利用1H NMR, ESI-MS, UV-Vis, 荧光光谱等测试手段研究了基于锌基-有机金属三元大环探针M-1对生物分子谷胱甘肽(GSH)的识别与传感。 并且, 通过研究识别过程中M-1与组成谷胱甘肽的氨基酸(半胱氨酸、 谷氨酸、 甘氨酸)的作用关系, 确立了M-1对GSH的识别机理。 结果表明, 化合物M-1在H2O/DMF(1∶9, φ)溶液中形成了稳定的［3+3］大环结构； 紫外滴定光谱表明, 向M-1中加入GSH后303 nm处吸收峰强度增加, 380 nm处吸收峰强度减弱, 在330 nm处出现了一个等吸收点, 紫外滴定和ESI-MS质谱证实了M-1能够1∶1包合GSH, 平衡常数(log KGSH)为462±015。 1H NMR表明谷胱甘肽在M-1中的构型为组成谷胱甘肽的谷氨酸通过羧基与金属中心之间的静电作用深深地进入M-1空穴内部。 荧光光谱表明, 向M-1中加入GSH时, 以330 nm的光激发, 发射波长从510 nm红移至540nm, 荧光强度增加1倍； 加入半胱氨酸、 谷氨酸时, 荧光强度分别增加04倍和02倍； 而加入甘氨酸时, 荧光没有变化。 综合上述结果证明了M-1空穴的限域作用及其底部三元环上的氨基和GSH上的巯基(半胱氨酸)间的氢键作用使M-1的电子构型发生转变, 进而引起紫外光谱和荧光光谱发生变化, 实现了大环化合物M-1对生物分子谷胱甘肽的可视化、 高灵敏度检测, 检测限达到30×10-6 mol·L-1。

Metal-organic supramolecular with well-defined nanosized molecular cavity is able to encapsulate some special guest substrates so that they have been widely applied in molecular recognition and molecular separations. In this work, a highly sensitive recognition of biological molecular γ-glutamyl-cysteinyl-glycine (GSH) was achieved with a trinuclear zinc-based metal-organic cyclohelicate fluorescence probe M-1, which was assembled with zinc ion and two tridentate (N2O) ligand with dansyl sulfonamide group and hydrogen bond site. The recognition process for GSH with M-1 was determined with 1H NMR, ESI-MS, UV-Vis and fluorescence spectra. To establish the recognition mechanism of GSH, its component amino acids (Cys, Glu, Gly) were investigated by spectroscopic titrations. The results show that the M-1 with trinuclear structure exhibits high stability in a water/DMF 1∶9 solution. UV-Vis adsorption titration revealed that a significant absorbance increase at 303 nm with the addition of GSH to the M-1 solution, but an absorbance decrease was observed at 380 nm. A sharp isobestic point was obtained at 330 nm. In addition, based on the UV-Vis adsorption titration results, ESI-MS analysis of M-1 confirmed that 1∶1 complexation stoichiometry of the host-guest behavior was obtained for GSH and the association constant (log KGSH) was calculated as 462±015. Moreover, 1H NMR titrations of M-1 upon the above amino acids revealed that the Glu residue of GSH was sent into M-1 cavity through the static interactions between the COO- groups and metal ions. In addition, it was found that the fluorescence intensity exhibits a two-fold enhancement, with the emission wavelength red-shifted from 510 to 540 nm upon the addition of GSH into M-1. Upon the addition of Cys and Glu in the solution of M-1, the luminescence intensity exhibits 04 times and 02 times enhancement, respectively, with the emission wavelength not being shifted. On the contrary, no change of the luminescence intensity was observed after adding the Gly to the solution of M-1. Based on the above analysis, it is confirmed that the joint effects of size limitation of the M-1 cavity and the hydrogen bonding interactions between Cys moiety of GSH and the amide groups sited in M-1 molecuar will generate measurable spectral changes, which lead to visualizing the highly sensitive recognition for GSH. The low detection limit was up to 30×10-6 mol·L-1.