Selective chelation of magnesium ions using phosphinate- containing ligands Christopher Hogg, J. A. Gareth Williams University of Durham, UK The magnesium ion has a well-known structural role in biology and is essential for all forms of life. However, there is still a lack of detailed understanding in how changes in Mg2+ concentrations in both cellular and extracellular environments are related to biological phenomena. There is, quite simply, a lack of water-soluble ligands that bind to Mg2+ with the necessary selectivity over Ca2+ and Zn2+, and/or Mg2+-bound bioconjugates (e.g., MgATP). For example, APTRA (o-aminophenol-N,N,O-triacetate; Figure 1) – the most popular ligating unit in commercially available Mg2+ probes – suffers heavily from interference from Ca2+ ions.[1]
Figure 1. Generalised structures of APTRA and the more Mg2+-selective APDAP Recently, we made a key step towards the creation of more Mg2+-selective sensors by developing the new ligand APDAP, an analogue of APTRA where one carboxylate binding group has been substituted for a phosphinate group (Figure 1). APDAP shows much higher selectivity for Mg2+ over Ca2+ and Zn2+, while maintaining a sufficiently high denticity to prevent interference from Mg2+-bound biomolecules. [2-4] In this presentation, we will describe a synthetic route to APDAP and a range of new derivatives from the cheap, non-toxic and readily available compound hypophosphorous acid (H3PO2). The versatile chemistry of phosphinic acids allows for the preparation of modified variants of the APDAP unit, providing a handle for tuning of important properties such as the binding profile and the lipophilicity. It also permits the inclusion of organelle targeting vectors – key to the future development of such probes for potential biological application. Current work on the incorporation of the APDAP unit into practicable, cell-permeable, luminescent probes will be discussed. References
1. E. R. H. Walter, C. Hogg, D. Parker, J. A. G Williams, Coord. Chem. Rev., 2021, 428, 213622. 2. E. R. H. Walter, M. A Fox, D. Parker, J. A. G. Williams, Dalton Trans., 2018, 47, 1879-1887. 3. E. R. H. Walter, J. A. G Williams, D. Parker, Chem. Eur. J., 2018, 24, 6432-6441. 4. E. R. H. Walter, J. A. G Williams, D. Parker, Chem. Eur. J., 2018, 24, 7724-7733.
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