Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia.
Dipartimento di Chimica, Università degli Studi di Milano, Via C. Golgi, 19, 20133 Milan, Italy.
Molecules. 2022 Jun 18;27(12):3918. doi: 10.3390/molecules27123918.
Cyclic pentaphenylalanine was studied as an efficient anion sensor for halides, thiocyanate and oxoanions in acetonitrile and methanol. Stability constants of the corresponding complexes were determined by means of fluorimetric, spectrophotometric, H NMR, and microcalorimetric titrations. A detailed structural overview of receptor-anion complexes was obtained by classical molecular dynamics (MD) simulations. The results of H NMR and MD studies indicated that the bound anions were coordinated by the amide groups of cyclopeptide, as expected. Circular dichroism (CD) titrations were also carried out in acetonitrile. To the best of our knowledge, this is the first example of the detection of anion binding by cyclopeptide using CD spectroscopy. The CD spectra were calculated from the structures obtained by MD simulations and were qualitatively in agreement with the experimental data. The stoichiometry of almost all complexes was 1:1 (receptor:anion), except for dihydrogen phosphate where the binding of dihydrogen phosphate dimer was observed in acetonitrile. The affinity of the cyclopeptide receptor was correlated with the structure of anion coordination sphere, as well as with the solvation properties of the examined solvents.
环状五苯丙氨酸被研究为一种在乙腈和甲醇中有效检测卤化物、硫氰酸根和氧阴离子的阴离子传感器。通过荧光、分光光度法、核磁共振（NMR）和微量量热滴定法确定了相应配合物的稳定常数。通过经典分子动力学（MD）模拟获得了受体-阴离子配合物的详细结构概述。NMR 和 MD 研究的结果表明，预期结合的阴离子与环肽的酰胺基团配位。还在乙腈中进行了圆二色性（CD）滴定。据我们所知，这是首次使用 CD 光谱法检测环肽与阴离子结合的实例。CD 光谱是根据 MD 模拟获得的结构计算得出的，与实验数据定性一致。除了在乙腈中观察到二氢磷酸盐二聚体的结合外，几乎所有配合物的计量比均为 1:1（受体：阴离子）。环肽受体的亲和力与阴离子配位球的结构以及所研究溶剂的溶剂化性质有关。
