Experimental31p nmr study of the influence of ionic strength on the apparent dissociation constant of mgatp

Multiparametric quantification of heterogeneity of metal ion concentrations, as demonstrated for [Mg2+] by way of 31P MRS

“…above 400 µM, chemical-shift changes as a function of [Mg 2+ ] variations become rather small and, therefore, yield more imprecise results. As with any other complex used for quantitation, the accuracy of the ATP/Mg 2+ method depends on the accuracy of the dissociation constant of the Mg 2+ complex (3,15,19,28,30). This is equally true for the classical ATP/Mg 2+ method and for our new approach introduced in this work.…”

Free magnesium concentration in isolated rabbit hearts subjected to high dose isoproterenol infusion: a 31P NMR study

“…It must be mentioned that [Mg 2+ ] i measured by 31 P NMR spectroscopy most probably represents only the cytoplasmic pool of [Mg 2+ ] i , because the NMR signals of ATP come from cytoplasmic ATP. The accuracy of these [Mg 2+ ] i measurements may be impaired by different sources of errors (Garfinkel and Garfinkel 1984;London 1991;Mosher et al 1992;Mottet et al 1994). Recently, new calibrations have been provided to improve the accuracy of the meas-urements (Williams et al 1993) and calculations of the uncertainty on the [Mg 2+ ] i estimated values have been improved considering pH i changes (see below).…”

“…Accurate determination of [Mg 2+ ] i by 31 P NMR depends on the precision in the estimation of K D and of [MgATP]/[ATP free ]. K D changes with temperature, pH, and ionic strength variations (Garfinkel and Garfinkel 1984;London 1991;Mottet et al 1994). In the present study, temperature did not change during the experiment.…”

“…With 31 P NMR spectroscopy, intracellular free magnesium concentration ([Mg 2+ ] i ) was previously measured in isolated hearts subjected to low doses of ISO (Headrick and Willis 1991;Nishimura et al 1993). However, the accuracy of [Mg 2+ ] i measurements by 31 P NMR may be impaired by various sources of errors (Garfinkel and Garfinkel 1984;London 1991;Mosher et al 1992;Mottet et al 1994). Recently, new calibrations have been provided to improve the accuracy of this method (Williams et al 1993).…”

31P MRSIat 7 T enables high‐resolution volumetric mapping of the intracellular magnesium ion content in human lower leg muscles

“…Finding a reason for this discrepancy is difficult due to the different approaches used in the latter cited approaches 4,13,27 and our work, demonstrating the need for further investigation of the processes influencing the chemical shifts of ATP. In addition to pH and temperature, 31,32 also the influence of the ionic strength was discussed to be considered in the characterization of the involved equilibria necessary for the calculation of [Mg 2+ free ] by means of 31 P MRS. 33…”