Zheng Yujun, Cao Xihui, Orbulescu Jhony, Konka Veeranjaneyulu, Andreopoulos Fotios M, Pham Si M, Leblanc Roger M
Department of Chemistry, University of Miami, Coral Gables, Florida 33124-0431, USA.
Anal Chem. 2003 Apr 1;75(7):1706-12. doi: 10.1021/ac026285a.
Fluorescent organic chemosensors for the detection of divalent copper with high selectivity and sensitivity are the subject of intense research in the recent years. Structurally, ionophore and fluorophore are two essential parts determining the resultant performance of the chemosensor. While much work has been focused on designing highly selective ligands, little attention has been paid to the possible influence of ionophore-fluorophore interaction on their properties in metal ion binding. We studied here fluorescent chemosensors based on the Gly-His peptidyl motif and found that the functionality of the chemosensors was greatly influenced by the spatial alignment of the fluorophore in the molecules. In Gly-His-Lys(Dns) (1), the dansyl group is on a side branch and does not interact with copper, while in Dpr(Dns)-His-Lys (2), the dansyl group is also on a side branch but the close placement allows it to directly participate in the binding with copper ions. Therefore, although dansyl can signal the binding event in both molecules, the mechanisms involved are quite different, and this difference resulted in different sensing performance, e.g., the selectivity. Even more strikingly, the dansyl group in Dns-Gly-His-Gly (3) exhibited a profound effect on the molecular complexation. The binding constant decreased, and binding mode was affected since only 1:1 binding was observed while in side-branch-labeled ligands, a 2:1 binding may also be involved. In contrast to those side-chain-labeled ligands, molecule 3 is extremely simple in structure and possesses superior detecting qualities such as selectivity, molecular sensitivity, and applicability in a wide range of pH.
近年来，用于高选择性和高灵敏度检测二价铜离子的荧光有机化学传感器一直是研究的热点。从结构上看，离子载体和荧光团是决定化学传感器最终性能的两个关键部分。虽然很多工作都集中在设计高选择性配体上，但离子载体 - 荧光团相互作用对其金属离子结合性质的潜在影响却很少受到关注。我们在此研究了基于甘氨酸 - 组氨酸肽基序的荧光化学传感器，发现荧光团在分子中的空间排列对化学传感器的功能有很大影响。在甘氨酸 - 组氨酸 - 赖氨酸（丹磺酰氯）（1）中，丹磺酰基团位于侧链上，不与铜离子相互作用，而在二肽（丹磺酰氯） - 组氨酸 - 赖氨酸（2）中，丹磺酰基团也位于侧链上，但位置靠近，使其能够直接参与与铜离子的结合。因此，尽管丹磺酰基团在这两个分子中都能指示结合事件，但所涉及的机制却大不相同，这种差异导致了不同的传感性能，例如选择性。更引人注目的是，丹磺酰甘氨酸 - 组氨酸 - 甘氨酸（3）中的丹磺酰基团对分子络合表现出深远影响。结合常数降低，结合模式也受到影响，因为只观察到1:1的结合，而在侧链标记的配体中，可能还涉及2:1的结合。与那些侧链标记的配体不同，分子3的结构极其简单，并具有诸如选择性、分子灵敏度以及在广泛pH范围内的适用性等优异的检测特性。
