New class of 19F pH indicators: fluoroanilines

The pH dependence of the 19F chemical shift has been characterized for a number of fluorine-substituted aniline derivatives. These compounds constitute a new class of 19F nuclear magnetic resonance (NMR) pH indicators, characterized by single 19F resonance lines with sensitivities ranging from 2 to...

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Bibliographic Details
Published in:Biophysical journal 1989-04, Vol.55 (4), p.799-804
Main Authors: Deutsch, C.J., Taylor, J.S.
Format: Article
Language:English
Subjects:
Aniline Compounds
Cells, Cultured
DNA Replication
Fluorine
Humans
Hydrogen-Ion Concentration
Indicators and Reagents
Lymphocytes - metabolism
Magnetic Resonance Spectroscopy - methods
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Summary:The pH dependence of the 19F chemical shift has been characterized for a number of fluorine-substituted aniline derivatives. These compounds constitute a new class of 19F nuclear magnetic resonance (NMR) pH indicators, characterized by single 19F resonance lines with sensitivities ranging from 2 to 7 ppm/pH unit near the aniline pKa; total shifts between conjugate acid and base of 5–15 ppm; and pKas ranging from 1 to 7. One compound, N,N-(methyl-2-carboxyisopropyl)-4-fluoroaniline, has a pKa of 6.8 and a sensitivity of 5 ppm/pH unit. This compound displays significant broadening of its 19F resonance near the aniline pKa (6.8), due to a decreased rate of exchange between conjugate acid and base species. Our results are consistent with slow dissociation of an intramolecular hydrogen bond in the zwitterionic species that limits the exchange rate between protonated and unprotonated forms for N,N-(methyl-2-carboxyisopropyl)-4-fluoroaniline.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(89)82879-6