Issue 19, 2021

Induced fit activity-based sensing: a mechanistic study of pyrophosphate detection with a “flexible” Fe-salen complex

Abstract

Activity-based sensing of biological targets is attracting increasing attention. In this work, we report detailed UV-Vis and fluorescence mechanistic studies on an Fe-salen based probe, [FeIII{salenMeCl2(SO3)2}OH2] for pyrophosphate (PPi) detection. In the presence of PPi as an analyte, the probe disassembles into its molecular subunits and releases a fluorescent signal. Our studies illustrate that the aqua form of the complex (1-OH2) is the active species and that upon substitution of Fe-coordinated H2O and an initial end-on coordination of HP2O73−, the “trapped” pyrophosphate species switches from a monodentate to a bidentate coordination mode (i.e. linkage isomerism) via a probable equilibrium process. The elusive intermediate is further stabilized by a hydrogen bonding interaction that activates the probe for the subsequent final irreversible rate-limiting step, and allows selective discrimination between the other pyrophosphate (H2P2O72− and P2O74−) species in favour of the HP2O73−. The flexible mode of molecular recognition and binding of HP2O73− by the tetradentate probe 1-OH2 is unexpected and most effective at physiological pH, and has precedence in enzymatic catalysis (i.e. induced fit principle). These binding properties explain the previously observed outstanding selectivity of 1-OH2 for pyrophosphate over other (poly)oxophosphates and potentially competing analytes.

Graphical abstract: Induced fit activity-based sensing: a mechanistic study of pyrophosphate detection with a “flexible” Fe-salen complex

Supplementary files

Article information

Article type
Research Article
Submitted
17 feb 2021
Accepted
19 mei 2021
First published
08 jun 2021
This article is Open Access
Creative Commons BY-NC license

Inorg. Chem. Front., 2021,8, 4313-4323

Induced fit activity-based sensing: a mechanistic study of pyrophosphate detection with a “flexible” Fe-salen complex

P. Yadav, O. Blacque, A. Roodt and F. Zelder, Inorg. Chem. Front., 2021, 8, 4313 DOI: 10.1039/D1QI00209K

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