Inorg. Chem. 1990,Li+ T , relaxation times presumably can be used as probes of Li' binding to the RBC membrane and for determining whether the extent and site of Li+ binding are different in RBCs from bipolar, hypertensive, and normotensive controls. Thus, the MIR approach (because of the its total noninvasiveness, easy visualization of Li+ pools, and ability to probe interactions between the Li' ion and RBC components) will be the method of choice to investigate whether Li+ transport and distribution parameters in RBCs can be used with confidence as genetic markers of bipolar disorder^)^ and h y p e r t e n~i o n .~~ 29. [3979][3980][3981][3982][3983][3984][3985] 3979 ( Received November 14, I989 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 the triphosphate, triethylenetetraminehexaacetate, bis(dihydroxyphosphiny1-methyl)phosphinate, and I ,4,7,1 O-tetrazacyclododecane-N,N',N",N"'-tetrakis(methanephosphonate) ligands, respectively. The apparent size and shape of Li+-free RBCs (red blood cells), studied by both scanning electron microscopy and Coulter counter methods, were unchanged by the presence of the above shift reagents at concentrations lower than 10 mM. However, Li+ incubation changed both the shape and size of RBCs. The rates of Na+-Li+ exchange in Li+-loaded RBCs measured by 7Li NMR spectroscopy in the presence of Dy(PPP);-, TI~(PPP),~-, or D~(PcPcP),~-were significantly higher than the rates measured in the absence of shift reagents by atomic absorption or in the presence of DY(TTHA)~-or DY(DOTP)~-by 7Li NMR spectroscopy. 31P and I9F NMR measurements of the membrane potential of Li+-free RBCs revealed that the shift reagents studied (except for Dy(TTHA)") do change the membrane potential, with the most negatively charged reagents having the largest effect. Thus, shift reagents must be used with caution in physiological NMR studies and in particular RBC applications.
The measurement of trace analytes in aqueous systems has become increasingly important for understanding ocean primary productivity. In oceanography, iron (Fe) is a key element in regulating ocean productivity, microplankton assemblages and has been identified as a causative element in the development of some harmful algal blooms. The chemosenor developed in this study is based on an indicator displacement approach that utilizes time-resolved fluorescence and fluorescence resonance energy transfer as the sensing mechanism to achieve detection of Fe3+ ions as low as 5 nM. This novel approach holds promise for the development of photoactive chemosensors for ocean deployment.
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