A Simple and Label-Free Detection of As3+ using 3-nitro-L-tyrosine as an As3+-chelating Ligand

Abstract

A simple and rapid As3+ detection method using 3-nitro-L-tyrosine (N-Tyr) is reported. We discovered the specific property of N-Tyr, which specifically chelates As3+. The reaction between As3+ and N-Tyr induces a prompt color change to vivid yellow, concomitantly increasing the absorbance at 430 nm. The selectivity for As3+ is confirmed by competitive binding experiments with various metal ions (Hg2+, Pb2+, Cd2+, Cr3+, Mg2+, Ni2+, Cu2+, Fe2+, Ca2+, Zn2+, and Mn2+). Also, the N-Tyr binding site, binding affinity, and As3+/N-Tyr reaction stoichiometry are investigated. The specific reaction is utilized to design a sensor that enables the quantitative detection of As3+ in the 0.1–100 μM range with good linearity (R2 = 0.995). Furthermore, the method’s applicability for the analysis of real samples, e.g., tap and river water, is successfully confirmed, with good recoveries (94.32–109.15%) using As3+-spiked real water samples. We believe that our discovering and its application for As3+ analysis can be effectively utilized in environmental analyses such as those conducted in water management facilities, with simplicity, rapidity, and ease.

Unnatural Amino Acids for Biological Spectroscopy and Microscopy

“…331−335 Recently, 3-nitrotyrosine as a fluorescent biosensor for As 3+ , Cl − and I − ions was also reported. 336,337 Similarly, it has been shown that 2-nitrotyrosine can act as a FRET quencher to Trp and has been used to study the binding structure of prolinerich peptides and SH3 domain from a yeast myosin. 312 In addition, it has been reported that several fluorotyrosines, such as 2-fluorotyrosine and 3-fluorotyrosine, can tune the fluorescence spectrum of GFP, 338,339 and that the fluorescence of 3-fluorotyrosine can be quenched by phosphate.…”

“…However, various Tyr-based UAAs have been shown to be useful as fluorescence quenchers of other biological fluorophores. − For example, 3-nitrotyrosine (3NT), which is nonfluorescent, is an efficient quencher of Tyr and Trp fluorescence, because its absorption spectrum is in the wavelength range of 300–450 nm (depending on pH, the λ ab of its neutral form is at 355 nm, whereas the λ ab of its ionized form is at 422 nm) and overlaps with the emission spectra of Tyr and Trp. , The Trp and 3NT fluorophore–quencher pair has an R 0 distance of ca. 26 Å and has been used to study protein folding and structural change, ,,− and protein–protein interactions. − Recently, 3-nitrotyrosine as a fluorescent biosensor for As 3+ , Cl – and I – ions was also reported. , Similarly, it has been shown that 2-nitrotyrosine can act as a FRET quencher to Trp and has been used to study the binding structure of proline-rich peptides and SH3 domain from a yeast myosin . In addition, it has been reported that several fluorotyrosines, such as 2-fluorotyrosine and 3-fluorotyrosine, can tune the fluorescence spectrum of GFP, , and that the fluorescence of 3-fluorotyrosine can be quenched by phosphate …”