Cellular cation transport studied by 6/7Li and 23Na NMR in a porous Mo132 Keplerate type nano-capsule as model system.
Li+ ions can interplay with other cations intrinsically present in the intra- and extra-cellular space (i.e. Na+, K+, Mg2+ and Ca2+) have therapeutic effects (e.g. in the treatment of bipolar disorder) or toxic effects (at higher doses), likely because Li+ interferes with the intra-/extra-cellular concentration gradients of the mentioned physiologically relevant cations. The cellular transmembrane transport can be modelled by molybdenum-oxide-based Keplerates, i.e. nano-sized porous capsules containing 132 Mo centres, monitored through 6/7Li as well as 23Na NMR spectroscopy. The effects on the transport of Li+ cations through the 'ion channels' of these model cells, caused by variations in water amount, temperature, and by the addition of organic cationic 'plugs' and the shift reagent [Dy(PPP)2](7-) are reported. In the investigated solvent systems, water acts as a transport mediator for Li+. Likewise, the counter-transport (Li+/Na+, Li+/K+, Li+/Cs+ and Li+/Ca2+) has been investigated by 7Li NMR and, in the case of Li+/Na+ exchange, by 23Na NMR, and it has been shown that most (in the case of Na+ and K+, all (Ca2+) or almost none (Cs+) of the Li cations is extruded from the internal sites of the artificial cell to the extra-cellular medium, while Na+, K+ and Ca2+ are partially incorporated.
Chemistry Department, University of Hamburg, 20146 Hamburg, Germany. rehder@chemie.uni-hamburg.de
Dieter
D
Rehder
Erhard T K
ET
Haupt
Achim
A
Müller
D002412:Cations; D017136:Ion Transport; D008094:Lithium; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008954:Models, Biological; D008982:Molybdenum; D053769:Nanocapsules / Q000737:chemistry*; D012964:Sodium; D013696:Temperature; D014867:Water / Q000737:chemistry
D002412:Cations; D053769:Nanocapsules; D014867:Water; D008982:Molybdenum; D008094:Lithium; D012964:Sodium