A tryptophan-containing open-chain framework for tuning a high selectivity for Ca2+ and 13C NMR observation of a
1Neurochemistry and Physical Organic Chemistry, Nankai University, Tianjin 300071, China.
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.
Related Concept Videos
NMR Spectroscopy of Aromatic Compounds
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
¹³C NMR: ¹H–¹³C Decoupling
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
NMR Spectroscopy Of Amines
Chemical Shift: Internal References and Solvent Effects
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)


![Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F63025.jpg&w=3840&q=50)