31P NMR measurements of intracellular pH in erythrocytes: Direct comparison with measurements using freeze-thaw and investigation into the influence of ionic strength and Mg2+
✍ Scribed by Aqqaluk Petersen; Jens Peter Jacobsen; Mogens Hørder
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- English
- Weight
- 490 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
The pH-dependent chemical shift behavior in "P NMR spectroscopy of inorganic phosphate (P,) and methylphosphonic acid (MeP) in solutions of various composition at 37°C are presented. An ionic strength dependent lowering of the pK. values of both P, and MeP is observed. 3 mmol/liter Mg2+ did not affect the pH-dependent chemical shift behavior of P, and MeP in solutions containing 135 mmol/liter KCI and 5 mmol/liter NaCI. This finding: was reinforced by adding 5 mmol/liter 2,3-diphosphoglycerate (2,3-DPG) and 1.5 mmol/liter ATP to solutions with 3 mmol/liter Mgz+. The presence of these Mg+-binding substaiices had no detectable effect on the chemical shift of P, and MeP at various pH values The pH dependence of the chemical shift of MeP, P,, and 2,3-DPG in oxygenated erythrolysates was compared to protein free model solutions. No significant differences could be detected for MeP and P, whereas there was a change in the chemical shift of about 0.1-0.2 ppm for both phosphates in 2,3-DPG. Finally intracellular pH estimated by "P NMR were compared to pH measured by electrode in freeze-thawed hemolysates. At an extracellular pH of 7.341 k 0.045 (SD) (n = 6) the intracellular pH was 7.160 f 0.014 (SD) by the freeze-thaw procedure and 7.213 f 0.027 (SD), 7.172 t-0.029 (SD), and 7.152 f 0.033 (SD) estimated by the chemical shift of MeP, and 3-phosphorus and 2-phosphorus of 2,3-DPG, respectively. o 1987 Academic press, Inc