title: Potential pitfall in the determination of free [Mg2+] by 31P NMR when using the beta/alpha-ATP peak height ratio method.
abstract: Recently, Clarke et al. (Clarke K, Kashiwaya Y, King MT, Gates D, Keon CA, Cross HR, Radda GK, Veech RL. The beta/alpha peak height ratio of ATP. A measure of free [Mg2+(free)] using 31P NMR, J. Biol. Chem. 1996;271:21142 21150.) reported a new method to noninvasively determine the concentration of intracellular free magnesium ([Mg2+(free)]) based on the measurement of the peak height ratio h(beta/alpha) of the beta- and alpha-ATP signals in 31P NMR spectra. h(beta/alpha) varies with [Mg2+(free)], however, the study presented here shows that h(beta/alpha) also strongly depends on the homogeneity of the static magnetic field. For this reason, we performed at a magnetic field strength of 1.5 T 31P NMR measurements of solutions that mimic intracellular medium. The magnetic field homogeneity was varied by changing the currents in the shim coils, and the effect on hbeta/alpha is demonstrated with and without proton decoupling. In both cases, h(beta/alpha) strongly depends on the magnetic field homogeneity and can therefore lead to a pitfall in the determination of [Mg2+(free)].
authors.affiliation: Hypertension and Diabetes Research Unit, Max Grundig Clinic, Bühl, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Widmaier
authors.forename: W I
authors.initials: WI
authors.lastname: Jung
authors.forename: G J
authors.initials: GJ
authors.lastname: Dietze
authors.forename: O
authors.initials: O
authors.lastname: Lutz
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis* / Q000737:chemistry; D005069:Evaluation Studies as Topic; D007424:Intracellular Fluid / Q000737:chemistry; D008274:Magnesium / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010758:Phosphorus; D012996:Solutions
chemical_list: D012996:Solutions; D010758:Phosphorus; D000255:Adenosine Triphosphate; D008274:Magnesium