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Li T, Liao Y, Jiang X, Mu D, Hou X, Zhang C, Deng P. pH detection in biological samples by 1D and 2D 1H- 31P NMR. Talanta 2017; 178:538-544. [PMID: 29136859 DOI: 10.1016/j.talanta.2017.09.085] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 09/19/2017] [Accepted: 09/30/2017] [Indexed: 11/29/2022]
Abstract
The chemical shifts of several important endogenous phosphorus compounds under different pH conditions were explored, including adenosine-5'-triphosphate, adenosine-5'-diphosphate, adenosine-5'-monophosphate, phosphorylcholine and phosphorylethanolamine. Their 31P NMR and 1H NMR chemical shifts were all pH-sensitive in the similar pH range. Two dimensional (2D) 1H-31P NMR spectra were found helpful to identify these endogenous phosphorus markers in biological samples from rather complicated NMR spectra. Herein, for the first time, a pH sensor based on 2D 1H-31P NMR was established and applied to biological samples analysis with pH values determined in good agreement with those by potentiometric method. Apart from being simple, green, rapid and less sample-consuming, information concerning both the endogenous phosphorus markers and pH status could be attained in a single NMR run, which demonstrated the great potential of this method in rare sample analysis and even disease diagnosis.
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Affiliation(s)
- Ting Li
- College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, China
| | - Yong Liao
- Institute for Viral Hepatitis, Department of Infectious Diseases, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, China
| | - Xiaoyan Jiang
- Institute for Viral Hepatitis, Department of Infectious Diseases, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, China
| | - Di Mu
- Institute for Viral Hepatitis, Department of Infectious Diseases, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, China
| | - Xiandeng Hou
- College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, China; Analytical & Testing Center, Sichuan University, Chengdu, Sichuan 610064, China
| | - Chunchun Zhang
- Analytical & Testing Center, Sichuan University, Chengdu, Sichuan 610064, China
| | - Pengchi Deng
- Analytical & Testing Center, Sichuan University, Chengdu, Sichuan 610064, China.
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Thétiot-Laurent S, Gosset G, Clément JL, Cassien M, Mercier A, Siri D, Gaudel-Siri A, Rockenbauer A, Culcasi M, Pietri S. New Amino-Acid-Based β-Phosphorylated Nitroxides for Probing Acidic pH in Biological Systems by EPR Spectroscopy. Chembiochem 2016; 18:300-315. [DOI: 10.1002/cbic.201600550] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Indexed: 01/06/2023]
Affiliation(s)
- Sophie Thétiot-Laurent
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
| | - Gaëlle Gosset
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
| | - Jean-Louis Clément
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
| | - Mathieu Cassien
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
| | - Anne Mercier
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
| | - Didier Siri
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
| | - Anouk Gaudel-Siri
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
| | - Antal Rockenbauer
- Research Centre for Natural Sciences of the Hungarian Academy of Sciences; Institute of Materials and Environmental Chemistry; Budapest University of Technology and Economics; 1117 Budapest Hungary
| | - Marcel Culcasi
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
| | - Sylvia Pietri
- Aix Marseille Univ; CNRS; ICR; UMR 7273; Avenue Escadrile Normandie Niemen 13397 Marseille France
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Couldwell DL, Dunford R, Kruger NJ, Lloyd DC, Ratcliffe RG, Smith AMO. Response of cytoplasmic pH to anoxia in plant tissues with altered activities of fermentation enzymes: application of methyl phosphonate as an NMR pH probe. ANNALS OF BOTANY 2009; 103:249-58. [PMID: 18824473 PMCID: PMC2707310 DOI: 10.1093/aob/mcn174] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 07/10/2008] [Accepted: 07/29/2008] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS Acidification of the cytoplasm is a commonly observed response to oxygen deprivation in plant tissues that are intolerant of anoxia. The response was monitored in plant tissues with altered levels of lactate dehydrogenase (LDH) and pyruvate decarboxylase (PDC) with the aim of assessing the contribution of the targeted enzymes to cytoplasmic pH (pH(cyt)) regulation. METHODS The pH(cyt) was measured by in vivo (31)P nuclear magnetic resonance (NMR) spectroscopy using methyl phosphonate (MeP) as a pH probe. The potential toxicity of MeP was investigated by analysing its effect on the metabolism of radiolabelled glucose. KEY RESULTS MeP accumulated to detectable levels in the cytoplasm and vacuole of plant tissues exposed to millimolar concentrations of MeP, and the pH-dependent (31)P NMR signals provided a convenient method for measuring pH(cyt) values in tissues with poorly defined signals from the cytoplasmic inorganic phosphate pool. Pretreatment of potato (Solanum tuberosum) tuber slices with 5 mm MeP for 24 h did not affect the metabolism of [U-(14)C]glucose or the pattern of (14)CO(2) release from specifically labelled [(14)C]-substrates. Time-courses of pH(cyt) measured before, during and after an anoxic episode in potato tuber tissues with reduced activities of LDH, or in tobacco (Nicotiana tabacum) leaves with increased activities of PDC, were indistinguishable from their respective controls. CONCLUSIONS MeP can be used as a low toxicity (31)P NMR probe for measuring intracellular pH values in plant tissues with altered levels of fermentation enzymes. The measurements on transgenic tobacco leaves suggest that the changes in pH(cyt) during an anoxic episode are not dominated by fermentation processes; while the pH changes in the potato tuber tissue with reduced LDH activity show that the affected isozymes do not influence the anoxic pH response.
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Affiliation(s)
| | | | - N. J. Kruger
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | | | - R. G. Ratcliffe
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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4
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Gosset G, Satre M, Blaive B, Clément JL, Martin JB, Culcasi M, Pietri S. Investigation of subcellular acidic compartments using α-aminophosphonate 31P nuclear magnetic resonance probes. Anal Biochem 2008; 380:184-94. [DOI: 10.1016/j.ab.2008.05.052] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Revised: 05/19/2008] [Accepted: 05/30/2008] [Indexed: 10/22/2022]
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5
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Gosset G, Martel S, Clément JL, Blaive B, Olive G, Culcasi M, Rosas R, Thévand A, Pietri S. Nouveaux marqueurs de pH utilisables en RMN du 31P. Détermination de la relaxation longitudinale en fonction de la structure chimique, de la température, du pH et du milieu biologique. CR CHIM 2008. [DOI: 10.1016/j.crci.2007.08.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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6
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Potapenko DI, Foster MA, Lurie DJ, Kirilyuk IA, Hutchison JMS, Grigor'ev IA, Bagryanskaya EG, Khramtsov VV. Real-time monitoring of drug-induced changes in the stomach acidity of living rats using improved pH-sensitive nitroxides and low-field EPR techniques. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 182:1-11. [PMID: 16798033 DOI: 10.1016/j.jmr.2006.06.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Revised: 04/18/2006] [Accepted: 06/04/2006] [Indexed: 05/10/2023]
Abstract
New improved pH-sensitive nitroxides were applied for in vivo studies. An increased stability of the probes towards reduction was achieved by the introduction of the bulky ethyl groups in the vicinity of the paramagnetic NO fragment. In addition, the range of pH sensitivity of the approach was extended by the synthesis of probes with two ionizable groups, and, therefore, with two pKa values. Stability towards reduction and spectral characteristics of the three new probes were determined in vitro using 290 MHz radiofrequency (RF)- and X-band electron paramagnetic resonance (EPR), longitudinally detected EPR (LODEPR), and field-cycled dynamic nuclear polarization (FC-DNP) techniques. The newly synthesized probe, 4-[bis(2-hydroxyethyl)amino]-2-pyridine-4-yl-2,5,5-triethyl-2,5-dihydro-1H-imidazol-oxyl, was found to be the most appropriate for the application in the stomach due to both higher stability and convenient pH sensitivity range from pH 1.8 to 6. LODEPR, FC-DNP and proton-electron double resonance imaging (PEDRI) techniques were used to detect the nitroxide localization and acidity in the rat stomach. Improved probe characteristics allowed us to follow in vivo the drug-induced perturbation in the stomach acidity and its normalization afterwards during 1 h or longer period of time. The results show the applicability of the techniques for monitoring drug pharmacology and disease in the living animals.
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Bergans N, Dresselaers T, Vanhamme L, Van Hecke P, Van Huffel S, Vanstapel F. Quantification of the glycogen 13C-1 NMR signal during glycogen synthesis in perfused rat liver. NMR IN BIOMEDICINE 2003; 16:36-46. [PMID: 12577296 DOI: 10.1002/nbm.812] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We studied glycogen synthesis from glucose in perfused livers of fed (n = 4) and 24 h starved (n = 7) rats. Glycogenolysis was inhibited by BAY R3401 (150 microM) and proglycosyn (100 microM). After 60 min, we replaced 99% (13)C-1 glucose by natural abundance glucose. This pulse-chase design allowed us to recognize residual ongoing futile glycogen turnover from the release of initially deposited (13)C-label, into the (13)C-free chase medium. Net residual turnover was less than 2 +/- 0.7% and 0.6 +/- 0.2% of 1-(13)C glycogen deposition rates of 0.31 +/- 0.04 and 0.99 +/- 0.04 micromol glucose g(-1) min(-1), in starved and fed livers, respectively. The 1-(13)C glycogen signal was monitored throughout the experiment with proton-decoupled (13)C NMR spectroscopy and analyzed in the time domain using AMARES. We noticed progressive line-broadening in any single experiment in the chase phase. One or a sum of two to three overlapping Lorentzians, with different exponential damping factors, were fitted to the signal. When the S/N was better than 40, the fit always delivered a small and a broad component. In the chase phase, the fit with a single Lorentzian resulted in a decline of glycogen signal by about 15 +/- 4 and 12 +/- 2% in starved and fed rats, respectively. This apparent decline in 1-(13)C glycogen signal could not be accounted for by the appearance of equivalent amounts of (13)C-labeled metabolites in the perfusate. The fit with a sum of two Lorentzians resulted in a decline of glycogen signal intensity of 7 +/- 5 and 5 +/- 3% in starved and fed rats, respectively, which reduced the apparent turnover to 8 +/- 9% and 6 +/- 4%, respectively. Quantification of the growing (13)C-1 glycogen signal requires a model function that accommodates changes in line shape throughout the period under study.
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Affiliation(s)
- N Bergans
- Biomedische NMR Eenheid, Afdeling Röntgendiagnose, Katholieke Universiteit Leuven, Leuven, Belgium
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8
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Martel S, Clément JL, Muller A, Culcasi M, Pietri S. Synthesis and 31P NMR characterization of new low toxic highly sensitive pH probes designed for in vivo acidic pH studies. Bioorg Med Chem 2002; 10:1451-8. [PMID: 11886807 DOI: 10.1016/s0968-0896(01)00414-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
With the aim to provide sensitive 31P NMR probes of intra- and extracellular pH gradients that may reach cellular acidic compartments in biological systems, new alpha-aminophosphonates were designed to meet basic requirements such as a low pK(a)s and a great chemical difference (Deltadelta(ab)) between the limiting 31P NMR chemical shifts in acidic (delta(a)) and basic (delta(b)) media. A series of six phosphorylated pyrrolidines and linear aminophosphonates were synthesized using aminophosphorylation reactions and were screened for cytotoxicity on cultured Müller cells. Among the compounds not being toxic under these conditions, three molecules were selected since they displayed the best in vitro (in several phosphate buffers and in a cytosol-like solution) properties as 31P NMR acidic pH markers, that is 3, 5 and 9, having the pK(a) values of 3.63, 5.89 and 5.66, respectively. The Deltadelta(ab) values of these pH markers were at least 3 times larger than that of standard 31P NMR probes, with a low sensitivity to ionic strength changes. From these data, it was proposed that 3, 5 and 9 could be used as reporting probes of subtle proton movements in acidic compartments, an area that still remains poorly investigated using non invasive 31P NMR methods.
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Affiliation(s)
- Sophie Martel
- Laboratoire Structure et Réactivité des Espèces Paramagnétiques, CNRS-UMR 6517 Universités d'Aix-Marseille I & III, Marseille, France
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9
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Pietri S, Martel S, Culcasi M, Delmas-Beauvieux MC, Canioni P, Gallis JL. Use of diethyl(2-methylpyrrolidin-2-yl)phosphonate as a highly sensitive extra- and intracellular 31P NMR pH indicator in isolated organs. Direct NMR evidence of acidic compartments in the ischemic and reperfused rat liver. J Biol Chem 2001; 276:1750-8. [PMID: 11013264 DOI: 10.1074/jbc.m008023200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The novel phosphorylated pyrrolidine diethyl(2-methylpyrrolidin-2-yl)phosphonate (DEPMPH) was evaluated as a (31)P NMR probe of the pH changes associated with ischemia/reperfusion of rat isolated hearts and livers. In vitro titration curves indicated that DEPMPH exhibited a 4-fold larger amplitude of chemical shift variation than inorganic phosphate yielding an enhanced NMR sensitivity in the pH range of 5.0-7.5 that allowed us to assess pH variations of less than 0.1 pH units. At the non-toxic concentration of 5 mm, DEPMPH distributed into external and cytosolic compartments in both normoxic organs, as assessed by the appearance of two resonance peaks. An additional peak was observed in normoxic and ischemic livers, assigned to DEPMPH in acidic vesicles (pH 5.3-5.6). During severe myocardial ischemia, a third peak corresponding to DEPMPH located in ventricular and atrial cavities appeared (pH 6.9). Mass spectrometry and NMR analyses of perchloric extracts showed that no significant metabolism of DEPMPH occurred in the ischemic liver. Reperfusion with plain buffer resulted in a rapid washout of DEPMPH from both organs. It was concluded that the highly pH-sensitive DEPMPH could be of great interest in noninvasive ex vivo studies of pH gradients that may be involved in many pathological processes.
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Affiliation(s)
- S Pietri
- Structure et Réactivité des Espèces Paramagnétiques, CNRS-UMR 6517 Universités d'Aix-Marseille I et III, F-13397 Marseille Cedex 20, France.
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10
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Sun Y, Sugawara M, Mulkern RV, Hynynen K, Mochizuki S, Albert M, Zuo CS. Simultaneous measurements of temperature and pH in vivo using NMR in conjunction with TmDOTP5-. NMR IN BIOMEDICINE 2000; 13:460-466. [PMID: 11252031 DOI: 10.1002/nbm.676] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
NMR techniques for temperature and pH measurements have attracted increasing interest in recent years, motivated in part by the growing importance of medical hyperthermia for the treatment of cancer. The chemical shifts of thulium 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetrakis(methylene phosphonate) (TmDOTP5-) have been studied as a function of temperature and pH. The results demonstrate that TmDOTP5- resonance shifts are highly sensitive to temperature (approximately 1.0 ppm/degrees C) and pH (approximately 3.2 ppm/pH unit) at clinically relevant field strengths. A new method is presented which utilizes two magnetically non-equivalent protons in TmDOTP5- for simultaneous NMR measurements of both temperature and pH. The difference in the chemical shift values of pairs of 1H resonances provides a temperature sensitivity of about 1.6 ppm/ degrees C. The technique is demonstrated in live rats undergoing ultrasound-induced hyperthermia therapy.
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Affiliation(s)
- Y Sun
- Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
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Vidal G, Thiaudiere E, Canioni P, Gallis JL. Aminomethylphosphonate and 2-aminoethylphosphonate as (31)P-NMR pH markers for extracellular and cytosolic spaces in the isolated perfused rat liver. NMR IN BIOMEDICINE 2000; 13:289-296. [PMID: 10960919 DOI: 10.1002/1099-1492(200008)13:5<289::aid-nbm647>3.0.co;2-g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Aminomethylphosphonate (NMePo) and 2-aminoethylphosphonate (NEthPo) were evaluated as alternative pH indicators in the isolated perfused rat liver using (31)P-nuclear magnetic resonance (NMR). NMePo did not distribute within cells and remained in the extracellular space. It exhibited pH titration with a low pK(a) value (5.35). This behaviour makes NMePo useful for extracellular volume or acidic pH determination. In contrast, NEthPo accumulated within cells without altering liver energetic steady state, evaluated from nucleosides triphosphates resonances, even for prolonged (100 min) experiments. Withdrawal of NEthPo from perfusate revealed a residual resonance corresponding to the internalized amount of this phosphonate. This fraction was almost stable vs time and allowed determination of spin-lattice relaxation time constant T(1) within the liver (2.2 +/- 0.3 s; n = 6). Comparison of the titration curves for NEthPo and inorganic phosphate revealed that the accuracy of pH determination within physiologic or acidic range in both cases was comparable. Finally, when extracellular pH was decreased, the NEthPo resonance frequency was found to undergo the same chemical shift variations as observed for cytosolic P(i) signal, which was in good agreement with a cytosolic accumulation of this phosphonate. Therefore, NEthPo could be considered as an interesting cytosolic pH probe suitable for (31)P-NMR measurements, especially when experimental conditions prevent reliable observation of cytosolic Pi resonance.
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Affiliation(s)
- G Vidal
- Résonance Magnétique des Systèmes Biologiques, UMR 5536 CNRS/Université Victor Segalen Bordeaux 2, Bordeaux Cedex, France
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Pietri S, Miollan M, Martel S, Le Moigne F, Blaive B, Culcasi M. 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. J Biol Chem 2000; 275:19505-12. [PMID: 10748044 DOI: 10.1074/jbc.m001784200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
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.
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Affiliation(s)
- S Pietri
- Structure et Réactivité des Espèces Paramagnétiques, CNRS-UMR 6517, France.
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Bruynseels K, Van Hecke P, Vanstapel F. Further observations on the uptake and effects of phosphonates in perfused rat liver studied by (31)P-NMR. NMR IN BIOMEDICINE 1999; 12:275-285. [PMID: 10484816 DOI: 10.1002/(sici)1099-1492(199908)12:5<275::aid-nbm567>3.0.co;2-s] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We examined the route of uptake of 2-aminoethylphosphonate (NEthPo) and of phenylphosphonate (PhePo; 10 mM each) in perfused liver by (31)P-NMR. Uptake of NEthPo was concentrative. The rate of uptake was reduced to 21 +/- 2% (n = 3; all percentages refer to control rates) by substituting choline for Na(+), and to 21 +/- 4% (n = 3), 32 +/- 6% (n = 5) and 70 +/- 5% (n = 3) by replacing Cl(-) by gluconate, SO(4)(2-) or NO(3)(-), respectively. Taurine (20 mM) reduced NEthPo uptake to 38 +/- 6% (n = 3). The data are consistent with uptake of NEthPo by the Na(+)-coupled Cl(-)-dependent beta-amino acid transporter. A small fraction of NEthPo was incorporated into phospholipid. PhePo uptake evolved over 1 h towards levels of the membrane-permeant volume marker dimethyl methylphosphonate. Uptake depended on H(+), and was inhibited by 4, 4'-diisothiocyanato-stilbene-2,2'-disulphonic acid (100 microM), bumetanide and furosemide (1 mM each) and alpha-cyano-4-OH-cinnamic acid (5 mM) to 31 +/- 4% (n = 4), 28 +/- 4% (n = 4), 27 +/- 5% (n = 6) and 40 +/- 7% (n = 4), respectively. These characteristics of PhePo uptake are reminiscent of H(+)-coupled monocarboxylate transport. The monocarboxylates, lactate and acetate (20 mM), and the substrate analogue, phenylalanine (20 mM), were not inhibitory, while benzoic acid (20 mM) slightly inhibited (to 82 +/- 5%; n = 4) PhePo uptake. The tested phosphonates (10 mM) did not significantly affect hepatic extraction of [(3)H]-cholate or [(3)H]-taurocholate (25 microM each; 1:3 bile salt:albumin). The monocarboxylate analogue, PhePo (10 mM), did not significantly interfere with disposal of lactate (0.3-5 mM).
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Affiliation(s)
- K Bruynseels
- Biomedical NMR Unit, Department of Radiology, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Herestraat 49, B-3000, Leuven, Belgium
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