Enhanced Binding of Zn2+ Using a Sulfur Version of o-Aminophenol-Triacetate (APTRA): Introducing S-APTRA and Derivatives
Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Ortho -aminophenol- N,N,O -triacetate (APTRA) is a pentadentate ligand adopted for the selective binding of Mg 2+ . It has been incorporated into fluorescent sensors for Mg 2+, though it binds Ca 2+ and Zn 2+ more avidly. Here, the synthesis of a sulfur analogue of APTRA is reported, namely ortho -aminothiophenol- N,N,S -triacetate, referred to as S-APTRA. The binding of this new pentadentate ligand to Zn 2+, Ca 2+, and Mg 2+ has been monitored in buffered aqueous solution by UV absorption spectroscopy. The replacement of the phenolic oxygen of APTRA by a sulfur atom renders S-APTRA capable of binding Zn 2+ in a biologically relevant range ( K d = 6.6 ± 0.3 nM) with high selectivity over Mg 2+ and Ca 2+ . The enhanced selectivity for Zn 2+ is in line with the principles of “hard and soft acids and bases.” A tetradentate analogue omitting the S-appended carboxylate group, S-APDIA, is also reported. Its lower denticity leads to decreased affinity for Zn 2+ ( K d = 8 ± 1 μM). The oxidation of S-APTRA and S-APDIA by m -CPBA leads to the sulfoxides SO-APTRA and SO-APDIA, which bind Zn 2+ yet more weakly ( K d = 260 ± 20 mM and 3.6 ± 0.3 mM, respectively). This new family of ligands may prove appealing in the development of new carboxylate-based zinc sensors.
Source: Inorganic Chemistry
Authors: Christopher Hogg, Laura L. Duncan, David Parker, J. A. Gareth Williams
Institution: Durham University
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Funder: Durham University
OpenAlex ID: W4410161564