Rosamine derivatives of o-aminothiophenol-triacetate (S-APTRA): a new class of selective fluorescent sensors for Zn².

Authors

Laura L Duncan, Dominic J Black, Robert Pal, J A Gareth Williams

Published in

Organic & biomolecular chemistry. Jul 07, 2026. Epub Jul 07, 2026.

Abstract

The Zn²⁺ ion has crucial roles in biology, such that the development of fluorescent probes for real-time monitoring of fluctuations in its concentration remains important. We describe a new class of probe that utilizes ortho-aminothiophenol-N,N,S-triacetate (S-APTRA) as the binding site for the metal ion, recently reported to bind Zn²⁺ with high selectivity over Ca²⁺ and Mg²⁺. The S-APTRA unit has been appended with a rosamine fluorophore by a sequence of formylation, condensation with 3-(dimethylamino)phenol, and oxidation. The resulting conjugate S-APTRA-Rosamine fluoresces only weakly in aqueous solution, but its emission is greatly enhanced by Zn²⁺, probably due to the suppression of a photoinduced electron transfer (PET) quenching process. The probe binds Zn²⁺ with a dissociation constant, K_d, of 55.7 ± 1.2 nM, matching well with [Zn²⁺] in many biological cells, with very high selectivity over Ca²⁺ and Mg²⁺, and with attractively low-energy emission in the orange-red region. A proof-of-concept imaging experiment in NIH 3T3 cells reveals that the probe can successfully signal changes in [Zn²⁺] by confocal fluorescence microscopy. Meanwhile, a tetradentate analogue omitting the S-bonded carboxylate also responds to Zn²⁺ but the affinity is tempered by a factor of around 10³. Sulfoxide derivatives of the two systems show no response.

PMID:
42411345
Bibliographic data and abstract were imported from PubMed on 07 Jul 2026.

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