alpha - and beta -phosphorylated amines and pyrrolidines, a new class of low toxic highly sensitive 31P NMR pH indicators. Modeling of pKa and chemical shift values as a function of substituents.
Fourteen linear and cyclic alpha- and beta-aminophosphonates in which the P-atom is substituted by alkoxy groups have been synthesized and evaluated as (31)P NMR pH markers in Krebs-Henseleit buffer. pK(a) values varied with substitution in the range 1.3-9.1, giving potentially access to a wide range of pH. Temperature had a weak influence on pH and a dramatic increase in ionic strength slightly modified the pK(a) of the pyrrolidine diethyl(2-methylpyrrolidin-2-yl)phosphonate (DEPMPH). All compounds displayed a 4-fold better NMR sensitivity than inorganic phosphate or other commonly used phosphonates, as assessed by differences delta(b)-delta(a) between the chemical shifts of the protonated and the unprotonated forms. In isolated perfused rat hearts, a non-toxic concentration window of 1.5-15 mm was determined for three representative compounds. Using empirical linear relationships, the experimental values of pK(a), delta(a), and delta(b) have been correlated with the two-dimensional structure, i.e. the chemical nature of substituents bonded to the secondary amine and P-atom. The data suggest that DEPMPH and its cyclic and linear variants are ideal versatile (31)P NMR probes for the study of tenuous pH changes in biological processes.
Pietri
S
S
Structure et Réactivité des Espèces Paramagnétiques, CNRS-UMR 6517, France. pietri@srepir1.univ-mrs.fr
Miollan
M
M
Martel
S
S
Le Moigne
F
F
Blaive
B
B
Culcasi
M
M
D000588:Amines / Q000138:chemical synthesis* / Q000633:toxicity; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000138:chemical synthesis* / Q000633:toxicity; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D015233:Models, Statistical; D009206:Myocardium / Q000378:metabolism; D063065:Organophosphonates; D010477:Perfusion; D010759:Phosphorus Isotopes; D010766:Phosphorylation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011759:Pyrrolidines / Q000138:chemical synthesis* / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels; D013696:Temperature
D000588:Amines; D007202:Indicators and Reagents; D063065:Organophosphonates; D010759:Phosphorus Isotopes; D011759:Pyrrolidines; D013113:Spin Labels; C113107:diethyl(2-methyl-2-pyrrolidinyl)phosphonate