Bis(2-quinolylmethyl)ethylenediaminediacetic acids (BQENDAs), TQEN–EDTA hybrid molecules as fluorescent zinc sensors
作者:Yuji Mikata、Saaya Takeuchi、Hideo Konno、Satoshi Iwatsuki、Sakiko Akaji、Ikuko Hamagami、Masato Aoyama、Keiko Yasuda、Satoshi Tamotsu、Shawn C. Burdette
DOI:10.1039/c4dt00261j
日期:——
Molecular hybrids of TQEN (N,N,Nâ²,Nâ²-tetrakis(2-quinolylmethyl)ethylenediamine) and EDTA (ethylenediamine-N,N,Nâ²,Nâ²-tetraacetic acid) were examined as fluorescent Zn2+ sensors. Upon the addition of Zn2+, N,N-BQENDA (N,N-bis(2-quinolylmethyl)ethylenediamine-Nâ²,Nâ²-diacetic acid, 1a) exhibits a 30-fold emission enhancement at 456 nm (λex = 315 nm, ÏZn = 0.018) in buffer (HEPES, pH = 7.5, 100 mM KCl). The fluorescence enhancement is Zn2+-specific as Cd2+ induces much smaller increases (ICd/I0 = 5 and ICd/IZn = 16%). These spectroscopic properties, as well as the excellent water-solubility, represent a significant improvement compared to the parent TQEN sensor (ÏZn = 0.007, ICd/IZn = 64%). The isoquinoline analog N,N-1-isoBQENDA (N,N-bis(1-isoquinolylmethyl)ethylenediamine-Nâ²,Nâ²-diacetic acid, 1b) possesses a similar Zn2+ fluorescence response to the parent 1-isoTQEN (N,N,Nâ²,Nâ²-tetrakis(1-isoquinolylmethyl)ethylenediamine) sensor, but exhibits diminished fluorescence intensity. Apo 1a and 1b extract more than 50% of the Zn2+ from an equimolar amount of [Zn(TPEN)]2+ (TPEN = N,N,Nâ²,Nâ²-tetrakis(2-pyridylmethyl)ethylenediamine) or [Zn(EDTA)]2â, whereas TPEN and EDTA cannot effectively remove Zn2+ from [Zn(1a)] and [Zn(1b)]. The reduction of steric crowding in [Zn(TQEN)]2+ resulting from the substitution of two quinolines with carboxylates enhances the interaction between the metal ion and the remaining quinoline nitrogen atoms. The stronger bonding interaction results in enhanced emission intensity, Zn2+ selectivity and metal ion affinity. This is in contrast to [Zn(1-isoTQEN)]2+ where the isoquinoline-carboxylate replacement does not relieve any coordination distortion, therefore no significant changes in fluorescence or metal binding properties are observed.
TQEN(N,N,N-2,N-2-四(2-喹啉甲基)乙二胺)和 EDTA(乙二胺-N,N,N-2,N-2-四乙酸)的分子杂化物作为荧光 Zn2+ 进行了检查传感器。添加 Zn2+ 后,N,N-BQENDA(N,N-双(2-喹啉甲基)乙二胺-N-N-二乙酸,1a)在 456 nm 处表现出 30 倍的发射增强(λ ex = 315 nm,ΔZn = 0.018),缓冲液(HEPES,pH = 7.5,100 mM KCl)中。荧光增强是 Zn2+ 特异性的,因为 Cd2+ 引起的增强要小得多(ICd/I0 = 5 且 ICd/IZn = 16%)。这些光谱特性以及优异的水溶性与母体 TQEN 传感器(ΔZn = 0.007,ICd/IZn = 64%)相比有了显着的改进。异喹啉类似物 N,N-1-isoBQENDA (N,N-双(1-异喹啉甲基)乙二胺-N-,N-二乙酸, 1b) 具有与母体 1-isoTQEN (N) 相似的 Zn2+ 荧光响应,N,N-,N-四(1-异喹啉基甲基)乙二胺)传感器,但荧光强度减弱。 Apo 1a 和 1b 从等摩尔量的 [Zn(TPEN)]2+ 中提取超过 50% 的 Zn2+(TPEN = N,N,N-2,N-2-四(2-吡啶甲基)乙二胺)或 [ Zn(EDTA)]2−,而 TPEN 和 EDTA 不能有效去除 [Zn(1a)] 和 [Zn(1b)] 中的 Zn2+。由于两个喹啉被羧酸盐取代而导致[Zn(TQEN)]2+中空间拥挤的减少,增强了金属离子和剩余喹啉氮原子之间的相互作用。更强的键合相互作用导致发射强度、Zn2+选择性和金属离子亲和力增强。这与 [Zn(1-isoTQEN)]2+ 相反,其中异喹啉-羧酸盐取代不会缓解任何配位畸变,因此没有观察到荧光或金属结合特性的显着变化。