Novel Sterically Crowded and Conformationally Constrained α-Aminophosphonates with a Near-Neutral pKa as Highly Accurate 31 P NMR pH Probes. Application to Subtle pH Gradients Determination in Dictyostelium discoideum Cells - Archive ouverte HAL Access content directly
Journal Articles Molecules Year : 2022

Novel Sterically Crowded and Conformationally Constrained α-Aminophosphonates with a Near-Neutral pKa as Highly Accurate 31 P NMR pH Probes. Application to Subtle pH Gradients Determination in Dictyostelium discoideum Cells

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Caroline Delehedde
  • Function : Author
  • PersonId : 1150049
Marcel Culcasi
Emilie Ricquebourg
  • Function : Author
  • PersonId : 1150051
Mathieu Cassien
  • Function : Author
  • PersonId : 1150052
Didier Siri
Bruno Blaive
  • Function : Author
  • PersonId : 1150053
Sylvia Pietri
  • Function : Author
  • PersonId : 952783

Abstract

In order to discover new 31 P NMR markers for probing subtle pH changes (<0.2 pH unit) in biological environments, fifteen new conformationally constrained or sterically hindered α-aminophosphonates derived from diethyl(2-methylpyrrolidin-2-yl)phosphonate were synthesized and tested for their pH reporting and cytotoxic properties in vitro. All compounds showed near-neutral pKas (ranging 6.28-6.97), chemical shifts not overlapping those of phosphorus metabolites, and spectroscopic sensitivities (i.e., chemical shifts variation Δδab between the acidic and basic forms) ranging from 9.2-10.7 ppm, being fourfold larger than conventional endogenous markers such as inorganic phosphate. X-ray crystallographic studies combined with predictive empirical relationships and ab initio calculations addressed the inductive and stereochemical effects of substituents linked to the protonated amine function. Satisfactory correlations were established between pKas and both the 2D structure and pyramidalization at phosphorus, showing that steric crowding around the phosphorus is crucial for modulating Δδab. Finally, the hit 31 P NMR pH probe 1b bearing an unsubstituted 1,3,2-dioxaphosphorinane ring, which is moderately lipophilic, nontoxic on A549 and NHLF cells, and showing pKa = 6.45 with Δδab = 10.64 ppm, allowed the first clear-cut evidence of trans-sarcolemmal pH gradients in normoxic Dictyostelium discoideum cells with an accuracy of <0.05 pH units.
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hal-03723716 , version 1 (15-07-2022)

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Attribution - CC BY 4.0

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Caroline Delehedde, Marcel Culcasi, Emilie Ricquebourg, Mathieu Cassien, Didier Siri, et al.. Novel Sterically Crowded and Conformationally Constrained α-Aminophosphonates with a Near-Neutral pKa as Highly Accurate 31 P NMR pH Probes. Application to Subtle pH Gradients Determination in Dictyostelium discoideum Cells. Molecules, 2022, 27 (14), pp.4506. ⟨10.3390/molecules27144506⟩. ⟨hal-03723716⟩
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