title: A tryptophan-containing open-chain framework for tuning a high selectivity for Ca2+ and 13C NMR observation of a Ca2+-indole interaction in aqueous solution.
abstract: Two molecular architectures featuring the cation-responsive tryptophan indole were designed and investigated for the development of a novel fluorescent chemosensor for Ca2+. We observed that the Trp-based open-framework chemosensor EW2 exhibits remarkable selectivity for Ca2+ over Mg2+, Ba2+, K+, Na+, and Li+ in water between pH 4.6 and 7.0 on the basis of Ca2+-induced high fluorescence enhancement of the Trp residue. A combined 13C NMR and CD spectroscopic study has demonstrated a dynamic reorientation of the indole ring due to the cation-indole interaction accompanying the Ca2+-induced dramatic fluorescence enhancement. The results suggest that the highly sensitive, metal-ion-dependent Trp indolyl C(3) chemical shifts may serve as a promising indicator for monitoring metal ion-indole noncovalent interaction in solution.
authors.affiliation: Neurochemistry and Physical Organic Chemistry, Nankai University, Tianjin 300071, China.
authors.forename: Yitong
authors.initials: Y
authors.lastname: Li
authors.forename: Chi Ming
authors.initials: CM
authors.lastname: Yang
mesh_terms: D002118:Calcium / Q000032:analysis / Q000737:chemistry*; D002247:Carbon Isotopes; D002413:Cations, Divalent; D008274:Magnesium / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D002413:Cations, Divalent; D014364:Tryptophan; D008274:Magnesium; D002118:Calcium