Abstract
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.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Chang Y. C., Graves D. J. Use of 6-fluoroderivatives of pyridoxal and pyridoxal phosphate in the study of the coenzyme function in glycogen phosphorylase. J Biol Chem. 1985 Mar 10;260(5):2709–2714. [PubMed] [Google Scholar]
- Deutsch C. J., Taylor J. S. Intracellular pH as measured by 19F NMR. Ann N Y Acad Sci. 1987;508:33–47. doi: 10.1111/j.1749-6632.1987.tb32892.x. [DOI] [PubMed] [Google Scholar]
- Deutsch C., Taylor J. S., Wilson D. F. Regulation of intracellular pH by human peripheral blood lymphocytes as measured by 19F NMR. Proc Natl Acad Sci U S A. 1982 Dec;79(24):7944–7948. doi: 10.1073/pnas.79.24.7944. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Metcalfe J. C., Hesketh T. R., Smith G. A. Free cytosolic Ca2+ measurements with fluorine labelled indicators using 19FNMR. Cell Calcium. 1985 Apr;6(1-2):183–195. doi: 10.1016/0143-4160(85)90043-0. [DOI] [PubMed] [Google Scholar]
- Smith G. A., Hesketh R. T., Metcalfe J. C., Feeney J., Morris P. G. Intracellular calcium measurements by 19F NMR of fluorine-labeled chelators. Proc Natl Acad Sci U S A. 1983 Dec;80(23):7178–7182. doi: 10.1073/pnas.80.23.7178. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Taylor J., Deutsch C. 19F-nuclear magnetic resonance: measurements of [O2] and pH in biological systems. Biophys J. 1988 Feb;53(2):227–233. doi: 10.1016/S0006-3495(88)83084-4. [DOI] [PMC free article] [PubMed] [Google Scholar]