Yao Zhiyi, Li Chun, Shi Gaoquan
Department of Chemistry, and the Key Laboratory of Bio-organic Phosphorous Chemistry and Chemical Biology, Tsinghua University, Beijing, China.
Langmuir. 2008 Nov 18;24(22):12829-35. doi: 10.1021/la802086d. Epub 2008 Oct 24.
Optically active supramolecular complexes of water-soluble achiral polythiophene (PT) derivatives, PMTPA or PMTEA (Chart 1), and folic acid have been prepared; and the complex formation processes have been studied by absorption, emission, and circular dichroism (CD) spectroscopies. The complexes exhibited unique split-type induced CDs in the pi-pi* transition region of PTs, indicating that the molecular chirality of the glutamic acid moiety in folic acid was expressed in PT backbones. The influences of temperature, solvent composition, and the structures of the inducing molecules on the chirality induction to PTs were also investigated, and a possible mechanism for the formation of chiral superstructures was proposed. Furthermore, it was found that, upon addition of folic acid into aqueous solution of PTs (PMTPA or PMTEA), a dramatic color change from yellow to purple along with the emission quenching of PT derivatives was observed. PMTEA, having one fewer carbon in the hydrophobic side chain relative to PMTPA, showed better selectivity toward folic acid sensing over ATP because of its higher solubility in water and the appropriate hydrophilic/hydrophobic balance in the complex. Therefore, it can be applied as a colorimetric and fluorescent probe for detecting folic acid with high selectivity and sensitivity. Besides naked-eye detection of folic acid, the detection limit can be extended to be 10 (-8) M by using fluorometry and PMTEA as the probing molecule.
已制备了水溶性非手性聚噻吩（PT）衍生物PMTPA或PMTEA（图1）与叶酸的旋光超分子复合物；并通过吸收光谱、发射光谱和圆二色光谱（CD）研究了复合物的形成过程。这些复合物在PT的π-π*跃迁区域表现出独特的分裂型诱导CD，表明叶酸中谷氨酸部分的分子手性在PT主链中得以体现。还研究了温度、溶剂组成和诱导分子结构对PT手性诱导的影响，并提出了手性超结构形成的可能机制。此外，发现向PT（PMTPA或PMTEA）水溶液中加入叶酸时，观察到颜色从黄色急剧变为紫色，同时PT衍生物的发射猝灭。与PMTPA相比，疏水侧链中碳原子少一个的PMTEA由于其在水中的溶解度更高以及复合物中合适的亲水/疏水平衡，对叶酸传感表现出比对ATP更好的选择性。因此，它可作为一种比色和荧光探针，用于高选择性和高灵敏度地检测叶酸。除了对叶酸进行肉眼检测外，使用荧光法并以PMTEA作为探测分子时，检测限可扩展至10^(-8) M。
