New Amino-Acid-Based ß-Phosphorylated Nitroxides for Probing Acidic pH in Biological Systems by EPR Spectroscopy.
Chembiochem
; 18(3): 300-315, 2017 02 01.
Article
em En
| MEDLINE
| ID: mdl-27885767
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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Base de dados:
MEDLINE
Assunto principal:
Espectroscopia de Ressonância de Spin Eletrônica
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Organofosfonatos
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Aminoácidos
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Óxidos de Nitrogênio
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article