New Amino‐Acid‐Based β‐Phosphorylated Nitroxides for Probing Acidic pH in Biological Systems by EPR Spectroscopy |
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| Authors: | Dr Sophie Thétiot‐Laurent Dr Gaëlle Gosset Dr Jean‐Louis Clément Dr Mathieu Cassien Dr Anne Mercier Dr Didier Siri Anouk Gaudel‐Siri Prof Antal Rockenbauer Dr Marcel Culcasi Dr Sylvia Pietri |
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| Affiliation: | 1. Aix Marseille Univ, CNRS, ICR, UMR 7273, Marseille, France;2. Research Centre for Natural Sciences of the Hungarian Academy of Sciences, Institute of Materials and Environmental Chemistry, Budapest University of Technology and Economics, Budapest, Hungary |
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| Abstract: | There is increasing interest in measuring pH in biological samples by using nitroxides with pH‐dependent electron paramagnetic resonance (EPR) spectra. Aiming to improve the spectral sensitivity (ΔaX) of these probes (i.e., the difference between the EPR hyperfine splitting (hfs) in their protonated and unprotonated forms), we characterized a series of novel linear α‐carboxy, α′‐diethoxyphosphoryl nitroxides constructed on an amino acid core and featuring an (α or α′)‐C?H bond. In buffer, the three main hfs (aN, aH, and aP) of their EPR spectra vary reversibly with pH and, from aP or aH titration curves, a two‐ to fourfold increase in sensitivity was achieved compared to reference imidazoline or imidazolidine nitroxides. The crystallized carboxylate 10 b (pKa ≈3.6), which demonstrated low cytotoxicity and good resistance to bioreduction, was applied to probe stomach acidity in rats. The results pave the way to a novel generation of highly sensitive EPR pH markers. |
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| Keywords: | EPR spectroscopy molecular dynamics nitroxide sensors stomach acidity |
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