Magnesium-Based Temperature Dependence of the ATP Chemical-Shift Separation δαβand Its Relation to Intracellular Free Magnesium
✍ Scribed by Stefan Widmaier; Thomas Hoess; Johannes Breuer; Wulf-Ingo Jung; Günther J. Dietze; Otto Lutz
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 228 KB
- Volume
- 113
- Category
- Article
- ISSN
- 1064-1866
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✦ Synopsis
Proton-decoupled 31 P NMR spectroscopy was performed in vitro
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[1] and in vivo in humans to investigate the temperature dependence of the chemical-shift separation d ab between the aand b-phosphorus resonances and the 31 P-31 P coupling constants of ATP using The chemical-shift limit of the fully complexed species is a 1.5 T whole-body imager. In vitro in the presence of magnesium, d MgATP ab and the limit of the uncomplexed species is d ATP ab . a linear temperature dependence of d ab was found that varied This equation can be rearranged to calculate the ratio of the systematically with Mg-to-ATP ratio ( R). This needs to be considconcentration of MgATP to free ATP ([MgATP]/[ATP free ]) ered in studies where d ab is used to determine temperature. A or by using the conservation of mass ([Mg total ] Å [Mg free ] second important point is the temperature dependence of 00.0128 { 0.0002 ppm/ЊC (mean { SD, n Å 6) of the chemical-shift limit / [MgATP], [ATP total ] Å [ATP free ] / [MgATP]) to obtain, d MgATP ab (T ) of mostly mono-magnesium-complexed ATP found at for example, the ratio of [MgATP] to [ATP total ]: R Å 2.2 { 0.2. This parameter is used in combination with the temperature dependences of the uncomplexed limit d ATP ab (T ) and [MgATP] [ATP total ] Å d ATP ab 0 d ab d ATP ab 0 d MgATP ab . [2] the dissociation constant K MgATP D (T ) for the determination of [Mg 2/ f ree ] at different temperatures. Preliminary studies in vivo show that d ab also decreases in human skeletal muscle with in-Furthermore, [Mg 2/ f ree ] can be calculated if the apparent discreasing temperature, similarly to the in vitro results. Therefore, sociation constant K MgATP D is known: interpretations of differences in d ab found in vivo must consider even small temperature differences to avoid significant errors in the determination of [Mg 2/ f ree ].