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Dören R, Panthöfer M, Prädel L, Tremel W, Mondeshki M. Lithium confinement and dynamics in hexagonal and monoclinic tungsten oxide nanocrystals: a 7Li solid state NMR study. Nanoscale 2022; 14:15348-15363. [PMID: 36218075 DOI: 10.1039/d2nr02492f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Mixed-valence tungsten bronzes AxWO3 (A = alkali metal, NH4+, etc.) are a series of compounds with adaptive structural and compositional features that make them a hot research topic in thermoelectrics, electrochromics, catalysis or energy applications in battery electrodes. The mixed hexagonal lithium ammonium bronze Lix(NH4)yWO3 is a new member of this structural family whose properties are compared to those of the pure hexagonal tungsten bronze (NH4)xWO3. Surface and structural (nanoconfined) Li+ cations were characterized by 7Li single pulse excitation and 1H-7Li cross-polarization (CP) NMR experiments. CP build-up curves and two-dimensional heteronuclear correlation solid-state NMR techniques provide information about the spatial connectivity between different proton and Li+ species. At 500 °C the bronze structurally transforms from the hexagonal to a monoclinic phase, and defects are formed that are characterized through the Li+ environment. 7Li exchange spectroscopy (EXSY) NMR experiments provide information about the chemical exchange between the lithium species. The measured 7Li T1 and T2 relaxation time constants and the T1/T2 ratio allow characterizing the local strength of Li+ binding.
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Affiliation(s)
- René Dören
- Department Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, D-55128 Mainz, Germany.
| | - Martin Panthöfer
- Department Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, D-55128 Mainz, Germany.
| | - Leon Prädel
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Wolfgang Tremel
- Department Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, D-55128 Mainz, Germany.
| | - Mihail Mondeshki
- Department Chemie, Johannes Gutenberg-Universität, Duesbergweg 10-14, D-55128 Mainz, Germany.
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Abstract
NMR spectroscopy has been applied to cells and tissues analysis since its beginnings, as early as 1950. We have attempted to gather here in a didactic fashion the broad diversity of data and ideas that emerged from NMR investigations on living cells. Covering a large proportion of the periodic table, NMR spectroscopy permits scrutiny of a great variety of atomic nuclei in all living organisms non-invasively. It has thus provided quantitative information on cellular atoms and their chemical environment, dynamics, or interactions. We will show that NMR studies have generated valuable knowledge on a vast array of cellular molecules and events, from water, salts, metabolites, cell walls, proteins, nucleic acids, drugs and drug targets, to pH, redox equilibria and chemical reactions. The characterization of such a multitude of objects at the atomic scale has thus shaped our mental representation of cellular life at multiple levels, together with major techniques like mass-spectrometry or microscopies. NMR studies on cells has accompanied the developments of MRI and metabolomics, and various subfields have flourished, coined with appealing names: fluxomics, foodomics, MRI and MRS (i.e. imaging and localized spectroscopy of living tissues, respectively), whole-cell NMR, on-cell ligand-based NMR, systems NMR, cellular structural biology, in-cell NMR… All these have not grown separately, but rather by reinforcing each other like a braided trunk. Hence, we try here to provide an analytical account of a large ensemble of intricately linked approaches, whose integration has been and will be key to their success. We present extensive overviews, firstly on the various types of information provided by NMR in a cellular environment (the "why", oriented towards a broad readership), and secondly on the employed NMR techniques and setups (the "how", where we discuss the past, current and future methods). Each subsection is constructed as a historical anthology, showing how the intrinsic properties of NMR spectroscopy and its developments structured the accessible knowledge on cellular phenomena. Using this systematic approach, we sought i) to make this review accessible to the broadest audience and ii) to highlight some early techniques that may find renewed interest. Finally, we present a brief discussion on what may be potential and desirable developments in the context of integrative studies in biology.
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Affiliation(s)
- Francois-Xavier Theillet
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
| | - Enrico Luchinat
- Dipartimento di Scienze e Tecnologie Agro-Alimentari, Alma Mater Studiorum - Università di Bologna, Piazza Goidanich 60, 47521 Cesena, Italy; CERM - Magnetic Resonance Center, and Neurofarba Department, Università degli Studi di Firenze, 50019 Sesto Fiorentino, Italy
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Abstract
In this chapter, we review the mechanism of action of lithium salts from a chemical perspective. A description on how lithium salts are used to treat mental illnesses, in particular bipolar disorder, and other disease states is provided. Emphasis is not placed on the genetics and the psychopharmacology of the ailments for which lithium salts have proven to be beneficial. Rather we highlight the application of chemical methodologies for the characterization of the cellular targets of lithium salts and their distribution in tissues.
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Mota de Freitas D, Castro MMCA, Geraldes CFGC. Is competition between Li+ and Mg2+ the underlying theme in the proposed mechanisms for the pharmacological action of lithium salts in bipolar disorder? Acc Chem Res 2006; 39:283-91. [PMID: 16618096 DOI: 10.1021/ar030197a] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Lithium salts have been in use for the treatment of bipolar disorder for more than 50 years, but their pharmacological mode of action remains a matter of conjecture. Li(+) and Mg(2+) share many physicochemical properties. Not surprisingly, many reported cellular targets for Li(+) action involve Mg(2+)-activated enzymes, which are inhibited by Li(+). In this Account, we describe results from our and other laboratories that suggest that a competition mechanism between Li(+) and Mg(2+) ions for Mg(2+)-binding sites in cellular components is the underlying theme in putative mechanisms of Li(+) action.
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Layden BT, Abukhdeir AM, Malarkey C, Oriti LA, Salah W, Stigler C, Geraldes CFGC, Mota de Freitas D. Identification of Li+ binding sites and the effect of Li+ treatment on phospholipid composition in human neuroblastoma cells: a 7Li and 31P NMR study. Biochim Biophys Acta Mol Basis Dis 2005; 1741:339-49. [PMID: 16115751 DOI: 10.1016/j.bbadis.2005.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 07/19/2005] [Accepted: 07/20/2005] [Indexed: 10/25/2022]
Abstract
Li(+) binding in subcellular fractions of human neuroblastoma SH-SY 5 Y cells was investigated using (7)Li NMR spin-lattice (T(1)) and spin-spin (T(2)) relaxation measurements, as the T(1)/T(2) ratio is a sensitive parameter of Li(+) binding. The majority of Li(+) binding occurred in the plasma membrane, microsomes, and nuclear membrane fractions as demonstrated by the Li(+) binding constants and the values of the T(1)/T(2) ratios, which were drastically larger than those observed in the cytosol, nuclei, and mitochondria. We also investigated by (31)P NMR spectroscopy the effects of chronic Li(+) treatment for 4--6 weeks on the phospholipid composition of the plasma membrane and the cell homogenate and found that the levels of phosphatidylinositol and phosphatidylserine were significantly increased and decreased, respectively, in both fractions. From these observations, we propose that Li(+) binding occurs predominantly to membrane domains, and that chronic Li(+) treatment alters the phospholipid composition at these membrane sites. These findings support those from clinical studies that have indicated that Li(+) treatment of bipolar patients results in irregularities in Li(+) binding and phospholipid metabolism. Implications of our observations on putative mechanisms of Li(+) action, including the cell membrane abnormality, the inositol depletion and the G-protein hypotheses, are discussed.
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Affiliation(s)
- Brian T Layden
- Department of Chemistry, Loyola University Chicago, 6525 North Sheridan Road, Chicago, Illinois 60626, USA
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Srinivasan C, Toon J, Amari L, Abukhdeir AM, Hamm H, Geraldes CFGC, Ho YK, Mota de Freitas D. Competition between lithium and magnesium ions for the G-protein transducin in the guanosine 5'-diphosphate bound conformation. J Inorg Biochem 2005; 98:691-701. [PMID: 15134914 DOI: 10.1016/j.jinorgbio.2003.12.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2003] [Revised: 12/29/2003] [Accepted: 12/31/2003] [Indexed: 11/18/2022]
Abstract
Li(+) is the most effective drug used to treat bipolar disorder; however, its exact mechanism of action has yet to be elucidated. One hypothesis is that Li(+) competes with Mg2+ for the Mg2+ binding sites on guanine-nucleotide binding proteins (G-proteins). Using 7Li T1 relaxation measurements and fluorescence spectroscopy with the Mg2+ fluorophore furaptra, we detected Li(+)/Mg(2+) competition in three preparations: the purified G-protein transducin (Gt), stripped rod outer segment membranes (SROS), and SROS with purified Gt reattached (ROS-T). When purified ROS-T, SROS or transducin were titrated with Li+ in the presence of fixed amounts of Mg(2+), the apparent Li(+) binding constant decreased due to Li(+)/Mg(2+) competition. Whereas for SROS the competition mechanism was monophasic, for G(t), the competition was biphasic, suggesting that in G(t), Li(+)/Mg(2+) competition occurred with different affinities for Mg(2+) in two types of Mg(2+) binding sites. Moreover, as [Li(+)] increased, the fluorescence excitation spectra of both ROS-T and G(t) were blue shifted, indicating an increase in free [Mg(2+)] compatible with Li(+) displacement of Mg(2+) from two low affinity Mg(2+) binding sites of G(t). G(t) release from ROS-T membrane was also inhibited by Li(+) addition. In summary, we found evidence of Li(+)/Mg(2+) competition in G(t)-containing preparations.
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Affiliation(s)
- Chandra Srinivasan
- Department of Chemistry, Loyola University Chicago, 6525 N. Sheridan Road, Chicago, IL 60626, USA
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Fonseca CP, Montezinho LP, Nabais C, Tomé AR, Freitas H, Geraldes CFGC, Castro MMCA. Effects of Li+ transport and intracellular binding on Li+/Mg2+ competition in bovine chromaffin cells. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 2004; 1691:79-90. [PMID: 15110989 DOI: 10.1016/j.bbamcr.2003.12.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2003] [Revised: 12/16/2003] [Accepted: 12/17/2003] [Indexed: 11/18/2022]
Abstract
Li(+) transport, intracellular immobilisation and Li(+)/Mg(2+) competition were studied in Li(+)-loaded bovine chromaffin cells. Li(+) influx rate constants, k(i), obtained by atomic absorption (AA) spectrophotometry, in control (without and with ouabain) and depolarising (without and with nitrendipine) conditions, showed that L-type voltage-sensitive Ca(2+) channels have an important role in Li(+) uptake under depolarising conditions. The Li(+) influx apparent rate constant, k(iapp), determined under control conditions by (7)Li NMR spectroscopy with the cells immobilised and perfused, was much lower than the AA-determined value for the cells in suspension. Loading of cell suspensions with 15 mmol l(-1) LiCl led, within 90 min, to a AA-measured total intracellular Li(+) concentration, [Li(+)](iT)=11.39+/-0.56 mmol (l cells)(-1), very close to the steady state value. The intracellular Li(+) T(1)/T(2) ratio of (7)Li NMR relaxation times of the Li(+)-loaded cells reflected a high degree of Li(+) immobilisation in bovine chromaffin cells, similar to neuroblastoma, but larger than for lymphoblastoma and erythrocyte cells. A 52% increase in the intracellular free Mg(2+) concentration, Delta[Mg(2+)](f)=0.27+/-0.05 mmol (l cells)(-1) was measured for chromaffin cells loaded with the Mg(2+)-specific fluorescent probe furaptra, after 90-min loading with 15 mmol l(-1) LiCl, using fluorescence spectroscopy, indicating significant displacement of Mg(2+) by Li(+) from its intracellular binding sites. Comparison with other cell types showed that the extent of intracellular Li(+)/Mg(2+) competition at the same Li(+) loading level depends on intracellular Li(+) transport and immobilisation in a cell-specific manner, being maximal for neuroblastoma cells.
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Affiliation(s)
- C P Fonseca
- Department of Biochemistry and Centre for Neuroscience of Coimbra, University of Coimbra, P.O. Box 3126, 3001-401 Coimbra, Portugal
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Layden BT, Abukhdeir AM, Williams N, Fonseca CP, Carroll L, Castro MMCA, Geraldes CFGC, Bryant FB, Freitas DMD. Effects of Li+ transport and Li+ immobilization on Li+/Mg2+ competition in cells: implications for bipolar disorder. Biochem Pharmacol 2003; 66:1915-24. [PMID: 14599549 DOI: 10.1016/j.bcp.2003.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Li(+)/Mg(2+) competition has been implicated in the therapeutic action of Li(+) treatment in bipolar illness. We hypothesized that this competition depended on cell-specific properties. To test this hypothesis, we determined the degree of Li(+) transport, immobilization, and Li(+)/Mg(2+) competition in lymphoblastomas, neuroblastomas, and erythrocytes. During a 50 mM/L Li(+)-loading incubation, Li(+) accumulation at 30 min (mmoles Li(+)/L cells) was the greatest in lymphoblastomas (11.1+/-0.3), followed by neuroblastomas (9.3+/-0.5), and then erythrocytes (4.0+/-0.5). Li(+) binding affinities to the plasma membrane in all three cell types were of the same order of magnitude; however, Li(+) immobilization in intact cells was greatest in neuroblastomas and least in erythrocytes. When cells were loaded for 30 min in a 50 mM/L Li(+)-containing medium, the percentage increase in free intracellular [Mg(2+)] in neuroblastoma and lymphoblastoma cells ( approximately 55 and approximately 52%, respectively) was similar, but erythrocytes did not exhibit any substantial increase ( approximately 6%). With the intracellular [Li(+)] at 15 mM/L, the free intracellular [Mg(2+)] increased by the greatest amount in neuroblastomas ( approximately 158%), followed by lymphoblastomas ( approximately 75%), and then erythrocytes ( approximately 50%). We conclude that Li(+) immobilization and transport are related to free intracellular [Mg(2+)] and to the extent of Li(+)/Mg(2+) competition in a cell-specific manner.
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Affiliation(s)
- Brian T Layden
- Department of Chemistry, Loyola University Chicago, 6525 N. Sheridan Rd., Chicago, IL 60626, USA
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Abstract
OBJECTIVES Previous findings have demonstrated Li+/Mg2+ competition at therapeutic intracellular Li+ levels after acute Li+ treatment in human neuroblastoma SH-SY5Y cells. In the current study, we examined whether Li+/Mg2+ competition exists at therapeutically relevant extra- and intracellular [Li+] after chronic Li+ loading times. METHODS In human neuroblastoma cells, intracellular free Mg2+ was determined by fluorescence spectroscopy with the fluorophore furaptra. Intracellular Li+ and Mg2+ were measured by atomic absorption spectrophotometry. RESULTS After loading of the neuroblastoma cells with 1-2 mM extracellular Li+ for 24-72 h, the observed, increased intracellular free [Mg2+] levels were significantly higher (p < 0.03) than those in matched Li+ free cells, and intracellular [Li+] was found to be at therapeutic intracellular levels (0.7-1.5 mM). CONCLUSIONS The results demonstrate that Li+/Mg2+ competition exists after chronic treatment with Li+ at therapeutically relevant intracellular Li+ levels in neuroblastoma cells. We found differences between acute and chronic Li+ treatment effects on the extent of Li+/Mg2+ competition. Possible reasons for these differences are discussed.
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Affiliation(s)
- Abde M Abukhdeir
- Department of Chemistry, Loyola University Chicago, Illinois 60626, USA
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Abstract
The applications of (7)Li NMR spectroscopy and imaging in biology and experimental medicine have been progressing steadily. The interest derives primarily from the clinical use of Li salts to treat mania and manic-depressive illness. One area of investigation is ionic transport across the cellular membrane and compartmentation, so as to elucidate the mechanism(s) of therapeutic action and toxicity in clinical practice. The second is the development of a noninvasive, in vivo analytical tool to measure brain Li concentrations in humans, both as an adjunct to treatment and as a mechanistic probe. Here we review progress to date in this area.
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Affiliation(s)
- R A Komoroski
- Department of Radiology, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
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Srinivasan C, Minadeo N, Geraldes CF, Mota de Freitas D. Competition between Li+ and Mg2+ for red blood cell membrane phospholipids: A 31P, 7Li, and 6Li nuclear magnetic resonance study. Lipids 1999; 34:1211-21. [PMID: 10606045 DOI: 10.1007/s11745-999-0474-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The mode of action of the lithium ion (Li+) in the treatment of manic depression or bipolar illness is still under investigation, although this inorganic drug has been in clinical use for 50 yr. Several research reports have provided evidence for Li+/Mg2+ competition in biomolecules. We carried out this study to characterize the interactions of Li+ and Mg2+ with red blood cell (RBC) membrane components to see whether Li+/Mg2+ competition occurs. 31P nuclear magnetic resonance chemical shift measurements of the phospholipids extracted from the RBC membranes indicated that the anionic phospholipids, phosphatidylserine and phosphatidylinositol, bind Li+ and Mg2+ most strongly. From 6Li relaxation measurements, the Li+ binding constant to the phospholipid extract was found to be 45 +/- 5 M(-1). Thus, these studies showed that the phospholipids play a major role in metal ion binding. 7Li spin-lattice relaxation measurements conducted on unsealed and cytoskeleton-depleted RBC membrane in the presence of magnesium indicated that the removal of the cytoskeleton increases lithium binding to the more exposed anionic phospholipids (357 +/- 24 M(-1)) when compared to lithium binding in the unsealed RBC membrane (221 +/- 21 M(-1)). Therefore, it can be seen that the cytoskeleton does not play a major role in Li+ binding or in Li+/Mg2+ competition.
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Affiliation(s)
- C Srinivasan
- Department of Chemistry, Loyola University Chicago, Illinois 60626, USA
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Srinivasan C, Minadeo N, Toon J, Graham D, Mota de Freitas D, Geraldes CF. Competition between Na(+) and Li(+) for unsealed and cytoskeleton-depleted human red blood cell membrane: a (23)Na multiple quantum filtered and (7)Li NMR relaxation study. J Magn Reson 1999; 140:206-217. [PMID: 10479564 DOI: 10.1006/jmre.1999.1813] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Evidence for competition between Li(+) and Na(+) for binding sites of human unsealed and cytoskeleton-depleted human red blood cell (csdRBC) membranes was obtained from the effect of added Li(+) upon the (23)Na double quantum filtered (DQF) and triple quantum filtered (TQF) NMR signals of Na(+)-containing red blood cell (RBC) membrane suspensions. We found that, at low ionic strength, the observed quenching effect of Li(+) on the (23)Na TQF and DQF signal intensity probed Li(+)/Na(+) competition for isotropic binding sites only. Membrane cytoskeleton depletion significantly decreased the isotropic signal intensity, strongly affecting the binding of Na(+) to isotropic membrane sites, but had no effect on Li(+)/Na(+) competition for those sites. Through the observed (23)Na DQF NMR spectra, which allow probing of both isotropic and anisotropic Na(+) motion, we found anisotropic membrane binding sites for Na(+) when the total ionic strength was higher than 40 mM. This is a consequence of ionic strength effects on the conformation of the cytoskeleton, in particular on the dimer-tetramer equilibrium of spectrin. The determinant involvement of the cytoskeleton in the anisotropy of Na(+) motion at the membrane surface was demonstrated by the isotropy of the DQF spectra of csdRBC membranes even at high ionic strength. Li(+) addition initially quenched the isotropic signal the most, indicating preferential Li(+)/Na(+) competition for the isotropic membrane sites. High ionic strength also increased the intensity of the anisotropic signal, due to its effect on the restructuring of the membrane cytoskeleton. Further Li(+) addition competed with Na(+) for those sites, quenching the anisotropic signal. (7)Li T(1) relaxation data for Li(+)-containing suspensions of unsealed and csdRBC membranes, in the absence and presence of Na(+) at low ionic strength, showed that cytoskeleton depletion does not affect the affinity of Na(+) for the RBC membrane, but increases the affinity of Li(+) by 50%. This clearly indicates that cytoskeleton depletion favors Li(+) relative to Na(+) binding, and thus Li(+)/Na(+) competition for its isotropic sites. Thus, this relaxation technique proves to be very sensitive to alkali metal binding to the membrane, detecting a more pronounced steric hindrance effect of the cytoskeleton network to binding of the larger hydrated Li(+) ion to the membrane phosphate groups.
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Affiliation(s)
- C Srinivasan
- Department of Chemistry, Loyola University of Chicago, 6525 N. Sheridan Road, Chicago, Illinois 60626, USA
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Amari L, Layden B, Rong Q, Geraldes CF, Mota de Freitas D. Comparison of fluorescence, (31)P NMR, and (7)Li NMR spectroscopic methods for investigating Li(+)/Mg(2+) competition for biomolecules. Anal Biochem 1999; 272:1-7. [PMID: 10405286 DOI: 10.1006/abio.1999.4169] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The biochemical action of lithium in the treatment of manic-depressive illness is still unknown. One hypothesis is that Li(+) competes for Mg(2+)-binding sites in biomolecules. We report here our studies on metal ion competition by three distinct methods: fluorescence, (31)P NMR, and (7)Li NMR spectroscopy, using ATP as a model ligand. By fluorescence spectroscopy, we used the dye, furaptra, by measuring the increases in Mg(2+) levels in an ATP solution as Li(+) levels were increased in the solution. This increase in Mg(2+) levels was indicated by increases in the fluorescence intensity ratio (335/370) of furaptra. By (31)P NMR spectroscopy, this competition was demonstrated by changes in the (31)P NMR spectrum of ATP. The Li(+)/Mg(2+) competition was indicated by predictable changes in the separation between the alpha and beta resonances of the phosphates of ATP. For (7)Li NMR spectroscopy, spin-lattice relaxation measurements were used, which provided free Li(+) concentrations that could be used for determining the free Mg(2+) values in ATP solutions. The values of the free Mg(2+) concentrations obtained by all three methods were in good agreement. The fluorescence and (7)Li NMR methods, however, proved to be more sensitive to low concentrations of Li(+) than the (31)P NMR method.
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Affiliation(s)
- L Amari
- Department of Chemistry, Loyola University Chicago, 6525 North Sheridan Road, Chicago, Illinois 60626, USA
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Abstract
The apparent concentration of lithium (Li) in vivo was determined for several regions in the brain and muscle of rats by 7Li NMR imaging at 4.7 T with inclusion of an external standard of known concentration and visibility. The average apparent concentrations were 10.1 mM for muscle, and 4.2-5.3 mM for various brain regions under the dosing conditions used. The results were compared to concentrations determined in vitro by high-resolution 7Li NMR spectroscopy of extracts of brain and muscle tissue from the same rats. The comparison provided estimates of the 7Li NMR visibility of the Li cation in each tissue region. Although there was considerable scatter of the calculated visibilities among the five rats studied, the results suggested essentially full visibility (96%) for Li in muscle, and somewhat reduced visibility (74-93%) in the various brain regions.
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Affiliation(s)
- R A Komoroski
- Departments of Radiology, Pathology, Biochemistry, and Psychiatry, University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, Arkansas, 72205, USA
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Juvvadi P, Kalapaty E. 7Li and 23Na NMR studies of transmembrane cation transport mediated by ionophore lasalocid A. J Pept Sci 1998; 4:15-20. [PMID: 9523752 DOI: 10.1002/(sici)1099-1387(199802)4:1%3c15::aid-psc96%3e3.0.co;2-e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ion transport across phospholipid vesicles was studied by 7Li and 23Na-NMR using an aqueous anionic paramagnetic shift reagent, dysprosium nitrilotriacetate [Dy(NTA)2](3-), mediated by ionophores, lasalocid A and A23187. The intra- and extracellular 7Li and 23Na-NMR signals were well separated (20 Hz) at mM concentration of the shift reagent. The observed data on the rate constant for lithium transport across DPPC vesicles at various concentrations of the ionophores indicated that lasalocid A is a more efficient carrier for lithium ion compared with the sodium ion transport by this ionophore, while A23187 was not specific to either of the ions (Li or Na).
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Affiliation(s)
- P Juvvadi
- The Rockefeller University, New York, NY 10021, USA
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Nikolakopoulos J, Zachariah C, de Freitas DM, Geraldes CF. Comparison of the use of gel threads and microcarrier beads in Li+ transport studies of human neuroblastoma SH-SY5Y cells. Inorganica Chim Acta 1996. [DOI: 10.1016/s0020-1693(96)05273-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Chi Y, Mota de Freitas D, Sikora M, Bansal VK. Correlations of Na+-Li+ exchange activity with Na+ and Li+ binding and phospholipid composition in erythrocyte membranes of white hypertensive and normotensive individuals: a nuclear magnetic resonance investigation. Hypertension 1996; 27:456-64. [PMID: 8698453 DOI: 10.1161/01.hyp.27.3.456] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Enhanced Na+-Li+ exchange activity has been reported in red blood cells (RBCs) of white patients with essential hypertension compared with RBCs of normotensive individuals. To understand the factors responsible for this finding, we applied novel and conventional spectroscopic and kinetic methods to blood samples from 10 hypertensive and 10 normotensive individuals. We measured the kinetic parameters (V std, V max, and K m) for RBC Na+-Li+ exchange by atomic absorption spectrophotometry and used 23Na and 7Li nuclear magnetic resonance relaxation methods to measure Na+ and Li+ binding to RBC membranes as well as 31P nuclear magnetic resonance spectroscopy to measure membrane phospholipid compositions. We found significant differences between the two groups for the affinity of Na+ for the RBC membrane (0.202 +/- 0.054 mmol/L-1 for hypertensive patients versus 0.296 +/- 0.071 mmol/L-1 for normotensive subjects, P<.005). The kinetic parameters of RBC Na+-Li+ exchange (V std, V max, and K m) were 0.32 +/- 0.09 and 0.66 +/- 0.17 mmol Li+/L cell.h and 160 +/- 62 mmol/L, respectively, for hypertensive patients versus 0.21 +/- 0.06 and 0.32 +/- 0.14 mmol Li+/L cell.h and 86 +/- 69 mmol/L for normotensive subjects (P<.05). The fractions of phosphatidylserine and phosphatidylethanolamine were 0.153 +/- 0.009 and 0.294 +/- 0.016 for hypertensive patients versus 0.138 +/- 0.013 and 0.325 +/- 0.018 for normotensive subjects (P<.05). The Na+ binding constants were negatively correlated with the Km values for both the hypertensive (r=-.61, P=.01) and normotensive (r=-.43, P=.04) groups. Changes in lipid-protein interactions in the RBC membranes of hypertensive patients appear to be responsible for weaker Na+ binding to the membrane and for the faster rates of RBC Na+-Li+ exchange.
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Affiliation(s)
- Y Chi
- Department of Chemistry, Loyola University of Chicago, Illinois 60626, USA
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Mota de Freitas D, Amari L, Srinivasan C, Rong Q, Ramasamy R, Abraha A, Geraldes CF, Boyd MK. Competition between Li+ and Mg2+ for the phosphate groups in the human erythrocyte membrane and ATP: an NMR and fluorescence study. Biochemistry 1994; 33:4101-10. [PMID: 8155627 DOI: 10.1021/bi00180a002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We investigated the mechanism of competition between Li+ and Mg2+ in Li(+)-loaded human red blood cells (RBCs) by making 7Li and 31P NMR and fluorescence measurements. We used 7Li NMR relaxation times to probe Li+ binding to the human RBC membrane and ATP; an increase in Mg2+ concentration caused an increase in both 7Li T1 and T2 values in packed Li(+)-loaded RBCs, in suspensions of Li(+)-loaded RBC ghosts, in suspensions of Li(+)-containing RBC membrane, and in aqueous solutions of ATP, indicating competition between Li+ and Mg2+ for binding sites in the membrane and ATP. We found that increasing concentrations of either Li+ or Mg2+ in the presence of human RBC membrane caused an increase in the 31P NMR chemical shift anisotropy parameter, which describes the observed axially symmetric powder pattern, indicating metal ion binding to the phosphate groups in the membrane. Competition between Li+ and Mg2+ for phosphate groups in ATP and in the RBC membrane was also observed by both fluorescence measurements and 31P NMR spectroscopy at low temperature. The ratio of the stoichiometric binding constants of Mg2+ to Li+ to the RBC membrane was approximately 20; the ratio of the conditional binding constants in the presence of a free intracellular ATP concentration of 0.2 mM was approximately 4, indicating that Li+ competes for approximately 20% of the Mg(2+)-binding sites in the RBC membrane. Our results indicate that, regardless of the spectroscopic method used, Li+ competes with Mg2+ for phosphate groups in both ATP and the RBC membrane; the extent of metal ion competition for the phosphate head groups of the phospholipids in the RBC membrane is enhanced by the presence of ATP. Competition between Li+ and Mg2+ for anionic phospholipids or Mg(2+)-activated proteins present in cell membranes may constitute the basis of a general molecular mechanism for Li+ action in human tissues.
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Affiliation(s)
- D Mota de Freitas
- Department of Chemistry, Loyola University of Chicago, Illinois 60626
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