NMR Study of Ionization of Biological Phosphates and Imidazole in Solutions and Gels

• Published in: Cryobiology Vol. 33; no. 1; pp. 62 - 69
• Main Authors: BURT, C.T., YANG, M., KOCH, R.L.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01-02-1996; Elsevier
• Subjects: Biological and medical sciences; Diverse techniques; Fundamental and applied biological sciences. Psychology; Molecular and cellular biology; Solvent effect; Phosphates; Organic solvent; NMR spectrometry; Investigation method; Biological material
• ISSN: 0011-2240; 1090-2392
• DOI: 10.1006/cryo.1996.0007

The use of nuclear magnetic resonance (NMR) spectroscopy for the study of the neutralization of inorganic phosphate or imidazole in H2O, dimethyl sulfoxide as an aqueous solution, and HPC (Klucel, HF grade, hydroxypropyl cellulose) gel was demonstrated. The results reaffirmed that the apparent pKaof a biological buffer can change to either the alkaline or the acidic side depending on the nature of the buffer and the mixed solvent systems used. The effect of temperature on pKaof the buffer system was also studied. A series of phosphates encountered in body tissues had their pKa's determined simultaneously at several temperatures in either saline or 10% glycerol. Little difference in pKa's was seen between saline and 10% glycerol. The state of ionization of an NMR observable species can be measured and related to a pH scale in any of these solvents. And of most interest, if the extremes of chemical shifts are known, the state of ionization can be calculated without reference to a pH.