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Identification of Li+ binding sites and the effect of Li+ treatment on phosphol...
Layden, Brian T.; Abukhdeir, Abde M.; Malarkey, Christopher; Oriti, Lisa A.; Salah, Wajeeh; Stigler, Claire; Geraldes, Carlos F. G. C.Li+ binding in subcellular fractions of human neuroblastoma SH-SY5Y cells was investigated using 7Li NMR spin-lattice (T1) and spin-spin (T2) relaxation measurements, as the T1/T2 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 T1/T2 ratios, wh...
Competition between lithium and magnesium ions for the G-protein transducin in ...
Srinivasan, Chandra; Toon, Jason; Amari, Louis; Abukhdeir, Abde M.; Hamm, Heidi; Geraldes, Carlos F. G. C.; Ho, Yee-Kin; Freitas, Duarte Mota deLi+ 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+/Mg2+ competition in three preparations: t...
Effects of Li+ transport and Li+ immobilization on Li+/Mg2+ competition in cell...
Layden, Brian T.; Abukhdeir, Abde M.; Williams, Nicole; Fonseca, Carla P.; Carroll, Laura; Castro, Margarita M. C. A.; Geraldes, Carlos F. G. C.Li+/Mg2+ 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+/Mg2+ competition in lymphoblastomas, neuroblastomas, and erythrocytes. During a 50 mmol/L Li+-loading incubation, Li+ accumulation at 30 min (...
Evaluation of [Co(gly)3]- as a 35Cl- NMR Shift Reagent for Cellular Studies
Diven, Conrad F.; Wang, Fei; Abukhdeir, Abde M.; Salah, Wajeeh; Layden, Brian T.; Geraldes, Carlos F. G. C.; Freitas, Duarte Mota deWe studied the efficacy of the tris-glycinatocobaltate(II) complex ([Co(gly)3]-) as a shift reagent (SR) for chloride by 35Cl NMR spectroscopy and compared to that of Co2+(aq). Due to the relatively low thermodynamic stability of [Co(gly)3]-, a 1:3 Co(II)/gly stoichiometric solution at physiological pH is approximately a 2:1 mixture of [Co(gly)2(H2O)2] and [Co(gly)(H2O)4]+. This SR was found to be stable up to ...
Competition between Na+ and Li+ for Unsealed and Cytoskeleton-Depleted Human Re...
Srinivasan, Chandra; Minadeo, Nicole; Toon, Jason; Graham, Daniel; Freitas, Duarte Mota de; Geraldes, Carlos F. G. C.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 23Na 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+...
Comparison of Fluorescence, 31P NMR, and 7Li NMR Spectroscopic Methods for Inve...
Amari, Louis; Layden, Brian; Rong, Qinfen; Geraldes, Carlos F. G. C.; Freitas, Duarte Mota deThe biochemical action of lithium in the treatment of manic-depressive illness is still unknown. One hypothesis is that Li+ competes for Mg2+-binding sites in biomolecules. We report here our studies on metal ion competition by three distinct methods: fluorescence, 31P NMR, and 7Li NMR spectroscopy, using ATP as a model ligand. By fluorescence spectroscopy, we used the dye, furaptra, by measuring the increases ...
Lithium-7 NMR relaxation study of lithium binding in human erythrocytes
Rong, Qinfen; Espanol, Maryceline; Freitas, Duarte Mota de; Geraldes, Carlos F. G. C.We used 7Li NMR spin-lattice (TI) and spin-spin (Tz) relaxation time measurements to investigate the binding of Li+ in human red blood cell (RBC) suspensions. In RBCs containing 1.4 mM Li+, the intracellular 7Li NMR T2 relaxation value (0.30 f 0.03 s) was much smaller than the corresponding TI value (6.0 f 0.1 s), yielding a ratio of TI to T2 of 20. For 1.5 mM LiCl solutions whose viscosities were adjusted to 5...
Physical basis for the resolution of intra- and extracellular cesium-133 NMR re...
Wittenkeller, Lisa; Freitas, Duarte Mota de; Geraldes, Carlos F. G. C.; Tomé, Angelo J. R.For human red blood cells (RBCs) loaded with Cs' and suspended in a shift reagent (SR) free medium, the extracellular 13'Cs+ NMR resonance was shifted upfield from the intracellular resonance. However, in the presence of the SRs Dy(PPP);-, Dy- (TTHA))-, and Tm(DOTP)S- [where Dy3+ and Tm3' denote dysprosium and thulium ions and PPPs-, TTHA6, and DOTPsrepresent the triphosphate, triethylenetetraminehexaacetate, a...
Multinuclear NMR study of the interaction of the shift reagent lanthanide(III) ...
Ramasamy, Ravichandran; Freitas, Duarte Mota de; Geraldes, Carlos F. G. C.; Peters, Joop A.The paramagnetic ion-induced relaxation rate enhancements of 6Li in adducts of Li+ and Ln(PPP)J- complexes (Ln = Dy, Tm) in aqueous solution show that up to seven monovalent counterions can coordinate in the second coordination sphere of the Ln(II1) ion to the outer oxygens of the triphosphate ligands. However, the pseudocontact ’Li NMR shift data suggest that in the second coordination sphere some preference o...
Effects of negatively charged shift reagents on red blood cell morphology, lith...
Ramasamy, Ravichandran; Freitas, Duarte Mota de; Jones, Warren; Wezeman, Frederick; Labotka, Richard; Geraldes, Carlos F. G. C.Lanthanide shift reagents have been used extensively in multinuclear magnetic resonance (NMR) applications in order to obtain information regarding ion distribution and transport in cellular systems. The aqueous reagents used in this study were Dy(PPP)J-, Tm( PPP)J-, Dy(TTHA)’-, Dy(PcPcP);-, and Dy(DOTP)’-, where Dy3+ and Tm3+ represent dysprosium and thulium ions and PPPs-, TTHA6-, PcPcPs-, and DOTP*- denote t...
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