (HNBO) chromophore and a di(2-picolyl)amine (DPA) metal chelator has been prepared and examined for zinc bioimaging. The probe exhibits zinc-induced fluorescence turn-on without any spectral shifts. Its crystal structure reveals that HNBO-DPA binds a zinc ion in a pentacoordinative fashion through the DPA and HNBO moieties. Steady-state photophysical studies establish zinc-induced deprotonation of the HNBO group. Nanosecond and femtosecond laser flash photolysis and electrochemical measurements provide evidence for zinc-induced modulation of photoinduced electron transfer (PeT) from DPA to HNBO. Thus, the zinc-responsive fluorescence turn-on is attributed to suppression of PeT exerted by deprotonation of HNBO and occupation of the electron pair of DPA, a conclusion that is further supported by density functional theory and time-dependent density functional theory (DFT/TD-DFT) calculations. Under physiological conditions (pH 7.0), the probe displays a 44-fold fluorescence turn-on in response to zinc ions with a K(d) value of 12 pM. The fluorescent response of the probe to zinc ions is conserved over a broad pH range with its excellent selectivity for zinc ions among biologically relevant metal ions. In particular, its sensing ability is not altered by divalent transition metal ions such as Fe(II), Cu(II), Cd(II), and Hg(II). Cell experiments using HNBO-DPA show its suitability for monitoring intracellular zinc ions. We have also demonstrated applicability of the probe to visualize intact zinc ions released from cells that undergo apoptosis. More interestingly, zinc-rich pools in zebrafish embryos are traced with HNBO-DPA during early developmental stages. The results obtained from the in vitro and in vivo imaging studies demonstrate the practical usefulness of the probe to detect zinc ions.
一种新的荧光锌传感器（HNBO-DPA）由 2-(2'-羟基-3'-萘基)苯并恶唑（HNBO）发色团和二（2-吡啶基）胺（DPA）金属螯合剂组成，用于锌的生物成像研究。该探针在没有任何光谱位移的情况下表现出锌诱导的荧光开启。其晶体结构表明，HNBO-DPA 通过 DPA 和 HNBO 部分以五配位方式结合锌离子。稳态光物理研究确定了 HNBO 基团的锌诱导去质子化。纳秒和飞秒激光闪光光解和电化学测量提供了锌诱导光诱导电子转移（PeT）从 DPA 到 HNBO 调制的证据。因此，锌响应的荧光开启归因于 HNBO 的去质子化和 DPA 的电子对占据对 PeT 的抑制，这一结论进一步得到密度泛函理论和含时密度泛函理论（DFT/TD-DFT）计算的支持。在生理条件（pH 7.0）下，探针对锌离子的荧光响应有 44 倍的开启，其 K(d)值为 12 pM。探针对锌离子的荧光响应在较宽的 pH 范围内保持不变，对生物相关金属离子中的锌离子具有优异的选择性。特别是，其传感能力不受二价过渡金属离子如 Fe(II)、Cu(II)、Cd(II)和 Hg(II)的影响。使用 HNBO-DPA 的细胞实验表明，它适用于监测细胞内锌离子。我们还证明了该探针可用于可视化细胞凋亡过程中释放的完整锌离子。更有趣的是，在早期发育阶段，HNBO-DPA 可以追踪斑马鱼胚胎中的富锌池。体外和体内成像研究的结果表明，该探针在检测锌离子方面具有实际用途。
